Table of contents
CSPICE_SCE2T converts ephemeris seconds past J2000 (ET) to
discrete, encoded spacecraft clock ("ticks").
Given:
sc a NAIF integer code for a spacecraft whose encoded SCLK value at
the epoch specified by `et' is desired.
help, sc
LONG = Scalar
et an epoch, specified as ephemeris seconds past J2000.
help, et
DOUBLE = Scalar
the call:
cspice_sce2t, sc, et, sclkdp
returns:
sclkdp an encoded integral spacecraft clock value.
help, sclkdp
DOUBLE = Scalar
`sclkdp' is an encoded representation of the total count of
spacecraft clock ticks measured from the time the spacecraft
clock started to the epoch `et': partition information IS
reflected in the encoded value. `sclkdp' is rounded to the
nearest integral double precision number.
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) Convert a UTC time to its corresponding CASSINI encoded
spacecraft clock ("ticks") value.
Use the meta-kernel shown below to load the required SPICE
kernels.
KPL/MK
File name: sce2t_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 sce2t_ex1
;;
;; Load the kernels for time conversion.
;;
cspice_furnsh, 'sce2t_ex1.tm'
;;
;; Assign values for the spacecraft ID (CASSINI).
;;
SC = -82
event_time = '2004 JUN 11 11:00:37.57200'
;;
;; Convert the time string to ephemeris time.
;;
cspice_str2et, event_time, et
;;
;; Convert the ephemeris time to the encoded s-clock
;; format.
;;
cspice_sce2t, sc, et, sclkdp
print, ' UTC Time Encoded SCLK'
print, '-------------------------- -------------------'
print, FORMAT='(A,2X,F19.6)', event_time, sclkdp
;;
;; 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:
UTC Time Encoded SCLK
-------------------------- -------------------
2004 JUN 11 11:00:37.57200 197483593295.000000
This function outputs discrete, encoded SCLK values. Since
continuous SCLK values are generally more useful, the newer
function cspice_sce2c (ET to continuous ticks) should normally be used
in place of this one. However, the functionality of this
routine is needed for converting ET to SCLK strings.
This function outputs encoded SCLK values. 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. Also, working with encoded SCLK reduces the
overhead of repeated conversion of character strings to integers
or double precision numbers.
To convert ET to a string representation of an SCLK value, use
the Icy function cspice_sce2s.
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 `sclkdp' 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
`sclkdp' 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 `sclkdp' will not be modified.
4) If the input `et' value is not representable as an encoded
spacecraft clock value for the spacecraft clock identified by
`sc', an error is signaled by a routine in the call tree of this
routine. The output argument `sclkdp' will not be modified.
5) If any of the input arguments, `sc' or `et', is undefined, an
error is signaled by the IDL error handling system.
6) If any of the input arguments, `sc' or `et', 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 `sclkdp' 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, 01-JUN-2021 (JDR)
Edited the header 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".
Removed note on deprecation of this function: cspice_sce2c IS
preferred over this routine, but this routine is not deprecated.
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)
ephemeris time to spacecraft_clock ticks
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