Inclusion of GPS clock estimates for satellites Sentinel-3A/3B in DORIS geodetic solutions
- PDF / 3,901,766 Bytes
- 20 Pages / 595.276 x 790.866 pts Page_size
- 25 Downloads / 183 Views
ORIGINAL ARTICLE
Inclusion of GPS clock estimates for satellites Sentinel-3A/3B in DORIS geodetic solutions Štepánek ˇ Petr1
· Duan Bingbing2
· Filler Vratislav1 · Hugentobler Urs2
Received: 12 March 2020 / Accepted: 31 August 2020 / Published online: 18 November 2020 © Springer-Verlag GmbH Germany, part of Springer Nature 2020
Abstract A unique architecture of Sentinel-3A and Sentinel-3B satellites includes the shared ultra-stable oscillator (USO) by the DORIS and GPS receivers. This concept enables to apply onboard GPS clock estimates in the DORIS processing substituting the DORIS polynomial clock model by the GPS epoch-wise model, together with a DORIS-specific clock offset. Such an approach is particularly profitable for the mitigation of the South Atlantic Anomaly (SAA) effect affecting the short-term frequency stability of the USO oscillator in the South America and South Atlantic region. The GPS clock behavior precisely maps the SAA effect and enables us to demonstrate a difference of the USO sensitivity to the SAA for Sentinel-3A and Sentinel-3B. We present world grid maps of clock time derivatives for both Sentinels, displaying a different sign of the direct effect and other differences in the USO memory/recovery effect. Moreover, we present the impact of SAA on 3D positioning where the largest SAA-related bias reaches several centimeters. We also determine an effect of the precise clock modeling on the Earth rotation parameter estimates. In addition to these improvements, the elimination of the SAA effect gives us an opportunity to get an almost SAA-free DORIS solution from Sentinel-3A and Sentinel-3B satellites. Using the combined solution of both Sentinels as a reference, we estimate the SAA effect on the DORIS beacon positions also for satellites Jason-2, Jason-3, Saral, Cryosat-2 and Hy-2A and find significant positioning biases for all the recent satellites except Saral. Keywords DORIS · Sentinel-3A · Sentinel-3B · South Atlantic Anomaly · GPS clocks
1 Introduction Doppler Orbitography and Radiopositioning Integrated by Satellite (DORIS) is a space geodetic measurement system similar to Global Navigation Satellite System (GNSS). A major difference to GNSS is that the signal sources are located at the ground stations, while the DORIS receivers are installed on the satellites. Another DORIS specificity is a lower number of satellites of the system (7 or less in time), low or middle Earth orbit (approx. 700–1300 km altitude) and specific characteristics of each DORIS satellite. All onboard DORIS receivers are equipped with ultrastable oscillators (USO, Auriol and Tourain 2010). Frequency variations of USO and corresponding satellite clocks
B
Štˇepánek Petr [email protected]
1
Research Institute of Geodesy, Topography and Cartography, Zdiby, Czech Republic
2
Institute for Astronomical and Physical Geodesy, Technical University of Munich, Munich, Germany
can be determined using DORIS pseudo-range measurements from a few stations equipped with atomic clocks (time-reference beacons). The c
Data Loading...
