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Difference between revisions of "Filling out the Geometry Orbiter Class"

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The ''Geometry_Orbiter'' class provides geometric values related to an orbiting or flyby spacecraft observation.  The values in this class are specific to a single reference frame at a single reference time for at most a single target.  You may repeat this class with differing values for one or all of those, if appropriate to the observation being labelled.
+
The ''Geometry_Orbiter'' class provides geometric values related to an orbiting or flyby spacecraft observation.  The values in this class are specific to a single reference frame at a single reference time (or time range) for at most a single target.  You may repeat this class with differing values for one or all of those, if appropriate to the observation being labelled.
  
 
== <geometry_reference_time> ==
 
== <geometry_reference_time> ==
 
''REQUIRED''
 
 
This is the UTC time for which the values in this class have been calculated.  It must be in the standard ''YYY-MM-DD'''''T'''''hh:mm:ss.sss'''''Z'''" format.
 
 
== <Reference_Frame_Identification> ==
 
 
''REQUIRED''
 
 
{| class="wikitable" style="background-color: yellow"
 
|
 
''Waiting on SPICE-related changes.''
 
|}
 
 
== <Central_Body_Identification> ==
 
  
 
''OPTIONAL''
 
''OPTIONAL''
  
{| class="wikitable" style="background-color: yellow"
+
This is the UTC time for which the values in this class have been calculated.  It must be in the standard ''YYYY-MM-DD'''''T'''''hh:mm:ss.sss'''''Z'''" format.
|
 
''Waiting on SPICE-related changes.''
 
|}
 
  
== <Coordinate_System> ==
+
Either this attribute, or the ''geometry_start_time''/''geometry_stop_time'' pair is required.  You are not prevented from including both, but that would be rather confusing and there is no place in this class for an explanatory comment - so avoid it.
  
''OPTIONAL''
+
== <geometry_start_time> and <geometry_stop_time> ==
 
 
This class defines a coordinate system. It specifies an origin, reference frame, type, and reference time.
 
 
 
=== <coordinate_system_type> ===
 
 
 
''REQUIRED''
 
 
 
This indicates the type of coordinates that will be used.  It must be one of the following standard values:
 
 
 
::* '''Cartesian'''
 
::* '''Planetocentric'''
 
::* '''Planetodetic'''
 
::* '''Planetographic'''
 
::* '''Spherical'''
 
 
 
=== <coordinate_system_time> ===
 
 
 
''REQUIRED''
 
 
 
This attribute provides a reference time for the instantiation of the coordinate system.  It must be in the standard "''YYYY-MM-DD'''''T'''''hh:mm:ss.sss''".  If the time is a UTC time, add the '''Z''' zone indicator at the end.
 
 
 
=== <Coordinate_System_Origin_Identification> ===
 
 
 
''REQUIRED''
 
 
 
{| class="wikitable" style="background-color: yellow"
 
|
 
''Waiting on SPICE-related changes.''
 
|}
 
 
 
=== <Reference_Frame_Identification> ===
 
 
 
''REQUIRED''
 
 
 
{| class="wikitable" style="background-color: yellow"
 
|
 
''Waiting on SPICE-related changes.''
 
|}
 
 
 
 
 
 
 
== <Target_Identification> ==
 
  
 
''OPTIONAL''
 
''OPTIONAL''
  
{| class="wikitable" style="background-color: yellow"
+
These are both optional, but if you use one you must also include the other.  (See also the note above for ''geometry_reference_time''.)  Use the start/stop pair when you have an extended observation for which you plan to provide pairs of geometric values corresponding to these times in the other subclasses of ''&lt;Geometry_Orbiter&gt;''.
|
 
''Waiting on SPICE-related changes.''
 
|}
 
  
 +
These must be UTC times in the standard ''YYYY-MM-DD'''''T'''''hh:mm:ss.sss'''''Z''' format.
  
== <Distances> ==
+
== <geometry_reference_time_tdb> ==
  
 
''OPTIONAL''
 
''OPTIONAL''
  
This class collects scalar point-to-point distance measurements for various named intervals of interest, as well as providing a class for specifying arbitrary distance measurements as needed.  Unless otherwise stated, distances are measured center-to-center, and references to "target" and "central body" refer to the objects identified in the ''&lt;Target_Identification&gt;'' and ''&lt;Central_Body_Identification&gt;'', respectively, in this ''&lt;Geometry_Orbiter&gt;'' class.
+
This should be the Barycentric Dynamical Time (or Ephemeris Time), equivalent to the ''&lt;geometry_reference_time_UTC&gt;'' listed above.  This is defined in the SPICE toolkit sense of a number of seconds since the J2000 epoch.
  
All distances are considered positive, and you must provide units of an appropriate type in each case.  For example:
+
== <Orbiter_Identification> ==
<pre>
 
    <spacecraft_to_target_center_distance unit="km">15.097</spacecraft_to_target_center_distance>
 
    <target_geocentric_distance unit="AU">17.9</target_geocentric_distance>
 
</pre>
 
 
 
=== <spacecraft_geocentric_distance> ===
 
  
 
''OPTIONAL''
 
''OPTIONAL''
  
Distance from the spacecraft to Earth
+
Use this class to identify geometric elements and reference points to be used in the ''Geometry_Orbiter'' subclasses that follow.
  
=== <spacecraft_heliocentric_distance> ===
+
=== <Central_Body_Identification> ===
  
 
''OPTIONAL''
 
''OPTIONAL''
  
Distance from the spacecraft to the sun
+
If the target of the following geometry is orbiting another body, that body is the "central body" and should be identified using this class.  It is filled out identically to the class of the same name on the [[Filling_out_the_Image_Display_Geometry_Class#.3CCentral_Body_Identification.3E|Filling Out the Image_Display_Geometry Class]] page on this wiki.
  
=== <spacecraft_to_central_body_distance> ===
+
=== <Geometry_Target_Identification> ===
  
 
''OPTIONAL''
 
''OPTIONAL''
  
Distance from the spacecraft to identified central body.
+
This class locally defines the concept of "target" to be the thing on the "to" end of the various vectors that follow in this ''Geometry_Orbiter'' class.  It may or may not be the same as the target of the product as a whole.  It is filled out identically to the class of the same name in the ''[[Filling_out_the_Image_Display_Geometry_Class#.3CGeometry_Target_Identification.3E|Image_Display_Geometry]]'' class.
  
=== <spacecraft_to_target_center_distance> ===
+
=== <Coordinate_System_Identification> ===
  
 
''OPTIONAL''
 
''OPTIONAL''
  
Distance from the spacecraft to the identified target.
+
This class is used to identify a "coordinate system" in the NAIF SPICE toolkit sense - both a reference frame and a well-defined origin, with a specific type of coordinates.
  
=== <spacecraft_to_target_boresight_intercept_distance> ===
+
==== <coordinate_system_type> ====
  
''OPTIONAL''
+
''REQUIRED''
 
 
Distance from the center of the spacecraft, measured along the boresight of the observing instrument, to the point where that line intercepts the surface of the identified target.
 
 
 
=== <spacecraft_to_target_subspacecraft_distance> ===
 
  
''OPTIONAL''
+
You must indicate the type of coordinates to be applied, which must be one of the following values:
  
Distance from the center of the spacecraft, measured along a line from the center of the spacecraft to the center of the identified target, to the point where that line intercepts the surface of the target.
+
* Azimuth-Elevation
 +
* Cartesian
 +
* Planetocentric
 +
* Planetodetic
 +
* Planetographic
 +
* Spherical
  
=== <target_geocentric_distance> ===
+
==== <coordinate_system_time_utc> ====
  
 
''OPTIONAL''
 
''OPTIONAL''
  
Distance from the identified target to Earth
+
If your coordinate system has a time dependence, this attribute should hold the relevant instantiation time in UTC, in the standard ''YYYY-MM-DD'''''T'''''hh:mm:ss.ss'''''Z''' format.
  
=== <target_heliocentric_distance> ===
+
==== <comment> ====
  
 
''OPTIONAL''
 
''OPTIONAL''
  
Distance from the identified target to the sun
+
Here is a place to add some clarifying explanation for uncommon coordinate systems. 
  
=== <target_ssb_distance> ===
+
==== <Coordinate_System_Origin_Identification> ====
 
 
''OPTIONAL''
 
 
 
Distance from the target to the Solar System Barycenter (SSB)
 
 
 
=== <Distance_Generic> ===
 
 
 
''OPTIONAL''
 
 
 
This class provides an opportunity to define and record a distance measurement not included in the preceding attributes of this class.  You must define the start point of the distance measurement as the "observer", and the end point as the "target" (in a generic sense, here).
 
 
 
==== <Observer_Identification> ====
 
  
 
''REQUIRED''
 
''REQUIRED''
  
{| class="wikitable" style="background-color: yellow"
+
This class indicates the fixed origin ([0,0,0] point, i.e.) of the coordinate system.  Apart from the class name, the content is filled out identically to the ''Geometry_Target_Identification'' class in the ''[[Filling_out_the_Image_Display_Geometry_Class#.3CGeometry_Target_Identification.3E|Image_Display_Geometry]]'' class.  That is, its attributes are:
|
 
''Waiting on SPICE-related changes.''
 
|}
 
 
 
==== <Target_identification> ====
 
  
''REQUIRED''
+
::* ''body_spice_name''
 +
::* ''name''
 +
::* ''pds:Internal_Reference''
  
{| class="wikitable" style="background-color: yellow"
+
==== <Reference_Frame_Identification> ====
|
 
''Waiting on SPICE-related changes.''
 
|}
 
 
 
==== <distance> ====
 
  
 
''REQUIRED''
 
''REQUIRED''
  
The actual distance measurement from ''observer'' to ''target''.  You must, as always, provide an appropriate unit of measure with this attributeMake sure you indicate the precise point (center, barycenter, intercept point, etc.) used for measurement at both the ''observer'' and the ''target''.
+
This class indicates the "orthogonal axes" part of the coordinate system definitionIt is filled out identically to the class of the same name in the ''[[Filling_out_the_Image_Display_Geometry_Class#.3CReference_Frame_Identification.3E|Image_Display_Geometry]]'' class.
 
 
  
  
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This class provides various ways of translating a pixel field of view to physical dimensions.  You must provide units for these attributes as appropriate.
 
This class provides various ways of translating a pixel field of view to physical dimensions.  You must provide units for these attributes as appropriate.
  
=== <horizontal_pixel_size_angular> ===
+
=== <pixel_field_of_view_method> ===
  
''OPTIONAL''
+
''REQUIRED''
  
This attribute gives the horizontal (as defined by the ''&lt;Display_Direction&gt;'' class) size of a pixel in terms of its angular size.   
+
This attribute indicates how the pixel FOV values, following, were derivedIt must have one of the following values:
 
 
=== <vertical_pixel_size_angular> ===
 
 
 
''OPTIONAL''
 
  
This attribute gives the vertical (as defined by the ''&lt;Display_Direction&gt;'' class) size of a pixel in terms of its angular size.
+
::* '''average''': The pixel FOV varies across the image; the value stated are the average FOV.
 +
::* '''central pixel''': The pixel FOV varies across the image; the value stated represents the FOV of the center pixel.
 +
::* '''constant''': The pixel FOV does not vary across the image.
  
=== <horizontal_pixel_scale_factor> ===
+
=== <horizontal_pixel_field_of_view> ===
  
 
''OPTIONAL''
 
''OPTIONAL''
  
This attribute gives the horizontal (as defined by the ''&lt;Display_Direction&gt;'' class) scaling factor needed to convert the width of a pixel to a linear extent at the point of interest - typically at the surface intercept point of a relatively close object, or at the distance of the center of a distant one.
+
This attribute gives the horizontal (as defined by the ''&lt;Display_Direction&gt;'' class) FOV of a single pixel in terms of its angular size.  You must specify angular units (typically "deg") for this value.
 
 
Units for this keyword are ''Units_of_Map_Scale'' - "km/pixel", for example.
 
