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Larets: Array Offset Information

Center of Mass Information:

The original Center of Mass (CoM) offset for the Larets satellite was 56.2 mm. Analysts have found that the CoM for Larets is different (larger by 6-7 mm) than the original value.

John Ries (Center for Space Research, University of Texas) reported at the ILRS Analysis Working Group Meeting in Frascati Italy (November 3, 2012) that he had adopted 65 mm as the value used in his work (ILRS AWG Meeting Minutes, 2012). However, Bloßfeld et al. (2018) used this value and found that the ILRS network scale was negatively affected by Larets observations.

Sośnica et al. (2015) determined value for the CoM value for Larets of 63.1 mm based on a range bias analysis. This range bias analysis might have included the impact of (1) the CoM used for LAGEOS-1,2 at the time, and (2) range biases at some SLR stations. Nonetheless, Sośnica (2024) finds that this derived value for all detector types has an uncertainty level of only ~2-3 mm. Ries (2024) in a separate analysis for the time span 2020 – 2024 finds that the value of 62.5 mm produces zero mean SLR residuals in his analyses, which are dependent on the current accepted value of the Earth GM (3.986004415 x 1014 m3/s2).

Therefore, for the present the ILRS recommends using the values of 62.5 mm from Ries (2024) or 63.1 mm from Sośnica et al. (2015), pending a detailed detector-specific and configuration-specific analysis for Larets as has been done for the other geodetic satellites.

References

  • Bloßfeld M., Rudenko S., Kehm A. et al. (2018) “Consistent estimation of geodetic parameters from SLR satellite constellation measurements”, J Geodesy, 92(9), 1003–1021, doi: 10.1007/s00190-018-1166-7
  • ILRS AWG (2012). “Minutes of the Fall Analysis Working Group (AWG) Meeting”, INFN/LNF, Frascati, Italy, November 3, 2012. URL: https://ilrs.gsfc.nasa.gov/docs/2012/AWG_Minutes_Frascati_2012.pdf
  • Ries, J. (2024). Center for Space Research, University of Texas, Austin, Texas, Communication to the ILRS Central Bureau
  • Sośnica K., Jäggi A., Meyer U. (2015). “Time variable Earth’s gravity field from SLR satellites”, J. Geodesy, 89, 945–950, doi: 10.1007/s00190-015-0825-1
  • Sośnica K., (2024). Institute of Geodesy and Geoinformatics, Wroclaw University of Environmental and Life Sciences, Wroclaw, Poland, Communication to the ILRS Central Bureau