CSPICE_ET2LST computes the local solar time at a given ephemeris epoch,
for an object on the surface of a body at a specified longitude.
Given:
et the ephemeris time(s) expressed as ephemeris seconds past
J2000 at which a local time is desired.
[1,n] = size(et); double = class(et)
body the SPICE IDcode of the body on which to measure local time.
[1,1] = size(body); int32 = class(body)
lon longitude (either planetocentric or planetographic)
in radians of the site on the surface
of body for which local time should be computed.
[1,1] = size(lon); double = class(lon)
type the name for the form of longitude supplied by the
variable 'lon'.
[1,c1] = size(type); char = class(type)
or
[1,1] = size(type); cell = class(type)
Allowed values are "PLANETOCENTRIC" and
"PLANETOGRAPHIC". Note the case of the letters
in type is insignificant. Both "PLANETOCENTRIC"
and "planetocentric" are recognized. Leading and
trailing blanks in type are not significant.
the call:
[ hr, min, sec, time, ampm] = cspice_et2lst( et, body, lon, type)
returns:
hr the value(s) describing the integral number of the local
"hour" of the site specified at epoch 'et'.
[1,n] = size(et); double = class(et)
Note that an "hour" of local time does not have the same duration
as an hour measured by conventional clocks. It is simply a
representation of an angle.
mn the value(s) describing the integral number of "minutes" past
the hour of the local time of the site at the epoch 'et'.
[1,n] = size(et); double = class(et)
Again note that a "local minute" is not the same as a minute you
would measure with conventional clocks.
sc the value(s) describing the integral number of "seconds" past
the minute of the local time of the site at the epoch 'et'.
[1,n] = size(et); double = class(et)
Again note that a "local second" is not the same as a second
you would measure with conventional clocks.
time the array of local time(s) on a "24 hour" local clock.
[n,c1] = size(segid); char = class(segid)
ampm array of local time(s) on a "12 hour" local clock together
with the traditional AM/PM label to indicate whether the sun has
crossed the local zenith meridian.
[n,c2] = size(segid); char = class(segid)
All output arguments return with the same measure of
vectorization, N, as 'et'.
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 leapseconds kernel.
%
cspice_furnsh( 'standard.tm' )
%
% Define two UTC time strings to 'utc'
%
utc = strvcat( '2002 SEP 02 00:00:00', ...
'2002 SEP 30 00:00:00' );
%
% Convert 'utc' the ephemeris time, 'et'
%
et zz = cspice_str2et(utc);
%
% Define a planetographic longitude in degrees, convert the
% value to radians
%
dlon = 326.17;
rlon = dlon * cspice_rpd;
%
% Convert inputs to Local Solar Time.
%
[hr, min, sec, time, ampm] = cspice_et2lst( et, ...
499, ...
rlon, ...
'PLANETOGRAPHIC');
fprintf( ['The local time at Mars %6.2f degrees E ' ...
'planetographic longitude:\n'], ...
dlon )
fprintf( ' at UTC %s, LST = %s\n', utc(1,:), ampm(1,:) )
fprintf( ' at UTC %s, LST = %s\n', utc(2,:), ampm(2,:) )
%
% It's always good form to unload kernels after use,
% particularly in MATLAB due to data persistence.
%
cspice_kclear
MATLAB outputs:
The local time at Mars 326.17 degrees E planetographic longitude:
at UTC 2002 SEP 02 00:00:00, LST = 03:25:35 A.M.
at UTC 2002 SEP 30 00:00:00, LST = 09:33:00 A.M.
None.
For important details concerning this module's function, please refer to
the CSPICE routine et2lst_c.
MICE.REQ
Mice Version 1.0.2, 05NOV2014, EDW (JPL)
Edited I/O section to conform to NAIF standard for Mice documentation.
Mice Version 1.0.1, 06MAY2009, EDW (JPL)
Added MICE.REQ reference to the Required Reading section.
Mice Version 1.0.0, 07MAR2007, EDW (JPL)
Compute the local time for a point on a body.
