Usage of angularSeparationOfPlanets

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Computes the current angular separation of two Solar System bodies at 0 UT on the current date, or the exact specified date string. Default viewing location is ALMA and default source of coordinates is the JPL Horizons telnet server. It computes great circle angle using the Vincenty formula. It returns the separation in radians. If the primary beam is specified (either via the frequency and diameter, or the vis parameters), then it will also return the separation in units of primary beam FWHM. See also angularSeparationOfStrings, angularSeparationOfFields, angularSeparation, angularSeparationRadians, and angularSeparationRadiansTuples.

Usage: angularSeparationOfPlanets(planet1='', planet2='',date='',observatory='ALMA', useJPL=True, target=None, returnComponents=False, verbose=False, vis='', bodyForScan='', frequency=None, diameter=None)
  • date: one possible format of the date string is: '2011-10-31 11:59:59' or simply '2011-10-31' for 0:00 UT. A list of allowed formats for date is at: http://ssd.jpl.nasa.gov/?horizons_doc#time
  • observatory: Observatories can be specifed by JPL ID string, or by the following names:
    • 'VLA' (which will be converted to = '-5')
    • 'GBT' (which will be converted to = '-9')
    • 'OVRO' (which will be converted to = '-81')
    • 'ALMA' (which will be converted to = '-7')
    • 'MAUNAKEA' (which will be converted to = '-80')
  • If useJPL=False, it will first attempt to use the casa ephemerides but this will fail for objects without a flux density model, and the JPL interface will then be used.
  • If returnComponents is True, it also returns the separation along the two coordinate system components via the following array: [separation, separationRA, separationDec, separationRA*cosine(Dec)]
  • If 'target' is specified as a valid RA/Dec, then the separation between it and planet1 will be computed.
  • Required format for target: HH[:MM:SS.S] [+]DD[:MM:SS.S].
  • If 'vis' is specified, then it will
    • use the time of the first scan on the target, or the start time of the ms if neither target is not found.
    • automatically search for Galilean moons and Titan in the fields list if no planet names are specified
    • use the median dish diameter and median of the mean frequencies of the OBSERVE_TARGET spws to compute the primary beam
  • 'bodyForScan' is passed to both calls to planet() to pick the date/time of the first scan on this body
  • If 'frequency' and 'diameter' are specified, these are passed to primaryBeamArcsec to compute the separation in beam diameters.

Examples:

CASA <3>: au.angularSeparationOfPlanets('Saturn','Titan','2012-04-28 00:00')
Contacting JPL Horizons for Saturn
MJD= 56045.00000, MJDseconds = 4842288000.0
Confirmed Observatory name =  ALMA 
Confirmed Target ID = 699 = Saturn
J2000 Position: 13:36:59.17, -007:07:44.215, rate: -10.5147, 3.8235 arcsec/hr
Angular diameter = 19.010220 arcsec
Contacting JPL Horizons for Titan
MJD= 56045.00000, MJDseconds = 4842288000.0
Confirmed Observatory name =  ALMA 
Confirmed Target ID = 606 = Titan
J2000 Position: 13:37:03.10, -007:06:59.983, rate: -7.5563, 3.6607 arcsec/hr
Angular diameter = 0.811515 arcsec
Separation = 0.000355473 rad = 0.0203671 deg = 73.3216 arcsec
RA separation = -0.00109133 hours

CASA <2>: au.angularSeparationOfPlanets('Saturn','Titan','2012-04-28 00:00',returnComponents=True)
Contacting JPL Horizons for Saturn
MJD= 56045.00000, MJDseconds= 4842288000.0, JD= 2456045.50000
LST day = 62769,  LST = 9.9074 hours (at longitude=-67.754929)
Julian day = 2456045.500000, MJD = 56045.000000, MJD seconds = 4842288000.000000
Confirmed Observatory name =  Atacama Large mm/sub-mm Array (ALMA) Center of Array
Confirmed Target ID = 699 = Saturn
Range rate = +6.066766 km/sec
J2000 Position: 13:36:59.17063, -007:07:44.21532
J2000 Rate: -10.5147, +3.8235 arcsec/hour (position angle = -70.0deg)
J2000 Rate: -0.002921, +0.001062 arcsec/second  (position angle = -70.0deg)
Angular diameter (major axis) = 19.010220 arcsec
Contacting JPL Horizons for Titan
MJD= 56045.00000, MJDseconds= 4842288000.0, JD= 2456045.50000
LST day = 62769,  LST = 9.9074 hours (at longitude=-67.754929)
Julian day = 2456045.500000, MJD = 56045.000000, MJD seconds = 4842288000.000000
Confirmed Observatory name =  Atacama Large mm/sub-mm Array (ALMA) Center of Array
Confirmed Target ID = 606 = Titan
Range rate = +4.301036 km/sec
J2000 Position: 13:37:03.09941, -007:06:59.98284
J2000 Rate: -7.5563, +3.6607 arcsec/hour (position angle = -64.2deg)
J2000 Rate: -0.002099, +0.001017 arcsec/second  (position angle = -64.2deg)
Angular diameter (major axis) = 0.811515 arcsec
Separation = 0.000355473 rad = 0.0203671 deg = 73.3216 arcsec
RA separation = -0.00109133 hours
  Out[2]: array([ 0.00035547, -0.00028571, -0.00021445, -0.0002835 ])

-- ToddHunter - 2012-04-27

This topic: ALMA > TWikiUsers > ToddHunter > CasaExtensions > AngularSeparationOfPlanets
Topic revision: 2013-04-29, ToddHunter
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