Modernizing and expanding the NASA Space Geodesy Network to meet future geodetic requirements

Abstract

NASA maintains and operates a global network of Very Long Baseline Interferometry (VLBI), Satellite Laser Ranging (SLR), and Global Navigation Satellite System ground stations as part of the NASA Space Geodesy Program. The NASA Space Geodesy Network (NSGN) provides the geodetic products that support Earth observations and the related science requirements as outlined by the US National Research Council (NRC in Precise geodetic infrastructure: national requirements for a shared resource, National Academies Press, Washington, 2010. http://nap.edu/12954, Thriving on our changing planet: a decadal strategy for Earth observation from space, National Academies Press, Washington, 2018. http://nap.edu/24938). The Global Geodetic Observing System (GGOS) and the NRC have set an ambitious goal of improving the Terrestrial Reference Frame to have an accuracy of 1 mm and stability of 0.1 mm per year, an order of magnitude beyond current capabilities. NASA and its partners within GGOS are addressing this challenge by planning and implementing modern geodetic stations colocated at existing and new sites around the world. In 2013, NASA demonstrated the performance of its next-generation systems at the prototype next-generation core site at NASA's Goddard Geophysical and Astronomical Observatory in Greenbelt, Maryland. Implementation of a new broadband VLBI station in Hawaii was completed in 2016. NASA is currently implementing new VLBI and SLR stations in Texas and is planning the replacement of its other aging domestic and international legacy stations. In this article, we describe critical gaps in the current global network and discuss how the new NSGN will expand the global geodetic coverage and ultimately improve the geodetic products. We also describe the characteristics of a modern NSGN site and the capabilities of the next-generation NASA SLR and VLBI systems. Finally, we outline the plans for efficiently operating the NSGN by centralizing and automating the operations of the new geodetic stations.

VLBI measurement of the vector baseline between geodetic antennas at Kokee Park Geophysical Observatory, Hawaii

“…Lösler et al (2019) measured the change in the shape of one of the 13.2 m VGOS antennas at the Onsala Space Observatory (OSO), Sweden, and found that the change in delay from 5° to 90° elevation angles is less than 1 mm, which would result in a vertical height error of less than 1 mm. Finite element modeling by the manufacturer of the new 12 m VGOS antenna at McDonald Observatory, Texas (Merkowitz et al 2018), which is identical to KOKEE12M, indicated that it should also have a sub-millimeter change in delay over the observing range for geodetic observations.…”

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

“…For any system data-related hardware upgrade, the ILRS has a minimum requirement of 20 LAGEOS and LAGEOS 2 passes along with 20 LARES satellite passes for QC analyses by the Analysis Standing Committee (ASC) (Otsubo et al 2018). The NASA Space Geodesy Project (SGP) (Merkowitz et al 2018) has established a more stringent longer duration (six or more months) testing, and the concurrent data generation capability easily supported such a long-term data comparison with no impact on the operational data. During the data gathering phase, the engineering analysis was performed periodically by Cybioms, using the full rate and the NP data.…”

Geodesic Support of Space Research

“…Создание единой координатной системы на территории разного масштаба отдельного государства, континента и всей Земли в целом входит в задачи космического геодезического обеспечения (Merkowitz et al, 2019). Применительно к геодезическому обеспечению космических исследований развитие получили специальные геодезические сети для космических исследований (Merkowitz, 2019).…”