Table of contents
CSPICE_SCT2E converts encoded spacecraft clock (`ticks')
to ephemeris seconds past J2000 (ET).
Given:
sc the scalar NAIF integer code for a spacecraft, one of whose
encoded clock values is represented by `sclkdp'.
help, sc
LONG = Scalar
sclkdp a double precision scalar encoded spacecraft clock value.
help, sclkdp
DOUBLE = Scalar
the call:
cspice_sct2e, sc, sclkdp, et
returns:
et the double precision epoch, specified as ephemeris seconds past
J2000, that corresponds to `sclkdp'.
help, et
DOUBLE = Scalar
None.
Any numerical results shown for this example may differ between
platforms as the results depend on the SPICE kernels used as input
and the machine specific arithmetic implementation.
1) Obtain from a CASSINI encoded spacecraft clock ("ticks") value
the corresponding ephemeris epoch and UTC time.
Use the meta-kernel shown below to load the required SPICE
kernels.
KPL/MK
File name: sct2e_ex1.tm
This meta-kernel is intended to support operation of SPICE
example programs. The kernels shown here should not be
assumed to contain adequate or correct versions of data
required by SPICE-based user applications.
In order for an application to use this meta-kernel, the
kernels referenced here must be present in the user's
current working directory.
The names and contents of the kernels referenced
by this meta-kernel are as follows:
File name Contents
--------- --------
naif0012.tls Leapseconds
cas00071.tsc CASSINI SCLK
\begindata
KERNELS_TO_LOAD = ( 'naif0012.tls',
'cas00071.tsc' )
\begintext
End of meta-kernel
Example code begins here.
PRO sct2e_ex1
;;
;; Load the leapseconds kernel for time conversion.
;;
cspice_furnsh, 'sct2e_ex1.tm'
;;
;; Assign values for the spacecraft ID (CASSINI).
;;
SC = -82
sclkdp = 197483593295.0d
;;
;; Convert 'sclkdp' for spacecraft 'SC' to ephemeris time.
;;
cspice_sct2e, SC, sclkdp, et
;;
;; Convert the ephemeris time to a UTC calendar string.
;;
cspice_et2utc, et, 'C', 3, utc
print, ' Encoded SCLK ET UTC Time'
print, '---------------- ---------------- ------------------------'
print, FORMAT='(F16.3,2X,F16.6,2X,A)', sclkdp, et, utc
;;
;; 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:
Encoded SCLK ET UTC Time
---------------- ---------------- ------------------------
197483593295.000 140223701.758428 2004 JUN 11 11:00:37.574
This routine operates on encoded SCLK values. These values
are obtained by calling the Icy routine cspice_scencd or other
SCLK conversion routines. The advantage of encoded SCLK, as
opposed to character string representations of SCLK is that
encoded SCLK values are easy to perform arithmetic operations on.
Additionally, working with encoded SCLK reduces the overhead of
repeated conversion of character strings to integers or double
precision numbers.
To convert a string representation of an SCLK value to ET, use
the Icy routine cspice_scs2e.
1) If an SCLK kernel has not been loaded, does not contain all of
the required data, or contains invalid data, an error is
signaled by a routine in the call tree of this routine. The
output argument `et' will not be modified. This routine assumes
that that an SCLK kernel appropriate to the spacecraft clock
identified by the input argument `sc' has been loaded.
2) If a leapseconds kernel is required for conversion between
SCLK and `et' but is not loaded, an error is signaled by a
routine in the call tree of this routine. The output argument
`et' will not be modified. When using SCLK kernels that map SCLK
to a time system other than `et' (also called barycentric
dynamical time---`TDB'), it is necessary to have a leapseconds
kernel loaded at the time this routine is called.
The time system that an SCLK kernel maps SCLK to is indicated
by the variable SCLK_TIME_SYSTEM_nn in the kernel, where nn
is the negative of the NAIF integer code for the spacecraft.
The time system used in a kernel is TDB if and only if the
variable is assigned the value 1.
3) If the clock type for the spacecraft clock identified by `sc' is
not supported by this routine, the error SPICE(NOTSUPPORTED)
is signaled by a routine in the call tree of this routine. The
output argument `et' will not be modified.
4) If the input argument `sclkdp' is invalid, an error is signaled
by a routine in the call tree of this routine. The output
argument `et' will not be modified.
5) If any of the input arguments, `sc' or `sclkdp', is undefined,
an error is signaled by the IDL error handling system.
6) If any of the input arguments, `sc' or `sclkdp', is not of the
expected type, or it does not have the expected dimensions and
size, an error is signaled by the Icy interface.
7) If the output argument `et' is not a named variable, an error
is signaled by the Icy interface.
None.
1) An SCLK kernel appropriate to the spacecraft clock identified
by `sc' must be loaded at the time this routine is called.
2) If the SCLK kernel used with this routine does not map SCLK
directly to barycentric dynamical time, a leapseconds kernel
must be loaded at the time this routine is called.
ICY.REQ
SCLK.REQ
None.
J. Diaz del Rio (ODC Space)
E.D. Wright (JPL)
-Icy Version 1.0.1, 13-AUG-2021 (JDR)
Edited the -Examples section to comply with NAIF standard. Added
example's problem statement and meta-kernel with CASSINI PDS
archived data. Reformatted example's output and changed calls
to "cspice_unload" by "cspice_kclear".
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)
spacecraft_clock ticks to ephemeris time
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