  
=== <vertical_pixel_scale_factor> ===
+
=== <vertical_pixel_field_of_view> ===
  
 
''OPTIONAL''
 
''OPTIONAL''
  
This attribute gives the vertical (as defined by the ''&lt;Display_Direction&gt;'' class) scaling factor needed to convert the height of a pixel to a linear extent at the point of interest - typically at the surface intercept point of a relatively close object, or at the distance of the center of a far-off one.   
+
This attribute gives the vertical (as defined by the ''&lt;Display_Direction&gt;'' class) FOV of a single pixel in terms of its angular sizeYou must specify angular units (typically "deg") for this value.
 
 
Units for this keyword are ''Units_of_Map_Scale'' - "km/pixel", for example.
 
  
 
=== <Pixel_Size_Projected> ===
 
=== <Pixel_Size_Projected> ===
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''OPTIONAL''
 
''OPTIONAL''
  
This class provides a more detailed way to define the projected footprint of a pixel field of view at the surface of a (resolved) target object.
+
This class provides a the size, in units of length, of a single pixel projected onto the surface of (or at the distance of) the relevant geometry target.
  
 
==== <reference_location> ====
 
==== <reference_location> ====
  
''REQUIRED''
+
''OPTIONAL''
  
This attribute identifies the point at which the following pixel values are calculated.  It must have one of the following values:
+
This attribute identifies the point on the target at which the following pixel values are calculated.  Either this or ''&lt;distance&gt;'' must be specified.  It must have one of the following values:
  
 
::* Boresight Intercept Point
 
::* Boresight Intercept Point
 +
::* Constant
 
::* Subspacecraft Point
 
::* Subspacecraft Point
 
::* Target Center
 
::* Target Center
  
The "target" is the object in the ''&lt;Target_Identification&gt;'' class of this ''&lt;Geometry_Orbiter&gt;'' class.
+
==== <distance> ====
 
 
==== <horizontal_pixel_size_projected> ====
 
  
 
''OPTIONAL''
 
''OPTIONAL''
  
This attribute gives the horizontal (as defined in the associated ''Display_Direction'' class) extent of a single pixel at the ''reference_location'', in units of length.
+
Distance to which the pixel is projected.  This is particularly useful when your target object occupies a small number of pixels rather than the entire image frame.  Either this or ''&lt;reference_location&gt;'' must be specified.  You must provide units of length for this value.
  
==== <vertical_pixel_size_projected> ====
+
==== <horizontal_pixel_footprint> ====
 
 
''OPTIONAL''
 
 
 
This attribute gives the vertical (as defined in the associated ''Display_Direction'' class) extent of a single pixel at the ''reference_location'', in units of length.
 
  
 +
''REQUIRED''
  
 +
This attribute gives the horizontal (as defined in the associated ''Display_Direction'' class) extent of a single pixel at the ''reference_location'' or ''distance'', in units of length.
  
== <Surface_Geometry> ==
+
==== <vertical_pixel_footprint> ====
 
 
''OPTIONAL''
 
 
 
This class collects various attributes related to geometry at the surface of the object in the ''&lt;Target_identification&gt;'' class of this ''&lt;Geometry_Orbiter&gt;'' class.
 
 
 
=== <Pixel_Intercept> ===
 
 
 
''OPTIONAL''
 
 
 
This class identifies the pixel at which the other values in the containing class are calculated.  Typically, one would use either the ''reference_pixel_location'' or the ''Reference_Pixel'' class to identify the reference point within the associated image.
 
 
 
==== <reference_pixel_location> ====
 
 
 
''OPTIONAL''
 
 
 
This identifies the pixel at which the other values in this class are calculated.  It must be one of the following values:
 
 
 
::* Center
 
::* Lower Left Corner
 
::* Lower Right Corner
 
::* Upper Left Corner
 
::* Upper Right Corner
 
 
 
==== <Reference_Pixel> ====
 
 
 
''OPTIONAL''
 
 
 
This class identifies a reference pixel by coordinates within the image, as described by the associated ''Display_Direction'' class.  It is filled out the same way here as the ''Reference_Pixel'' class in ''[[Filling_out_the_Image_Display_Geometry_Class#.3CReference_Pixel.3E|Image_Display_Geometry]]''.
 
 
 
==== <pixel_latitude> ====
 
 
 
''OPTIONAL''
 
 
 
This is the planetocentric latitude on the surface of the identified target at the center of the reference pixel.  You must include units of measure for this attribute.
 
 
 
==== <pixel_longitude> ====
 
 
 
''OPTIONAL''
 
 
 
This is the planetocentric longitude on the surface of the identified target at the center of the reference pixel.  You must include units of measure for this attribute.
 
 
 
=== <Footprint_Vertices> ===
 
 
 
''OPTIONAL''
 
 
 
This class defines the footprint associated with an observation as a series of pixels defining a polygon.  Include one ''&lt;Pixel_Intercept&gt;'' subclass for each vertex.  You must have at least three of these; you may have as many as you like.  The vertices should be defined in an order that is clockwise (as seen in the displayed image) around the perimeter of the footprint.
 
 
 
==== <Pixel_Intercept> ====
 
  
 
''REQUIRED''
 
''REQUIRED''
  
You must have at least three of these subclasses, and you may have as many as you need.  It is filled out identically to the ''[[#.3CPixel_Intercept.3E|Pixel_Intercept]]'' in the ''&lt;Surface_Geometry&gt;'' class, above.
+
This attribute gives the vertical (as defined in the associated ''Display_Direction'' class) extent of a single pixel at the ''reference_location'' or ''distance'', in units of length.
  
=== <subsolar_azimuth> ===
 
  
''OPTIONAL''
+
== <Distances> ==
 
 
This is the angle, measures clockwise from a line extending from the center of the image to the center of the right edge, to the subsolar point on the identified target.  You must specify units of measure for this attribute.
 
 
 
=== <subsolar_latitude> ===
 
  
 
''OPTIONAL''
 
''OPTIONAL''
  
This attribute contains the planetocentric latitude of the subsolar point on the identified target.  You must provide units of measure for this attribute.
+
This class is a container for other classes used to list scalar distance measurements of various types. These classes collect point-to-point distance measurements (that is, magnitudes rather than vectors) for various named intervals of interest, as well as providing a class for specifying arbitrary distance measurements as needed.  Unless otherwise stated, distances are measured center-to-center, and references to "target" and "central body" refer to the objects identified previously in this ''&lt;Geometry_Orbiter&gt;'' class.
  
=== <subsolar_longitude> ===
+
To avoid a ''lot'' of tedious repetition, these class and attribute descriptions are somewhat abbreviated. In general, the containing class will be described briefly, and the individual distance attributes will merely be listed - their names being self-explanatory.
  
''OPTIONAL''
+
=== General Notes: ===
  
This attribute contains the planetocentric longitude of the subsolar point on the identified target. You must provide the units of measure for this attribute.
+
* All distance attributes are optional in their respective classes; none may be repeated.
 +
* All distances are considered positive.
 +
* All distances are named by their start and end points; terms like "target" and "central body" are as defined for this ''Geometry_Orbiter'' class.
 +
* Unless otherwise indicated by their names, all measurements are considered to be center-to-center.
 +
* All values require units of length for each value, though that unit can vary among attributes in a class.  For example:
 +
<pre>
 +
    <spacecraft_target_center_distance unit="km">15.097</spacecraft_target_center_distance>
 +
    <target_geocentric_distance unit="AU">17.9</target_geocentric_distance>
 +
</pre>
  
=== <subspacecraft_azimuth> ===
+
=== <comment> ===
  
 
''OPTIONAL''
 
''OPTIONAL''
  
This is the angle, measures clockwise from a line extending from the center of the image to the center of the right edge, to the subspacecraft point on the identified target.  You must specify units of measure for this attribute.
+
Here is a place to provide any additional explanatory text that might be apropos.
  
=== <subspacecraft_latitude> ===
+
=== <Distances_Specific> ===
  
 
''OPTIONAL''
 
''OPTIONAL''
  
This attribute contains the planetocentric latitude of the subspacecraft point on the identified targetYou must provide units of measure for this attribute.
+
This container class lists specific named distances often used for searching through data collections from a single sourceUnlike other distance classes, these attributes may be listed in any order.
  
=== <subspacecraft_longitude>> ===
+
==== Distances Included: ====
  
''OPTIONAL''
+
::* ''spacecraft_geocentric_distance''
 +
::* ''spacecraft_heliocentric_distance''
 +
::* ''spacecraft_central_body_distance''
 +
::* ''spacecraft_target_center_distance''
 +
::* ''spacecraft_target_boresight_intercept_distance''
 +
::* ''spacecraft_target_subspacecraft_distance''
 +
::* ''target_geocentric_distance''
 +
::* ''target_heliocentric_distance''
 +
::* ''target_ssb_distance'' - "SSB" stands for "Solar System Barycenter"
  
This attribute contains the planetocentric longitude of the subspacecraft point on the identified target.  You must provide the units of measure for this attribute.
+
=== <Distances_Min_Max> ===
 
 
 
 
== <Illumination_Geometry> ==
 
  
 
''OPTIONAL''
 
''OPTIONAL''
  
This class provides attributes to describe the field of view lighting.
+
This container class lists minimum and maximum distances often used for constraining searches through data collections from a single source.  You are required to provide these values in min/max pairs.  If you don't have min/max pairs for one or more values, use the ''&lt;Distances_Specific&gt;'' class and the corresponding single attribute.
 
 
=== <Illumination_Single_Values> ===
 
  
''OPTIONAL''
+
==== Distances Included: ====
  
This class provides illumination information referenced to a single point in the image when displayed as described in the associated ''Display_Direction'' class.  The "target" in these classes is the object identified in the ''&lt;Target_Identification&gt;'' class of this ''&lt;Geometry_Orbiter&gt;'' class.
+
::* ''minimum_spacecraft_geocentric_distance''
 +
::* ''maximum_spacecraft_geocentric_distance''
 +
::* ''minimum_spacecraft_heliocentric_distance''
 +
::* ''maximum_spacecraft_heliocentric_distance''
 +
::* ''minimum_spacecraft_central_body_distance''
 +
::* ''maximum_spacecraft_central_body_distance''
 +
::* ''minimum_spacecraft_target_center_distance''
 +
::* ''maximum_spacecraft_target_center_distance''
 +
::* ''minimum_spacecraft_target_boresight_intercept_distance''
 +
::* ''maximum_spacecraft_target_boresight_intercept_distance''
 +
::* ''minimum_spacecraft_target_subspacecraft_distance''
 +
::* ''maximum_spacecraft_target_subspacecraft_distance''
 +
::* ''minimum_target_geocentric_distance''
 +
::* ''maximum_target_geocentric_distance''
 +
::* ''minimum_target_heliocentric_distance''
 +
::* ''maximum_target_heliocentric_distance''
 +
::* ''minimum_target_ssb_distance'' - "SSB" stands for "Solar System Barycenter"
 +
::* ''maximum_target_ssb_distance'' - "SSB" stands for "Solar System Barycenter"
  
==== <reference_location> or <reference_pixel_location> ====
+
=== <Distances_Start_Stop> ===
  
 
''OPTIONAL''
 
''OPTIONAL''
  
You must specify one or the other of these reference points to indicate the point at which the following illumination values are calculated.
+
This container class lists distances often used for constraining searches through data collections from a single source calculated at the ''&lt;geometry_start_time&gt;'' and ''&lt;geometry_stop_time&gt;'' defined at the top of this ''Geometry_Orbiter'' class. You are required to provide these values in start/stop pairs.  If you don't have start/stop pairs for one or more values, use the ''&lt;Distances_Specific&gt;'' class and the corresponding single attribute.
  
''reference_location'' must have one of these values:
+
==== Distances Included: ====
::* Boresight Intercept Point
 
::* Subspacecraft Point
 
::* Target Center
 
  
''reference_pixel_location'' must have one of these values:
+
::* ''start_spacecraft_geocentric_distance''
::* Center
+
::* ''stop_spacecraft_geocentric_distance''
::* Lower Left Corner
+
::* ''start_spacecraft_heliocentric_distance''
::* Lower Right Corner
+
::* ''stop_spacecraft_heliocentric_distance''
::* Upper Left Corner
+
::* ''start_spacecraft_central_body_distance''
::* Upper Right Corner
+
::* ''stop_spacecraft_central_body_distance''
 +
::* ''start_spacecraft_target_center_distance''
 +
::* ''stop_spacecraft_target_center_distance''
 +
::* ''start_spacecraft_target_boresight_intercept_distance''
 +
::* ''stop_spacecraft_target_boresight_intercept_distance''
 +
::* ''start_spacecraft_target_subspacecraft_distance''
 +
::* ''stop_spacecraft_target_subspacecraft_distance''
 +
::* ''start_target_geocentric_distance''
 +
::* ''stop_target_geocentric_distance''
 +
::* ''start_target_heliocentric_distance''
 +
::* ''stop_target_heliocentric_distance''
 +
::* ''start_target_ssb_distance'' - "SSB" stands for "Solar System Barycenter"
 +
::* ''stop_target_ssb_distance'' - "SSB" stands for "Solar System Barycenter"
  
==== <Reference_Pixel> ====
+
=== <Distance_Generic> ===
  
 
''OPTIONAL''
 
''OPTIONAL''
  
This class identifies the reference pixel within the imageIt is identical to the ''Reference_Pixel'' class in ''[[Filling_out_the_Geometry_Orbiter_Class#.3CReference_Pixel.3E|<Geometry_Orbiter>]]''.
+
This class is used to define a distance measurement between a starting point, called the "observer", and an ending point, called the "target". You must explicitly identify the "observer" and "target", as well as providing the distanceYou may repeat this class as many times as needed to define various distances.
  
==== <emission_angle> ====
+
==== <Observer_Identification> ====
  
''OPTIONAL''
+
''REQUIRED''
  
This is the angle between the surface normal vector at the intercept point and a vector from the intercept point to the spacecraft. You must indicate units of measure for this attribute.
+
The class has the same content, and is filled out the same way, as the ''&lt;Geometry_Target_Identification&gt;'' class in the ''[[Filling_out_the_Image_Display_Geometry_Class#.3CGeometry_Target_Identification.3E|Image_Display_Geometry]]'' class.
  
==== <incidence_angle> ====
+
==== <Geometry_Target_Identification> ====
  
''OPTIONAL''
+
''REQUIRED''
  
This is the angle between the surface normal vector at the intercept point and a vector from the intercept point to the sun. You must indicate units of measure for this attribute.
+
This class is filled out identically to the class of the same name in the ''[[Filling_out_the_Image_Display_Geometry_Class#.3CGeometry_Target_Identification.3E|Image_Display_Geometry]]'' class.
  
==== <phase_angle> ====
+
==== <distance> ====
 
 
''OPTIONAL''
 
 
 
This is the angle between the vector from the intercept point to the source of illumination (e.g., the sun), and the vector from the intercept point to the observer (typically an instrument).  You must specify units of measure for this attribute.
 
 
 
==== <solar_elongation> ====
 
 
 
''OPTIONAL''
 
 
 
This is the angle between the vector from the intercept point to observer (typically an instrument) and the vector from the intercept point to the sun.  You must specify units of measure for this attribute.
 
 
 
 
 
=== <Illumination_FOV_Range_Values> ===
 
 
 
''OPTIONAL''
 
 
 
This class collects attributes that describe illumination parameters as minimum/maximum pairs.  The attributes have the same physical definitions as in the ''&lt;Illumination_Single_Values&gt;'' class.
 
 
 
==== <illumination_range_designation> ====
 
  
 
''REQUIRED''
 
''REQUIRED''
  
This attribute indicates whether the remaining values in this class refer to the entire field of view, or just that portion of the target (identified in this ''Geometry_Orbiter'' class) that is within the field of viewIt must have one of either '''Field of View''', corresponding to the former case, or '''Target''' for the latter.
+
The center-to-center, positive distance between the observer and the target.  You must provide units of length for this value.
  
==== <minimum_emission_angle> ====
+
== <Surface_Geometry> ==
  
 
''OPTIONAL''
 
''OPTIONAL''
  
This attribute is the minimum value of the emission angle relevant to the observation.  You must provide units of measure for this attribute.
+
This class is a container for other classes used to list surface coordinates of various types. These classes collect surface orientation for various named angles of interest either as single values, min/max ranges, or start/stop values. Concepts like "latitude" and "longitude" are interpreted with respect to the specific target in question, as identified previously in this ''&lt;Geometry_Orbiter&gt;'' class.
  
==== <maximum_emission_angle> ====
+
To avoid some tedious repetition, these class and attribute descriptions are somewhat abbreviated. In general, the containing class will be described briefly, attributes unique to each class will be described as usual, the individual angle attributes will merely be listed with abbreviated descriptions mainly concerning valid ranges.
  
''OPTIONAL''
+
=== General Notes: ===
  
This attribute is the maximum value of the emission angle relevant to the observation. You must provide units of measure for this attribute.
+
* All attributes are optional in their respective classes unless otherwise indicated; none may be repeated.
 +
* All angles require units of angle for each value. Though that unit can vary among attributes in a class, typically all values will be given in units of degrees.  For example:
 +
<pre>
 +
    <subsolar_azimuth unit="deg">15.097</subsolar_azimuth>
 +
    <spacecraft_longitude unit="deg">17.9</spacecraft_longitude>
 +
</pre>
  
==== <minimum_incidence_angle> ====
+
=== <comment> ===
  
 
''OPTIONAL''
 
''OPTIONAL''
  
This attribute is the minimum value of the incidence angle relevant to the observation.  You must provide units of measure for this attribute.
+
Here is a place to provide any additional explanatory text that might be apropos.
  
==== <maximum_incidence_angle> ====
+
=== <Surface_Geometry_Specific> ===
  
 
''OPTIONAL''
 
''OPTIONAL''
  
This attribute is the maximum value of the incidence angle relevant to the observation.  You must provide units of measure for this attribute.
+
This container class lists specific named distances as well as surface intercept points.
  
==== <minimum_phase_angle> ====
+
==== <Pixel_Intercept> ====
  
 
''OPTIONAL''
 
''OPTIONAL''
  
This attribute is the minimum value of the phase angle relevant to the observationYou must provide units of measure for this attribute.
+
This class defines the latitude and longitude on the surface of the target for the projection of a single, specified pixel.  It may be repeatedUse it when the points involved do ''not'' represent the observation footprint.
  
==== <maximum_phase_angle> ====
+
===== <reference_pixel_location> =====
  
 
''OPTIONAL''
 
''OPTIONAL''
  
This attribute is the maximum value of the phase angle relevant to the observationYou must provide units of measure for this attribute.
+
Either this attribute or the ''&lt;Reference_Pixel&gt;'' class, following, must be specified. This attribute is a human-readable indication of where the reference pixel is, when the image is displayed as indicated in the ''Image_Display_Geometry'' classIt must have one of the following values:
  
== A Word About Geometry Vectors ==
+
::* Center
 +
::* Lower Left Corner
 +
::* Lower Right Corner
 +
::* Upper Left Corner
 +
::* Upper Right Corner
  
The various vectors in the Geometry Discipline dictionary are derived from common parent classes, providing consistent structure and terminology.  The "specific' vectors listed below have been defined for the set of vectors that appear in the majority of orbiter/flyby data products.  For these vectors the start and end point ("observer" and "target", in general terms) and coordinate system are part of the definition of the vector itself.  You should use these specific vectors whenever they might reasonably apply, as they provide a common nomenclature for these values that users can key into across the archive.
+
===== <Reference_Pixel> =====
 
 
When you need to specify a vector for a quantity outside this standard set, use the generic vector classes, which allow you to specify observer, target, and coordinate system.
 
 
 
The details of the structure of each family of vectors in the Geometry Discipline dictionary are summarized on the [[Filling Out the Geometry Vector Classes]] page.
 
 
 
== <Specific_Position_Vectors> ==
 
  
 
''OPTIONAL''
 
''OPTIONAL''
  
This class collects vector positions to and from various end points into a single class. In the vector names, the first object named (on the left) is taken as the "observer", the second as the "target", for purposes of identifying the direction of measurement.  So in the ''Sun_To_Spacecraft_Position_Vector_Cartesian'', the sun is treated as the "observer" and the spacecraft as the "target" for purposes of defining the vector.  Unless otherwise indicated, all positions are measured from and to the center of mass.
+
Either ''&lt;reference_pixel_location&gt;'', above, or this class must be specified. This class procides a more precise indication of where the reference pixel occurs in the image.  It is filled out identically to the class of the same name in the ''[[Filling_out_the_Image_Display_Geometry_Class#.3CReference_Pixel.3E|Image_Display_Geometry]]'' class.
  
These vectors are all specific instances of the more generic position vectors, and they follow the same constraints and naming conventions, except as noted in the generic vector descriptions.
+
===== <pixel_latitude> =====
  
You may include only those position vectors of interest, but the vectors you use must appear in this order.  You may repeat any of these vectors as many times as you like, but the repetitions must be grouped together.  If you have positions to document that are not included in this class, use the ''[[#.3CGeneric_Vectors.3E|<Generic_Vectors>]]'' class and its subclasses to define and describe them.  If you prefer to group your vectors by coordinate system rather than content, use the ''[[#.3CSpecific_Cartesian_Vectors.3E|<Specific_Cartesian_Vectors>]]'' and ''[[#.3CSpecific_Planetocentric_Vectors.3E|<Specific_Planetocentric_Vectors>]]'' classes.
+
''REQUIRED''
  
=== <Central_Body_To_Spacecraft_Position_Vector_Cartesian> ===
+
Planetocentric latitude of the pixel projected onto the target, in the range &plusmn;90&deg;
  
''OPTIONAL''
+
===== <pixel_longitude> =====
  
Position of the spacecraft as viewed from the central body (around which another body is orbiting). It is filled out as a specific form of the ''[[Filling_Out_the_Geometry_Vector_Classes#.3CPosition_Vector_Cartesian_Generic.3E|<Position_Vector_Cartesian_Generic>]]'' class.
+
''REQUIRED''
  
=== <Central_Body_To_Target_Position_Vector_Cartesian> ===
+
Planetocentric longitude of the pixel projected onto the target, in the range 0-360&deg;
  
''OPTIONAL''
+
==== <Footprint_Vertices> ====
 
 
Position of the target identified by the ''Target_Identification'' in this ''Geometry_Orbiter'' class, as viewed from the central body (around which another body, typically the target, is orbiting).  It is filled out as a specific form of the ''[[Filling_Out_the_Geometry_Vector_Classes#.3CPosition_Vector_Cartesian_Generic.3E|<Position_Vector_Cartesian_Generic>]]'' class.
 
 
 
=== <Spacecraft_To_Target_Position_Vector_Cartesian> ===
 
  
 
''OPTIONAL''
 
''OPTIONAL''
  
Position of the target identified by the ''Target_Identification'' in this ''Geometry_Orbiter'' class, as viewed from the spacecraft.  It is filled out as a specific form of the ''[[Filling_Out_the_Geometry_Vector_Classes#.3CPosition_Vector_Cartesian_Generic.3E|<Position_Vector_Cartesian_Generic>]]'' class.
+
If you have a series of pixel intercept points that define the footprint of the observation, use this wrapper class to list them.  It contains a list of two or more ''&lt;Pixel_Intercept&gt;'' classes that should be filled out the same way as described above.  You should list the pixels either in clockwise or counterclockwise sequence around the perimeter of the footprint, so that line segments drawn between succesive pixels (the last connecting back to the first) will produce the footprint on the image.
  
