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

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== <geometry_reference_time> ==
 
== <geometry_reference_time> ==
  
''REQUIRED''
+
''OPTIONAL''
 
 
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.
 
 
 
== <Central_Body_Identification> ==
 
  
''OPTIONAL''
+
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.
  
This class provides a number of options for identifying a physical object to be subsequently referenced in this instance of the ''&lt;Geometry_Orbiter&gt;'' class by the term "central body".  You must provide at least one of the included attributes or subclasses; you may provide more than one but they should reference ''the same physical object''.  You may ''not'' repeat this class, but you may use it in conjunction with the ''&lt;Target_Identification&gt;'' class.  This class is used in cases where the target of the observation, say a moon or planetary ring, is orbiting or otherwise bound to another object, like a planet, which is also identifiable in the observation.  This "other object" is referenced in these classes as the "central body".
+
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.
  
=== <body_spice_name> ===
+
== <geometry_start_time> and <geometry_stop_time> ==
  
 
''OPTIONAL''
 
''OPTIONAL''
  
This is the NAIF-assigned or NAIF-recognized identifier for a physical object - in this case, the central body.
+
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;''.
  
{| class="wikitable" style="background-color: yellow"
+
These must be UTC times in the standard ''YYYY-MM-DD'''''T'''''hh:mm:ss.sss'''''Z'''" format.
| ''It is not clear if or how this value will be validated and verified for correctness.''
 
|}
 
  
=== <name> ===
+
== <Orbiter_Identification> ==
  
 
''OPTIONAL''
 
''OPTIONAL''
  
This attribute should be a name that provides sufficient identification for the object to be uniquely identified - especially in light of the fact that no object type is indicated.  You should use whatever naming conventions would normally apply.  For example, if you are naming a small body, or submitting the data to the Small Bodies Node, then you should follow the conventions described on the [[Target_Names|SBN Target Names Stylesheet]] on this wiki.
+
Use this class to identify geometric elements and reference points to be used in the ''Geometry_Orbiter'' subclasses that follow.
  
=== <Internal_Reference> ===
+
=== <Central_Body_Identification> ===
  
 
''OPTIONAL''
 
''OPTIONAL''
  
If the object you're trying to identify has a corresponding context product in the PDS archives, you can use this class to link to that explicitly.
+
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.
  
As in other cases in the ''&lt;Geometry&gt;'' class, the attributes of the ''Internal_Reference'' class are in the PDS4 core namespace.  See [[Filling_out_the_SPICE_Kernel_Files_Class#.3CInternal_Reference.3E|Filling out the SPICE_Kernel_Files Class: Internal_Reference]] for more info.
+
=== <Geometry_Target_Identification> ===
  
{| class="wikitable" style="background-color: yellow"
+
''OPTIONAL''
| '''''Note'':''' ''The ''reference_type'' attribute for this class has no defined values.  I would expect values along the lines of ''"geometry_orbiter_to_target"'' if this is going to follow the same patterns established in the PDS core namespace.''
 
|}
 
  
 +
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.
  
********PICK UP HERE**********
+
=== <Coordinate_System_Identification> ===
  
 +
''OPTIONAL''
  
== <Coordinate_System_Identification> ==
+
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.
  
''OPTIONAL''
+
==== <coordinate_system_type> ====
  
This class defines a coordinate system. It specifies an origin, reference frame, type, and reference time.
+
''REQUIRED''
  
{| class="wikitable" style="background-color: yellow"
+
You must indicate the type of coordinates to be applied, which must be one of the following values:
| ''I would strongly advise including an optional comment or description attribute in this class.''
 
|}
 
  
=== <coordinate_system_type> ===
+
* Azimuth-Elevation
 +
* Cartesian
 +
* Planetocentric
 +
* Planetodetic
 +
* Planetographic
 +
* Spherical
  
''REQUIRED''
+
==== <coordinate_system_time> ====
  
This indicates the type of coordinates that will be used.  It must be one of the following standard values:
+
''OPTIONAL''
  
::* '''Azimuth-Elevation'''
+
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.
::* '''Cartesian'''
 
::* '''Planetocentric'''
 
::* '''Planetodetic'''
 
::* '''Planetographic'''
 
::* '''Spherical'''
 
  
=== <coordinate_system_time> ===
+
==== <comment> ====
  
''REQUIRED''
+
''OPTIONAL''
  
This attribute provides a reference time for the instantiation of the coordinate systemIt 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.
+
Here is a place to add some clarifying explanation for uncommon coordinate systems.   
  
