Filling out the Geometry Orbiter Class

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.

<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-DDThh:mm:ss.sssZ" format.

<Reference_Frame_Identification>

REQUIRED

Waiting on SPICE-related changes.

<Central_Body_Identification>

OPTIONAL

Waiting on SPICE-related changes.

<Coordinate_System>

OPTIONAL

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-DDThh:mm:ss.sss". If the time is a UTC time, add the Z zone indicator at the end.

<Coordinate_System_Origin_Identification>

REQUIRED

Waiting on SPICE-related changes.

<Reference_Frame_Identification>

REQUIRED

Waiting on SPICE-related changes.

<Target_Identification>

OPTIONAL

Waiting on SPICE-related changes.

<Distances>

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 <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

Waiting on SPICE-related changes.

<Target_identification>

REQUIRED

Waiting on SPICE-related changes.

<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 this <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 this <Geometry_Orbiter> 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 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 <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.

<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, 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

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 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 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.

<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 this <Geometry_Orbiter> class.

<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 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 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 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 <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 this Geometry_Orbiter class) that is within the field of view. It must have one of 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 relevant to the observation. Use must provide units of measure for this attribute.

<maximum_emission_angle>

OPTIONAL

This attribute is the maximum value of the emission angle relevant to the observation. Use must provide units of measure for this attribute.

<minimum_incidence_angle>

OPTIONAL

This attribute is the minimum value of the incidence angle relevant to the observation. Use must provide units of measure for this attribute.

<maximum_incidence_angle>

OPTIONAL

This attribute is the maximum value of the incidence angle relevant to the observation. Use must provide units of measure for this attribute.

<minimum_phase_angle>

OPTIONAL

This attribute is the minimum value of the phase angle relevant to the observation. Use must provide units of measure for this attribute.

<maximum_phase_angle>

OPTIONAL

This attribute is the maximum value of the phase angle relevant to the observation. Use must provide units of measure for this attribute.

<Specific_Position_Vectors>

OPTIONAL

<Central_Body_To_Spacecraft_Position_Vector_Cartesian>

OPTIONAL

<Central_Body_To_Target_Position_Vector_Cartesian>

OPTIONAL

<Spacecraft_To_Target_Position_Vector_Cartesian>

OPTIONAL

<Central_Body_To_Spacecraft_Position_Vector_Planetocentric>

OPTIONAL

<Central_Body_To_Target_Position_Vector_Planetocentric>

OPTIONAL

<Spacecraft_To_Target_Position_Vector_Planetocentric>

OPTIONAL

<SSB_To_Central_Body_Position_Vector_Cartesian>

OPTIONAL

<SSB_To_Spacecraft_Position_Vector_Cartesian>

OPTIONAL

<SSB_To_Target_Position_Vector_Cartesian>

OPTIONAL

<Sun_To_Central_Body_Position_Vector_Cartesian>

OPTIONAL

<Sun_To_Spacecraft_Position_Vector_Cartesian>

OPTIONAL

<Sun_To_Target_Position_Vector_Cartesian>

OPTIONAL

<Earth_To_Central_Body_Position_Vector_Cartesian>

OPTIONAL

<Earth_To_Spacecraft_Position_Vector_Cartesian>

OPTIONAL

<Earth_To_Target_Position_Vector_Cartesian>

OPTIONAL

<Specific_Velocity_Vectors>

OPTIONAL

<Spacecraft_Relative_To_Central_Body_Velocity_Vector_Cartesian>

OPTIONAL

<Spacecraft_Relative_To_Target_Velocity_Vector_Cartesian>

OPTIONAL

<Spacecraft_Relative_To_Earth_Velocity_Vector_Cartesian>

OPTIONAL

<Spacecraft_Relative_To_SSB_Velocity_Vector_Cartesian>

OPTIONAL

<Spacecraft_Relative_To_Sun_Velocity_Vector_Cartesian>

OPTIONAL

<Target_Relative_To_Central_Body_Velocity_Vector_Cartesian>

OPTIONAL

<Target_Relative_To_Spacecraft_Velocity_Vector_Cartesian>

OPTIONAL

<Target_Relative_To_Earth_Velocity_Vector_Cartesian>

OPTIONAL

<Target_Relative_To_SSB_Velocity_Vector_Cartesian>

OPTIONAL

<Target_Relative_To_Sun_Velocity_Vector_Cartesian>

OPTIONAL

<Spacecraft_Relative_To_Target_Velocity_Vector_Planetocentric>

OPTIONAL

<Target_Relative_To_Central_Body_Velocity_Vector_Planetocentric>

OPTIONAL

<Target_Relative_To_Spacecraft_Velocity_Vector_Planetocentric>

OPTIONAL

<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. The vectors included in this class, in label order, are:

Position Vectors

• Central_Body_To_Spacecraft_Position_Vector_Cartesian
• Central_Body_To_Target_Position_Vector_Cartesian
• Spacecraft_To_Target_Position_Vector_Cartesian
• SSB_To_Central_Body_Position_Vector_Cartesian
• SSB_To_Spacecraft_Position_Vector_Cartesian
• SSB_To_Target_Position_Vector_Cartesian
• Sun_To_Central_Body_Position_Vector_Cartesian
• Sun_To_Spacecraft_Position_Vector_Cartesian
• Sun_To_Target_Position_Vector_Cartesian
• Earth_To_Central_Body_Position_Vector_Cartesian
• Earth_To_Spacecraft_Position_Vector_Cartesian
• Earth_To_Target_Position_Vector_Cartesian

Velocity Vectors

• Spacecraft_Relative_To_Central_Body_Velocity_Vector_Cartesian
• Spacecraft_Relative_To_Target_Velocity_Vector_Cartesian
• Spacecraft_Relative_To_Earth_Velocity_Vector_Cartesian
• Spacecraft_Relative_To_SSB_Velocity_Vector_Cartesian
• Spacecraft_Relative_To_Sun_Velocity_Vector_Cartesian
• Target_Relative_To_Central_Body_Velocity_Vector_Cartesian
• Target_Relative_To_Spacecraft_Velocity_Vector_Cartesian
• Target_Relative_To_Earth_Velocity_Vector_Cartesian
• Target_Relative_To_SSB_Velocity_Vector_Cartesian
• 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>

REQUIRED

<Velocity_Vector_Cartesian_Generic>

OPTIONAL

<x_velocity>

REQUIRED

<y_velocity>

REQUIRED

<z_velocity>

REQUIRED

<light_time_correction_applied>

REQUIRED

<Coordinate_System>

OPTIONAL

<Observer_Identification>

REQUIRED

<Target_Identification>

REQUIRED

<Acceleration_Vector_Cartesian_Generic>

OPTIONAL

<x_acceleration>

REQUIRED

<y_acceleration>

REQUIRED

<z_acceleration>

REQUIRED

<light_time_correction_applied>

REQUIRED

<Coordinate_System>

OPTIONAL

<Observer_Identification>

REQUIRED

<Target_Identification>

REQUIRED

<Position_Vector_Planetocentric_Generic>

OPTIONAL

<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

<Observer_Identification>

REQUIRED

<Target_Identification>

REQUIRED