Bernese GNSS Software, Version 5.4 Last mod.: 06-May-2022

Installation of the JPL planetary and lunar ephemerides

Table of Contents

1. Source of Ephemerides

2. Requirements

3. Installation Procedure

   3.1 Download the Ephemerides
   3.2 Concatenate the ASCII Files
   3.3 Convert the File to Binary
   3.4 Check the Integrity of the Binary Ephemeris file

4. Providing the JPL Ephemerides to the Bernese Software

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1. Source of Ephemerides

The JPL ephemerides are prepared at JPL by M.E.Standish et al. Information may be found at

http://ssd.jpl.nasa.gov?planet_eph_export

The ephemerides may be downloaded from JPL by the link given in section "Download" (3.1)

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2. Requirements

The Fortran programs needed for the installation of the JPL ephemerides on your computer are included in the distribution of the Bernese GNSS Software in the $XG (%XG% on windows) directory. These programs are supplied by JPL and have been slightly adapted to simplify the usage in the context of Bernese Software.

Make sure, the Bernese environment variable $XG (%XG%) is defined and points to the correct directory on your system. Check this by typing "echo $XG" ("echo %XG%"). If the variable is undefined or incorrectly defined, load the Bernese environment variables by:

UNIX platforms:
Depending on your shell use
. BERN54/LOADGPS.setvar or source BERN54/LOADGPS.setvar
(adapt the path to LOADGPS.setvar if necessary).
You can add this step into your login script.

WINDOWS platform:
You need to re-login after running the software installation scripts. If you need to redefine the variables you need to edit the user environment variables in the registry key HKCU\Environment

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3. Installation Procedure

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3.1 Download Files from JPL

The ephemeris package is available from the anonymous ftp server

ftp://ssd.jpl.nasa.gov.

When connected change to the directory pub/eph/planets/ascii/de421.

In ASCII mode, download the following files to a target directory:

header.421: contains header info for the DE421 ephemeris
testpo.421: test data
ascp1900.421: covers the time interval between 1900 and 2050
ascp2050.421: covers the time interval between 2050 and 2200

In the terminal, change into the target directory, and follow the steps in the next sections.

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3.2 Concatenate the ASCII Files

In your terminal, concatenate the header file and the ASCII ephemeris files to one temporary file using the following commands on your OS:

• Windows:
  copy header.421+ascp1900.421 temp.421

• UNIX:
  cat header.421 > temp.421
cat ascp1900.421 >> temp.421

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3.3 Convert the File to Binary

The concatenated file needs to be converted into binary format on the target machine using the program "ASC2EPH".

1. Prepare an input file ASC2EPH.INP containing:

   • the filename of the concatenated ASCII file.
   • the filename of the resulting binary file.

   Example for ASC2EPH.INP:

   temp.421  
   JPLEPH

2. Run program ASC2EPH in the directory of the file "temp.421":

   • Windows:
     Use the command: %XG%\ASC2EPH.exe

   • UNIX:
     Use the command: ${XG}/ASC2EPH

This will create the file JPLEPH containing the binary DE421 ephemeris.

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3.4 Check the Integrity of the Binary Ephemeris File

1. Prepare an input file TESTEPH.INP containing:

   • Name of the test-data file (testpo.421)
   • Name of the file to be tested (Ex. JPLEPH)
   • DE number of the ephemeris (421)

   Example for TESTEPH.INP:

      `testpo.421`  
      `JPLEPH`  
      `421`  

   • windows: use the command %XG%\TESTEPH.exe
   • UNIX : use the command ${XG}/TESTEPH

There should be no warnings or errors.

The output of the program "TESTEPH" will report the time span of the newly generated ephemeris file JPLEPH given in Julian Ephemeris Days (2414992.50 to 2469808.50).
The last column shows the differences to the test file. In the example below, the differences are insignificant.

Example output:

 line -- jed --  ... --- jpl value ---   --- user value --    -- difference --

 100 2418032.5   ...       7.6240319961279          7.6240319961279  0.26645E-14
 200 2421076.5   ...   8  16.6129622249319         16.6129622249319  0.35527E-14
 300 2424120.5   ...  11   0.0055634044434          0.0055634044434  0.86736E-18
 400 2427163.5   ...  10   0.0067338692435          0.0067338692435  0.00000E+00
 ...

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4. Providing the JPL Ephemerides to the Bernese Software

Within the Bernese GNSS Software the JPL ephemerides file

• must be located in the directory of general files:
  %MODEL% (Windows notation) resp. ${MODEL} (UNIX notation)
• must have the default name DE421.EPH.

To implement the newly generated ephemeris file into the Bernese GNSS Software simply copy the file "JPLEPH" to the expected name and location:

• Windows: copy JPLEPH %MODEL%\DE421.EPH

• UNIX : cp JPLEPH $MODEL/DE421.EPH

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