=== <Central_Body_To_Spacecraft_Position_Vector_Planetocentric> ===
+
===== <Pixel_Intercept> =====
  
''OPTIONAL''
+
''REQUIRED''
  
Position of the spacecraft as viewed from the central body (around which another body is orbiting), in planetocentric coordinates.  It is filled out as a specific form of the ''[[Filling_Out_the_Geometry_Vector_Classes#.3CPosition_Vector_Planetocentric_Generic.3E|<Position_Vector_Cartesian_Generic>]]'' class.
+
You must have at least two occurrences of this class; you may have as many as needed to define the footprint.
  
=== <Central_Body_To_Target_Position_Vector_Planetocentric> ===
+
==== Angles Included: ====
  
''OPTIONAL''
+
::* ''subsolar_azimuth''
 +
::* ''subsolar_latitude''
 +
::* ''subsolar_longitude''
 +
::* ''subspacecraft_azimuth''
 +
::* ''subspacecraft_latitude''
 +
::* ''subspacecraft_longitude''
  
Position of the target identified by the ''Target_Identification'' in this ''Geometry_Orbiter'' class, as viewed from the central body (around which another body, typically the target, is orbiting).  It is filled out as a specific form of the ''[[Filling_Out_the_Geometry_Vector_Classes#.3CPosition_Vector_Planetocentric_Generic.3E|<Position_Vector_Cartesian_Generic>]]'' class.
+
=== <Surface_Geometry_Min_Max> ===
 
 
=== <Spacecraft_To_Target_Position_Vector_Planetocentric> ===
 
  
 
''OPTIONAL''
 
''OPTIONAL''
  
Position of the target identified by the ''Target_Identification'' in this ''Geometry_Orbiter'' class as viewed from the spacecraftIt is filled out as a specific form of the ''[[Filling_Out_the_Geometry_Vector_Classes#.3CPosition_Vector_Planetocentric_Generic.3E|<Position_Vector_Cartesian_Generic>]]'' class.
+
This class lists min/max pairs of geometric angles calculated for the target surface.  You must provide both minimum and maximum for any particular angleIf you have geometry for specific points rather than ranges, use the ''&lt;Surface_Geometry_Specific&gt;'' class to provide those values.
  
=== <SSB_To_Central_Body_Position_Vector_Cartesian> ===
+
==== Angles Included: ====
  
''OPTIONAL''
+
::* ''minimum_latitude''
 +
::* ''maximum_latitude''
 +
::* ''minimum_longitude''
 +
::* ''maximum_longitude''
 +
::* ''minimum_subsolar_azimuth''
 +
::* ''maximum_subsolar_azimuth''
 +
::* ''minimum_subsolar_latitude''
 +
::* ''maximum_subsolar_latitude''
 +
::* ''minimum_subsolar_longitude''
 +
::* ''maximum_subsolar_longitude''
 +
::* ''minimum_subspacecraft_azimuth''
 +
::* ''maximum_subspacecraft_azimuth''
 +
::* ''minimum_subspacecraft_latitude''
 +
::* ''maximum_subspacecraft_latitude''
 +
::* ''minimum_subspacecraft_longitude''
 +
::* ''maximum_subspacecraft_longitude''
  
Position of the central body (around which another body is orbiting), as viewed from the Solar System Barycenter (SSB). It is filled out as a specific form of the ''[[Filling_Out_the_Geometry_Vector_Classes#.3CPosition_Vector_Cartesian_Generic.3E|<Position_Vector_Cartesian_Generic>]]'' class.
 
  
=== <SSB_To_Spacecraft_Position_Vector_Cartesian> ===
+
=== <Surface_Geometry_Start_Stop> ===
  
 
''OPTIONAL''
 
''OPTIONAL''
  
Position of the spacecraft as viewed from the Solar System Barycenter (SSB). It is filled out as a specific form of the ''[[Filling_Out_the_Geometry_Vector_Classes#.3CPosition_Vector_Cartesian_Generic.3E|<Position_Vector_Cartesian_Generic>]]'' class.
+
If you have surface geometry calculated at the ''geometry_start'' and ''geometry_stop'' times included in this ''&lt;Geometry_Orbiter&gt;'' class, use this class to list the corresponding values.  You must list these angles in start/stop pairs. If you have geometry for specific points rather than time ranges, use the ''&lt;Surface_Geometry_Specific&gt;'' class to provide those values.
  
=== <SSB_To_Target_Position_Vector_Cartesian> ===
+
==== <lat_long_method> ====
  
 
''OPTIONAL''
 
''OPTIONAL''
  
Position of the object indicated by the ''Target_identification'' of this ''Geometry_Orbiter'' class as viewed from the Solar System Barycenter (SSB). It is filled out as a specific form of the ''[[Filling_Out_the_Geometry_Vector_Classes#.3CPosition_Vector_Cartesian_Generic.3E|<Position_Vector_Cartesian_Generic>]]'' class.
+
This attribute is required if your ''Surface_Geometry_Start_Stop'' class includes start/stop latitude or longitude. It must have one of the following values:
  
=== <Sun_To_Central_Body_Position_Vector_Cartesian> ===
+
::;center
 +
:::The latitude/longitude values are those at the center of the field of view at the beginning and end of the observation
 +
::;median
 +
:::The latitude/longitude values are the median values at the beginning and end of the observation.
 +
::;mean
 +
:::The latitude/longitude values are the mean values at the beginning and end of the observation.
  
''OPTIONAL''
+
==== Angles Included: ====
  
Position of the central body (around which another body, typically the target, is orbiting) as viewed from the sun.  It is filled out as a specific form of the ''[[Filling_Out_the_Geometry_Vector_Classes#.3CPosition_Vector_Cartesian_Generic.3E|<Position_Vector_Cartesian_Generic>]]'' class.
+
::* ''start_latitude''
 +
::* ''stop_latitude''
 +
::* ''start_longitude''
 +
::* ''stop_longitude''
 +
::* ''start_subsolar_azimuth''
 +
::* ''stop_subsolar_azimuth''
 +
::* ''start_subsolar_latitude''
 +
::* ''stop_subsolar_latitude''
 +
::* ''start_subsolar_longitude''
 +
::* ''stop_subsolar_longitude''
 +
::* ''start_subspacecraft_azimuth''
 +
::* ''stop_subspacecraft_azimuth''
 +
::* ''start_subspacecraft_latitude''
 +
::* ''stop_subspacecraft_latitude''
 +
::* ''start_subspacecraft_longitude''
 +
::* ''stop_subspacecraft_longitude''
  
=== <Sun_To_Spacecraft_Position_Vector_Cartesian> ===
+
== <Illumination_Geometry> ==
  
 
''OPTIONAL''
 
''OPTIONAL''
  
Position of the spacecraft as viewed from the sun.  It is filled out as a specific form of the ''[[Filling_Out_the_Geometry_Vector_Classes#.3CPosition_Vector_Cartesian_Generic.3E|<Position_Vector_Cartesian_Generic>]]'' class.
+
This class is a container for other classes used illumination angles of various types. These classes collect various named angles of interest either as single values, min/max ranges, or start/stop values. Angle names should be self-explanatory.
  
=== <Sun_To_Target_Position_Vector_Cartesian> ===
+
To avoid some tedious repetition, these class and attribute descriptions are somewhat abbreviated. In general, the containing class will be described briefly, attributes unique to each class will be described as usual, the individual angle attributes will merely be listed with abbreviated descriptions mainly concerning valid ranges where appropriate.
  
''OPTIONAL''
+
=== General Notes: ===
  
Position of the object indicated by the ''Target_identification'' of this ''Geometry_Orbiter'' class as viewed from the sun. It is filled out as a specific form of the ''[[Filling_Out_the_Geometry_Vector_Classes#.3CPosition_Vector_Cartesian_Generic.3E|<Position_Vector_Cartesian_Generic>]]'' class.
+
* The container classes themselves may not be repeated.
 +
* All attributes are optional in their respective classes unless otherwise indicated; none may be repeated.
 +
* All angles require units of angle for each value. Typically all values will be given in units of degrees. For example:
 +
<pre>
 +
    <emission_angles unit="deg">15.097</emission_angle>
 +
    <start_solar_elongation unit="deg">17.9</start_solar_elongation>
 +
</pre>
  
=== <Earth_To_Central_Body_Position_Vector_Cartesian> ===
+
=== <comment> ===
  
 
''OPTIONAL''
 
''OPTIONAL''
  
Position of the central body (around which another body is orbiting) as viewed from Earth. It is filled out as a specific form of the ''[[Filling_Out_the_Geometry_Vector_Classes#.3CPosition_Vector_Cartesian_Generic.3E|<Position_Vector_Cartesian_Generic>]]'' class.
+
Here is a place to provide any additional explanatory text that might be apropos.
  
=== <Earth_To_Spacecraft_Position_Vector_Cartesian> ===
+
=== <Illumination_Specific> ===
  
 
''OPTIONAL''
 
''OPTIONAL''
  
Position of the spacecraft as viewed from Earth. It is filled out as a specific form of the ''[[Filling_Out_the_Geometry_Vector_Classes#.3CPosition_Vector_Cartesian_Generic.3E|<Position_Vector_Cartesian_Generic>]]'' class.
+
This class provides illumination angles at a specific point in the image. This point must be specified in exactly one way: either through the ''reference_location'' attribute; the ''reference_pixel_location'' attribute; or the ''&lt;Reference_Pixel&gt;'' subclass.
  
=== <Earth_To_Target_Position_Vector_Cartesian> ===
+
==== <reference_location> ====
  
 
''OPTIONAL''
 
''OPTIONAL''
  
Position of the object indicated by the ''Target_identification'' of this ''Geometry_Orbiter'' class as viewed from Earth. It is filled out as a specific form of the ''[[Filling_Out_the_Geometry_Vector_Classes#.3CPosition_Vector_Cartesian_Generic.3E|<Position_Vector_Cartesian_Generic>]]'' class.
+
This defines a reference location in terms of some property of or point in the field of view. If present, this must have one of the following values:
  
== <Specific_Velocity_Vectors> ==
+
:::* '''Boresight Intercept Point'''
 +
:::* '''Constant'''
 +
:::* '''Subspacecraft Point'''
 +
:::* '''Target Center'''
  
''OPTIONAL''
+
==== <reference_pixel_location> ====
 
 
This class collects vector velocities into a single class.  In general terms, each vector records the velocity of a "target" as perceived by an "observer".  In the class names, the "target" comes first (on the left), and the "observer" comes second.  So in the ''Spacecraft_Relative_to_Earth_Velocity_Vector_Cartesian'' class, the spacecraft is taken as the "target" and Earth is taken as the "observer" for purposes of defining the velocity. Unless otherwise indicated, all velocities are measured from and to the center of mass.
 
 
 
These vectors are all specific instances of the more generic velocity vectors, and the follow the same conventions, except as noted in the generic vector descriptions.
 
 
 
You may include only those velocity vectors of interest, but the vectors you use must appear in this order.  You may repeat any of these vectors as many times as you like, but the repetitions must be grouped together.  If you have velocities to document that not included in this class, use the ''[[#.3CGeneric_Vectors.3E|<Generic_Vectors>]]'' class and its subclasses to define and describe them.  If you prefer to group your vectors by coordinate system rather than content, use the ''[[#.3CSpecific_Cartesian_Vectors.3E|<Specific_Cartesian_Vectors>]]'' and ''[[#.3CSpecific_Planetocentric_Vectors.3E|<Specific_Planetocentric_Vectors>]]'' classes.
 
