EAGLE/ICECAP II RADARGRAMS

• Other Authors: BLANKENSHIP, DONALD D (hasPrincipalInvestigator), ROBERTS, JASON LEIGH (hasPrincipalInvestigator), ROBERTS, JASON LEIGH (processor), GREENBAUM, JAMIN S. (hasPrincipalInvestigator), YOUNG, DUNCAN A. (hasPrincipalInvestigator), YOUNG, DUNCAN A. (processor), VAN OMMEN, TAS (hasPrincipalInvestigator), LE MEUR, EMMANUEL (hasPrincipalInvestigator), BEEM, LUCAS H (hasPrincipalInvestigator), Australian Antarctic Data Centre (publisher)
• Format: Dataset
• Language: unknown
• Published: Australian Antarctic Data Centre
• Subjects: climatologyMeteorologyAtmosphere; environment; geoscientificInformation; GLACIER THICKNESS/ICE SHEET THICKNESS; EARTH SCIENCE; CRYOSPHERE; GLACIERS/ICE SHEETS; RADARGRAM; ICE PENETRATING RADAR; RADIO ECHO SOUNDING; HiCARS2 > Hi-Capability Radar Sounder Version2; BT-67 > Basler BT-67; CONTINENT > ANTARCTICA > Cook Ice Shelf; Denman Glacier; George V Coast; Knox Coast; Sabrina Coast; Totten Glacier; GEOGRAPHIC REGION > POLAR; OCEAN > SOUTHERN OCEAN; Antarctic; Southern Ocean; Antarc*; Antarctica; Australian Antarctic Division; Ice Sheet; Ice Shelf; Ice Shelves
• Online Access: https://researchdata.ands.org.au/eagleicecap-ii-radargrams/1356131; https://doi.org/10.26179/5bcff4afc287d; https://data.aad.gov.au/metadata/records/AAS_4346_EAGLE_ICECAP_LEVEL2_RADAR_DATA; http://nla.gov.au/nla.party-617536

These radargrams were collected as part of the ICECAP (International Collaborative Exploration of the Cryosphere through Airborne Profiling) collaboration in 2015/16 (ICP7) and 2016/17 (ICP8). These data were in part funded by the US National Science Foundation (grant PLR-1543452 to UTIG), Antarctic Gateway, ACE-CRC the G. Unger Vetlesen Foundation, and supported by the Australian Antarctic Division through project AAS-4346. These data collection represents georeferenced, time registered instrument measurements (L1B data) converted to SI units, and is of most interest to users who wish to reprocess the data. Users interested in geophysical observables should used the derived Level 2 dataset. The data format are netCDF3 files, following the formats used for NASA/AAD/UTIG's ICECAP/OIB project at NASA's NSIDC DAAC. Metadata fields can be accessed using the open source ncdump tool, or c, python or matlab modules. See https://www.loc.gov/preservation/digital/formats/fdd/fdd000330.shtml for resources on NetCDF-3, and https://nsidc.org/data/IR2HI1B/versions/1 for a description of the similar OIB dataset. RADAR Ice penetrating radar provides the geometry of the ice shelves and outlet glaciers, and provides constraints on properties at the base of the ice (e.g. subglacial waters, sub ice shelf melting) ER2HI1B georeferenced radar echo data; 4 Hz NetCDF Data Acquisition Parameters A 1-μsec transmitted chirp was used for both surface and bed. Two 14-bit digitizer channels with offset receiver gain were used to record returned echoes over 64 μsec, accommodating 120 dB of dynamic range, including accurate representations of power of the surface and bed echoes. Bandwidth: 52.5-67.5 MHz Tx power: 5700 W Waveform: 1 μsec FM chirp generation, analog down-conversion to 10 MHz center Sampling: 12-bit ADC at 50 MHz sampling Record window: 64.74 μsec Acquisition: two gain channels separated by 47 dB Dynamic Range: 120 dB Monostatic Rx/Tx Data rate: 2.2 MB/sec Maximum Doppler frequency: 36 Hz Pulse Repetition Frequency: 6250 Hz Onboard stacking: 32x Processing Approach Unfocused Synthetic aperture radar (SAR) processing was done (internally referred to as pik1). This is a quick form of processing with no dependencies on other instruments. The first 10 recorded stacks are coherently summed resulting in a 20 Hz sample rate. Then, a narrow band notch filter is applied at 10 MHz to remove local oscillator (LO) leakage. The pulse is compressed using frequency domain convolution of over-scaled synthetic chirp waveform. This results in gains of 83 dB from overscaled chirp, 11.7 dB from range compression, and -3 dB from Hanning window. These are converted to magnitude and five of these stacks are incoherently summed resulting in the final 4 Hz sample rate. Error Sources For this Level 1B product, errors in power may be due to transmitter or receiver malfunctions. Elevated background noise may occur with areas of strong surface scattering (for example crevasses) or Radio Frequency (RF) noise from anthropogenic sources (for example radio calls from the aircraft or other radar systems).