=== <Coordinate_System_Origin_Identification> ===
+
==== <Coordinate_system_Origin_Identification> ====
  
 
''REQUIRED''
 
''REQUIRED''
  
This class identifies the origin of the coordinate system - not necessarily the end point of any particular vector defined within that coordinate system.  Apart from the enclosing tag name (''Coordinate_System_Origin_Identification'' as opposed to ''Central_Body_Identification''), this class is filled out identically to the [[#.3CCentral_Body_Identification.3E|&lt;Central_body_Identification&gt;]] class, described above.
+
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:
  
{| class="wikitable" style="background-color:yellow"
+
::* ''body_spice_name''
| ''Is this sufficiently precise?  If you name a body, like "Jupiter", is it clear that you mean the center of mass (or do you mean the barycenter, or some geometric center of a reference surface)?''
+
::* ''name''
|}
+
::* ''Internal_Reference''
  
=== <Reference_Frame_Identification> ===
+
==== <Reference_Frame_Identification> ====
  
 
''REQUIRED''
 
''REQUIRED''
  
This class defines the reference frame for the coordinate system.  It is filled out identically to the [[#.3CReference_Frame_Identification.3E|&lt;Reference_Frame_Identification&gt;]] class described above.
+
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 ''[[Filling_out_the_Image_Display_Geometry_Class#.3CReference_Frame_Identification.3E|Image_Display_Geometry]]'' class.
  
{| class="wikitable" style="background-color:yellow"
 
| ''Why would this ever be different from the higher-level ''Reference_Frame_Identification''?  What wouls that mean?  Where would a data preparer explain that strange-seeming situation?''
 
|}
 
  
  
== <Target_Identification> ==
 
 
''OPTIONAL''
 
  
This class identifies the origin of the coordinate system - not necessarily the end point of any particular vector defined within that coordinate system.  Apart from the enclosing tag name (''Target_Identification'' as opposed to ''Central_Body_Identification''), this class is filled out identically to the [[#.3CCentral_Body_Identification.3E|&lt;Central_body_Identification&gt;]] class, described above.
 
  
{| class="wikitable" style="background-color: yellow"
 
|
 
''The more I think about it, the more I dislike re-using the "Target_Identification" name for a different purpose here.  And I also wonder if just proving a body identification is sufficiently precise here, as well.''
 
|}
 
  
 
== <Distances> ==
 
== <Distances> ==

Revision as of 15:15, 30 March 2016

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.

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_timepair 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.

<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 [[ Filling_out_the_Image_Display_Geometry_Class#.3CGeometry_Target_Identification.3E|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>

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 [ Filling_out_the_Image_Display_Geometry_Class#.3CGeometry_Target_Identification.3E|Image_Display_Geometry]] class. That is, its attributes are:

  • body_spice_name
  • name
  • 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.




<Distances>

OPTIONAL

This class collects 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 in the <Target_Identification> and <Central_Body_Identification>, respectively, in this <Geometry_Orbiter> class.

All distances are considered positive, and you must provide units of an appropriate type in each case. For example:

     <spacecraft_to_target_center_distance unit="km">15.097</spacecraft_to_target_center_distance>
     <target_geocentric_distance unit="AU">17.9</target_geocentric_distance>

<spacecraft_geocentric_distance>

OPTIONAL

Distance from the spacecraft to Earth

<spacecraft_heliocentric_distance>

OPTIONAL

Distance from the spacecraft to the sun

<spacecraft_to_central_body_distance>

OPTIONAL

Distance from the spacecraft to identified central body.

