GENESIS: co-location of geodetic techniques in space

Abstract

Improving and homogenizing time and space reference systems on Earth and, more specifically, realizing the Terrestrial Reference Frame (TRF) with an accuracy of 1 mm and a long-term stability of 0.1 mm/year are relevant for many scientific and societal endeavors. The knowledge of the TRF is fundamental for Earth and navigation sciences. For instance, quantifying sea level change strongly depends on an accurate determination of the geocenter motion but also of the positions of continental and island reference stations, such as those located at tide gauges, as well as the ground stations of tracking networks. Also, numerous applications in geophysics require absolute millimeter precision from the reference frame, as for example monitoring tectonic motion or crustal deformation, contributing to a better understanding of natural hazards. The TRF accuracy to be achieved represents the consensus of various authorities, including the International Association of Geodesy (IAG), which has enunciated geodesy requirements for Earth sciences. Moreover, the United Nations Resolution 69/266 states that the full societal benefits in developing satellite missions for positioning and Remote Sensing of the Earth are realized only if they are referenced to a common global geodetic reference frame at the national, regional and global levels. Today we are still far from these ambitious accuracy and stability goals for the realization of the TRF. However, a combination and co-location of all four space geodetic techniques on one satellite platform can significantly contribute to achieving these goals. This is the purpose of the GENESIS mission, a component of the FutureNAV program of the European Space Agency. The GENESIS platform will be a dynamic space geodetic observatory carrying all the geodetic instruments referenced to one another through carefully calibrated space ties. The co-location of the techniques in space will solve the inconsistencies and biases between the different geodetic techniques in order to reach the TRF accuracy and stability goals endorsed by the various international authorities and the scientific community. The purpose of this paper is to review the state-of-the-art and explain the benefits of the GENESIS mission in Earth sciences, navigation sciences and metrology. This paper has been written and supported by a large community of scientists from many countries and working in several different fields of science, ranging from geophysics and geodesy to time and frequency metrology, navigation and positioning. As it is explained throughout this paper, there is a very high scientific consensus that the GENESIS mission would deliver exemplary science and societal benefits across a multidisciplinary range of Navigation and Earth sciences applications, constituting a global infrastructure that is internationally agreed to be strongly desirable. Graphical Abstract

Satellite laser ranging to BeiDou-3 satellites: initial performance and contribution to orbit model improvement

“…However, SLR may also deliver some information about the along-track (2%) and cross-track components (2%). Furthermore, it enables the performance of independent GNSS orbit solutions based solely on laser observations (Pavlis 1995;Bury et al 2019b), or the combination of both SLR and GNSS observations (Thaller et al 2011;Hackel et al 2015;Bury et al 2020a;Delva et al 2023). Finally, the SLR observations of GNSS satellites can be used for determining global geodetic parameters and terrestrial reference frame realization (Sośnica et al 2018(Sośnica et al , 2019Bury et al 2021;Strugarek et al 2021).…”

Effect of station selection on VLBI-to-GNSS orientation transfer using space-ties onboard a next generation Galileo satellite

“…Ground networks tracking such satellites can be tied through common orbital parameters, even if they have no common sites [4]. Dedicated space missions have been proposed to exploit the possible advantage of space ties to realize a common geodetic reference frame including an onboard broadband VLBI transmitter (VT) tailored to transmitting quasar-like signals [5][6][7][8]. As the signals of such transmitters are similar to quasars, they can be conveniently processed with similar methodologies as the classical VLBI observations [9].…”

Toward a Geodesy and Time Reference in Space (GETRIS): A Study of Apparent Satellite Clocks of a Future GNSS Satellite Constellation

“…The GENESIS satellite mission [6] has a similar approach as the one we follow with the GETRIS concept. By a collocated use of geodetic techniques in space-GNSS, SLR, VLBI and DORIS (Doppler Orbitography and Radiopositioning Integrated by Satellite)-the time and space reference systems on Earth are aimed to be improved and homogenized.…”