Independent DEM of Antarctica Using GNSS‐R Data From TechDemoSat‐1

Abstract

The first digital elevation model (DEM) of the Antarctic ice sheet derived from Global Navigation Satellite Systems-Reflectometry (GNSS-R) data from the UK TechDemoSat-1 satellite is presented. This is obtained using 32 months of data from the mission. This opportunistic and inexpensive method is shown to produce encouraging results from the technology demonstration platform of TechDemoSat-1, with median bias under 18 m and root-mean-square difference under 91 m when compared to the CryoSat-2 1-km DEM v1.0. Discrepancies between the two data sets are explored along with possible causes of such differences and potential improvements to further optimize this technique for future GNSS-R missions.Plain Language Summary Obtaining measurements of the Antarctic ice sheet is critical for understanding the effects that climate change might be having on it and its potential future contribution to rising sea levels. The only practical way to do this is by using satellite data, and this has been done successfully previously from the CryoSat-2 satellite, which carries a radar altimeter. However, due to its orbit, it cannot measure an area near the South Pole. Here we demonstrate that measurements of the Antarctic ice sheet, including the vicinity of the South Pole, can be made by taking advantage of GPS signals that bounce off the ice sheet surface. The data are obtained from the UK's TechDemoSat-1 mission, which carries a simple low-cost receiver to pick up the reflected GPS signals. The results from this demonstration mission (which was not designed to survey ice sheets) are promising, showing the potential of this approach for measuring the ice sheet in the future with a dedicated satellite mission.

Sea Ice Detection Using GNSS‐R Data From TechDemoSat‐1

“…This technique is at present largely used to study winds over the ocean (e.g., Foti et al, 2015;Foti et al, 2017;Ruf & Balasubramaniam, 2018). However, other Earth observation applications, such as ice sheet and ocean altimetry (e.g., Cardellach et al, 2004;Cartwright et al, 2018;, the monitoring of soil moisture (Chew et al, 2016), and the cryosphere (e.g., Belmonte Rivas et al, 2010;Gleason, 2006), are also being investigated. Cryospheric applications include the detection and altimetry of sea ice (e.g., Alonso-Arroyo et al, 2017;Hu et al, 2017;Li et al, 2017;Yan & Huang, 2016), the altimetry of glacial ice (e.g., Cardellach et al, 2004;Cartwright et al, 2018;Rius et al, 2017), and permittivity of reflective surfaces (Belmonte Rivas et al, 2010;Fabra et al, 2012).…”

Improved GNSS-R bi-static altimetry and independent DEMs of Greenland and Antarctica from TechDemoSat-1

“…It has been investigated for other applications such as altimetry of the ice sheets and oceans (eg. Cardellach et al (2004); Cartwright et al (2018); Clarizia et al (2016)), soil moisture (Chew et al, 2016) and monitoring of the cryosphere (eg. Belmonte Rivas et al (2010); Cartwright et al (2019); Fabra et al (2012)).…”

“…Belmonte Rivas et al (2010); Cartwright et al (2019); Fabra et al (2012)). The technique has been found to be highly beneficial when applied to the cryosphere not only for sea ice detection (Alonso-Arroyo et al, 2017;Cartwright et al, 2019;Yan and Huang, 2016) and characterisation (Rodriguez-Alvarez et al, 2019) but also for sea ice altimetry (Hu et al, 2017;Li et al, 2017) and glacial ice altimetry (Cartwright et al, 2018;Rius et al, 2017).…”

“…In these cases, spaceborne platforms have been able to achieve root-mean-square (RMS) errors of below 5 m when applied to limited tracks using the group delay (Hu et al, 2017) and below 5 cm where phase delay is available (Li et al, 2017). As more GNSS-R data have become available from the Low Earth Orbiter TechDemoSat-1 (TDS-1), it has been possible to use a larger collection of reflections for the construction of Digital Elevation Models (DEMs) of the larger ice sheets, such as Antarctica (Cartwright et al, 2018). The use of GNSS-R offers a unique opportunity to measure the elevation of ice over the South Pole due to the wide variety of incidence angles available through bi-static altimetry enabling this technique to be unrestricted by the orbital constraints of traditional monostatic radar altimetry.…”

“…These further improve understanding of ice dynamics and potential sea level rise associated with ice sheets. This paper builds upon earlier work done by Cartwright et al (2018), using an algorithm developed by Clarizia et al (2016) for the estimation of sea surface height. Here we use improved re-tracking combined with expansion of the GNSS-R dataset and enhanced processing to yield higher accuracies over the Antarctic Ice Sheet.…”