<spacecraft_to_target_center_distance>

OPTIONAL

Distance from the spacecraft to the identified target.

<spacecraft_to_target_boresight_intercept_distance>

OPTIONAL

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

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.

<target_geocentric_distance>

OPTIONAL

Distance from the identified target to Earth

<target_heliocentric_distance>

OPTIONAL

Distance from the identified target to the sun

<target_ssb_distance>

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

This class identifies the start point of the distance measurement. Apart from the enclosing tag name (Observer_Identification as opposed to Central_Body_Identification), this class is filled out identically to the <Central_body_Identification> class, described above.

<Target_Identification>

REQUIRED

This class identifies the end point of the distance measurement. Apart from the enclosing tag name (Target_Identification as opposed to Central_Body_Identification), this class is filled out identically to the <Central_body_Identification> class, described above.

Even more qualms about "target" confusion...

<distance>

REQUIRED

The actual distance measurement from observer to target. You must, as always, provide an appropriate unit of measure with this attribute. Make sure you indicate the precise point (center, barycenter, intercept point, etc.) used for measurement at both the observer and the target.


<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.

<horizontal_pixel_size_angular>

OPTIONAL

This attribute gives the horizontal (as defined by the <Display_Direction> class) size of a pixel in terms of its angular size.

<vertical_pixel_size_angular>

OPTIONAL

This attribute gives the vertical (as defined by the <Display_Direction> class) size of a pixel in terms of its angular size.

<horizontal_pixel_scale_factor>

OPTIONAL

This attribute gives the horizontal (as defined by the <Display_Direction> 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.

Units for this keyword are Units_of_Map_Scale - "km/pixel", for example.

<vertical_pixel_scale_factor>

OPTIONAL

This attribute gives the vertical (as defined by the <Display_Direction> 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.

Units for this keyword are Units_of_Map_Scale - "km/pixel", for example.

<Pixel_Size_Projected>

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.

<reference_location>

REQUIRED

This attribute identifies the point at which the following pixel values are calculated. It must have one of the following values:

  • Boresight Intercept Point
  • Subspacecraft Point
  • Target Center

The "target" is the object in the <Target_Identification> class of the containing <Geometry_Orbiter> class.

<horizontal_pixel_size_projected>

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.

<vertical_pixel_size_projected>

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.


<Surface_Geometry>

OPTIONAL

This class collects various attributes related to geometry at the surface of the object in the <Target_identification> class of the containing <Geometry_Orbiter> class.

<Pixel_Intercept>

OPTIONAL

This class identifies the pixel at which the other values in the containing class are calculated. You must provide either the reference_pixel_location or the Reference_Pixel class to identify the reference point within the associated image.

This constraint is not enforced.

<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 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 (in the range 0-360°) 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 <Pixel_Intercept> 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.

I'm guessing this is what the mangled definition in the schema was eventually going to say. Really shouldn't drink that much when you're working on this stuff.

<Pixel_Intercept>

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 Pixel_Intercept in the <Surface_Geometry> class, above.

<subsolar_azimuth>

OPTIONAL

This is the angle, measured 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

This attribute contains the planetocentric latitude of the subsolar point on the identified target. You must provide units of measure for this attribute.

<subsolar_longitude>

OPTIONAL

This attribute contains the planetocentric longitude (in the range 0-360°) of the subsolar point on the identified target. You must provide the units of measure for this attribute.

<subspacecraft_azimuth>

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.

<subspacecraft_latitude>

OPTIONAL

This attribute contains the planetocentric latitude of the subspacecraft point on the identified target. You must provide units of measure for this attribute.

<subspacecraft_longitude>>

OPTIONAL

This attribute contains the planetocentric longitude (in the range 0-360°) of the subspacecraft point on the identified target. You must provide the units of measure for this attribute.


<Illumination_Geometry>

OPTIONAL

This class provides attributes to describe the field of view lighting conditions.

<Illumination_Single_Values>

OPTIONAL

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 <Target_Identification> class of the containing <Geometry_Orbiter> class.