 
 
=== <Spacecraft_Relative_To_Central_Body_Velocity_Vector_Cartesian> ===
 
  
 
''OPTIONAL''
 
''OPTIONAL''
  
Velocity of the spacecraft as observed from the central body (around which another body is orbiting).  This is a specific form of the ''[[Filling_Out_the_Geometry_Vector_Classes#.3CVelocity_Vector_Cartesian_Generic.3E|<Velocity_Vector_Cartesian_Generic>]]'' class.
+
This defines a reference location in terms of a particular pixel location in the image when displayed according to the display settings established for this ''Geometry'' class. If present, it must have one of the following values:
  
=== <Spacecraft_Relative_To_Target_Velocity_Vector_Cartesian> ===
+
:::* '''Center'''
 +
:::* '''Lower Left Corner'''
 +
:::* '''Lower Right Corner'''
 +
:::* '''Upper Left Corner'''
 +
:::* '''Upper Right Cornet'''
  
''OPTIONAL''
+
==== <Reference_Pixel> ====
 
 
Velocity of the spacecraft as observed from the object indicated by the ''Target_Identification'' in this ''Geometry_Orbiter'' class. This is a specific form of the ''[[Filling_Out_the_Geometry_Vector_Classes#.3CVelocity_Vector_Cartesian_Generic.3E|<Velocity_Vector_Cartesian_Generic>]]'' class.
 
 
 
=== <Spacecraft_Relative_To_Earth_Velocity_Vector_Cartesian> ===
 
  
 
''OPTIONAL''
 
''OPTIONAL''
  
Velocity of the spacecraft as observed from Earth. This is a specific form of the ''[[Filling_Out_the_Geometry_Vector_Classes#.3CVelocity_Vector_Cartesian_Generic.3E|<Velocity_Vector_Cartesian_Generic>]]'' class.
+
This class defines a reference location in terms of pixel subscripts in the image array. It is filled out identically to the class of the same name in the ''[[Filling_out_the_Image_Display_Geometry_Class#.3CReference_Pixel.3E|Image_Display_Geometry]]'' class.
  
=== <Spacecraft_Relative_To_SSB_Velocity_Vector_Cartesian> ===
+
==== Angles Included: ====
  
''OPTIONAL''
+
At least one of these must be present.
  
Velocity of the spacecraft as observed from the Solar System Barycenter (SSB).  This is a specific form of the ''[[Filling_Out_the_Geometry_Vector_Classes#.3CVelocity_Vector_Cartesian_Generic.3E|<Velocity_Vector_Cartesian_Generic>]]'' class.
+
::* ''emission_angle''
 +
::* ''incidence_angle''
 +
::* ''phase_angle''
 +
::* ''solar_elongation''
  
=== <Spacecraft_Relative_To_Sun_Velocity_Vector_Cartesian> ===
+
=== <Illumination_Min_Max> ===
  
 
''OPTIONAL''
 
''OPTIONAL''
  
Velocity of the spacecraft as observed from the sun. This is a specific form of the ''[[Filling_Out_the_Geometry_Vector_Classes#.3CVelocity_Vector_Cartesian_Generic.3E|<Velocity_Vector_Cartesian_Generic>]]'' class.
+
This class gives illumination angles as min/max ranges.  You must supply these values in min/max pairs. If you have single values, use the ''&lt;Illumination_Specific&gt;'' class, above.
  
=== <Target_Relative_To_Central_Body_Velocity_Vector_Cartesian> ===
+
==== Angles Included: ====
  
''OPTIONAL''
+
::* ''minimum_emission_angle''
 +
::* ''maximum_emission_angle''
 +
::* ''minimum_incidence_angle''
 +
::* ''maximum_incidence_angle''
 +
::* ''minimum_phase_angle''
 +
::* ''maximum_phase_angle''
 +
::* ''minimum_solar_elongation''
 +
::* ''maximum_solar_elongation''
  
Velocity of the object indicated by the ''Target_Identification'' in this ''Geometry_Orbiter'' class, as observed from the central body (around which another body, typically the target, is orbiting). This is a specific form of the ''[[Filling_Out_the_Geometry_Vector_Classes#.3CVelocity_Vector_Cartesian_Generic.3E|<Velocity_Vector_Cartesian_Generic>]]'' class.
+
=== <Illumination_Start_Stop> ===
 
 
=== <Target_Relative_To_Spacecraft_Velocity_Vector_Cartesian> ===
 
  
 
''OPTIONAL''
 
''OPTIONAL''
  
Velocity of the object indicated by the ''Target_Identification'' in this ''Geometry_Orbiter'' class, as observed from the spacecraft. This is a specific form of the ''[[Filling_Out_the_Geometry_Vector_Classes#.3CVelocity_Vector_Cartesian_Generic.3E|<Velocity_Vector_Cartesian_Generic>]]'' class.
+
This class lists illumination angles calculated for the corresponding ''geometry_start_time'' and ''geometry_stop_time'' of this ''&lt;Geometry_Orbiter&gt;'' class.  You must provide start/stop time pairs for this class.
  
=== <Target_Relative_To_Earth_Velocity_Vector_Cartesian> ===
+
==== Angles Included: ====
  
''OPTIONAL''
+
::* ''start_emission_angle''
 +
::* ''stop_emission_angle''
 +
::* ''start_incidence_angle''
 +
::* ''stop_incidence_angle''
 +
::* ''start_phase_angle''
 +
::* ''stop_phase_angle''
 +
::* ''start_solar_elongation''
 +
::* ''stop_solar_elongation''
  
Velocity of the object indicated by the ''Target_Identification'' in this ''Geometry_Orbiter'' class, as observed from Earth. This is a specific form of the ''[[Filling_Out_the_Geometry_Vector_Classes#.3CVelocity_Vector_Cartesian_Generic.3E|<Velocity_Vector_Cartesian_Generic>]]'' class.
+
== <Vectors> ==
 
 
=== <Target_Relative_To_SSB_Velocity_Vector_Cartesian> ===
 
  
 
''OPTIONAL''
 
''OPTIONAL''
  
Velocity of the object indicated by the ''Target_Identification'' in this ''Geometry_Orbiter'' class, as observed from the Solar System Barycenter (SSB). This is a specific form of the ''[[Filling_Out_the_Geometry_Vector_Classes#.3CVelocity_Vector_Cartesian_Generic.3E|<Velocity_Vector_Cartesian_Generic>]]'' class.
+
This class is a container for other classes used to define vectors  for various positions and velocities of interest. Two of the optional subclasses collect vectors in specific coordinate systems types - Cartesian and Planetocentric.  The third optional subclass provides a mechanism for defining position and velocity vectors outside those included in the first two classes.  Unless otherwise stated, positions and velocities are measured center-to-center, and references to "target" and "central body" refer to the objects identified previously in this ''&lt;Geometry_Orbiter&gt;'' class.
  
=== <Target_Relative_To_Sun_Velocity_Vector_Cartesian> ===
+
To avoid a ''lot'' of tedious repetition, these class and attribute descriptions are somewhat abbreviated. In general, the containing class will be described briefly, and the individual vectors  classes will merely be listed - their names being self-explanatory.  All vectors of similar type (all
 +
Cartesian velocity vectors, for example) will have the same attribute content.
  
''OPTIONAL''
+
=== General Notes: ===
  
Velocity of the object indicated by the ''Target_Identification'' in this ''Geometry_Orbiter'' class, as observed from the sun. This is a specific form of the ''[[Filling_Out_the_Geometry_Vector_Classes#.3CVelocity_Vector_Cartesian_Generic.3E|<Velocity_Vector_Cartesian_Generic>]]'' class.
+
The various vectors in the Geometry Discipline dictionary are derived from common parent classes, providing consistent structure and terminology.  The "specific' vectors listed below have been defined for the set of vectors that appear in the majority of orbiter/flyby data products.  For these vectors the start and end points ("observer" and "target", in general terms) and coordinate system are part of the definition of the vector itself.  You should use these specific vectors whenever they might reasonably apply, as they provide a common nomenclature for these values that users can key into across the archive. When you need to specify a vector for a quantity outside this standard set, use the generic vectors, which allow you to specify observer, target, and coordinate system.
  
=== <Spacecraft_Relative_To_Target_Velocity_Vector_Planetocentric> ===
+
The details of the structure of each family of vectors in the Geometry Discipline dictionary are summarized on the [[Filling Out the Geometry Vector Classes]] page.
  
''OPTIONAL''
+
'''Additional Notes: '''
  
Velocity of the spacecraft as observed from the object indicated by the ''Target_Identification'' in this ''Geometry_Orbiter'' class. This is a specific form of the ''[[Filling_Out_the_Geometry_Vector_Classes#.3CVelocity_Vector_Planetocentric_Generic.3E|<Velocity_Vector_Planetocentric_Generic>]]'' class.
+
Within each of the wrapper classes and unless otherwise noted:
 +
* All vectors are optional.
 +
* Vectors may be in any order (this is ''not'' the usual case for PDS4 label classes and attributes).
  
=== <Target_Relative_To_Central_Body_Velocity_Vector_Planetocentric> ===
+
{| class="wikitable" style="background-color: lightcyan"
 
+
|
''OPTIONAL''
+
'''Note:''' ''Vectors can also be repeated an arbitrary number of times within their respective classes.  This seems like a bad idea for the non-Generic classes, on the face of it. If you have a reason for duplicating vectors inside this class, please use the ''&lt;comment&gt;'' attribute to provide some explanation for this unusual situation.''
 
+
|}
Velocity of the object indicated by the ''Target_Identification'' in this ''Geometry_Orbiter'' class, as observed from the central body (around which another body, typically the target, is orbiting). This is a specific form of the ''[[Filling_Out_the_Geometry_Vector_Classes#.3CVelocity_Vector_Planetocentric_Generic.3E|<Velocity_Vector_Planetocentric_Generic>]]'' class.
 
 
 
=== <Target_Relative_To_Spacecraft_Velocity_Vector_Planetocentric> ===
 
 
 
''OPTIONAL''
 
 
 
Velocity of the object indicated by the ''Target_Identification'' in this ''Geometry_Orbiter'' class, as observed from the as observed from the spacecraft. This is a specific form of the ''[[Filling_Out_the_Geometry_Vector_Classes#.3CVelocity_Vector_Planetocentric_Generic.3E|<Velocity_Vector_Planetocentric_Generic>]]'' class.
 
 
 
== <Specific_Cartesian_Vectors> ==
 
 
 
''OPTIONAL''
 
 
 
If you prefer, you may group your vectors according to the vector type (Cartesian vs. planetocentric) rather than their content (position vs. velocity).  This class combines all the Cartesian vectors mentioned in the previous two classes into a single class.  Each is optional in this class - use the ones that apply. You may also repeat any of these, provided the repetitions are adjacent. The vectors included in this class, in label order, are:
 
:''Position Vectors''
 
::* [[#.3CCentral_Body_To_Spacecraft_Position_Vector_Cartesian.3E|Central_Body_To_Spacecraft_Position_Vector_Cartesian]]
 
::* [[#.3CCentral_Body_To_Target_Position_Vector_Cartesian.3E|Central_Body_To_Target_Position_Vector_Cartesian]]
 
::* [[#.3CSpacecraft_To_Target_Position_Vector_Cartesian.3E|Spacecraft_To_Target_Position_Vector_Cartesian]]
 
::* [[#.3CSSB_To_Central_Body_Position_Vector_Cartesian.3E|SSB_To_Central_Body_Position_Vector_Cartesian]]
 
::* [[#.3CSSB_To_Spacecraft_Position_Vector_Cartesian.3E|SSB_To_Spacecraft_Position_Vector_Cartesian]]
 
::* [[#.3CSSB_To_Target_Position_Vector_Cartesian.3E|SSB_To_Target_Position_Vector_Cartesian]]
 
::* [[#.3CSun_To_Central_Body_Position_Vector_Cartesian.3E|Sun_To_Central_Body_Position_Vector_Cartesian]]
 
::* [[#.3cSun_To_Spacecraft_Position_Vector_Cartesian.3E|Sun_To_Spacecraft_Position_Vector_Cartesian]]
 
::* [[#.3CSun_To_Target_Position_Vector_Cartesian.3E|Sun_To_Target_Position_Vector_Cartesian]]
 
::* [[#.3CEarth_To_Central_Body_Position_Vector_Cartesian.3E|Earth_To_Central_Body_Position_Vector_Cartesian]]
 
