CSPICE_DELTET returns value of Delta ET (ETUTC)
for an input epoch.
For important details concerning this module's function, please refer to
the CSPICE routine deltet_c.
Given:
epoch the double precision scalar or Nvector of
epochs at which "delta ET" is to be computed.
'epoch' may be either UTC or ephemeris seconds
past J2000, as specified by 'eptype'.
eptype the scalar string indicating the type of input
epoch. It may be either of the following:
"UTC" UTC seconds past J2000 UTC.
"ET" Ephemeris seconds past J2000 TDB,
also known as barycentric
dynamical time (TDB).
the call:
cspice_deltet, epoch, eptype, delta
returns:
delta the double precision scalar or Nvector
values of
"delta ET" = ET  UTC
at the input 'epoch'. This is added to UTC to
give ET, or subtracted from ET to give UTC.
'delta' return with the same measure of
vectorization (N) as 'epoch'.
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.
;;
;; Load a leapsecond file.
;;
cspice_furnsh, 'standard.tm
;;
;; Define times of interest and the array size
;; parameter.
;;
SIZE = 2004  1997 +1
UTC_1997 = 'Jan 1 1997'
UTC_2004 = 'Jan 1 2004'
;;
;; Convert the UTC time strings to ET.
;;
cspice_str2et, UTC_1997, et_1997
cspice_str2et, UTC_2004, et_2004
;;
;; Calculate the ETUTC delta at Jan 1 1997
;; and Jan 1 2004.
;;
cspice_deltet, et_1997, 'ET', delt_1997
cspice_deltet, et_2004, 'ET', delt_2004
print, 'Scalar:'
print, 'Delta 1997: ', delt_1997
print, 'Delta 2004: ', delt_2004
;;
;; Given an array of 'SIZE' ephemeris times
;; starting from value 'et_1997' with graduations
;; of the number of seconds per Julian year, return
;; the ETUTC delta value for each time.
;;
et = dindgen(SIZE)*cspice_jyear() + et_1997
cspice_deltet, et, 'ET', delt
;;
;; Convert 'et' to 'utc'.
;;
cspice_et2utc, et, 'C', 3, utc
print, 'Vector:'
for i=0, (SIZE1) do begin
print, utc[i], ', delta ', delt[i]
endfor
;;
;; It's always good form to unload kernels after use,
;; particularly in IDL due to data persistence.
;;
cspice_kclear
IDL outputs:
Scalar:
Delta 1997: 62.183935
Delta 2004: 64.183912
Vector:
1997 JAN 01 00:00:00.000, delta 62.183935
1998 JAN 01 05:59:59.000, delta 63.183935
1999 JAN 01 11:59:58.000, delta 64.183935
2000 JAN 01 17:59:58.000, delta 64.183935
2000 DEC 31 23:59:58.000, delta 64.183934
2002 JAN 01 05:59:58.000, delta 64.183934
2003 JAN 01 11:59:58.000, delta 64.183934
2004 JAN 01 17:59:58.000, delta 64.183933
None.
ICY.REQ
TIME.REQ
Icy Version 1.0.2, 29SEP2007, EDW (JPL)
Replaced the comment fragment in the I/O section
"return with the same order"
with
"return with the same measure of vectorization"
Replaced cspice_unload call in example section with
cspice_kclear.
Icy Version 1.0.1, 12JUN2006, EDW (JPL)
Added the output corresponding to the example code.
Corrected Version ID for the 20SEP2003 notation.
Icy Version 1.0.0, 20SEP2003, EDW (JPL)
difference between ephemeris time and utc
