The ISIS3 Attached Spice Format

Overview

Running the spiceinit application with attach=true will attach all of the SPICE data required by the camera model directly to the Cube. There are 6 locations information is added to the Cube:

• The Kernels group
• The NaifKeywords group
• The InstrumentPointing Table
• The InstrumentPosition Table
• The BodyRotation Table
• The SunPosition Table

The following sections outline what is stored in each of these locations. The spiceinit application documentation shows what textual information is added to these locations.

The Kernels Group

Before spiceinit

The Kernels group is already a part of the Cube label after ingestion (it is nested under the IsisCube object). Usually, the only information it contains after ingestion is the NaifFrameCode keyword. The NaifFrameCode keyword contains the NAIF code for the instrument. So, information about the instrument will be stored as INS{NaifFrameCode}_{Some property} in the NAIF kernels. For example the NaifFrameCode for Kaguya Terrain Camera 2 is -131371. So, the focal length for Kaguya Terrain Camera 2 is stored as INS-131371_FOCAL_LENGTH. Usually, the NAIF ID for the instrument is also the NAIF ID for the sensor reference frame. If this is not the case, then there will be also be a NaifCkCode keyword in the Kernels group that contains the NAIF ID for the sensor reference frame.

After spiceinit

All of the kernels used will be added to the Kernels group under the following keywords:

• LeapSecond
• TargetAttitudeShape
• TargetPosition
• InstrumentPointing
• Instrument
• SpacecraftClock
• InstrumentPosition
• InstrumentAddendum

If a shapemodel is is used, then that shapemodel will also be specified by the ShapeModel keyword. The InstrumentPositionQuality and InstrumentPointingQuality keywords will specify the quality of the kernels used for the InstrumentPositon and InstrumentPointing Tables. Finally, the CameraVersion keyword specifies the version of the camera model that the Cube will now work with.

The NaifKeywords Group

The NaifKeywords group is not a part of the Cube prior to spiceinit being run. After spiceinit, the group is located at the very end of the Cube label.

This group contains all of the keywords and values collected from the SPICE kernel pool. Some examples what is usually contained in the NaifKeywords group are the target body radii, the instrument focal length, distortion model coefficients, and the transformations between image pixels and detector pixels.

The sensor model specifies what is contained in the NaifKeywords group. Keywords and values are added to the NaifKeywords group by the following Spice class methods (methods in italics are protected):

• getDouble
• getInteger
• getString
• readValue
• storeResult
• storeValue

The sensor model and its maps use these methods to get any keyword values they need from the SPICE kernel pool. The keyword and its values are then stored in the NaifKeywords group as a keyword, value pair. For example, if getDouble was called with the NAIF keyword INS-131371_FOCAL_LENGTH, then INS-131371_FOCAL_LENGTH would be added to the NaifKeywords group as a PVL keyword whose values is the value returned by the NAIF SPICE ToolKit. Any future calls to access keyword values that have been stored use the NaifKeywords group instead of the SPICE kernel pool.

ISIS Tables

The InstrumentPointing Table, InstrumentPosition Table, BodyRotation Table, and SunPosition Table are ISIS Tables. These are tables of binary information stored on the Cube file. Each Table consists of two parts; the label, and the binary data.

ISIS Table Labels

The labels for all of the Tables in a Cube file are located in the Cube label after the IsisCube object. Each label is an object called Table, each Table is identified by the values of its Name keyword. So, the InstrumentPointing Table label is the Table object whose Name keyword has a value of InstrumentPointing. The Table label also contains information about where the binary data is stored in the StartByte and Bytes keywords. The format of the table is defined by the Records`` and ByteOrder keywords and the Field groups. The Records keyword specifies how many records, or rows, there are in the Table. Each Field group describes a field, or column, in the table. Each Field group contains a Name keyword that describes the field's name, a Type keyword that describes what type of binary data that field contains, and a Size keyword that describes how many pieces of binary data are stored in that field.

ISIS Table Binary Data

The binary data for ISIS Tables are stored as contiguous blocks of binary data at the end of the Cube file. Each record, or row, in the Table is stored contiguously starting with the first record. Within a record, the values for each field, or column, are stored in the order that the Field groups are stored in the Table Label.

The InstrumentPointing Table

The InstrumentPointing Table contains information needed to rotate from the J2000 reference frame to the sensor reference frame. It is not a part of the Cube prior to spiceinit being run. After spiceinit, the label for the Table is located after the IsisCube object in the Cube label and the binary table data is located at the end of the file.

The InstrumentPointing Table Label

The InstrumentPointing Table's label contains all of the information described in ISIS Table Labels along some additional keywords. The TimeDependentFrames and ConstantFrames keywords contain the NAIF codes of the reference frames that are rotated through. These keywords should be read right to left, so the start frame is last in the value array and the final frame is first in the value array. The ConstantRotation keyword contains a 3x3 rotation matrix that rotates from the last time dependent frame to the final frame, that is the frames in the ConstantFrames keyword. The rotations through the frames in the TimeDependentFrames are stored in the binary portion of the InstrumentPointing Table. The CkTableStartTime and CkTableEndTime keywords contain the valid time range for the rotation information in the InstrumentPointing Table. The CkTableOriginalSize keyword describes how many records were in the InstrumentPointing Table prior to any reduction steps. The FrameTypeCode keyword describes what type of NAIF SPICE C Kernel the rotation information came from. The Kernels keyword contains the SPICE Kernels the rotation information came from.

The InstrumentPointing Table Binary Data

The InstrumentPointing Table's binary data contains the rotations from the starting frame (always J2000) to the last time dependent frame (usually the spacecraft). This data can be stored in two formats:

• A quaternion cache
• coefficients for Euler angles

Quaternion Cache

After spiceinit, the InstrumentPointing Table binary data is always a quaternion cache. Each record contains, a rotation quaternion, the time for that quaternion, and optionally the 3-element rotational velocity. The quaternions use NAIF's format which is not the same as the standard quaternion format. NAIF stores the quaternion as (w, x, y, z). Most other tools and libraries store the quaternion as (x, y, z, w).