Analysis Products

The ILRS provides a service to utilize Satellite and Lunar Laser Ranging data to generate geodetic, geodynamic, and geophysical scientific products.

Currently, five SLR analysis groups (ASI, DGFI, GFZ, JCET and NSGF) provide direct input for the official ILRS products (station
coordinates and Earth Orientation Parameters, EOPs). The results of the ILRS POS+EOP pilot project were evaluated during the AWG meeting in San Fernando. The five contributors were acknowledged and given an official status. In addition, ASI was selected as the official ILRS primary combination center, and DGFI was selected as the official ILRS backup combination center, each for a two-year term. As well as the contributors of individual solutions, these combination centers must follow strict timelines and provide routine products of the highest possible quality. Weekly, official ILRS products from these two combination centers are now available in SINEX format each Wednesday at CDDIS and EDC. Analysis centers will again compete for the ILRS combination and backup center in mid-2006, at the International Laser Ranging Workshop in Australia. All groups are encouraged to develop (the quality of) their contributions further.

The ILRS now generates weekly, unconstrained solutions for station coordinates (valid for the mid-point of each 7-day interval) and EOPs (x-pole, y-pole and Length-Of-Day (LOD), all of them for 1-day intervals). These results are stored in subdirectories of the form "pos+eop/YYMMDD", where "YYMMDD" is the date (YY=2 digit year, MM=2 digit month, and DD=2 digit day) of the end of each 7-day interval. Within each subdirectory, one finds so-called individual solutions and combination solutions, that are explained below.For the individual contributions to the POS+EOP project filenames are of the form (examples reflect CDDIS archive):

ftp://cddis.gsfc.nasa.gov/pub/slr/products/pos+eop/YYMMDD/CENTER.pos+eop.YYMMDD.v1.snx.Z

Here, "CENTER" is replaced by the name of the actual contributor. It is the first solution that is generated for this period and by this analysis center, hence "v1". If re-computations are necessary, the version number will be increased by one; solutions for new weeks will start with "v1", however. The results are stored in the SINEX format (".snx"). The reader is refered to the COMMENTS section of each solution (in the file itself) or more general explanations of SINEX for further details of the solution and/or the format.

The official ILRS primary product on POS+EOP is labeled as:

ftp://cddis.gsfc.nasa.gov/pub/slr/products/pos+eop/YYMMDD/ilrsa.pos+eop.YYMMDD.v1.snx.Z

In a similar fashion, the EOP solutions (w.r.t. ITRF2000) generated by the official ILRS primary combination center are named:

ftp://cddis.gsfc.nasa.gov/pub/slr/products/pos+eop/YYMMDD/ilrsa.eop.YYMMDD.v1.snx.Z

The ILRS also has an official backup combination center, and its products are labeled

ftp://cddis.gsfc.nasa.gov/pub/slr/products/pos+eop/YYMMDD/ilrsb.pos+eop.YYMMDD.v1.snx.Z
ftp://cddis.gsfc.nasa.gov/pub/slr/products/pos+eop/YYMMDD/ilrsb.eop.YYMMDD.v1.snx.Z

Currently, the ILRS AWG is in the process of computing similar solutions for the years before the workshop in San Fernando. At this moment, the AWG works on solutions going back to the launch date of LAGEOS-2 (i.e. November 1992). It is foreseen that this will (at a later stage) be followed by computations for the time frame extending back to September 1983, the beginning of the MERIT campaign.

Historical products include: