Methodology:

Radio-echo sounding (RES) data were acquired over the Institute and Moller ice streams in the Weddell Sea sector of West Antarctica during the Institute-Moller Antarctic Funding Initiative (IMAFI) project from 23rd December 2010 to 9th January 2011. RES data were acquired with the British Antarctic Survey (BAS) Polarimetric radar Airborne Science Instrument (PASIN) radar, using the BAS Twin Otter aircraft "Bravo Lima" as the aerogeophysical platform. The PASIN antenna array is an eight-element folded dipole array attached below the starboard and port wings for reception and transmission. In addition to RES data, the project acquired aerogravity, aeromagnetic, LiDAR, GPS and radar altimeter data. A high-resolution survey grid, with primary line-spacing of 7.5 km, and tielines at 25 km spacing, was acquired over the central part of the ice stream catchments. Additional exploratory aerogeophysical flight lines were acquired to connect the IMAFI survey to existing surveys in adjacent ice streams catchments (e.g. Pine Island Glacier). The survey was flown in a stepped pattern, to achieve level flight that was required for simultaneous acquisition of airborne gravity data. Most data were acquired with a ground clearance <500 m.

The BAS PASIN radar operates at a centre frequency of 150 MHz (Corr et al., 2007). The system transmits interleaved pulse and CHIRP waveforms, the former designed to resolve near-surface internal layering, and the latter for imaging of bed topography in areas of thick ice. The data described here were processed from the CHIRP dataset alone. The CHIRP has a bandwidth of 10 MHz, 4 kW of transmit power, an effective pulse repetition frequency of 312.5 Hz and a receiver sampling frequency of 22 Hz. Further detailed information describing the PASIN system can be found in Corr et al., (2007). Positioning of the aircraft was by differential GPS instruments on the aircraft, processed relative to a GPS base station at the field camp.

Data processing and analysis of the IMAFI RES data is described in detail in Ross et al., (2012) and Jeofry et al., (2018). Raw RES data were processed using Doppler processing (Hélière et al., 2007) to migrate radar-scattering hyperbola in the along-track direction, and then sampled at 13 Hz to produce along-track measurements ('traces') at ~10 m spacing. SEG-Y files of these data were produced, and imported into ProMAX, where semi-automatic picking of the ice-bed interface was undertaken by a single operator. The range from the aircraft to the ice surface was determined using the aircraft radar altimeter, or where the radar altimeter data was of poor quality, nadir LiDAR measurements. Ice thickness (in metres) was determined by multiplying the two-way travel-time between the picked ice surface and ice sheet bed by 0.168 m ns-1, and applying an approximately 10 m correction for the firn layer (Ross et al., 2012). Values of ice surface and bed elevation were then calculated relative to the WGS84 ellipsoid. The spatial reference system was WGS84 EPSG4326.

Note: the SEGY files available here are not georeferenced/contain error in the XY coordinates found in the binary headers. The georeferenced SEGY files for the SAR and non-SAR data can be found at: https://doi.org/10.5285/f32b298b-7906-4360-9e34-16739af73bb7

Data collection:

The BAS Polarimetric radar Airborne Science Instrument (PASIN) radar operates at a centre frequency of 150 MHz, 10 MHz bandwidth and a data acquisition rate of 13 Hz giving a spatial sampling interval of ~10m. The PASIN system interleaves a pulse for imaging layering in the upper half of the ice column and CHIRP signal for imaging the deep ice column and bed topography. The system was installed on the BAS de Havilland Twin Otter aircraft with four-element folded dipole array attached below the starboard and port wings for reception and transmission, respectively.

Data quality:

Crossover analysis shows the RMS error of <18.3 m across the dataset (Ross et al., 2012; Jeofry et al., submitted).

Note: the SEGY files available here are not georeferenced/contain error in the XY coordinates found in the binary headers. The georeferenced SEGY files for the SAR and non-SAR data can be found at: https://doi.org/10.5285/f32b298b-7906-4360-9e34-16739af73bb7