cspice_et2lst |
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## AbstractCSPICE_ET2LST computes the local solar time for an object on the surface of a body at a specified longitude and ephemeris epoch. For important details concerning this module's function, please refer to the CSPICE routine et2lst_c. ## I/OGiven: et the double precision scalar or N-vector ephemeris epoch expressed in TDB seconds past the J2000 epoch at which a local time is desired. body the scalar integer NAIF ID-code of a body on which local time is to be measured. lon the scalar double precision longitude (either planetocentric or planetographic) in radians of the site on the surface of body for which local time should be computed. type the scalar string describing the form of longitude supplied by the variable 'lon'. Allowed values: "PLANETOCENTRIC" "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: ## ExamplesAny 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. ;; ;; Define an arbitrary ephemeris time, ;; (July 4 2004 18:00:00) target body, ;; longitude (rads) and, the type of longitude. ;; et = 142236064.18399799d body = 499 lon = 326.17d * cspice_rpd() type = 'PLANETOCENTRIC' SIZE = 5 ;; ;; Load an SPK, PCK and leapsecond file. ;; cspice_furnsh, 'standard.tm' ;; ;; Calculate the local solar time defined by the inputs. ;; ## ParticularsRegarding planetographic longitude ---------------------------------- In the planetographic coordinate system, longitude is defined using the spin sense of the body. Longitude is positive to the west if the spin is prograde and positive to the east if the spin is retrograde. The spin sense is given by the sign of the first degree term of the time-dependent polynomial for the body's prime meridian Euler angle "W": the spin is retrograde if this term is negative and prograde otherwise. For the sun, planets, most natural satellites, and selected asteroids, the polynomial expression for W may be found in a SPICE PCK kernel. The earth, moon, and sun are exceptions: planetographic longitude is measured positive east for these bodies. If you wish to override the default sense of positive planetographic longitude for a particular body, you can do so by defining the kernel variable BODY<body ID>_PGR_POSITIVE_LON where <body ID> represents the NAIF ID code of the body. This variable may be assigned either of the values 'WEST' 'EAST' For example, you can have this routine treat the longitude of the earth as increasing to the west using the kernel variable assignment BODY399_PGR_POSITIVE_LON = 'WEST' Normally such assignments are made by placing them in a text kernel and loading that kernel via cspice_furnsh. ## Required ReadingICY.REQ TIME.REQ ## Version-Icy Version 1.0.3, 05-JAN-2011, EDW (JPL) Corrected header typo, furnsh_c replaced with cspice_furnsh. -Icy Version 1.0.2, 29-JAN-2009, EDW (JPL) Minor edits to header text. Replace argument description comment "returns with the same order" with "returns with the same measure of vectorization" -Icy Version 1.0.1, 07-NOV-2005, EDW (JPL) The treatment of planetographic longitude has been updated in et2lst_c.c to be consistent with the SPICE planetographic/rectangular coordinate conversion routines. The effect of this change is that the default sense of positive longitude for the moon is now east; also, the default sense of positive planetographic longitude now may be overridden for any body. -Icy Version 1.0.0, 20-SEP-2004, EDW (JPL) ## Index_EntriesCompute the local time for a point on a body. |

Wed Apr 5 17:58:01 2017