NASA will be performing network maintenance on Tuesday May 16, 2023, from 11:00 AM EDT (15:00 UTC) to 1:00 PM EDT (17:00 UTC), resulting in short, intermittent outages. You may experience network difficulties accessing the ILRS website and ALL CDDIS services during the maintenance window. If you experience problems outside this window, contact support-cddis@earthdata.nasa.gov.

close window
-->

Consolidated Prediction Format (CPF)

Version 1.00
Superseded by CPF v2.00 on 1 October 2021

Prior to June 2008, the satellite laser ranging stations used the standard 'Tuned IRV' prediction format. This format consists of daily satellite state vector (x,y,and z positions and velocities at a given time plus other parameters) tuned to specific field integrator software and gravity field to provide maximum accuracy over the integration period. Lunar laser ranging stations have used multi-year ephemeris with lunar and planetary ephemeris software packages.

These procedures had worked well through the years, but new requirements made it necessary to update our prediction techniques. Remote receivers and transponders were on the horizon for the moon, planets and extraterrestrial missions. Some of these were to be launched in the near future. The previous prediction format could not accommodate this need. In addition, with the Galileo constellation on the horizon and the possibility of more GPS satellites with retro-reflectors, the ILRS had to improve both day- and night-time ranging to high satellites, which means improving our prediction capability.

The ILRS Predictions Formats Study Group created a Consolidated Prediction Format (CPF) for laser ranging that accurately predicts positions and ranges for a much wider variety of laser ranging targets than had been previously possible. The predictions provide daily tables of x,y, and z positions for each target that can be interpolated for very accurate predictions. There are three target classes consolidated under this format (1) Passive retro-reflectors (including earth orbiting, in lunar orbit, and on the moon) (2) asynchronous transponders, and (3) synchronous transponders. Aside from the expanded format capability, the new prediction system greatly improved tracking on low satellites because the full modeling potential of the orbit computation at the prediction center is passed on to the stations. Drag files and special maneuver files are no longer necessary.

At the ILRS Governing Board Meeting in Eastbourne in October, 2005, this new CPF Format was adopted for implementation into the ILRS network.

An explanation of the format can be found in the CPF Prediction Format document and appendices that include:

  • Appendix A. Prediction Format
  • Appendix B. Sample Prediction Configurations
  • Appendix C. How to Create Condolidated Prediction Format Files: A Cookbook
  • Appendix D. Consolidated Prediction Format User's Guide
  • Appendix E. Maximum Prediction Grid Spacings

It may be helpful to review Appendices C and D prior to reading the material in Appendix A and B.

Sample software code is available to accommodate all targets. Using the sample code will save considerable time and avoid confusion. A page of errata is also available.

The ILRS adopted this new format as of June 30, 2006 and discontinued the 'Tuned IRV' format thereafter. Stations were asked to implement the new format prior to that time; predictions centers were asked to implement the new format by February 1, 2006.

For reference, CPF files can be found at:

For reference, Tuned IRV format files can be found at:

Version 2.00
The current official ILRS format
Superseded v1.00 on 1 October 2021

Version 2 of the CPF format has been finalized. The main changes are to the C4 Transponder Configuration record for the ELT mission and sub-daily ephemeris sequence number field in the H1 record and in the file name to allow for transponders like ELT and very low satellites needing more than 10 prediction updates per day. The target type has been split into target class and target location for logistical reasons, and the headers are now free-format like the data records. The manual has been revised to remove many of the comparisons with the TIV format.

  • The revised format document can be found here.
  • The sample code can be found here.
  • A directory with one day of v1 CPFs and the corresponding v2 CPFs is here.
  • A v2_errata_page has been created to annotate changes to/problems in the documentation and source code.

For reference, CPF files can be found at: