Table of contents
CSPICE_SCFMT converts encoded spacecraft clock ticks to character clock
format.
Given:
sc the scalar NAIF ID number for the spacecraft whose clock's time
is being decoded.
help, sc
LONG = Scalar
ticks the scalar double precision encoding of a clock time in units of
ticks.
help, ticks
DOUBLE = Scalar
Partition information is not reflected in this value.
An analogy may be drawn between a spacecraft clock and
a standard wall clock. The number of ticks
corresponding to the wall clock string
hh:mm:ss
would be the number of seconds represented by that
time.
For example,
Clock string Number of ticks
------------ ---------------
00:00:10 10
00:01:00 60
00:10:00 600
01:00:00 3600
01:01:00 3660
If `ticks' contains a fractional part the result is the
same as if `ticks' had been rounded to the nearest whole
number.
See the -Examples section below for examples of
actual spacecraft clock conversions.
the call:
cspice_scfmt, sc, ticks, clkstr
returns:
clkstr the scalar spacecraft clock string corresponding to `ticks'.
help, clkstr
STRING = Scalar
Partition information is not included in `clkstr'.
Using Galileo as an example, the full format clock
string is
wwwwwwww:xx:y:z
where z is a mod-8 counter (values 0-7) which
increments approximately once every 8 1/3 ms., y is a
mod-10 counter (values 0-9) which increments once
every time z turns over, i.e., approximately once every
66 2/3 ms., xx is a mod-91 (values 0-90) counter
which increments once every time y turns over, i.e.,
once every 2/3 seconds. wwwwwwww is the Real-Time Image
Count (RIM), which increments once every time xx turns
over, i.e., once every 60 2/3 seconds. The roll-over
expression for the RIM is 16777215, which corresponds
to approximately 32 years.
wwwwwwww, xx, y, and z are referred to interchangeably
as the fields or components of the spacecraft clock.
SCLK components may be separated by any of these five
characters: ' ' ':' ',' '-' '.'
The delimiter used is determined by a kernel pool
variable and can be adjusted by the user.
Some spacecraft clock components have offset, or
starting, values different from zero. For example,
with an offset value of 1, a mod 20 counter would
cycle from 1 to 20 instead of from 0 to 19.
See the SCLK required reading for a detailed
description of the Voyager and Mars Observer clock
formats.
None.
Any numerical results shown for these examples may differ between
platforms as the results depend on the SPICE kernels used as input
and the machine specific arithmetic implementation.
1) The following code example finds partition start and stop
times for the Stardust spacecraft from a spacecraft clock
kernel file. Since those times are always returned in units
of ticks, the program uses cspice_scfmt to print the times in
Stardust clock format.
Use the SCLK kernel below to load the Stardust time
correlation data and spacecraft clock partition information.
sdu_sclkscet_00074.tsc
Example code begins here.
PRO scfmt_ex1
;;
;; Assign the value for the Stardust spacecraft ID.
;;
sc = -29
;;
;; Load the SCLK file.
;;
cspice_furnsh, 'sdu_sclkscet_00074.tsc'
;;
;; Retrieve the arrays for start and stop
;; of the partitions as measures in ticks.
;;
cspice_scpart, sc, pstart, pstop
;;
;; Obtain the dimension of the arrays 'pstart' & 'pstop'.
;; Note: nparts becomes a 1-vector, so use nparts[0] for the
;; dimension value.
;;
nparts = size(pstart, /dim)
;;
;; Loop over each array value.
;;
for i = 0, (nparts[0]-1) do begin
cspice_scfmt, sc, pstart[i], start
cspice_scfmt, sc, pstop[i], stop
print, 'Partition: ', i
print, 'Start : ', start
print, 'Stop : ', stop
print
endfor
;;
;; It's always good form to unload kernels after use,
;; particularly in IDL due to data persistence.
;;
cspice_kclear
END
When this program was executed on a Mac/Intel/IDL8.x/64-bit
platform, the output was:
Partition: 0
Start : 0000000000.000
Stop : 0602741011.080
Partition: 1
Start : 0602741014.217
Stop : 0605660648.173
Partition: 2
Start : 0605660649.000
Stop : 0631375256.224
Partition: 3
Start : 0631375257.000
Stop : 0633545577.218
Partition: 4
Start : 0633545578.000
Stop : 0644853954.043
Partition: 5
Start : 0644853954.000
Stop : 0655316480.089
Partition: 6
Start : 0655316480.000
Stop : 0660405279.066
Partition: 7
Start : 0660405279.000
Stop : 0670256568.229
Partition: 8
Start : 0670256569.000
Stop : 0674564039.091
Partition: 9
Start : 0674564040.000
Stop : 4294537252.255
2) Below are some examples illustrating various input numbers of
ticks and the resulting clock string outputs for the Galileo
spacecraft.
ticks clkstr
---------------- --------------------
-1 Error: Ticks must be a positive number
0 '00000000:00:0:0'
1 '00000000:00:0:1'
1.3 '00000000:00:0:1'
1.5 '00000000:00:0:2'
2 '00000000:00:0:2'
7 '00000000:00:0:7'
8 '00000000:00:1:0'
80 '00000000:01:0:0'
88 '00000000:01:1:0'
7279 '00000000:90:9:7'
7280 '00000001:00:0:0'
1234567890 '00169583:45:6:2'
The following examples are for the Voyager 2 spacecraft.
Note that the third component of the Voyager clock has an
offset value of one.
ticks clkstr
---------------- --------------------
-1 Error: Ticks must be a positive number
0 '00000:00:001'
1 '00000:00:002'
1.3 '00000:00:002'
1.5 '00000:00:003'
2 '00000:00:003'
799 '00000:00:800'
800 '00000:01:001'
47999 '00000:59:800'
48000 '00001:00:001'
3145727999 '65535:59:800'
The routine cspice_sctiks performs the inverse operation to cspice_scfmt,
converting from clock format to number of ticks.
Note the important difference between cspice_scfmt and cspice_scdecd.
cspice_scdecd converts some number of ticks since the spacecraft clock
start time to a character string which includes a partition number.
cspice_scfmt, which is called by cspice_scdecd, does not make use of
partition information.
1) If the data type for the spacecraft is not supported, the
error SPICE(NOTSUPPORTED) is signaled by a routine in the call
tree of this routine.
2) If the value for `ticks' is negative, an error is signaled
by a routine in the call tree of this routine.
3) If the SCLK kernel file does not contain data for the
spacecraft specified by `sc', an error is signaled by a routine
in the call tree of this routine.
4) If any of the input arguments, `sc' or `ticks', is undefined,
an error is signaled by the IDL error handling system.
5) If any of the input arguments, `sc' or `ticks', is not of the
expected type, or it does not have the expected dimensions and
size, an error is signaled by the Icy interface.
6) If the output argument `clkstr' is not a named variable, an
error is signaled by the Icy interface.
None.
None.
ICY.REQ
SCLK.REQ
None.
J. Diaz del Rio (ODC Space)
E.D. Wright (JPL)
-Icy Version 1.0.1, 17-JUN-2021 (JDR)
Edited to header to comply with NAIF standard. Added
reference to required SCLK and created complete example from
existing code fragment using Stardust PDS archived data.
Added -Parameters, -Exceptions, -Files, -Restrictions,
-Literature_References and -Author_and_Institution sections, and
completed -Particulars section.
Removed reference to the routine's corresponding CSPICE header from
-Abstract section.
Added arguments' type and size information in the -I/O section.
-Icy Version 1.0.0, 16-JUN-2003 (EDW)
convert spacecraft_clock ticks to character clock format
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