📚 OBSNTERP.TXT
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49 lines***** File OBSNTERP.TXT
The Fortran source code OBSNTERP.FOR is an interactive, seven-point
Lagrange interpolation program that will return ephemeris data for periodic
comet Halley over the interval November 26, 1981 through June 23, 1989, when
it is run on the table EPHEM.TAB (in the EPHEM directory). VAX/VMS and MS-DOS
executables of OBSNTERP are called VAXNTERP.EXE and PCNTERP.EXE, respectively;
like OBSNTERP.FOR, they are stored in the \SOFTWARE\OBSNTERP directory of this
disc. To run the program, type PCNTERP <carriage return> (or VAXNTERP <cr>)
and respond to the prompts. 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 61, which was based upon 7469
astrometric positions over the interval August 21, 1835 through January 9,
1989. (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 Dr.
Pasadena, CA 91109
[NOTE: this write-up by R. N. Wimberly was modified slightly to take account
of the generation at NASA/GSFC of executable modules of the source code
OBSNTERP.FOR. -- M. B. Niedner, Jr.]