KPL/SCLK Mariner 9 SCLK File =========================================================================== This file is a SPICE spacecraft clock (SCLK) kernel containing information required for the Mariner 9 spacecraft on-board clock (Data Acquisition System -- DAS -- clock) to Ephemeris Time (ET) conversion. Version and Date -------------------------------------------------------- Version 1.0 -- September 23, 1999 -- Boris Semenov, NAIF/JPL Initial release. Production/History of this SCLK file -------------------------------------------------------- This file is solely based on the correlation between GMT and DAS times extracted from Mariner 9 Camera SEDR database. Since no information regarding accuracy of the original correlation was available at the time when this file was created, it was assumed that original DAS time conversion to UTC was correct. The DAS-ET time correlation information stored in this file was derived using the procedure described below. An ET time corresponding to each DAS time was computed from SEDR GMT. The actual SEDR DAS time was compared with the ideal DAS time (DAS counter running at constant 1.2 seconds per DAS tick rate) and plotted as a function of ET seconds since the first ET time registered in the SEDR. This plot shows that though the DAS clock seems to have been running at a fairly constant rate, about 1.19999605 seconds per tick, it was reset multiple times during SEDR time span. All resets seemed to have happened between series of times corresponding to individual orbit data collection sessions and, therefore, the actual reset time couldn't be determined from that function. To make sure that mapping contained in the SCLK file would not provide bogus results for the intervals around resets, these intervals were excluded from consideration. Then a linear function was fit to each of the data intervals between resets (between the first point after previous reset and the last point before the next reset) and the function and valid conversion interval information was stored in this file. The DAS clock mapping contained in this file is consistent with respect to the original SEDR time mapping to about 0.1 second for most of the mission and is better that 0.05 sec for the main mission (1971-320 ... 1972-076) where SEDR time correlation data was much more dense and consistent. Valid Conversion Intervals -------------------------------------------------------- This SCLK file will provide time conversion between DAS and ET time for the following DAS ranges ONLY: START DAS STOP DAS ----------- ---------- 1491192 1657861 1672706 1749705 1779190 4940814 4986238 5023162 5058058 10494473 10563119 10721003 11442909 11482143 11619965 11658919 11796786 11836125 11973784 12013123 12150187 12188931 12326056 12364450 12499155 12538704 12685638 12910057 12985387 13165390 13313240 13360384 13460068 13511832 Those same intervals but given in terms of UTC time: START UTC STOP UTC ---------------------- ---------------------- 1971-315//08:33:19.750 1971-317//16:06:41.895 1971-318//12:45:53.665 1971-319//14:25:52.162 1971-320//14:30:38.306 1971-364//12:22:54.543 1971-365//11:41:26.187 1971-365//23:59:54.841 1972-001//11:37:49.774 1972-076//23:45:46.314 1972-081//17:48:58.147 1972-083//22:26:38.326 1972-160//21:09:24.963 1972-161//10:14:05.609 1972-163//21:12:33.299 1972-164//10:11:37.946 1972-167//21:07:59.234 1972-168//10:14:45.879 1972-170//21:06:57.642 1972-171//10:13:44.287 1972-174//21:10:01.974 1972-175//10:04:54.622 1972-177//21:10:25.441 1972-178//09:58:18.090 1972-181//20:50:25.092 1972-182//10:01:23.737 1972-189//08:59:04.227 1972-192//11:47:26.145 1972-216//20:25:02.690 1972-219//08:25:05.583 1972-286//07:31:22.127 1972-286//23:14:14.742 1972-290//07:37:56.410 1972-291//00:53:13.007 For any DAS or UTC outside the intervals listed above the SPICE System will not support time conversion and SCLK routines will signal an error stating that the input SCLK or ET time was outside of the ranges supported by this SCLK file. An important exception exists for the following exact DAS values, for which an error will not be signaled but conversion will be incorrect and will result in completely bogus ET value: DAS values that yield incorrect conversion to ET -------------------------- 1657862 1749706 4940815 5023163 10494474 10721004 11482144 11658920 11836126 12013124 12188932 12364451 12538705 12910058 13165391 13360385 13511833 The reason for incorrect conversion for these times, which are ends of the SCLK partitions defined by this file, is the fact that non-continuous Mariner 9 DAS time mapping was "packaged" into the SCLK type 1 structure that by definition represents continuous clocks. In this SCLK Type 1 concept the last tick of partition "i" corresponds to exact same time moment as the first tick of partition "i+1", which is not true for DAS time mapping in which these points are disjoint. Usage -------------------------------------------------------- This file must be loaded into the user's program by a call to the LDPOOL subroutine CALL LDPOOL( 'this_file_name' ) in order to use the SPICELIB SCLK family of subroutines to convert Mariner 9 DAS clock to ET and vice versa. References -------------------------------------------------------- 1. SCLK Required Reading Document Inquiries -------------------------------------------------------- If you have any questions regarding this file contact NAIF at JPL Charles H. Acton, Jr., NAIF Manager (818) 354-3869 Chuck.Acton@jpl.nasa.gov Boris V. Semenov, NAIF Team Member (818) 354-8136 Boris.Semenov@jpl.nasa.gov Kernel DATA -------------------------------------------------------- \begindata SCLK_KERNEL_ID = ( @1999-09-22/12:15:00 ) SCLK_DATA_TYPE_9 = ( 1 ) SCLK01_TIME_SYSTEM_9 = ( 1 ) SCLK01_N_FIELDS_9 = ( 1 ) SCLK01_MODULI_9 = ( 20000000 ) SCLK01_OFFSETS_9 = ( 0 ) SCLK01_OUTPUT_DELIM_9 = ( 1 ) SCLK_PARTITION_START_9 = ( 1491192, 1672706, 1779190, 4986238, 5058058, 10563119, 11442909, 11619965, 11796786, 11973784, 12150187, 12326056, 12499155, 12685638, 12985387, 13313240, 13460068 ) SCLK_PARTITION_END_9 = ( 1657862, 1749706, 4940815, 5023163, 10494474, 10721004, 11482144, 11658920, 11836126, 12013124, 12188932, 12364451, 12538705, 12910058, 13165391, 13360385, 13511833 ) SCLK01_COEFFICIENTS_9 = ( 0, -888031559.067, 1.19999607, 166670, -887757205.152, 1.19999607, 243670, -887578120.511, 1.199996027, 3405295, -883700272.629, 1.19999607, 3442220, -883614088.042, 1.199996053, 8878636, -876679819.667, 1.19999607, 9036521, -869842192.852, 1.19999607, 9075756, -869582804.516, 1.19999607, 9114711, -869237478.581, 1.19999607, 9154051, -868978340.173, 1.19999607, 9193391, -868632555.841, 1.19999607, 9232136, -868373332.374, 1.19999607, 9270531, -868028932.723, 1.19999607, 9310081, -867380412.589, 1.19999607, 9534501, -865006454.126, 1.19999607, 9714505, -859004874.690, 1.19999607, 9761650, -858658880.407, 1.19999607 ) \begintext