If I'm following the logic of other classes correctly, then it seems to me like there should be a requirement that exactly one of reference_location, reference_pixel_location, or Reference_Pixel should be required. That's not what's happening in the schema, and what is in the schema is weird - the first two are in an optional "choice" construct, while the last isn't. Is this another LDDTool issue?

<reference_location> or <reference_pixel_location>

OPTIONAL

You must specify one or the other of these reference points to indicate the point at which the following illumination values are calculated.

reference_location must have one of these values:

  • Boresight Intercept Point
  • Subspacecraft Point
  • Target Center

reference_pixel_location must have one of these values:

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

<Reference_Pixel>

OPTIONAL

This class identifies the reference pixel within the image. It is identical to the Reference_Pixel class in <Geometry_Orbiter>.

<emission_angle>

OPTIONAL

This is the angle (in the range 0-180°) 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.

<incidence_angle>

OPTIONAL

This is the angle (in the range 0-180°) 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.

<phase_angle>

OPTIONAL

This is the angle (in the range 0-180°) 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 (in the range 0-180°) 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 <Illumination_Single_Values> class.

<illumination_range_designation>

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 the containing Geometry_Orbiter class) that is within the field of view. It must have one of two values: either Field of View, corresponding to the former case; or Target for the latter.

<minimum_emission_angle>

OPTIONAL

This attribute is the minimum value of the emission angle (in the range 0-180°) relevant to the observation. You must provide units of measure for this attribute.

<maximum_emission_angle>

OPTIONAL

This attribute is the maximum value of the emission angle (in the range 0-180°) relevant to the observation. You must provide units of measure for this attribute.

<minimum_incidence_angle>

OPTIONAL

This attribute is the minimum value of the incidence angle (in the range 0-180°) relevant to the observation. You must provide units of measure for this attribute.

<maximum_incidence_angle>

OPTIONAL

This attribute is the maximum value of the incidence angle (in the range 0-180°) relevant to the observation. You must provide units of measure for this attribute.

<minimum_phase_angle>

OPTIONAL

This attribute is the minimum value of the phase angle (in the range 0-180°) relevant to the observation. You must provide units of measure for this attribute.

<maximum_phase_angle>

OPTIONAL

This attribute is the maximum value of the phase angle (in the range 0-180°) relevant to the observation. You must provide units of measure for this attribute.


A Word About Geometry Vectors

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 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

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.

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.

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 <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 <Specific_Cartesian_Vectors> and <Specific_Planetocentric_Vectors> classes.

<Central_Body_To_Spacecraft_Position_Vector_Cartesian>

OPTIONAL

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 <Position_Vector_Cartesian_Generic> class.

<Central_Body_To_Target_Position_Vector_Cartesian>

OPTIONAL

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 <Position_Vector_Cartesian_Generic> class.

<Spacecraft_To_Target_Position_Vector_Cartesian>

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 <Position_Vector_Cartesian_Generic> class.

<Central_Body_To_Spacecraft_Position_Vector_Planetocentric>

OPTIONAL

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 <Position_Vector_Cartesian_Generic> class.

<Central_Body_To_Target_Position_Vector_Planetocentric>

OPTIONAL

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 <Position_Vector_Cartesian_Generic> class.

<Spacecraft_To_Target_Position_Vector_Planetocentric>

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 <Position_Vector_Cartesian_Generic> class.

<SSB_To_Central_Body_Position_Vector_Cartesian>

OPTIONAL

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 <Position_Vector_Cartesian_Generic> class.

<SSB_To_Spacecraft_Position_Vector_Cartesian>

OPTIONAL

Position of the spacecraft as viewed from the Solar System Barycenter (SSB). It is filled out as a specific form of the <Position_Vector_Cartesian_Generic> class.

<SSB_To_Target_Position_Vector_Cartesian>

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 <Position_Vector_Cartesian_Generic> class.

<Sun_To_Central_Body_Position_Vector_Cartesian>

OPTIONAL

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 <Position_Vector_Cartesian_Generic> class.

