Transitioning the NASA SLR network to Event Timing Mode for reduced systematics, improved stability and data precision

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dc.contributor.authorVarghese, Thomas
dc.contributor.authorRicklefs, Randall L.
dc.contributor.authorPavlis, Erricos C.
dc.contributor.authorKuzmicz-Cieslak, Magdalena
dc.contributor.authorMerkowitz, Stephen M.
dc.date.accessioned2020-01-29T18:37:34Z
dc.date.available2020-01-29T18:37:34Z
dc.date.issued2019-11-21
dc.description.abstractNASA’s legacy Satellite Laser Ranging (SLR) network produces about one-third of the global SLR data to support space geodesy. This network of globally distributed stations has been using Time Interval Units (TIU) for range measurements for the last 25 + years. To improve the reliability of the SLR network and satisfy the need for stable millimeter precision data, a phased replacement of the TIUs in the network with picosecond-precise Event Timer Modules was initiated in 2015. This scheme allowed the time of flight and laser transmit epoch measurement to one picosecond resolution. For a network with global scientific impact, transitioning to a new data generation metrological scheme requires significant data scrutiny and long-term science data validation. Any long-term testing/measurement has the potential to interrupt the station’s daily operational data flow to the International Laser Ranging Service (ILRS) as the station under test will have to put its test data into quarantine. We have demonstrated a very effective way to test and implement the new device without removing the old hardware and without the need for the orbit analysis. This operationally noninvasive scheme performed concurrent test measurements enabling uninterrupted operational data flow to the users, while allowing simultaneous test data capture for short- and long-term systematics and stability analysis. Extensive analysis of the test data was performed by the NASA SLR engineering team and the ILRS Analysis Standing Committee, to uncover biases and any dependencies on the satellite ranges (for nonlinear scale issues). Multi-ETM comparison was also performed at two of the SLR stations through the interchange of hardware to establish the inter-device range biases and stability. Such benchmarked hardware was subsequently sent to the remaining stations to allow traceability and normalize the network performance. The range bias intercomparison performed using the multiyear SLR data analysis agreed well with the engineering changes, thus validating the approach to flush out station-specific ranging systematics affecting precise orbit determination. Such an improvement and rebalancing of the current network will allow an orderly transition of the current NASA SLR network operating at a maximum rate of 10 Hz to the NASA next generation Space Geodesy Satellite Laser Ranging (SGSLR) network operating at 2 kHz (McGarry et al. in J Geod, 2018. https://doi.org/10.1007/s00190-018-1191-6; Merkowitz et al. in J Geod, 2018. https://doi.org/10.1007/s00190-018-1204-5).en_US
dc.description.sponsorshipThe authors wish to acknowledge the SLR operations program management at NASA codes 453 and 61A and the SLR network operations team at the OC and the NASA feld stations. E. C. Pavlis and M. Kuzmicz-Cieslak acknowledge the support of NASA Grant NNX15AT34A. We thank the referees for their reviews and many helpful comments.en_US
dc.description.urihttps://link.springer.com/article/10.1007/s00190-019-01326-xen_US
dc.format.extent11 pagesen_US
dc.genrejournal articlesen_US
dc.identifierdoi:10.13016/m2u7pb-k9xa
dc.identifier.citationVarghese, Thomas; Ricklefs, Randall L.; Pavlis, Erricos C.; Kuzmicz-Cieslak, Magdalena; Merkowitz, Stephen M.; Transitioning the NASA SLR network to Event Timing Mode for reduced systematics, improved stability and data precision; Journal of Geodesy, Volume 93, Issue 11, pp 2345–2355 (2019); https://link.springer.com/article/10.1007/s00190-019-01326-xen_US
dc.identifier.urihttps://doi.org/10.1007/s00190-019-01326-x
dc.identifier.urihttp://hdl.handle.net/11603/17187
dc.language.isoen_USen_US
dc.publisherSpringer Berlin Heidelbergen_US
dc.relation.isAvailableAtThe University of Maryland, Baltimore County (UMBC)
dc.relation.ispartofUMBC Joint Center for Earth Systems Technology
dc.rightsThis item is likely protected under Title 17 of the U.S. Copyright Law. Unless on a Creative Commons license, for uses protected by Copyright Law, contact the copyright holder or the author.
dc.rightsPublic Domain Mark 1.0*
dc.rightsThis work was written as part of one of the author's official duties as an Employee of the United States Government and is therefore a work of the United States Government. In accordance with 17 U.S.C. 105, no copyright protection is available for such works under U.S. Law.
dc.rights.urihttp://creativecommons.org/publicdomain/mark/1.0/*
dc.subjectsatellite laser rangingen_US
dc.subjectevent timer moduleen_US
dc.subjecttime interval uniten_US
dc.subjectNASA SLR networken_US
dc.subjectrange biasen_US
dc.titleTransitioning the NASA SLR network to Event Timing Mode for reduced systematics, improved stability and data precisionen_US
dc.typeTexten_US

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