SLR Analysis Center (AC) Orbit Product (weekly files, generated weekly)

doi: 10.5067/SLR/SLR_ILRSACORB_001

Data Center Citation

Noll, Carey E., The Crustal Dynamics Data Information System: A resource to support scientific analysis using space geodesy, Advances in Space Research, Volume 45, Issue 12, 15 June 2010, Pages 1421-1440, ISSN 0273-1177,

Data Citation

International Laser Ranging Service (ILRS), SLR Analysis Center (AC) Orbit Product, Greenbelt, MD, USA:NASA Crustal Dynamics Data Information System (CDDIS), Accessed [[enter user data access date]] at doi: 10.5067/SLR/SLR_ILRSACORB_001.

Other standard citation formats may be used for this data set and can be found at the DOI Citation Formatter website.

More information about CDDIS data citations and acknowledgments is available.


  • Name: SLR Analysis Center (AC) Orbit Product
  • Format: SP3c format
  • Spatial Coverage: 90.0 to -90.0, 180.0 to -180.0
  • Temporal Coverage: 1976-01-01 to present
  • Temporal Resolution: weekly
  • File Size: 30kb
  • Platforms: etalon1, etalon2, lageos1, lageos2


ILRS Analysis Centers provide weekly satellite orbit solutions for LAGEOS-1 and -2 and Etalon-1 and -2 to the CDDIS using pre-determined schedules. The orbits are computed using SLR data collected over the previous seven days; their reference frame is the Earth Centered-Earth Fixed (ECEF) realized by the latest SLR reference frame and the IERS Bulletin A EOP series (USNO). The ILRS combination centers retrieve these solutions to produce the ILRS-A and ILRS-B combined product, which is then in turn archived at the CDDIS. These combination solutions are considered the official ILRS orbit products.

The AC ILRS orbit solutions, consists of weekly orbit files, generated on a weekly basis approximately 10 days after the end of the solution week. All orbit solution files utilize the Extended Standard Product - 3 (SP3c) format.

The ILRS orbit products are archived in subdirectories by satellite and date; the date is the end of the 7-day interval spanned by the orbit. Each subdirectory contains the individual AC solutions, the two combined solutions and corresponding summary files.

Data Access

SLR Analysis Center (AC) Orbit Products are online:

in subdirectories by satellite name and week as follows:


Code Meaning
SATNAME etalon1, etalon2, lageos1, lageos2, ajisai, lares, larets, starlette, and stella
YY 2-digit year
MM 2-digit month
DD 2-digit day
Bundesamt für Kartographie und Geodäesie (BKG) Germany
Deutsches Geodätisches Forschungsinstitut (DGFI) Germany
ESA/ESOC, Germany
Helmholtz Centre Potsdam German Research Centre for Geosciences (GFZ), Germany
ILRS primary combination solution
ILRS backup combination solution
Italian Space Agency, Centro di Geodesia Spaziale "G. Colombo" (ASI/CGS), Italy
Joint Center for Earth System Technology/Goddard Space Flight Center (JCET/GSFC) Greenbelt, Maryland, USA
NERC Space Geodesy Facility (NSGF) formely RGO Satellite Laser Ranging Group, United Kingdom
XX numeric version number
gz gzipped file