Abstract
The UK’s TechDemoSat-1 (TDS-1), launched 2014, has demonstrated the use of global positioning system (GPS) signals for monitoring ocean winds and sea ice. Here it is shown, for the first time, that Galileo and BeiDou signals detected by TDS-1 show similar promise. TDS-1 made seven raw data collections, recovering returns from Galileo and BeiDou, between November 2015 and March 2019. The retrieved open ocean delay Doppler maps (DDMs) are similar to those from GPS. Over sea ice, the Galileo DDMs show a distinctive triple peak. Analysis, adapted from that for GPS DDMs, gives Galileo’s signal-to-noise ratio (SNR), which is found to be inversely sensitive to wind speed, as for GPS. A Galileo track transiting from open ocean to sea ice shows a strong instantaneous SNR response. These results demonstrate the potential of future spaceborne constellations of GNSS-R (global navigation satellite system–reflectometry) instruments for exploiting signals from multiple systems: GPS, Galileo, and BeiDou.
Highlights
Global navigation satellite system–reflectometry (GNSS-R) is a rapidly developing approach to Earth observation that makes use of signals of opportunity from global navigation satellite systems (GNSS), which have been reflected from the Earth’s surface
The existing receivers can be adapted to the acquisition of navigation signals within a similar frequency spectrum transmitted by other navigation systems, which potentially allows for a significantly larger number of simultaneous reflections available within the footprint of the GNSS-R sensor, which should translate into higher sampling
A first comparison between forward-scattered correlated power maps incoming from Galileo, BeiDou and global positioning system (GPS) constellations is presented in this study, using ground-processed data collected between November 2015 and March 2019 by the UK TDS-1 mission
Summary
Global navigation satellite system–reflectometry (GNSS-R) is a rapidly developing approach to Earth observation that makes use of signals of opportunity from global navigation satellite systems (GNSS), which have been reflected from the Earth’s surface. The existing receivers can be adapted to the acquisition of navigation signals within a similar frequency spectrum transmitted by other navigation systems (including the European Galileo and the Chinese BeiDou), which potentially allows for a significantly larger number of simultaneous reflections available within the footprint of the GNSS-R sensor, which should translate into higher sampling. The combination of a large number of simultaneous reflections alongside the potential for affordable multi-satellite constellations [12] offers the opportunity to build up an Earth observation system delivering global coverage and high revisit frequency on a relatively low budget. Enabling GNSS-R sensors to use signals incoming from multiple navigation systems requires extensive adaptation work including signal processing optimization to account for different signal characteristics
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