::* [[#.3CEarth_To_Spacecraft_Position_Vector_Cartesian.3E|Earth_To_Spacecraft_Position_Vector_Cartesian]]
 
::* [[#.3CEarth_To_Target_Position_Vector_Cartesian.3E|Earth_To_Target_Position_Vector_Cartesian]]
 
:''Velocity Vectors''
 
::* [[#.3CSpacecraft_Relative_To_Central_Body_Velocity_Vector_Cartesian.3E|Spacecraft_Relative_To_Central_Body_Velocity_Vector_Cartesian]]
 
::* [[#.3CSpacecraft_Relative_To_Target_Velocity_Vector_Cartesian.3E|Spacecraft_Relative_To_Target_Velocity_Vector_Cartesian]]
 
::* [[#.3CSpacecraft_Relative_To_Earth_Velocity_Vector_Cartesian.3E|Spacecraft_Relative_To_Earth_Velocity_Vector_Cartesian]]
 
::* [[#.3CSpacecraft_Relative_To_SSB_Velocity_Vector_Cartesian.3E|Spacecraft_Relative_To_SSB_Velocity_Vector_Cartesian]]
 
::* [[#.3CSpacecraft_Relative_To_Sun_Velocity_Vector_Cartesian.3E|Spacecraft_Relative_To_Sun_Velocity_Vector_Cartesian]]
 
::* [[#.3CTarget_Relative_To_Central_Body_Velocity_Vector_Cartesian.3E|Target_Relative_To_Central_Body_Velocity_Vector_Cartesian]]
 
::* [[#.3CTarget_Relative_To_Spacecraft_Velocity_Vector_Cartesian.3E|Target_Relative_To_Spacecraft_Velocity_Vector_Cartesian]]
 
::* [[#.3CTarget_Relative_To_Earth_Velocity_Vector_Cartesian.3E|Target_Relative_To_Earth_Velocity_Vector_Cartesian]]
 
::* [[#.3CTarget_Relative_To_SSB_Velocity_Vector_Cartesian.3E|Target_Relative_To_SSB_Velocity_Vector_Cartesian]]
 
::* [[#.3CTarget_Relative_To_Sun_Velocity_Vector_Cartesian.3E|Target_Relative_To_Sun_Velocity_Vector_Cartesian]]
 
 
 
== <Specific_Planetocentric_Vectors> ==
 
 
 
''OPTIONAL''
 
 
 
If you prefer, you may group your vectors according to the vector type (Cartesian vs. planetocentric) rather than their content (position vs. velocity).  This class combines all the planetocentric vectors mentioned in the first two "Specific Vectors'' classes into a single class.  Each is optional in this class - use the ones that apply. The vectors included in this class, in label order, are:
 
:''Position Vectors''
 
::* Central_Body_To_Spacecraft_Position_Vector_Planetocentric
 
::* Central_Body_To_Target_Position_Vector_Planetocentric
 
::* Spacecraft_To_Target_Position_Vector_Planetocentric
 
::* Spacecraft_Relative_To_Target_Velocity_Vector_Planetocentric
 
::* Target_Relative_To_Central_Body_Velocity_Vector_Planetocentric
 
::* Target_Relative_To_Spacecraft_Velocity_Vector_Planetocentric
 
 
 
 
 
== <Generic_Vectors> ==
 
 
 
''OPTIONAL''
 
 
 
=== <Position_Vector_Cartesian_Generic> ===
 
 
 
''OPTIONAL''
 
 
 
==== <x_position> ====
 
 
 
''REQUIRED''
 
 
 
==== <y_position> ====
 
 
 
''REQUIRED''
 
 
 
==== <z_position> ====
 
 
 
''REQUIRED''
 
 
 
==== <light_time_correction_applied> ====
 
 
 
''REQUIRED''
 
 
 
==== <Coordinate_System> ====
 
 
 
''OPTIONAL''
 
 
 
==== <Observer_Identification> ====
 
 
 
''REQUIRED''
 
  
==== <Target_Identification> ====
+
=== <comment> ===
 
 
''REQUIRED''
 
 
 
=== <Velocity_Vector_Cartesian_Generic> ===
 
  
 
''OPTIONAL''
 
''OPTIONAL''
  
==== <x_velocity> ====
+
If there is any additional explanation needed or desired regarding the contents of the following classes, here's a place for it.  Note that there are no comment fields in the individual wrapper classes
  
''REQUIRED''
+
=== <Vectors_Cartesian_Specific> ===
 
 
==== <y_velocity> ====
 
 
 
''REQUIRED''
 
 
 
==== <z_velocity> ====
 
 
 
''REQUIRED''
 
 
 
==== <light_time_correction_applied> ====
 
 
 
''REQUIRED''
 
 
 
==== <Coordinate_System> ====
 
  
 
''OPTIONAL''
 
''OPTIONAL''
  
==== <Observer_Identification> ====
+
If present, this class must contain at least one of the following vectors. The abbreviation "SSB" stands for ''Solar System Barycenter''.
  
''REQUIRED''
+
The ''Position'' vectors below are filled out as described for the ''[[Filling_Out_the_Geometry_Vector_Classes#.3CVector_Cartesian_Position_Generic.3E|Vector_Cartesian_Position_Generic]]'' class on the [[Filling Out the Geometry Vector Classes]] page on this wiki, with the exceptions noted for specific vectors vs. generic ones.
  
==== <Target_Identification> ====
+
The ''Velocity'' vectors below are filled out as described for the ''[[Filling_Out_the_Geometry_Vector_Classes#.3CVector_Cartesian_Velocity_Generic.3E|Vector_Cartesian_Velocity_Generic]]'' class on the [[Filling Out the Geometry Vector Classes]] page on this wiki, with the exceptions noted for specific vectors vs. generic ones.
  
''REQUIRED''
+
==== Vectors Included: ====
 
 
=== <Acceleration_Vector_Cartesian_Generic> ===
 
 
 
''OPTIONAL''
 
 
 
==== <x_acceleration> ====
 
 
 
''REQUIRED''
 
 
 
==== <y_acceleration> ====
 
 
 
''REQUIRED''
 
 
 
==== <z_acceleration> ====
 
  
''REQUIRED''
+
::* ''Vector_Cartesian_Position_Central_Body_To_Spacecraft''
 
+
::* ''Vector_Cartesian_Position_Central_Body_To_Target''
==== <light_time_correction_applied> ====
+
::* ''Vector_Cartesian_Position_Earth_To_Central_Body''
 
+
::* ''Vector_Cartesian_Position_Earth_To_Spacecraft''
''REQUIRED''
+
::* ''Vector_Cartesian_Position_Earth_To_Target''
 +
::* ''Vector_Cartesian_Position_SSB_To_Central_Body''
 +
::* ''Vector_Cartesian_Position_SSB_To_Spacecraft''
 +
::* ''Vector_Cartesian_Position_SSB_To_Target''
 +
::* ''Vector_Cartesian_Position_Spacecraft_To_Target''
 +
::* ''Vector_Cartesian_Position_Sun_To_Central_Body''
 +
::* ''Vector_Cartesian_Position_Sun_To_Spacecraft''
 +
::* ''Vector_Cartesian_Position_Sun_To_Target''
 +
::* ''Vector_Cartesian_Velocity_Spacecraft_Relative_To_Central_Body''
 +
::* ''Vector_Cartesian_Velocity_Spacecraft_Relative_To_Earth''
 +
::* ''Vector_Cartesian_Velocity_Spacecraft_Relative_to_SSB''
 +
::* ''Vector_Cartesian_Velocity_Spacecraft_Relative_To_Sun''
 +
::* ''Vector_Cartesian_Velocity_Spacecraft_Relative_To_Target''
 +
::* ''Vector_Cartesian_Velocity_Target_Relative_To_Central_Body''
 +
::* ''Vector_Cartesian_Velocity_Target_Relative_To Earth''
 +
::* ''Vector_Cartesian_Velocity_Target_Relative_To_SSB''
 +
::* ''Vector_Cartesian_Velocity_Target_Relative_To_Spacecraft''
 +
::* ''Vector_Cartesian_Velocity_Target_Relative_To_Sun''
  
==== <Coordinate_System> ====
+
=== <Vectors_Planetocentric_Specific> ===
  
 
''OPTIONAL''
 
''OPTIONAL''
  
==== <Observer_Identification> ====
+
If present, this class must contain at least one of the following vectors.
  
''REQUIRED''
+
The ''Position'' vectors below are filled out as described for the ''[[Filling_Out_the_Geometry_Vector_Classes#.3CVector_Planetocentric_Position_Generic.3E|Vector_Planetocentric_Position_Generic]]'' class on the [[Filling Out the Geometry Vector Classes]] page on this wiki, with the exceptions noted for specific vectors vs. generic ones.
  
==== <Target_Identification> ====
+
The ''Velocity'' vectors below are filled out as described for the ''[[Filling_Out_the_Geometry_Vector_Classes#.3CVector_Planetocentric_Velocity_Generic.3E|Vector_Planetocentric_Velocity_Generic]]'' class on the [[Filling Out the Geometry Vector Classes]] page on this wiki, with the exceptions noted for specific vectors vs. generic ones.
  
''REQUIRED''
+
==== Vectors Included: ====
  
=== <Position_Vector_Planetocentric_Generic> ===
+
::* ''Vector_Planetocentric_Position_Central_Body_To_Spacecraft''
 +
::* ''Vector_Planetocentric_Position_Central_Body_To_Target''
 +
::* ''Vector_Planetocentric_Position_Spacecraft_To_Target''
 +
::* ''Vector_Planetocentric_Velocity_Spacecraft_Relative_To_Target''
 +
::* ''Vector_Planetocentric_Velocity_Target_Relative_To_Central_Body''
 +
::* ''Vector_Planetocentric_Velocity_Target_Relative_To_Spacecraft''
  
''OPTIONAL''
+
=== <Generic_Vectors> ===
 
 
==== <radius_position> ====
 
 
 
''REQUIRED''
 
 
 
==== <longitude_position> ====
 
 
 
''REQUIRED''
 
 
 
==== <latitude_position> ====
 
 
 
''REQUIRED''
 
 
 
==== <light_time_correction_applied> ====
 
 
 
''REQUIRED''
 
 
 
==== <Coordinate_System> ====
 
 
 
''OPTIONAL''
 
 
 
==== <Observer_Identification> ====
 
 
 
''REQUIRED''
 
 
 
==== <Target_Identification> ====
 
 
 
''REQUIRED''
 
 
 
=== <Velocity_Vector_Planetocentric_Generic> ===
 
 
 
''OPTIONAL''
 
 
 
==== <radial_velocity> ====
 
 
 
''OPTIONAL''
 
 
 
==== <longitude_velocity> ====
 
 
 
''OPTIONAL''
 
 
 
==== <latitude_velocity> ====
 
 
 
''OPTIONAL''
 
 
 
==== <light_time_correction_applied> ====
 
 
 
''REQUIRED''
 
 
 
==== <Coordinate_System> ====
 
  
 
''OPTIONAL''
 
''OPTIONAL''
  
==== <Observer_Identification> ====
+
This class is used when the start point, end point, or both are not covered by the vectors of the preceding specific classes.  Five generic vector types are provided.  You may repeat these classes as needed for however many vectors you need to define.
  
''REQUIRED''
+
The contents and procedures for filling out the generic vector classes are detailed on the [[Filling Out the Geometry Vector Classes]] page on this wiki.
  
==== <Target_Identification> ====
+
==== Vectors Included: ====
  
''REQUIRED''
+
::* ''Vector_Cartesian_Acceleration_Generic''
 +
::* ''Vector_Cartesian_Position_Generic''
 +
::* ''Vector_Cartesian_Velocity_Generic''
 +
::* ''Vector_Planetocentric_Position_Generic''
 +
::* ''Vector_Planetocentric_Velocity_Generic''

Latest revision as of 21:19, 17 January 2017

The Geometry_Orbiter class provides geometric values related to an orbiting or flyby spacecraft observation. The values in this class are specific to a single reference frame at a single reference time (or time range) for at most a single target. You may repeat this class with differing values for one or all of those, if appropriate to the observation being labelled.

