PDS_VERSION_ID = PDS3 RECORD_TYPE = STREAM OBJECT = TEXT INTERCHANGE_FORMAT = ASCII PUBLICATION_DATE = 2008-11-12 NOTE = "Viking Orbiter C-Kernel Information" END_OBJECT = TEXT END General Information About SPICE C-Kernels ========================================= In the SPICE system, pointing data for an instrument platform, or for a specific instrument, are stored C-kernels. The pointing of a platform or an instrument is often expressed in terms of a transformation matrix from some standard inertial reference frame to a instrument-fixed frame. In the past, the instrument was often a camera, and the transformation was thus dubbed the ``C-matrix''; hence the choice of C as the name for the pointing kernel. The data contained in C-kernel files can be accessed and manipulated using the SPICE Toolkit APIs, calls to which can be integrated into user application programs. The information regarding how to obtain the SPICE system toolkit for a number of languages and computer platforms is located in the ``/software'' subdirectory of the main directory of this data set. To use C-kernels, a Spacecraft Clock Kernel (SCLK) is required. Also, for C-Kernels containing orientation of a project-defined frames, a Frame Definitions File is required. Refer to the ``ck.req'' document provided with the toolkit to get more information on how to access C-kernel data. Viking Orbiter C-kernels Contained in This Data Set =================================================== The following Viking Orbiter C-kernels are provided in this data set (only name portion of the file name is shown on the right; the extension of all file names is ``.bc''): -- Viking Orbiter Scan Platform Orientation CK Files: vo1_sedr VO1 scan platform orientation CK files containing vo1_sedr_ck2 a combination of data from SEDR (Supplemental Experiment Data Record) files generated by the Viking Project and GEM (Viking Image Geometry) files generated by USGS, Flagstaff. vo2_sedr VO2 scan platform orientation CK files containing vo2_sedr_ck2 a combination of data from SEDR (Supplemental Experiment Data Record) files generated by the Viking Project and GEM (Viking Image Geometry) files generated by USGS, Flagstaff. vo1_rmb VO1 scan platform orientation CK files containing vo1_rmb_ck2 orientation data reconstructed during cartographic image registration by R.M. Batson, USGS. Some of Batson's data were not included in this file because of time tag problems. vo2_rmb VO2 scan platform orientation CK files containing vo2_rmb_ck2 orientation data reconstructed during cartographic image registration by R.M. Batson, USGS. Some of Batson's data were not included in this file because of time tag problems. vo1_davs VO1 scan platform orientation CK files containing vo1_davs_ck2 orientation data reconstructed during cartographic image registration by M. Davies, Rand Corporation. vo2_davs VO2 scan platform orientation CK files containing vo2_davs_ck2 orientation data reconstructed during cartographic image registration by M. Davies, Rand Corporation. vo1_maut VO1 scan platform orientation CK files containing vo1_maut_ck2 orientation data reconstructed during automated cartographic image registration by M. Caplinger, Malin Space Science Systems (MSSS). vo2_maut VO2 scan platform orientation CK files containing vo2_maut_ck2 orientation data reconstructed during automated cartographic image registration by M. Caplinger, Malin Space Science Systems (MSSS). vo1_mman VO1 scan platform orientation CK files containing vo1_mman_ck2 orientation data reconstructed during manual cartographic image registration by M. Caplinger, Malin Space Science Systems (MSSS). vo2_mman VO2 scan platform orientation CK files containing vo2_mman_ck2 orientation data reconstructed during manual cartographic image registration by M. Caplinger, Malin Space Science Systems (MSSS). vo1_swu VO1 scan platform orientation CK files containing vo1_swu_ck2 orientation data reconstructed during cartographic image registration by S. Wu, USGS. vo2_swu VO2 scan platform orientation CK files containing vo2_swu_ck2 orientation data reconstructed during cartographic image registration by S. Wu, USGS. Both files in each pair (e.g. ``vo2_swu.bc'' and ``vo2_swu_ck2.bc'') contain the same orientation data. The difference between the files is that the file without ``_ck2'' in the name is the original Type 1 CK file included in the first archive release while the file with ``_ck2'' in the name is a more usable Type 2 CK file added to the archive in the second release. The Type 2 CK files were created when it became apparent that the Type 1 CK files containing discrete data were virtually unusable with the high level SPICE interfaces relying on the Frames Subsystem due to round off in time conversions. In the Type 2 CK files each discrete pointing instance was ``expanded'' into a 2 second window, guaranteeing that time round off would no longer have effect when the CK is used with the high level SPICE interfaces. For this reason, the ``_ck2'' CK files supersede the original CK files and should be used in all applications requiring VO camera pointing knowledge. All C-Kernels included in this data set contain actual orientation data. Kernel File Details =================== The most detailed description of the data in a binary CK file is provided in metadata included inside the comment area of the file. This information can be viewed using utility programs COMMNT and SPACIT included into the NAIF Toolkit. Of the CK files provided in this directory the files ``vo1_sedr*.bc'' and ``vo2_sedr*.bc'' contain the most complete, but probably the least accurate, set of orientation information. All CK files in this directory were generated and can be read using the fictitious SPICE spacecraft clock coefficients (SCLK) files ``vo1_fict.tsc'' and ``vo2_fict.tsc''. These SCLK files do NOT represent real Viking Orbiter clocks but rather just count milliseconds since some initial epoch. Each of the files in this directory contains the orientation of the instrument platform of the corresponding VO spacecraft relative to the inertial reference frame B1950. This orientation was calculated from source data representing camera orientation relative B1950 by excluding the transformation from a platform frame to a camera frame. This transformation was defined for each camera by a set of camera mounting alignment angles. The values of these angles were taken from SEDR data set and are stored in VO IK files ``vo1_visa.ti'', ``vo1_visb.ti'', ``vo2_visa.ti'' and ``vo2_visb.ti''. The platform orientations data sets calculated from camera A and camera B orientation were merged together and stored in a single file for each spacecraft. Note that the orientation correction resulting from the cartographic image registration was applied to orientation on each camera independently and it's quite possible that the constraint of constant relative alignment of the cameras was not taken into account during this process. That could cause inconsistency between orientation points on one orbit submitted by two cameras when the data is merged together for a platform on some orbits. Contact Information =================== Regarding VO project specific information provided in this data set and for general information about SPICE system: Charles H. Acton, Jr, (818)-354-3869, Chuck.Acton@jpl.nasa.gov, or Boris Semenov (818)-354-8136 Boris.Semenov@jpl.nasa.gov address: Navigation and Ancillary Information Facility (NAIF) Jet Propulsion Laboratory MS 301-125L 4800 Oak Grove Drive Pasadena CA 91109 USA