| Date: | 2024-06-14 16:13:27 | |
| Sender: | ”Lemoine, Frank G. (GSFC-61A0)” <frank.g.lemoine@nasa.gov> | |
| Subject: | [SLR-Mail] No.2844: Update of Geodetic Satellite Center-of-Mass (CoM) Information on the ILRS website | |
| Author: | F.G. Lemoine | |
| Content: | Author: F.G. Lemoine Dear Colleagues: This email is to inform you that we have updated the Center-of-Mass (Array offset) information on the ILRS website (https://ilrs.gsfc.nasa.gov) for the following geodetic satellites: Ajisai, LAGEOS-1 & 2, LARES, Starlette & Stella, & Etalon-1& 2. The objective of this email is to make sure you are aware of the latest work, and ask the community of SLR data users to use these latest geodetic satellite CoM corrections, in conjunction with the most recent ILRS Data Handling File for to obtain the best possible scientific results when processing SLR data. We have noticed through interactions with some colleagues, and presentations at the April 2024 EGU, that some are still using older CoM corrections for the geodetic satellites. Previously, Center-of-Mass (CoM) values used for Ajisai, LAGEOS1,2 & the Etalons relied on the work of Otsubo and Appleby (J. Geophys Res., 2003, doi: 10.1029/2002JB002209). These values have been superceded by the new work described by Rodrguez et al. (J. Geodesy, 2019, doi: 10.1007/s00190-019-01315-0). The new values can result in a 20 mm change for big targets (i.e. Etalon and Ajisai) and 4-5 mm change for the LAGEOS satellites compared to the earlier modelling. The new work also provides new CoM corrections for Starlette and Stella. Ries (2008), Sosnica et al. (2014) and Otsubo et al. (2015) had recommended an avg. CoM offset of 78 mm for these satellites, larger than the value of 75 mm supplied at the outset of these satellite missions, and used for many years. In the most recent work, Jos Rodrguez (IGN, Spain) together with Graham Appleby (BGS, UK) and Toshimichi Otsubo (Hitotsubashi University, Tokyo, Japan) have modelled the most relevant effects to compute tables of CoM corrections for the geodetic satellites listed above. The corrections attempt to account to the best extent possible for the relevant documented change in configurations at the laser ranging stations of the ILRS. The latest models are available from a data server at IGN Spain (see below). The tar files contain the data tables, and example software to read this information to return the desired CoM value for a particular satellite on a certain date. Users should read carefully the lastest ILRS Data Handling File (DHF) and use the CoM model specified in the Data Handling File. This is because the applied biases for ILRS stations in the DHF are tied to the CoM model that is used. When using these CoM models in analysis of SLR data , the following citation should be used for any publications: Rodrguez J., Appleby G. & Otsubo, T. (2019). Upgraded modelling for the determination of centre of mass corrections of geodetic SLR satellites: impact on key parameters of the terrestrial reference frame, J. Geodesy, 93, 25532568, doi:10.1007/s00190-019-01315-0. A summary of recent updates is also available in a technical report prepared by Jos Rodrguez: Rodrguez J C. (2022). Centre of mass corrections updates for geodetic spherical satellites: Changes in the latest releases in preparation for the computation of ITRF2020 products, Technical Report IT-CDT 2022-11, Yebes Observatory, Spain, Nov. 22, 2022. URL: https://datos-geodesia.ign.es/SLR/centre_of_mass_models/reports_and_presentations/2022.JCR.IT-CDT-2022-11.CoMupdateGeodSphericalSats.pdf The link to download the latest CoM models for the geodetic satellites, as well as documentation materials is as follows: URL: https://datos-geodesia.ign.es/SLR/centre_of_mass_models/ Please do not hesitate to contact the Rodriguez et al. (2019) authors [Jos Rodriguez, Yebes Observatory, IGN Spain; Toshi Otsubo, Hitotsubashi University, Tokyo, Japan; Graham Appleby, BGS & NERC Space Geodesy Facility] or the ILRS central bureau in the event you have any questions. Sincerely, Frank G. Lemoine on behalf of the ILRS Central Bureau ---------------------------------------- Geodesy & Geophysics Laboratory NASA Goddard Space Flight Center |