CARMA Ephemeris

Carma Ephemeris :

The Carma ephemeris uses the USNO/NOVAS library for various calculations. The ephemeris data are either from tables in $CARMA/conf/catalogs, or tables prepared by JPL, via the Horizons systems:

JPL HORIZONS (web interface to ephemeris)
USNO/NOVAS (software library with which CARMA interfaces for RA/DEC and AZ/EL computations)

Although all major planets are by default present, transient objects like asteroids and comets are not, and you will need to provide an ephemeris for the period around your observation.

Generating your own solar system ephemeris

There are three ways to generate the VECTOR Ephemeris files for solar system targets:

edit the template in $CARMA/conf/catalogs/horizons.job (don't forget to edit your email in the EMAIL_ADDR directive) and email it per instructions in that file . You will get an email back with the ephem file embedded. Use awk (as per instructions in the template) or an editor to get the data lines.
use the web interface, save the output and edit out the non-data lines.
a telnet interface, as described on horizons web page

The resulting file should look something like this:

#     JD                           date                   X          Y                      Z                     VX                    VY               VZ     
2453870.500000000, A.D. 2006-May-15 00:00:00.0000,-5.465227102812747E-01, -7.833548627966440E-01,-2.894963713205840E-01,  2.040779775667518E-02,-5.228213740077321E-03, -7.051900383075237E-03,
2453870.583333333, A.D. 2006-May-15 02:00:00.0000,-5.448215004089416E-01, -7.837897446353480E-01,-2.900837333555622E-01,  2.042123503452728E-02,-5.208944593118194E-03, -7.044784550018225E-03,
2453870.666666667, A.D. 2006-May-15 04:00:00.0000,-5.431191718016970E-01, -7.842230192634879E-01,-2.906705014276759E-01,  2.043464737011887E-02,-5.189640693874762E-03, -7.037645272212271E-03,
2453870.750000000, A.D. 2006-May-15 06:00:00.0000,-5.414157265442097E-01, -7.846546837868722E-01,-2.912566735826597E-01,  2.044803461546170E-02,-5.170302086300463E-03, -7.030482536695162E-03,

Once you have this file, copy it to /arrayt/rt/catalogs/SOURCE.ephem, in upper case. Test it by trying

     checksource source=source mjd=53870.1

Please note that ephem tables need to be stored in UPPER CASE!, and remember mjd = jd - 2400000.5

Generating your own catalog

The ucat command (from $CARMA//scripts/python/subarrayCommands.py) is used to set an alternative catalog of sources to be searched before the system catalog. They must be placed in /arrayt/rt/catalogs/catalog.cat, in matching case. Example:

    checksource source=N3870 catalog=/array/rt/catalogs/kartik.cat

The corresponding entry in the catalog file looks as follows:

# Kartik's catalog
# NOTE: SOURCE NAMES MAY NOT EXCEED 8 CHARACTERS
#
#| Source |   RA          |   DEC        | Parallax | Velocity | VelFrame | VelDef |  PMRA     | PMDEC     |  ID  |  PntType |   Comments |
#|  s     |   hms         |   dms        |    r     |    r     |    s     |   s    |   r       |   r       |  i   |  s       |    s       |
#|        |               |              |  arcsec  |   km/s   |          |        |  asec/cent|  asec/cent|      |          |            |
N3870       11:45:56.6       50:11:59.10    0.0        756.0        LSR      RADIO    0.000       0.000      1       RADIO
NGC5194     12:00:00         10:00:00       0.0       1000.0        LSR      RADIO    0.000       0.000      1       RADIO

Within sac the command would be:

	ucat('kartik.cat')
	info('N3870')

Last updated: 24-aug-2006 PJT