***** File OBSNTERP.TXT
Observation Interpolation Program
The program OBSNTERP is an interactive, seven point Lagrange inter-
polation program that will return ephemeris data for periodic comet Giacobini-
Zinner over the interval January 5, 1984 through May 27, 1987. To run the
program, type OBSNTERP <carriage return> and respond to the prompts. The
executable requires a math co-processor. The Fortran source code is given in
the files labeled with the extension .FOR and the ephemeris data table for
comet Giacobini-Zinner is EPHEM.TAB. You can speed up the interpolation time
by shortening the data table to include only the interval that you require and
by requesting output for dates in chronological order. The information in the
data table was generated with IHW orbit number 37, which was based upon 1145
astrometric positions over the interval March 11, 1972 through March 31, 1987.
(Each line of the table is a fixed width of 110 characters plus <CR> <LF>.)
The definition of each output quantity is given below:
Date: Calendar date and Julian date (times in these ephemerides are
universal times).
RA, DEC: Geocentric right ascension and declination referred to the
mean equator and equinox of 1950.0 - light time corrections
have been applied.
DELTA: Geocentric distance of comet in AU.
DELDOT: Geocentric velocity of comet in km/sec.
R: Heliocentric distance of comet in AU.
RDOT: Heliocentric velocity of comet in km/sec.
THETA: Sun-Earth-Comet angle in degrees.
BETA: Sun-Comet-Earth angle in degrees.
MOON: Comet-Earth-Moon angle in degrees.
PSANG: Position angle of extended Sun-Comet vector.
PSAMV: Position angle of minus comet velocity vector.
(Position angles are measured east from north.)
Ravenel N. Wimberly
Astrometry Team Member
Jet Propulsion Laboratory
4800 Oak Grove Drive
Pasadena, CA 91109