******************************************************************************** Orientation of the Voyager 1 Scan Platform during the Saturn Encounter ====================================================================== Version 3: Continuous, Uncorrected ISS+UVS SEDR Pointing ======================================================== This is a Type 3 (linear interpolation) C kernel containing pointing information for the Voyager 1 scan platform during the Saturn encounter. Note that the scan platform's coordinate system is defined as coincident with that of the narrow-angle camera. This C kernel describes the pointing relative to the J2000 coordinate frame almost continuously during the encounter. Data Summary ------------ This C kernel was generated using the pointing information encapsulated in two "Supplemental Experiment Data Record" (SEDR) files from the Voyager project: (1) The Imaging Science Subsystem (ISS) SEDR file; (2) The Ultraviolet Spectrometer (UVS) SEDR file. These files were originally generated shortly after the Voyager flyby in Vax binary format. The ISS file was provided by the Multimission Image Processing Laboratory (MIPL) at JPL. The UVS file was provided by Jay Holberg at the University of Arizona's Lunar and Planetary Laboratory. Pedigree -------- Only one correction was applied to the ISS SEDR data. The SEDR file provides pointing information for both the wide- and narrow-angle cameras. These cameras have a small offset, which is recorded in the Voyager Frames kernel. However, it became apparent that the SEDR file was generated using an incorrect value for this offset. The (incorrect) value used in the SEDR file was revealed as a constant offset between the optic axes of wide- and narrow-angle images shuttered simultaneously. By removing this offset, it was possible to determine the orientation of the scan platform in a consistent manner, regardless of whether the SEDR data described a a wide- or a narrow-angle image. Note that this information is preserved in C kernel V1SAT_VERSION1_TYPE1_ISS_SEDR.ck The UVS SEDR shows many incompatibilities with the ISS SEDR at the level of ~ 1 degree. Its pointing information is preserved in the C kernel V1SAT_VERSION2_TYPE3_UVS_SEDR.ck In those cases where the SEDR files disagree, the ISS SEDR data have generally been found to be more accurate. However, the ISS SEDR file only describes the scan platform orientation at the time when images were taken, leaving long intervals of the Voyager encounter with no pointing information. The key advantage of the UVS SEDR file is its continuity, because it records the UVS instrument's orientation every 48 seconds (except for one gap post-encounter). The information from these two SEDR files was merged as follows. (1) At the times of Voyager images, the scan platform orientation derived from the ISS SEDR file was deemed accurate. (2) At each of these moments, a pointing offset in narrow-angle camera coordinates was determined to align the UVS SEDR boresight with the narrow-angle camera's boresight. (3) At intervening times where only UVS pointing information was available, linear interpolation was performed between the times of the nearest, adjacent images. (4) The C kernel was generated using SPICE program MSOPCK. Accuracy -------- Long experience with the ISS SEDR file has revealed its pointing information to be accurate to typically ~ 100 narrow-angle pixels, which is equivalent to ~ 0.05 degrees or ~ 1 milliradian. It is reasonable to assume that this C kernel has comparable accuracy, except perhaps during long periods of time during which no images were taken. However, it is not possible to test this assumption. Note that a "C-smithed" version of this C kernel is now available and is likely to have finer accuracy. See file V1SAT_VERSION5_TYPE3_MERGED_CSMITHED.ck Contact Information ------------------- Mark R. Showalter Manager, PDS Rings Node SETI Institute mshowalter@seti.org ******************************************************************************** MSOPCK SETUP FILE: V1SAT_VERSION3_TYPE3_MERGED_SEDR.ker ******************************************************************************** \begindata INTERNAL_FILE_NAME = 'V1SAT_VERSION3_TYPE3_MERGED_SEDR.ck' COMMENTS_FILE_NAME = 'V1SAT_VERSION3_TYPE3_MERGED_SEDR_comments.txt' LSK_FILE_NAME = 'NAIF0007.tls' SCLK_FILE_NAME = 'VG100008.tsc' FRAMES_FILE_NAME = 'VG1_V02.tf' CK_TYPE = 3 INSTRUMENT_ID = -31100 REFERENCE_FRAME_NAME = 'J2000' ANGULAR_RATE_PRESENT = 'NO' ANGULAR_RATE_PRESENT = 'MAKE UP/NO AVERAGING' DOWN_SAMPLE_TOLERANCE = 0. MAXIMUM_VALID_INTERVAL = 2000 INPUT_DATA_TYPE = 'MATRICES' INPUT_TIME_TYPE = 'SCLK' PRODUCER_ID = 'Mark R. Showalter/PDS Rings Node' \begintext ******************************************************************************** RUN-TIME OBTAINED META INFORMATION: ******************************************************************************** PRODUCT_CREATION_TIME = 2007-01-02T22:17:03 START_TIME = 1980-08-22T23:10:10.455 STOP_TIME = 1980-12-16T02:08:35.137 ******************************************************************************** INTERPOLATION INTERVALS IN THE FILE SEGMENTS: ******************************************************************************** SEG.SUMMARY: ID -31100, COVERG: 1980-08-22T23:10:10.455 1980-10-17T13:10:58.781 -------------------------------------------------------------------------------- 1980-08-22T23:10:10.455 1980-10-17T13:10:58.781 SEG.SUMMARY: ID -31100, COVERG: 1980-10-17T13:10:58.781 1980-12-14T02:13:23.137 -------------------------------------------------------------------------------- 1980-10-17T13:10:58.781 1980-11-20T23:59:47.066 1980-11-21T05:31:47.066 1980-11-21T19:20:35.066 1980-11-24T18:10:59.066 1980-11-24T22:52:35.066 1980-11-25T00:00:35.066 1980-12-14T02:13:23.137 SEG.SUMMARY: ID -31100, COVERG: 1980-12-14T02:13:23.137 1980-12-16T02:08:35.137 -------------------------------------------------------------------------------- 1980-12-14T02:13:23.137 1980-12-16T02:08:35.137 ********************************************************************************