<Sun_To_Spacecraft_Position_Vector_Cartesian>

OPTIONAL

Position of the spacecraft as viewed from the sun. It is filled out as a specific form of the <Position_Vector_Cartesian_Generic> class.

<Sun_To_Target_Position_Vector_Cartesian>

OPTIONAL

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 <Position_Vector_Cartesian_Generic> class.

<Earth_To_Central_Body_Position_Vector_Cartesian>

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 <Position_Vector_Cartesian_Generic> class.

<Earth_To_Spacecraft_Position_Vector_Cartesian>

OPTIONAL

Position of the spacecraft as viewed from Earth. It is filled out as a specific form of the <Position_Vector_Cartesian_Generic> class.

<Earth_To_Target_Position_Vector_Cartesian>

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 <Position_Vector_Cartesian_Generic> class.

<Specific_Velocity_Vectors>

OPTIONAL

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. (Note that this is the opposite order from that in the specific position vector names.) 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 <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 <Specific_Cartesian_Vectors> and <Specific_Planetocentric_Vectors> classes.

<Spacecraft_Relative_To_Central_Body_Velocity_Vector_Cartesian>

OPTIONAL

Velocity of the spacecraft as observed from the central body (around which another body is orbiting). This is a specific form of the <Velocity_Vector_Cartesian_Generic> class.

<Spacecraft_Relative_To_Target_Velocity_Vector_Cartesian>

OPTIONAL

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 <Velocity_Vector_Cartesian_Generic> class.

<Spacecraft_Relative_To_Earth_Velocity_Vector_Cartesian>

OPTIONAL

Velocity of the spacecraft as observed from Earth. This is a specific form of the <Velocity_Vector_Cartesian_Generic> class.

<Spacecraft_Relative_To_SSB_Velocity_Vector_Cartesian>

OPTIONAL

Velocity of the spacecraft as observed from the Solar System Barycenter (SSB). This is a specific form of the <Velocity_Vector_Cartesian_Generic> class.

<Spacecraft_Relative_To_Sun_Velocity_Vector_Cartesian>

OPTIONAL

Velocity of the spacecraft as observed from the sun. This is a specific form of the <Velocity_Vector_Cartesian_Generic> class.

<Target_Relative_To_Central_Body_Velocity_Vector_Cartesian>

OPTIONAL

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 <Velocity_Vector_Cartesian_Generic> class.

<Target_Relative_To_Spacecraft_Velocity_Vector_Cartesian>

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 <Velocity_Vector_Cartesian_Generic> class.

<Target_Relative_To_Earth_Velocity_Vector_Cartesian>

OPTIONAL

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 <Velocity_Vector_Cartesian_Generic> class.

<Target_Relative_To_SSB_Velocity_Vector_Cartesian>

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 <Velocity_Vector_Cartesian_Generic> class.

<Target_Relative_To_Sun_Velocity_Vector_Cartesian>

OPTIONAL

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 <Velocity_Vector_Cartesian_Generic> class.

<Spacecraft_Relative_To_Target_Velocity_Vector_Planetocentric>

OPTIONAL

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 <Velocity_Vector_Planetocentric_Generic> class.

<Target_Relative_To_Central_Body_Velocity_Vector_Planetocentric>

OPTIONAL

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 <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 <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
Velocity Vectors

<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. You may repeat a vector if needed. The vectors included in this class, in label order, are:

<Generic_Vectors>

OPTIONAL

The Generic_Vectors class allows you to define new point-to-point vectors for position, velocity, and acceleration as you need them. You should use specific versions of vectors when they already exist, but if you have a concept not covered by those, here's where it goes. Their detailed descriptions have been pulled out onto a separate Filling Out the Geometry Vector Classes page for referencing and cross-referencing, since the attributes of these generic vectors are supersets of the attributes used to define the specific vectors.

Generic vector classes must be created in the following order, although you may repeat classes as needed. That is, you may define as many <Velocity_Vector_Cartesian_Generic> classes as you like before moving on to any <Acceleration_Vector_Cartesian_Generic> classes.

These are the generic vector classes available, in label order: