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<p>This is an example line of NSF COLDEX MARFA ice penetrating radar data (CLX/MKB2o/R66a) that has been processed to provide azimuthal information about radar echos from below, and to the front and back of the aircraft. The input was 1 meter slow time resampled coherent range record with phase intact. The data were pulse compressed and an azimuth fast Fourier transform was used to convert to azimuth angles in 1 km chunks, then slices at -19°, +19˚ and nadir were selected for these numpy arrays. These can be displayed as an RGB image with Blue = nadir, red = forward and green = rear</p> <p>The nadir slice should dominate specular echos, as seen with englacial reflecting horizons; where this trades to more balanced returns across all three channels, scattering dominates, as with rough bed rock or volume scattering. A gmt text file contains information about where this transition occurs in the ice column.</p> <p>Details in delay Doppler processing can be found in <a href="http://pds-geosciences.wustl.edu/mro/mro-m-sharad-5-radargram- v1/mrosh_2001/document/rgram_processing.pdf">Campbell et al., 2014</a>; the idea for using this approach for looking at englacial structure was discussed by <a href="https://doi.org/10.5194/egusphere-egu23-2856">Arenas-Pingarrón, Á. et al., 2023</a>. Details of HiCARs/MARFA focused processing can be found in <a href="http://dx.doi.org/10.1109/TGRS.2007.897416">Peters et al., 2007</a>.</p> 

The Center for Oldest Ice Exploration (COLDEX) is a US initiative funded to search for climate records over the last 5 million years, including locating sites for an accessible continuous ice core going back 1.5 million years. As part of this effort, COLDEX has mapped the southern flank of Dome A, East Antarctica using an instrumented Basler, including dual frequency radar observations of the ice sheet and ice bed, as well as potential fields measurements (see presentation by Kerr in EGU session G4.3) across two field seasons from Amundsen-Scott South Pole Station. The aerogeophysical system included both the UTIG VHF MARFA radar system operating at 52.5-67.5 MHz, as well as a new large high resolution UHF array from CReSIS operating at 670-750 MHz operating simultaneously. A goal of this project was to obtain airborne repeat interferometry for segments of the survey, as well as directly feed ice sheet models using englacial isochrons (see Singh presentation in EGU session CR5.6). These goals lead to a survey explicitly designed around ice sheet flow lines. While prior work had sampled the region at lithospheric scales, the COLDEX survey had two components - the first was to map the region at crustal scales (line spacing of 15 km), and the second was to map subareas at ice sheet scales (line spacing of 3 km). Immediate observations include an extensive basal unit and strong discontinuity in englacial stratigraphy that runs across the survey area and appears correlated with changes in bed interface properties. The airborne campaign will be used to inform follow up ground campaigns to understand processes relevant for old ice preservation. 

This is a pointer to the Open Polar Radar website and flight based CReSIS SAR processed data. These transect projected radargrams were collected as part of the Center for Oldest Ice Exploration (COLDEX) Science and Technology Center (https://www.coldex.org) in the 2022/23 (CXA1) and 2023/24 (CXA2) airborne field seasons. Raw 3 TB data from both seasons is deposited at the USAP data center at https://doi.org/10.15784/601768. The set of images in this archive was designed for easy, non expert, access to radargrams, organized according to survey design. 2022-23 (CXA1) flight based HDF5/matlab format data is available here: https://data.cresis.ku.edu/data/rds/2022_Antarctica_BaslerMKB/ 2023-24 (CXA2) flight based data HDF5/matlab format is available here: https://data.cresis.ku.edu/data/rds/2023_Antarctica_BaslerMKB/ 2022-23 (CXA1) transect based (science organized) unfocused data in netCDF format is available here: https://doi.org/10.18738/T8/XPMLCC 2023-24 (CXA2) transect based (science organized) unfocused data in netCDF format is available here: https://doi.org/10.18738/T8/FV6VNT Reprojected transect based images (science organized) in standard image (png, jpg) formats will be available here: ttps://doi.org/10.18738/T8/NEF2XM 

