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