Data Corrections

SLR stations are capable of measuring ranges very precisely and accurately, but a misconfigured SLR system sometimes introduces systematic errors in the data. Engineering analysis can uncover the error sources and frequently corrected range data is recoverable.

Currently data corrections are available in two formats (free format and pseudo-SINEX). Data Corrections pre 1 January 1999 are in free format available from slr_problems_index.html . Data Corrections post Jan 1, 1999 are available in pseudo-SINEX format (Reference SLRmail#1020).

Files have been created by the ILRS Analysis Working Group for use with SLR data; these files are maintained by (and accessible from) DGFI on behalf of the AWG:

  • The ILRS Discontinuities File is used to keep track of the various solution numbers and includes the information available after each new development of an ITRF.
  • The ILRS Data Handling File summarizes in a common format all information on range-, time- or pressure errors from all SLR tracking stations, adopted by the ILRS Analysis Working Group. Additionally the file contains a list of stations with periods of data to be excluded from processing.

Station-dependent Target Signature Corrections (CoM)

The ILRS AWG has adopted since October 1st 2013 a new, station- and time-dependent model for the corrections to be applied to SLR data from each geodetic target, to account for the fact that the laser reflector arrays (LRA) are not responding as "points" and they are not located at the center of gravity of the spacecraft. This commonly termed "Center of Mass—CoM" correction depends on various factors, beyond the obvious one of the geometry of the spacecraft. One of these is the mode of operation of the tracking system, which can change at times due to various considerations and decisions of the station crew. Based on these and the post-processing treatment of the raw data in forming the commonly used Normal Points (NP) at the station, one can develop for each spacecraft a table of appropriate CoM corrections to be applied during data reduction. These corrections have been compiled in tables for the two LAGEOS, two ETALON and the Ajisai LRAs. An appropriate piece of s/w has been developed by Graham Appleby of NERC, that makes use of these tables and based on the user’s input for a station ID and other information, it returns the CoM correction most appropriate for that occasion. The s/w package and the tables which are dynamically updated as new stations join the network or old stations change their operational mode, are maintained at DGFI’s web server:

  • Software package for CoM Correction Determination
  • System Configuration and CoM Corrections for LAGEOS
  • System Configuration and CoM Corrections for Etalon
  • System Configuration and CoM Corrections for Ajisai