Lowell Observatory IDL Ephemeris Tools

Quite a few routines in my IDL Library depend on external programs to compute ephemeris information based on the orbit element database maintained at Lowell Observatory (eg., ephem.pro, sspos.pro, obsprop.pro). These programs are setup to run as pipes and are used as such in the IDL routines. We provide pre-compiled binaries for Linux and Solaris and a special extraction from the orbit element database for use external to Lowell.

Setup of support programs

Setup of support files

The files needed to run geteph/getinfo need to be placed in various directories. Pointers to the directories are created via environment variables named NAIF_DIR, LOC_DIR, COM_DIR, and AST_DIR. The first two contain files that vary slowly (on decade timescales). The files in the second pair of directory change on a daily basis (about 4:30pm MST).

Note that you can have the environment variables pointing to different directories, or the same directory. Most of the files are in binary formats. The programs automatically handle the conversion to other byte orders.

setenv AST_DIR '/pathtotheastfiles'

The following files (~94Mb) must be in AST_DIR:

ast.dat
cover.dat
mb.dat

These files can be downloaded here and contain (binary) asteroid elements data as of the date of creation of the files and should be downloaded regularly.

setenv COM_DIR '/pathtothecomfiles'

The following files (~32Mb) must be in COM_DIR (it can be the same place as AST_DIR):

eco_names.dat
eco_apparitions.dat
eco_ele.dat
eco_orbits.dat

These files can be downloaded from here and contain (binary) comet elements data as of the date of creation of the files and should be downloaded regularly.

setenv NAIF_DIR '/pathtothenaiffiles'

NAIF_DIR contains the binary .bsp ephemeris files as well as the ASCII leapseconds file, leapseconds.ker. You must have the leapseconds file. You can download one or more .bsp ephemeris files.

These files can be downloaded from here. The .bsp files need only be downloaded once. The .ker file can be edited should a new leapsecond be added (or you can download a new version). You only need to download those .bsp files which contain the objects you are interested in. There is a "summary" file in the ftp area which contains a summary listing of each of the .bsp files available. Note that some of the .bsp files contain the ephemerides for the Earth and Sun and some do not. If you download a file without the Earth or Sun (eg jup035-5.bsp) and do not download any other file that contains the Earth/Sun, you will need to also download the de405s.bsp file.

setenv LOC_DIR '/pathtothelocfiles'

The following files (88Mb) must be in LOC_DIR:

de405.dat
obsv8.dat
plpos.dat
leapsec.dat

These files can be downloaded from here. obsv8.dat is a (binary) list of MPC observatory sites. This file changes occasionally, but unless you are running ephemerides for unusual observatories, you probably won't need to update the file. plpos.dat is a (binary) file of planetary positions used for the integrator. This can be downloaded once. de405.dat is the (binary) JPL DE405 planetary ephemeris. This can be downloaded once. leapsec.dat is a second (ASCII) leapseconds file and, like the one above, can be edited should a new leapsecond be added. This will be updated here as new leap seconds are announced.