KPL/SCLK SMART-1 SCLK File =========================================================================== This file is a SPICE spacecraft clock (SCLK) kernel containing information required for SMART-1 spacecraft on-board clock to UTC conversion. Production/History of this SCLK file -------------------------------------------------------- This file was generated using data from the SMART-1 time correlation data spreadsheet (Timecorrelation.xls) as follows: - the clock resets and intervals between them were identified from the spreadsheet data - for each interval between resets the difference of the OBT from the spreadsheet OBT-SCET correlation pairs and an ``ideal'' OBT computed for the same SCETs but assuming an ``ideal'' clock running at the same rate as UTC was computed and plotted - based on the analysis of the plots a single clock rate was picked for each of the intervals except for the interval following the last clock reset (or more specifically the switch from the side A to the side B on 2004-169T12:00); that last interval had to be broken into three intervals -- 2004-169T12:00 to 2005-045T00:00, 2005-045T00:00 to 2005-048T12:00 and 2005-048T12:00 to infinity -- because the plots indicated that on 2005-048T12:00 the trend has changed back to what it was on side A. - the clock correlation reference points and rates determined as the result of this analysis were formatted as a SCLKvSCET file, which was converted to the this SCLK file using the MAKCLK utility program. A comparison of the correlation provided by this SCLK kernel with the OBT-SCET time points from the spreadsheet was performed to validate this file. The comparison showed that this SCLK kernel matches the spreadsheet data during the intervals listed below to better the specified deltas: Begin time, SCET End time, SCET DELTA, sec (1) ----------------- ----------------- ---------- 2003-270T23:56:27 2004-169T12:00:03 0.3 2004-169T12:00:03 2004-316T08:00:00 1.0 (2) 2004-316T08:00:00 2005-045T00:00:03 0.02 2005-045T00:00:03 2005-048T12:00:00 0.7 (3) 2005-048T12:00:00 2006-246T05:42:20 0.02 (1) The outlier points from the spreadsheet indicating physically impossible clock deviations were excluded from validation. (2) The spreadsheet data for the first 150 days after switch to side seem much noisier than for the other period. (3) Because the actual time at which the trend switched back to that of the side A is not known, the delta for this artificially introduced interval is considered to be the maximum difference between the two trends at that time. An additional validation was performed by comparing the correlation provided by this SCLK kernel to the raw time packets for a number of days in January 2006. For all checked packet sets the difference was under 0.02 seconds shown for this time period in the table above. Usage -------------------------------------------------------- This file must be loaded into the user's program by a call to the FURNSH subroutine CALL FURNSH( 'this_file_name' ) in order to use the SPICELIB SCLK family of subroutines to convert SM1 spacecraft on-board clock to ET and vice versa. SCLK Format -------------------------------------------------------- The on-board clock, the conversion for which is provided by this SCLK file, consists of two fields: SSSSSSSSSS:FFFFF where: SSSSSSSSSS -- count of on-board seconds FFFFF -- count of fractions of a second with one fraction being 1/65536 of a second SCLKvSCET Data Used as Input to MAKCLK -------------------------------------------------------- The SCLKvSET file that was converted to this SCLK kernels using the MAKCLK program contained the following time correlation data: *____SCLK0________ ________SCET0________ _DUT__ __SCLKRATE__ 9.13107 2003-270T23:56:27.043 64.184 0.999999961384 1.12452 2003-271T23:13:20.191 64.184 0.999999961384 8.60293 2003-273T07:12:22.290 64.184 0.999999961384 108.60948 2003-274T13:58:14.511 64.184 0.999999961384 252.24248 2003-287T07:58:31.854 64.184 0.999999961384 9.01835 2003-296T08:54:03.585 64.184 0.999999961384 1.03604 2004-056T13:20:25.026 64.184 0.999999974116 9758320.19661 2004-169T12:00:03.475 64.184 0.999999916735 30623922.07209 2005-045T00:00:03.547 64.184 1.000002444048 30926318.19661 2005-048T12:00:00.476 64.184 0.999999979441 References -------------------------------------------------------- 1. SCLK Required Reading Document 2. SMART-1 Time Correlation Spreadsheet (Timecorrelation.xls) 3. MAKCLK User' Guide Inquiries -------------------------------------------------------- If you have any questions regarding this file contact Joe Zender 0031 (0)71 565 4919 Joe.Zender@esa.int or Jose Luis Vazquez-Garcia 0034 91 8131 310 jlvazquez@sciops.esa.int or Boris V. Semenov (818) 354-8136 Boris.Semenov@jpl.nasa.gov Kernel DATA -------------------------------------------------------- \begindata SCLK_KERNEL_ID = ( @2006-10-31/15:42:59.00 ) SCLK_DATA_TYPE_238 = ( 1 ) SCLK01_TIME_SYSTEM_238 = ( 2 ) SCLK01_N_FIELDS_238 = ( 2 ) SCLK01_MODULI_238 = ( 4294967296 65536 ) SCLK01_OFFSETS_238 = ( 0 0 ) SCLK01_OUTPUT_DELIM_238 = ( 1 ) SCLK_PARTITION_START_238 = ( 6.0293100000000E+05 7.7988000000000E+04 5.8458100000000E+05 7.1388360000000E+06 1.6539320000000E+07 5.9165900000000E+05 6.9140000000000E+04 6.3952127918100E+11 ) SCLK_PARTITION_END_238 = ( 5.4933816100000E+09 7.5460308790000E+09 7.2588424170000E+09 7.2202735815000E+10 5.1195683219000E+10 7.0883677874900E+11 6.3952517572700E+11 2.8147497671065E+14 ) SCLK01_COEFFICIENTS_238 = ( 0.0000000000000E+00 1.1797905122700E+08 9.9999996146361E-01 5.4927786790000E+09 1.1806286437500E+08 9.9999996144456E-01 1.3038731570000E+10 1.1817800647400E+08 9.9999996134844E-01 2.0296989406000E+10 1.1828875869500E+08 9.9999996138058E-01 9.2492586385000E+10 1.1939037603800E+08 9.9999996138694E-01 1.4367173028400E+11 1.2017130776900E+08 9.9999996138371E-01 8.5250791737400E+11 1.3098728921000E+08 9.9999997411620E-01 1.4920330239610E+12 1.4074566765900E+08 9.9999991670513E-01 2.8594811041810E+12 1.6161126773100E+08 1.0000024438059E+00 2.8792989408890E+12 1.6191366466000E+08 9.9999997944100E-01 ) \begintext