STScI Logo

hstephem stsdas.hst_calib.ctools



hstephem -- Convert the Space Telescope orbit ephemeris file to an STSDAS table.


hstephem infile outtable


This task converts the archived ST definitive orbit ephemeris file (an ORB file) to a FITS or STSDAS table. At the present time, ORB files can be delivered from the archive in FITS format, in which case the files should be used directly in odelaytime, and hstephem cannot be used to convert the format. Prior to April 2000, ORB files were archived in ORX format, which is a VAX binary format, and it is necessary to run hstephem to convert these files to either a FITS table or an STSDAS table before using with odelaytime. ORX-format files have the extension ".orx".

The ephemeris contains spacecraft positions and velocities. They are recorded every minute, and each file covers either two days (i.e. 2881 points) or three days (i.e. 4321 points). All files before Oct 24, 1995 are two-day ephemeris, all files after Nov 7, 1995 are three-day ephemeris, files between these two dates are either two-day or three-day ephemeris.

This task has been successfully tested on SUN, VAX, DEC-station and Linux.


infile = "" [string]
Name of the input file template. If there is more than one file, they must be contiguous, i.e. the first entry of the second file must be the same as the last entry of the first table, etc.
outtable = "" [string]
Name of the output table. It contains the following columns:

TIME    Time for X, Y, Z, VX, VY, VZ, relative to header keyword
            FIRSTMJD, in days (double)
X       X component of the state vector, in km (double)
Y       Y component of the state vector, in km (double)
Z       Z component of the state vector, in km (double)
VX      X component of the orbital velocity, in km/s (double)
VY      Y component of the orbital velocity, in km/s (double)
VZ      Z component of the orbital velocity, in km/s (double)

The output table also contains the following header keywords:

FIRSTMJD  The epoch of the first row in the table, in MJD
HISTORY   The name(s) of the input file(s) used to generate this table


1. Combine all .orx files beginning with the string "pba" to an ephemeris table:

to> hstephem pba*.orx orbit.fits



This task was written by J.-C. Hsu.



Source Code · Package Help · Search Form · STSDAS