Contents

<geometry_reference_time>

OPTIONAL

This is the UTC time for which the values in this class have been calculated. It must be in the standard YYYY-MM-DDThh:mm:ss.sssZ" format.

Either this attribute, or the geometry_start_time/geometry_stop_time pair is required. You are not prevented from including both, but that would be rather confusing and there is no place in this class for an explanatory comment - so avoid it.

<geometry_start_time> and <geometry_stop_time>

OPTIONAL

These are both optional, but if you use one you must also include the other. (See also the note above for geometry_reference_time.) Use the start/stop pair when you have an extended observation for which you plan to provide pairs of geometric values corresponding to these times in the other subclasses of <Geometry_Orbiter>.

These must be UTC times in the standard YYYY-MM-DDThh:mm:ss.sssZ format.

<geometry_reference_time_tdb>

OPTIONAL

This should be the Barycentric Dynamical Time (or Ephemeris Time), equivalent to the <geometry_reference_time_UTC> listed above. This is defined in the SPICE toolkit sense of a number of seconds since the J2000 epoch.

<Orbiter_Identification>

OPTIONAL

Use this class to identify geometric elements and reference points to be used in the Geometry_Orbiter subclasses that follow.

<Central_Body_Identification>

OPTIONAL

If the target of the following geometry is orbiting another body, that body is the "central body" and should be identified using this class. It is filled out identically to the class of the same name on the Filling Out the Image_Display_Geometry Class page on this wiki.

<Geometry_Target_Identification>

OPTIONAL

This class locally defines the concept of "target" to be the thing on the "to" end of the various vectors that follow in this Geometry_Orbiter class. It may or may not be the same as the target of the product as a whole. It is filled out identically to the class of the same name in the Image_Display_Geometry class.

<Coordinate_System_Identification>

OPTIONAL

This class is used to identify a "coordinate system" in the NAIF SPICE toolkit sense - both a reference frame and a well-defined origin, with a specific type of coordinates.

<coordinate_system_type>

REQUIRED

You must indicate the type of coordinates to be applied, which must be one of the following values:

  • Azimuth-Elevation
  • Cartesian
  • Planetocentric
  • Planetodetic
  • Planetographic
  • Spherical

<coordinate_system_time_utc>

OPTIONAL

If your coordinate system has a time dependence, this attribute should hold the relevant instantiation time in UTC, in the standard YYYY-MM-DDThh:mm:ss.ssZ format.

<comment>

OPTIONAL

Here is a place to add some clarifying explanation for uncommon coordinate systems.

<Coordinate_System_Origin_Identification>

REQUIRED

This class indicates the fixed origin ([0,0,0] point, i.e.) of the coordinate system. Apart from the class name, the content is filled out identically to the Geometry_Target_Identification class in the Image_Display_Geometry class. That is, its attributes are:

  • body_spice_name
  • name
  • pds:Internal_Reference

<Reference_Frame_Identification>

REQUIRED

This class indicates the "orthogonal axes" part of the coordinate system definition. It is filled out identically to the class of the same name in the Image_Display_Geometry class.


<Pixel_Dimensions>

OPTIONAL

This class provides various ways of translating a pixel field of view to physical dimensions. You must provide units for these attributes as appropriate.

<pixel_field_of_view_method>

REQUIRED

This attribute indicates how the pixel FOV values, following, were derived. It must have one of the following values:

  • average: The pixel FOV varies across the image; the value stated are the average FOV.
  • central pixel: The pixel FOV varies across the image; the value stated represents the FOV of the center pixel.
  • constant: The pixel FOV does not vary across the image.

<horizontal_pixel_field_of_view>

OPTIONAL

This attribute gives the horizontal (as defined by the <Display_Direction> class) FOV of a single pixel in terms of its angular size. You must specify angular units (typically "deg") for this value.

<vertical_pixel_field_of_view>

OPTIONAL

This attribute gives the vertical (as defined by the <Display_Direction> class) FOV of a single pixel in terms of its angular size. You must specify angular units (typically "deg") for this value.

<Pixel_Size_Projected>

OPTIONAL

This class provides a the size, in units of length, of a single pixel projected onto the surface of (or at the distance of) the relevant geometry target.

<reference_location>

OPTIONAL

This attribute identifies the point on the target at which the following pixel values are calculated. Either this or <distance> must be specified. It must have one of the following values:

  • Boresight Intercept Point
  • Constant
  • Subspacecraft Point
  • Target Center

<distance>

OPTIONAL

Distance to which the pixel is projected. This is particularly useful when your target object occupies a small number of pixels rather than the entire image frame. Either this or <reference_location> must be specified. You must provide units of length for this value.

<horizontal_pixel_footprint>

REQUIRED

This attribute gives the horizontal (as defined in the associated Display_Direction class) extent of a single pixel at the reference_location or distance, in units of length.

<vertical_pixel_footprint>

REQUIRED

This attribute gives the vertical (as defined in the associated Display_Direction class) extent of a single pixel at the reference_location or distance, in units of length.


<Distances>

OPTIONAL

This class is a container for other classes used to list scalar distance measurements of various types. These classes collect point-to-point distance measurements (that is, magnitudes rather than vectors) for various named intervals of interest, as well as providing a class for specifying arbitrary distance measurements as needed. Unless otherwise stated, distances are measured center-to-center, and references to "target" and "central body" refer to the objects identified previously in this <Geometry_Orbiter> class.

To avoid a lot of tedious repetition, these class and attribute descriptions are somewhat abbreviated. In general, the containing class will be described briefly, and the individual distance attributes will merely be listed - their names being self-explanatory.

General Notes:

  • All distance attributes are optional in their respective classes; none may be repeated.
  • All distances are considered positive.
  • All distances are named by their start and end points; terms like "target" and "central body" are as defined for this Geometry_Orbiter class.
  • Unless otherwise indicated by their names, all measurements are considered to be center-to-center.
  • All values require units of length for each value, though that unit can vary among attributes in a class. For example:
     <spacecraft_target_center_distance unit="km">15.097</spacecraft_target_center_distance>
     <target_geocentric_distance unit="AU">17.9</target_geocentric_distance>

<comment>

OPTIONAL

Here is a place to provide any additional explanatory text that might be apropos.

<Distances_Specific>

OPTIONAL

This container class lists specific named distances often used for searching through data collections from a single source. Unlike other distance classes, these attributes may be listed in any order.

Distances Included:

  • spacecraft_geocentric_distance
  • spacecraft_heliocentric_distance
  • spacecraft_central_body_distance
  • spacecraft_target_center_distance
  • spacecraft_target_boresight_intercept_distance
  • spacecraft_target_subspacecraft_distance
  • target_geocentric_distance
  • target_heliocentric_distance
  • target_ssb_distance - "SSB" stands for "Solar System Barycenter"

<Distances_Min_Max>

OPTIONAL

This container class lists minimum and maximum distances often used for constraining searches through data collections from a single source. You are required to provide these values in min/max pairs. If you don't have min/max pairs for one or more values, use the <Distances_Specific> class and the corresponding single attribute.

Distances Included:

  • minimum_spacecraft_geocentric_distance
  • maximum_spacecraft_geocentric_distance
  • minimum_spacecraft_heliocentric_distance
  • maximum_spacecraft_heliocentric_distance
  • minimum_spacecraft_central_body_distance
  • maximum_spacecraft_central_body_distance
  • minimum_spacecraft_target_center_distance
  • maximum_spacecraft_target_center_distance
  • minimum_spacecraft_target_boresight_intercept_distance
  • maximum_spacecraft_target_boresight_intercept_distance
  • minimum_spacecraft_target_subspacecraft_distance
  • maximum_spacecraft_target_subspacecraft_distance
  • minimum_target_geocentric_distance
  • maximum_target_geocentric_distance
  • minimum_target_heliocentric_distance
  • maximum_target_heliocentric_distance
  • minimum_target_ssb_distance - "SSB" stands for "Solar System Barycenter"
  • maximum_target_ssb_distance - "SSB" stands for "Solar System Barycenter"

<Distances_Start_Stop>

OPTIONAL

This container class lists distances often used for constraining searches through data collections from a single source calculated at the <geometry_start_time> and <geometry_stop_time> defined at the top of this Geometry_Orbiter class. You are required to provide these values in start/stop pairs. If you don't have start/stop pairs for one or more values, use the <Distances_Specific> class and the corresponding single attribute.

Distances Included:

  • start_spacecraft_geocentric_distance
  • stop_spacecraft_geocentric_distance
  • start_spacecraft_heliocentric_distance
  • stop_spacecraft_heliocentric_distance
  • start_spacecraft_central_body_distance
  • stop_spacecraft_central_body_distance
  • start_spacecraft_target_center_distance
  • stop_spacecraft_target_center_distance
  • start_spacecraft_target_boresight_intercept_distance
  • stop_spacecraft_target_boresight_intercept_distance
  • start_spacecraft_target_subspacecraft_distance
  • stop_spacecraft_target_subspacecraft_distance
  • start_target_geocentric_distance
  • stop_target_geocentric_distance
  • start_target_heliocentric_distance
  • stop_target_heliocentric_distance
  • start_target_ssb_distance - "SSB" stands for "Solar System Barycenter"
  • stop_target_ssb_distance - "SSB" stands for "Solar System Barycenter"

<Distance_Generic>

OPTIONAL

This class is used to define a distance measurement between a starting point, called the "observer", and an ending point, called the "target". You must explicitly identify the "observer" and "target", as well as providing the distance. You may repeat this class as many times as needed to define various distances.

<Observer_Identification>

REQUIRED

The class has the same content, and is filled out the same way, as the <Geometry_Target_Identification> class in the Image_Display_Geometry class.

<Geometry_Target_Identification>

REQUIRED

This class is filled out identically to the class of the same name in the Image_Display_Geometry class.

<distance>

REQUIRED

The center-to-center, positive distance between the observer and the target. You must provide units of length for this value.

<Surface_Geometry>

OPTIONAL

This class is a container for other classes used to list surface coordinates of various types. These classes collect surface orientation for various named angles of interest either as single values, min/max ranges, or start/stop values. Concepts like "latitude" and "longitude" are interpreted with respect to the specific target in question, as identified previously in this <Geometry_Orbiter> class.

To avoid some tedious repetition, these class and attribute descriptions are somewhat abbreviated. In general, the containing class will be described briefly, attributes unique to each class will be described as usual, the individual angle attributes will merely be listed with abbreviated descriptions mainly concerning valid ranges.

General Notes:

  • All attributes are optional in their respective classes unless otherwise indicated; none may be repeated.
  • All angles require units of angle for each value. Though that unit can vary among attributes in a class, typically all values will be given in units of degrees. For example:
     <subsolar_azimuth unit="deg">15.097</subsolar_azimuth>
     <spacecraft_longitude unit="deg">17.9</spacecraft_longitude>

<comment>

OPTIONAL

Here is a place to provide any additional explanatory text that might be apropos.

<Surface_Geometry_Specific>

OPTIONAL

This container class lists specific named distances as well as surface intercept points.

<Pixel_Intercept>

OPTIONAL

This class defines the latitude and longitude on the surface of the target for the projection of a single, specified pixel. It may be repeated. Use it when the points involved do not represent the observation footprint.

<reference_pixel_location>

OPTIONAL

Either this attribute or the <Reference_Pixel> class, following, must be specified. This attribute is a human-readable indication of where the reference pixel is, when the image is displayed as indicated in the Image_Display_Geometry class. It must have one of the following values:

  • Center
  • Lower Left Corner
  • Lower Right Corner
  • Upper Left Corner
  • Upper Right Corner
<Reference_Pixel>

OPTIONAL

Either <reference_pixel_location>, above, or this class must be specified. This class procides a more precise indication of where the reference pixel occurs in the image. It is filled out identically to the class of the same name in the Image_Display_Geometry class.

