Remote Sensing capability of GNSS signal power estimates: Analyzing long-term MOSAiC reflectometry data

Abstract

A remote sensing experiment has been conducted aboard the German Research icebreaker Polarstern during the MOSAiC expedition in Arctic sea ice under variable conditions. Signal links of a ship-based receiver to transmitters of Global Navigation Satellite Systems (GNSS) have been observed with high data rate (200 Hz raw samples) over the one-year period of the expedition, September 2019 to October 2020. The dedicated GNSS receiver setup is equipped with two antennas: one for conventional tracking of the GNSS signal, on a master channel, and another one to obtain dual-polarization data (left- and right-handed circular polarized), on slave channels. The main objective of the experiment is to establish a reflectometry concept for sea-ice monitoring based on power estimates of the GNSS signal (separately, for direct and reflected links). Additionally, the integrity of the power estimates in the Arctic will be assessed focusing on potential disturbances of signal propagation in the high-latitude ionosphere. Preliminary results show that reflectivity and relative permittivity of the sea-ice covered surface can be derived, ship-based, from GNSS power estimates. The respective permittivity time series of the expedition's first leg is validated against ancillary ice type and ice concentration data that was gathered continuously by observers on the ship (ASSIST protocol). The generally low level of permittivity estimates can be related to the dominating ice type (second-year ice) and the low air temperature, usually below -10°C, during the first leg. The preliminary results indicate rather stable conditions of the direct signal, without signatures of ionospheric disturbances (S4 index of signal strength fluctuations < 0.6). Currently, the study of the first leg data is completed and investigation is extended to the other leg.