SCFMT ( Convert SCLK "ticks" to character clock format)
SUBROUTINE SCFMT ( SC, TICKS, CLKSTR )
Convert encoded spacecraft clock ticks to character clock format.
SCLK
CONVERSION
TIME
INTEGER SC
DOUBLE PRECISION TICKS
CHARACTER*(*) CLKSTR
Variable I/O Description
-------- --- --------------------------------------------------
SC I NAIF spacecraft identification code.
TICKS I Encoded representation of a spacecraft clock count.
CLKSTR O Character representation of a clock count.
SC is the NAIF ID number for the spacecraft whose clock's
time is being decoded.
TICKS is the double precision encoding of a clock time in
units of ticks. 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.
CLKSTR is the spacecraft clock character string
corresponding to TICKS. 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.
1) If the data type for the spacecraft is not supported
then the error SPICE(NOTSUPPORTED) is signalled.
2) If the value for TICKS is negative, the error is diagnosed
by routines called by this routine.
3) If the SCLK kernel file does not contain data for the
spacecraft specified by SC, then the error is diagnosed
by routines called by this routine.
4) If the declared length of SCLKCH is not large enough to
contain the output clock string the error
is diagnosed by a routine called by this routine.
None.
This routine determines which data type the spacecraft clock
belongs to and then calls FMTnn, where nn corresponds to the
data type code. FMTnn then handles the actual conversion from
ticks to clock string format.
The routine SCTIKS performs the inverse operation to SCFMT,
converting from clock format to number of ticks.
Note the important difference between SCFMT and SCDECD. SCDECD
converts some number of ticks since the spacecraft clock start
time to a character string which includes a partition number.
SCFMT, which is called by SCDECD, does not make use of partition
information.
The following program fragment finds partition start and stop
times for the Galileo spacecraft from a spacecraft clock partition
kernel file, called SCLK.KER. Since those times are always
returned in units of ticks, the program uses SCFMT to print the
times in Galileo clock format.
CHARACTER*(30) START
CHARACTER*(30) STOP
SC = -77
CALL FURNSH ( 'SCLK.KER' )
CALL SCPART ( SC, NPARTS, PSTART, PSTOP )
DO I = 1, NPARTS
CALL SCFMT ( SC, PSTART( I ), START )
CALL SCFMT ( SC, PSTOP ( I ), STOP )
WRITE (*,*)
WRITE (*,*) 'Partition ', I, ':'
WRITE (*,*) 'Start = ', START
WRITE (*,*) 'Stop = ', STOP
END DO
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 '0:00:0:0'
1 '0:00:0:1'
1.3 '0:00:0:1'
1.5 '0:00:0:2'
2 '0:00:0:2'
7 '0:00:0:7'
8 '0:00:1:0'
80 '0:01:0:0'
88 '0:01:1:0'
7279 '0:90:9:7'
7280 '1:00:0:0'
1234567890 '169583:45:6:2'
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'
None.
None.
J.M. Lynch (JPL)
R.E. Thurman (JPL)
SPICELIB Version 1.0.2, 22-AUG-2006 (EDW)
Replaced references to LDPOOL with references
to FURNSH.
SPICELIB Version 1.0.1, 17-APR-1992 (JML) (WLT)
The exceptions section was updated to state that an error
is signalled if SCLKCH is not declared big enough to
contain the output spacecraft clock string.
The wording to exception number three was changed.
Miscellaneous minor updates to the header were performed.
Comment section for permuted index source lines was added
following the header.
SPICELIB Version 1.0.0, 06-SEP-1990 (JML) (RET)
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