<pixel_latitude>

REQUIRED

Planetocentric latitude of the pixel projected onto the target, in the range ±90°

<pixel_longitude>

REQUIRED

Planetocentric longitude of the pixel projected onto the target, in the range 0-360°

<Footprint_Vertices>

OPTIONAL

If you have a series of pixel intercept points that define the footprint of the observation, use this wrapper class to list them. It contains a list of two or more <Pixel_Intercept> classes that should be filled out the same way as described above. You should list the pixels either in clockwise or counterclockwise sequence around the perimeter of the footprint, so that line segments drawn between succesive pixels (the last connecting back to the first) will produce the footprint on the image.

<Pixel_Intercept>

REQUIRED

You must have at least two occurrences of this class; you may have as many as needed to define the footprint.

Angles Included:

  • subsolar_azimuth
  • subsolar_latitude
  • subsolar_longitude
  • subspacecraft_azimuth
  • subspacecraft_latitude
  • subspacecraft_longitude

<Surface_Geometry_Min_Max>

OPTIONAL

This class lists min/max pairs of geometric angles calculated for the target surface. You must provide both minimum and maximum for any particular angle. If you have geometry for specific points rather than ranges, use the <Surface_Geometry_Specific> class to provide those values.

Angles Included:

  • minimum_latitude
  • maximum_latitude
  • minimum_longitude
  • maximum_longitude
  • minimum_subsolar_azimuth
  • maximum_subsolar_azimuth
  • minimum_subsolar_latitude
  • maximum_subsolar_latitude
  • minimum_subsolar_longitude
  • maximum_subsolar_longitude
  • minimum_subspacecraft_azimuth
  • maximum_subspacecraft_azimuth
  • minimum_subspacecraft_latitude
  • maximum_subspacecraft_latitude
  • minimum_subspacecraft_longitude
  • maximum_subspacecraft_longitude


<Surface_Geometry_Start_Stop>

OPTIONAL

If you have surface geometry calculated at the geometry_start and geometry_stop times included in this <Geometry_Orbiter> class, use this class to list the corresponding values. You must list these angles in start/stop pairs. If you have geometry for specific points rather than time ranges, use the <Surface_Geometry_Specific> class to provide those values.

<lat_long_method>

OPTIONAL

This attribute is required if your Surface_Geometry_Start_Stop class includes start/stop latitude or longitude. It must have one of the following values:

center
The latitude/longitude values are those at the center of the field of view at the beginning and end of the observation
median
The latitude/longitude values are the median values at the beginning and end of the observation.
mean
The latitude/longitude values are the mean values at the beginning and end of the observation.

Angles Included:

  • start_latitude
  • stop_latitude
  • start_longitude
  • stop_longitude
  • start_subsolar_azimuth
  • stop_subsolar_azimuth
  • start_subsolar_latitude
  • stop_subsolar_latitude
  • start_subsolar_longitude
  • stop_subsolar_longitude
  • start_subspacecraft_azimuth
  • stop_subspacecraft_azimuth
  • start_subspacecraft_latitude
  • stop_subspacecraft_latitude
  • start_subspacecraft_longitude
  • stop_subspacecraft_longitude

<Illumination_Geometry>

OPTIONAL

This class is a container for other classes used illumination angles of various types. These classes collect various named angles of interest either as single values, min/max ranges, or start/stop values. Angle names should be self-explanatory.

To avoid some tedious repetition, these class and attribute descriptions are somewhat abbreviated. In general, the containing class will be described briefly, attributes unique to each class will be described as usual, the individual angle attributes will merely be listed with abbreviated descriptions mainly concerning valid ranges where appropriate.

General Notes:

  • The container classes themselves may not be repeated.
  • All attributes are optional in their respective classes unless otherwise indicated; none may be repeated.
  • All angles require units of angle for each value. Typically all values will be given in units of degrees. For example:
     <emission_angles unit="deg">15.097</emission_angle>
     <start_solar_elongation unit="deg">17.9</start_solar_elongation>

<comment>

OPTIONAL

Here is a place to provide any additional explanatory text that might be apropos.

<Illumination_Specific>

OPTIONAL

This class provides illumination angles at a specific point in the image. This point must be specified in exactly one way: either through the reference_location attribute; the reference_pixel_location attribute; or the <Reference_Pixel> subclass.

<reference_location>

OPTIONAL

This defines a reference location in terms of some property of or point in the field of view. If present, this must have one of the following values:

  • Boresight Intercept Point
  • Constant
  • Subspacecraft Point
  • Target Center

<reference_pixel_location>

OPTIONAL

This defines a reference location in terms of a particular pixel location in the image when displayed according to the display settings established for this Geometry class. If present, it must have one of the following values:

  • Center
  • Lower Left Corner
  • Lower Right Corner
  • Upper Left Corner
  • Upper Right Cornet

<Reference_Pixel>

OPTIONAL

This class defines a reference location in terms of pixel subscripts in the image array. It is filled out identically to the class of the same name in the Image_Display_Geometry class.

Angles Included:

At least one of these must be present.

  • emission_angle
  • incidence_angle
  • phase_angle
  • solar_elongation

<Illumination_Min_Max>

OPTIONAL

This class gives illumination angles as min/max ranges. You must supply these values in min/max pairs. If you have single values, use the <Illumination_Specific> class, above.

Angles Included:

  • minimum_emission_angle
  • maximum_emission_angle
  • minimum_incidence_angle
  • maximum_incidence_angle
  • minimum_phase_angle
  • maximum_phase_angle
  • minimum_solar_elongation
  • maximum_solar_elongation

<Illumination_Start_Stop>

OPTIONAL

This class lists illumination angles calculated for the corresponding geometry_start_time and geometry_stop_time of this <Geometry_Orbiter> class. You must provide start/stop time pairs for this class.

Angles Included:

  • start_emission_angle
  • stop_emission_angle
  • start_incidence_angle
  • stop_incidence_angle
  • start_phase_angle
  • stop_phase_angle
  • start_solar_elongation
  • stop_solar_elongation

<Vectors>

OPTIONAL

This class is a container for other classes used to define vectors for various positions and velocities of interest. Two of the optional subclasses collect vectors in specific coordinate systems types - Cartesian and Planetocentric. The third optional subclass provides a mechanism for defining position and velocity vectors outside those included in the first two classes. Unless otherwise stated, positions and velocities are measured center-to-center, and references to "target" and "central body" refer to the objects identified previously in this <Geometry_Orbiter> class.

To avoid a lot of tedious repetition, these class and attribute descriptions are somewhat abbreviated. In general, the containing class will be described briefly, and the individual vectors classes will merely be listed - their names being self-explanatory. All vectors of similar type (all Cartesian velocity vectors, for example) will have the same attribute content.

General Notes:

The various vectors in the Geometry Discipline dictionary are derived from common parent classes, providing consistent structure and terminology. The "specific' vectors listed below have been defined for the set of vectors that appear in the majority of orbiter/flyby data products. For these vectors the start and end points ("observer" and "target", in general terms) and coordinate system are part of the definition of the vector itself. You should use these specific vectors whenever they might reasonably apply, as they provide a common nomenclature for these values that users can key into across the archive. When you need to specify a vector for a quantity outside this standard set, use the generic vectors, which allow you to specify observer, target, and coordinate system.

The details of the structure of each family of vectors in the Geometry Discipline dictionary are summarized on the Filling Out the Geometry Vector Classes page.

Additional Notes:

Within each of the wrapper classes and unless otherwise noted:

  • All vectors are optional.
  • Vectors may be in any order (this is not the usual case for PDS4 label classes and attributes).

Note: Vectors can also be repeated an arbitrary number of times within their respective classes. This seems like a bad idea for the non-Generic classes, on the face of it. If you have a reason for duplicating vectors inside this class, please use the <comment> attribute to provide some explanation for this unusual situation.

<comment>

OPTIONAL

If there is any additional explanation needed or desired regarding the contents of the following classes, here's a place for it. Note that there are no comment fields in the individual wrapper classes

<Vectors_Cartesian_Specific>

OPTIONAL

If present, this class must contain at least one of the following vectors. The abbreviation "SSB" stands for Solar System Barycenter.

The Position vectors below are filled out as described for the Vector_Cartesian_Position_Generic class on the Filling Out the Geometry Vector Classes page on this wiki, with the exceptions noted for specific vectors vs. generic ones.

The Velocity vectors below are filled out as described for the Vector_Cartesian_Velocity_Generic class on the Filling Out the Geometry Vector Classes page on this wiki, with the exceptions noted for specific vectors vs. generic ones.

Vectors Included:

  • Vector_Cartesian_Position_Central_Body_To_Spacecraft
  • Vector_Cartesian_Position_Central_Body_To_Target
  • Vector_Cartesian_Position_Earth_To_Central_Body
  • Vector_Cartesian_Position_Earth_To_Spacecraft
  • Vector_Cartesian_Position_Earth_To_Target
  • Vector_Cartesian_Position_SSB_To_Central_Body
  • Vector_Cartesian_Position_SSB_To_Spacecraft
  • Vector_Cartesian_Position_SSB_To_Target
  • Vector_Cartesian_Position_Spacecraft_To_Target
  • Vector_Cartesian_Position_Sun_To_Central_Body
  • Vector_Cartesian_Position_Sun_To_Spacecraft
  • Vector_Cartesian_Position_Sun_To_Target
  • Vector_Cartesian_Velocity_Spacecraft_Relative_To_Central_Body
  • Vector_Cartesian_Velocity_Spacecraft_Relative_To_Earth
  • Vector_Cartesian_Velocity_Spacecraft_Relative_to_SSB
  • Vector_Cartesian_Velocity_Spacecraft_Relative_To_Sun
  • Vector_Cartesian_Velocity_Spacecraft_Relative_To_Target
  • Vector_Cartesian_Velocity_Target_Relative_To_Central_Body
  • Vector_Cartesian_Velocity_Target_Relative_To Earth
  • Vector_Cartesian_Velocity_Target_Relative_To_SSB
  • Vector_Cartesian_Velocity_Target_Relative_To_Spacecraft
  • Vector_Cartesian_Velocity_Target_Relative_To_Sun

<Vectors_Planetocentric_Specific>

OPTIONAL

If present, this class must contain at least one of the following vectors.

The Position vectors below are filled out as described for the Vector_Planetocentric_Position_Generic class on the Filling Out the Geometry Vector Classes page on this wiki, with the exceptions noted for specific vectors vs. generic ones.

The Velocity vectors below are filled out as described for the Vector_Planetocentric_Velocity_Generic class on the Filling Out the Geometry Vector Classes page on this wiki, with the exceptions noted for specific vectors vs. generic ones.

Vectors Included:

  • Vector_Planetocentric_Position_Central_Body_To_Spacecraft
  • Vector_Planetocentric_Position_Central_Body_To_Target
  • Vector_Planetocentric_Position_Spacecraft_To_Target
  • Vector_Planetocentric_Velocity_Spacecraft_Relative_To_Target
  • Vector_Planetocentric_Velocity_Target_Relative_To_Central_Body
  • Vector_Planetocentric_Velocity_Target_Relative_To_Spacecraft

<Generic_Vectors>

OPTIONAL

This class is used when the start point, end point, or both are not covered by the vectors of the preceding specific classes. Five generic vector types are provided. You may repeat these classes as needed for however many vectors you need to define.

The contents and procedures for filling out the generic vector classes are detailed on the Filling Out the Geometry Vector Classes page on this wiki.

Vectors Included:

  • Vector_Cartesian_Acceleration_Generic
  • Vector_Cartesian_Position_Generic
  • Vector_Cartesian_Velocity_Generic
  • Vector_Planetocentric_Position_Generic
  • Vector_Planetocentric_Velocity_Generic