SLR monthly normal point data summary


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 monthly normal point data summary, Greenbelt, MD, USA:NASA Crustal Dynamics Data Information System (CDDIS), Accessed [[enter user data access date]] at doi:10.5067/SLR/slr_data_monthlysum_npt_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 monthly normal point data summary
  • Format: ASCII text format
  • Spatial Coverage: 90.0 to -90.0, 180.0 to -180.0
  • Temporal Coverage: 1983-01-01 to present
  • Temporal Resolution: Monthly
  • File Size: 0.25Mb
  • Platforms: See ILRS mission information


Laser ranging normal points constitute the primary ILRS data product; they are generated following the conclusion of the laser pass and typically transmitted to the CDDIS within hours of the observation. SLR normal point data are transmitted in hourly and daily files where each files contain all data collected by the ILRS operations center in the previous hour or daily time period. Each day, the CDDIS updates monthly satellite-specific files containing all normal point data received to date for the month. The summary files summarize the data passes of the monthly normal point data files.

CRD format started testing in 2008 and became operational in January 2011. ILRS/CSTG formats were used for normal point data from 1976 through 2011.

Data Access

SLR monthly normal point data summary files are online. The starting directory varies based on the CRD format version available. Differences between the versions are documented on the ILRS website at and

in subdirectories by satellite name and year as follows:

SATNAME/YYYY/sum/SATNAME_YYYYMM.sumnpt_crd directory

SATNAME/YYYY/sum/SATNAME_sum.YYMMnpt directory

Code Meaning
SATNAME Satellite name
YYYY4-digit year
YY 2-digit year
MM 2-digit month