PLANET

##
PLANET

            [ASTRO\]PLANET [name] [/DRAW [Arg1 ... ArgN]]  [/EPHEMERIS  FileName
        NEW|APPEND] [/QUIET] [/BEAM beam]

        Compute  the  coordinates  of  a Solar System object. Known objects are:
        MOON, SUN, MERCURY, VENUS, MARS, JUPITER, SATURN, URANUS, NEPTUNE. If no
        name  is  entered, all objects are selected. The Option /DRAW is used to
        plot the object symbol on the screen.

        The PLANET command output the planet coordinates (apparent RA,  apparent
        DEC,  Azimuth and Elevation at time of computation) and the sun distance
        (with a warning message if this distance os  lower  than  the  telescope
        limit).  PLANET also indicates the geocentric (DE) and heliocentric (DS)
        distances of the object (in AU), the apparent minor and major  diameters
        (Min and Maj in arcsec), the position angle of the central meridian (PA,
        east from north, in degrees), the brightness temperature (TB in K),  the
        flux  (S  in  Jy)  at the current frequency, the frequency (in GHz), the
        beam (in arcsec), the main beam temperature (Tmb in K),  the  associated
        flux (in Jy) and the planet size convolved with the telescope beam (size
        in arcsec).

        For the Moon, the Sun and Mercury, the brightness temperature is a fixed
        value.   For Mars, the brightness temperature is scaled according to the
        heliocentric distance.  For Venus, the brightness temperature is comput-
        ed  at  the  current  frequency  using a reference value at 100GHz and a
        spectral index.

        As of July 2023, for Jupiter, Saturn, Uranus and Neptune the  brightness
        temperature is interpolated from tabulated values of model spectra. (Be-
        fore that, Jupiter and Saturn brightness temperatures were fixed  values
        while a spectral index was taken into account for Uranus and Neptune).

        The method used to get the planet brightness temperature is given in the
        command output and in the sic variable ASTRO%PLANET%TB_METHOD  (MODEL  =
        interpolation  from  model, SPIDX = computed from value and spectral in-
        dex)

        The accuracy of the planet brightness temperatures as computed in  ASTRO
        is estimated to be on the order of 5%.

        The  frequency  can  be  entered  by updating the variable FREQUENCY (in
        GHz).

        PLANET /QUIET suppresses all the printouts on the screen.

        Without the option /BEAM, the beam used is deduced from the current  ob-
        servatory  and  frequency.  User may override this default by giving non
        zero beam size (in arcsec) as an argument of the /BEAM option.

        All these parameters are also also written in SIC variables, in the  AS-
        TRO%PLANET%  structure.  Just  enter EXAMINE ASTRO%PLANET% to get a com-
        plete list of these variables.

Subsections

- PLANET /DRAW
- PLANET /EPHEMERIS