Laser ranging stations require satellite orbit information in order to point their instrument to the correct location and acquire returns from the retroreflectors. Mission operations groups generate these predicted future orbits from calculated ranging data orbits. Predicted orbit files typically contain orbit information for multiple days. Predictions are primarily available in daily files sorted by year and satellite; predictions for lower orbiting satellites, however, are often transmitted several times per day.
The Consolidated Prediction Format (CPF) is now used operationally for satellite predictions within the International Laser Ranging Service (ILRS); CPF provides orbit data that accurately predict positions and ranges for a large variety of targets in tables of X , Y , and Z positions, which can be interpolated for accurate predictions. Satellite Laser Ranging (SLR) stations download these prediction files and coordinate tracking schedules for satellite acquisition. Satellite prediction files are archived on NASA’s Crustal Dynamics Data Information System (CDDIS) by year and satellite. In addition, stations can retrieve the latest predicted orbit file for all laser tracked satellites in a single subdirectory, current.
DOI: https://doi.org/10.5067/SLR/SLR_ILRSORBPRED_001
The CPF standard was first adopted on June 30, 2006 as version 1. March 1, 2022, the CPF standard was officially updated to version 2 of the format. Version 1 CPF files can be found in the starting directory https://cddis.nasa.gov/archive/slr/cpf_predicts/.
The starting directory for Version 2 CPF files is: https://cddis.nasa.gov/archive/slr/cpf_predicts_v2/
Append the following directory and file names to the starting directory:
YYYY/SATNAME/SATNAME_cpf_YYMMDD_###VV.CEN
and
YYYY/current/SATNAME_cpf_YYMMDD_###VV.CENcontains the most recent CPFs
as described in the table below.
Code | Meaning |
---|---|
SATNAME | Satellite Name |
YYYY | 4-digit year |
YY | 2-digit year |
MM | 2-digit month |
DD | 2-digit day |
### | ephemeris version number |
VV | version within the day |
CEN | mission group generating the prediction |