LARES: Array Offset Information
Center of Mass Information:
The ILRS originally adopted 133 mm for the LARES Center-of-Mass (CoM) correction, assuming that its reflectors behave like LAGEOS and that the system response function is symmetric. Neubert and Otsubo (2012) provided a refinement using real data from Potsdam and Herstmonceux in the computation, Otsubo et al. (2015, J.Geodesy) showed that the systematic differences between the possible values for the CoM can reach up 8 mm peak to peak. The centroid value of 127 mm of the LARES response function is in agreement with an independent study (Arnold, ILRS Workshop 2013) that derived a centroid value of 128 mm with a 1 mm uncertainty. Updated values for all stations are provided by Rodríguez et al. (2019), as described below.
José Rodríguez (IGN, Spain) in collaboration with Graham Appleby (BGS, UK) and Toshimichi Otsubo (Hitotsubashi University, Tokyo, Japan) has modelled the most relevant effects to compute tables of CoM corrections for the geodetic satellites including LARES. 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 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:
Rodríguez 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, 2553–2568, doi:10.1007/s00190-019-01315-0.
A summary of recent updates is also available in a technical report prepared by José Rodríguez:
Rodríguez 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.
Link to download the latest CoM models for the geodetic satellites (including LARES), as well as documentation materials:
URL: https://datos-geodesia.ign.es/SLR/centre_of_mass_models/
Other references:
- Neubert R. and Otsubo T. (2012). “The Centre of Mass Correction of LARES and LAGEOS”, paper presented at the 2012 International Technical Laser Workshop, Frascati, Italy, Nov. 5-9, 2012.
URL: http://www.lnf.infn.it/conference/laser2012/2tuesday/3_4_4neubert/neubert_l.pdf - Arnold, David A. (2013). “Preliminary Transfer Function of the LARES Satellite”, paper presented at the 18th International Workshop on Laser Ranging, Fujiyoshida, Japan, 11-15, 2013.
URL: https://ilrs.gsfc.nasa.gov/lw18/docs/papers/Session10/13-04-08-Arnold.pdf - Otsubo T., Sherwood R.A., Appleby G.M. et al. (2015). “Center-of-mass corrections for sub-cm-precision laser-ranging targets: Starlette, Stella and LARES,” J. Geodesy, 89, 303–312, doi:1007/s00190-014-0776-y.
