cspice_phaseq |
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## AbstractCSPICE_PHASEQ computes the apparent phase angle for a target, observer, illuminator set of ephemeris objects. For important details concerning this module's function, please refer to the CSPICE routine phaseq_c. ## I/OGiven: et double precision scalar the time in ephemeris seconds past J2000 TDB at which to compute the phase angle. target scalar string naming the target body. Optionally, you may supply a string containing the integer ID code for the object. For example both "MOON" and "301" are legitimate strings that indicate the Moon is the target body. Case and leading or trailing blanks are not significant in the string 'target'. illmn scalar string naming the illuminating body. Optionally, you may supply a string containing the integer ID code for the object. For example both "SUN" and "10" are legitimate strings that indicate the sun is the illuminating body. Case and leading or trailing blanks are not significant in the string 'illmn'. In most cases, 'illmn' is the sun. obsrvr scalar string naming the observer body. Optionally, you may supply a string containing the integer ID code for the object. For example both "MOON" and "301" are legitimate strings that indicate the Moon is the observer body. Case and leading or trailing blanks are not significant in the string 'obsrvr'. abcorr scalar string indicating the aberration corrections to apply to the state evaluations to account for one-way light time and stellar aberration. This routine accepts only reception mode aberration corrections. See the Aberration Correction Required Reading (abcorr.req) for a detailed description of the aberration correction options. For convenience, the appropriate aberration options are listed below: 'NONE' Apply no correction. Returns the "true" geometric state. 'LT' "Reception" case: correct for one-way light time using a Newtonian formulation. 'LT+S' "Reception" case: correct for one-way light time and stellar aberration using a Newtonian formulation. 'CN' "Reception" case: converged Newtonian light time correction. 'CN+S' "Reception" case: converged Newtonian light time and stellar aberration corrections. Case and leading or trailing blanks are not significant in the string 'abcorr'. the call: phaseq = ## ExamplesThe numerical results shown for these examples may differ across platforms. The results depend on the SPICE kernels used as input, the compiler and supporting libraries, and the machine specific arithmetic implementation. Use the meta-kernel shown below to load the required SPICE kernels. KPL/MK File name: standard.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 --------- -------- de421.bsp Planetary ephemeris pck00009.tpc Planet orientation and radii naif0009.tls Leapseconds \begindata KERNELS_TO_LOAD = ( 'de421.bsp', 'pck00009.tpc', 'naif0009.tls' ) \begintext Example: Determine the time intervals from December 1, 2006 UTC to January 31, 2007 UTC for which the sun-moon-earth configuration phase angle satisfies the relation conditions with respect to a reference value of .57598845 radians (the phase angle at January 1, 2007 00:00:00.000 UTC, 33.001707 degrees). Also determine the time windows corresponding to the local maximum and minimum phase angles, and the absolute maximum and minimum phase angles during the search interval. The configuration defines the sun as the illuminator, the moon as the target, and the earth as the observer. MAXWIN = 5000L TIMFMT = 'YYYY-MON-DD HR:MN:SC.###' TIMLEN = 41 relate = [ '=', '<', '>', $ 'LOCMIN', 'ABSMIN', 'LOCMAX', 'ABSMAX' ] ;; ;; Load kernels. ;; cspice_furnsh, 'standard.tm' ;; ;; Store the time bounds of our search interval in ;; the cnfine confinement window. ;; cspice_str2et, [ '2006 DEC 01', '2007 JAN 31'], et ;; ;; Search using a step size of 1 day (in units of seconds). ;; The reference value is 0.57598845 radians. We're not using the ;; adjustment feature, so we set 'adjust' to zero. ;; target = 'MOON' illmn = 'SUN' abcorr = 'LT+S' obsrvr = 'EARTH' refval = 0.57598845D adjust = 0.D step = cspice_spd() nintvls = MAXWIN cnfine = cspice_celld( 2 ) cspice_wninsd, et[0], et[1], cnfine result = cspice_celld( MAXWIN*2) for j=0, 6 do begin print, 'Relation condition: ', relate[j] ;; ;; Perform the search. The SPICE window 'result' contains ;; the set of times when the condition is met. ;; cspice_gfpa, target, illmn, abcorr, $ obsrvr, relate[j], refval, $ adjust, step, nintvls,$ cnfine, result ;; ;; List the beginning and ending times in each interval ;; if 'result' contains data. ;; count = cspice_wncard( result ) if ( count eq 0 ) then begin print, 'Result window is empty.' endif else begin for i= 0L, (count - 1L ) do begin ;; ;; Fetch the endpoints of the Ith interval ;; of the result window. ;; cspice_wnfetd, result, i, left, right cspice_timout, [left, right], TIMFMT, TIMLEN, timstr phaseq = ## ParticularsThis routine returns the phase angle using the location of the bodies (if point objects) or the centers of the bodies (if finite bodies). ILLMN OBS ILLMN as seen ^ / from TARG at | / ET - LT. | / >|..../< phase angle | / . | / . | / . |v TARG as seen from OBS SEP . TARG at ET . / / v PI = SEP + PHASE so PHASE = PI - SEP ## Required ReadingICY.REQ ABCORR.REQ ## Version-Icy Version 1.0.1, 02-FEB-2017, EDW (JPL), BVS (JPL) Eliminated typo in example code; no change to functionality. Shortened permutted index entry. -Icy Version 1.0.0, 11-NOV-2013, EDW (JPL) ## Index_Entriescompute phase angle for arbitrary illumination source |

Wed Apr 5 17:58:02 2017