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Recent studies have demonstrated that wideband microwave radiometers provide significant potential for profiling important subsurface polar firn characteristics necessary to understand the dynamics of the cryosphere and predict future changes in ice and snow coverage. Different frequencies within the wide spectra of radiometers result in different electromagnetic propagation losses and thus reveal characteristics at different depths in ice and snow. This paper, expanding on those investigations, explores the utilization of the Global Precipitation Measurement (GPM) constellation as a single wideband (6.93 GHz–91.655 GHz) spaceborne radiometer, covering the entire microwave spectrum from C-band to W-band, to profile subsurface properties of the Antarctic firn. Results of the initial analyses over Concordia and Vostok Stations in Antarctica indicate that GPM brightness temperature measurements provide critical information regarding the subsurface temperatures and physical properties of the firn from the surface down to several meters of depth. Considering the high spatiotemporal coverage of polar-orbiting spaceborne radiometers, these results are promising for future continent-level thermal and physical characterization of the Antarctic firn. [ABSTRACT FROM AUTHOR]

The National Aeronautics and Space Administration's (NASA's) Soil Moisture Active–Passive (SMAP) radiometer has been providing geolocated power moments measured within a 24 MHz band in the protected portion of L-band, i.e., 1400–1424 MHz, with 1.2 ms and 1.5 MHz time and frequency resolutions, as its Level 1A data. This paper presents important spectral and temporal properties of the radio frequency interference (RFI) in the protected portion of L-band using SMAP Level 1A data. Maximum and average bandwidth and duration of RFI signals, average RFI-free spectrum availability, and variations in such properties between ascending and descending satellite orbits have been reported across the world. The average bandwidth and duration of individual RFI sources have been found to be usually less than 4.5 MHz and 4.8 ms; and the average RFI-free spectrum is larger than 20 MHz in most regions with exceptions over the Middle East and Central and Eastern Asia. It has also been shown that, the bandwidth and duration of RFI signals can vary as much as 10 MHz and 10 ms, respectively, between ascending and descending orbits over certain locations. Furthermore, to identify frequencies susceptible to RFI contamination in the protected portion of L-band, observed RFI signals have been assigned to individual 1.5 MHz SMAP channels according to their frequencies. It has been demonstrated that, contrary to common perception, the center of the protected portion can be as RFI contaminated as its edges. Finally, there have been no significant correlations noted among different RFI properties such as amplitude, bandwidth, and duration within the 1400–1424 MHz band. [ABSTRACT FROM AUTHOR]