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SPICE


Introduction


Once an image has been correctly ingested into ISIS3 (meaning that the ISIS3 cube label contains all required mission-specific keywords), additional navigational and ancillary information (SPICE) is required in order to calibrate and geometrically/photometrically process the data. ISIS3 utilizes software supplied by the Navigation and Ancillary Information Facility (NAIF).

SPICE (Spacecraft & Planetary ephemerides, Instrument C-matrix and Event kernels) refers to all the information that is required and computed in order for ISIS3 to map each image onto a surface with reference to spacecraft position, sun position, instrument and mission activities.

SPICEINIT


The ISIS3 application spiceinit adds the necessary SPICE information to an image cube. It is important to note that if spiceinit is unsuccessful then further cartographic processing will not be possible.

Required Mission Keywords

At a minimum 'spiceinit' requires SpacecraftName, InstrumentId, TargetName, StartTime and StopTime. These keywords are loaded at the ingestion step (Importing Mission Data).

See also: Mission Specific Programs

ISIS3 SPICE Labels

  • The information supplied by spiceinit is placed in the Group=Kernels and Group=Instrument label portion of the ISIS3 image cube.
  • Information on the quality of the kernels is added to keywords within the Kernels Group (InstrumentPointingQuality and InstrumentPositionQuality
  • SPICE computation results can also be attached to the blob portion of the ISIS3 image cube (i.e., parameter ATTACH=TRUE - the current spiceinit default).
  • See also in the ISIS3 Documentation: Label Dictionary

Camera Pointing


Spiceinit will load the location and filename of the camera pointing kernel (CK) in the ISIS3 keyword InstrumentPointing.

Which file that is loaded depends on a couple of things:

First, the StartTime of the image must be found within any CK kernel

Secondly, The user can specify what type of CK kernel

  • CKSMITHED - This is considered camera pointing that has been through a bundle-adjustment and most likely the most accurate; this level of pointing is not often available and might not include the entire collection of mission image data.
  • CKRECON - The default ck kernel for spiceinit. This kernel is the mission actual and is often improved on by NAIF or the mission navigation team.
  • CKPREDICTED - The least desired, but "better than nothing" kernel that is most available during real-time on newly acquired mission data.
  • CKNADIR - Nadir pointing is computed if no CK kernels exist (''Requirements...under construction'')

TIPs:

  • All parameters above can be set to =TRUE and spiceinit will search and load in a hierarchical order from c-smithed first to predicted last. Be aware if processing multiple files and allowing inconsistencies in different ck sources.
  • The InstrumentPointingQuality keyword will be added to the Kernels Group with a value indicating what quality of camera pointing was found and loaded for the input image (InstrumentPointingQuality = Reconstructed or Predicted).

Spacecraft Position


Spiceinit will load the location and filename of the spacecraft pointing kernel (SPK) in the ISIS3 keyword InstrumentPosition.

Which file that is loaded depends on a couple of things:

First, the StartTime of the image must be found within any SPK kernel

Secondly, The user can specify what type of SPK kernel

  • SPKSMITHED - This is considered camera pointing that has been through a bundle-adjustment and most likely the most accurate; this level of pointing is not often available and might not include the entire collection of mission image data.
  • SPKRECON - The default spk kernel for spiceinit. This kernel is the mission actual and is often improved on by NAIF or the mission navigation team.
  • SPKPREDICTED - The least desired, but "better than nothing" kernel that is most available during real-time on newly acquired mission data.

TIPs:

  • All parameters above can be set to =TRUE and spiceinit will search and load in a hierarchical order from c-smithed first to predicted last. Be aware if processing multiple files and allowing inconsistencies in different spk sources.
  • The InstrumentPositionQuality keyword will be added to the Kernels Group with a value indicating what quality of camera pointing was found and loaded for the input image (InstrumentPositionQuality = Reconstructed or Predicted).

Shape Model


Under Construction!!

References & Related Resources


  1. About NAIF
  2. About NAIF SPICE
  3. NAIF Software Toolkit