ESCHER (Exploration of Saline Cryospheric Habitats with Europa Relevance) is a NASA funded PSTAR (Planetary Science and Technology from Analog Research) program with the general geophysical goals of characterizing the subglacial environment of Devon Ice Cap in Nunavut, Canada as a potential planetary analog. The project seeks to gather additional evidence for unique chemistry in the subglacial hydrological system and to further the technical development of the scientific instrumentation. ESCHER represents the first field deployment of a multi-polarization radar system on an A-Star 350 B2 helicopter platform. This is the sixth polar deployment of this helicopter geophysical system, and the first in the arctic. The previous helicopter-based systems expeditions were KRT1, KRT2, ASE2, ASE3, ASE4. Similar results for ASE3 are described in Pierce et al, 2023, and Pierce et al, 2024. The science goals include characterizing the subglacial environment from the summit of Devon Ice Cap to Sverdrup Glacier’s marine termination. The study area includes three linked geographical regions: i) The summit area where Rutishauser et al. (2020), presented further evidence for the existence of fluid at the base of Devon Ice Cap; ii) the shoulder region of the ice cap, just upstream of the ice flow that enters the outlet valleys of Fox and Sverdrup Glaciers. This region includes the hypothesized distributed hydrological system that transitions into channelized geometry, and iii) The Sverdrup/Fox valley glaciers, tidewater terminus, and locations of subglacial discharge. The study region also includes the upper catchment of the Crocker Bay Glaciers and some of the western land terminating flanks of the ice cap. All data in this collection is derived from a multipolarization version of the Helicopter Radar (HERA) system (Lindzey et al., 2017, 2022). Included in this dataset are the Level 2 time registered geophysical observables for the specific lines mentioned in Pierce et al., (2024); ice thickness, partial bed reflectivity, surface reflectivity, bed and surface elevation derived both from incoherent processing (IR2HI2) and focused processing (IRFOC2; Peters et al., 2007); no multipolarization processing is included here. Also included is specularity content (IRSPC2; Schroeder et al., 2014, Young et al, 2016). Data consists of ASCII tab delimited tables, with header describing the columns and key metadata on a per transect basis. Images showing simple maps of values are also included. The following transects are included: DEV3/PER0a/Y79a DEV3/PER0a/Y80a DEV3/PER0a/Y81a DEV3/PER0a/Y82a DEV3/PER0a/Y83a DEV3/PER0a/Y84a DEV3/PER0a/Y85a DEV3/PER0a/Y86a DEV3/PER0a/Y87a References: Pierce, C., 2024, Advanced Analysis of the Sub-Glacial Environment Using Radar Echo Sounding Simulations, Ph. D. Thesis, Montana State University Pierce, C., Gerekos, C., Skidmore, M., Beem, L., Blankenship, D., Lee, W. S., Adams, E., Lee, C.-K., and Stutz, J., 2024, Characterizing sub-glacial hydrology using radar simulations, The Cryosphere, 18, 4, 1495--1515, 10.5194/tc-18-1495-2024 Pierce, C., Skidmore, M., Beem, L., Blankenship, D., Adams, E., and Gerekos, C., 2024, Exploring canyons beneath Devon Ice Cap for sub-glacial drainage using radar and thermodynamic modeling, Journal Of Glaciology, 1--18, 10.1017/jog.2024.49 Lindzey, L., Quartini, E., Buhl, D., Blankenship, D., Richter, T., Greenbaum, J., and Young, D., 2017, KRT1/LGV1 Season Field Report, 237 10.26153/tsw/11620 Lindzey, L. E., Beem, L. H., Young, D. A., Quartini, E., Blankenship, D. D., Lee, C.-K., Lee, W. S., Lee, J. I., and Lee, J., 2020, Aerogeophysical characterization of an active subglacial lake system in the David Glacier catchment, Antarctica, The Cryosphere, 14, 7, 2217--2233, 10.5194/tc-14-2217-2020 Peters, M. E., Blankenship, D. D., Carter, S. P., Young, D. A., Kempf, S. D., and Holt, J. W., 2007, Along-track Focusing of Airborne Radar Sounding Data From West Antarctica for Improving Basal Reflection Analysis and Layer Detection, IEEE Transactions On Geoscience And Remote Sensing, 45, 9, 2725-2736, 10.1109/TGRS.2007.897416Rutishauser, A., Blankenship, D. D., Young, D. A., Wolfenbarger, N. S., Beem, L. H., Skidmore, M. L., Dubnick, A., and Criscitiello, A. S., 2022, Radar sounding survey over Devon Ice Cap indicates the potential for a diverse hypersaline subglacial hydrological environment, The Cryosphere, 16, 379-395, https://doi.org/10.5194/tc-16-379-2022 Schroeder, D. M., Blankenship, D. D., Raney, R. K., and Grima, C., 2015, Estimating subglacial water geometry using radar bed echo specularity: application to Thwaites Glacier, West Antarctica, IEEE Geoscience And Remote Sensing Letters, 12, 3, 443-447, 10.1109/LGRS.2014.2337878 Young, D. A., Schroeder, D. M., Blankenship, D. D., Kempf, S. D., and Quartini, E., 2016, The distribution of basal water between Antarctic subglacial lakes from radar sounding, Philosophical Transactions Of The Royal Society A, 374, 20140297, 1-21, 10.1098/rsta.2014.0297 

Geophysical Investigations of Marie Byrd Land Lithospheric Evolution (GIMBLE) The PIs propose to use airborne geophysics to provide detailed geophysical mapping over the Marie Byrd Land dome of West Antarctica. They will use a Basler equipped with advanced ice penetrating radar, a magnetometer, an airborne gravimeter and laser altimeter. They will test models of Marie Byrd Land lithospheric evolution in three ways: 1) constrain bedrock topography and crustal structure of central Marie Byrd Land for the first time; 2) map subglacial geomorphology of Marie Byrd Land to constrain landscape evolution; and 3) map the distribution of subglacial volcanic centers and identify active sources. Marie Byrd Land is one of the few parts of West Antarctica whose bedrock lies above sea level; as such, it has a key role to play in the formation and decay of the West Antarctic Ice Sheet (WAIS), and thus on eustatic sea level change during the Neogene. Several lines of evidence suggest that the topography of Marie Byrd Land has changed over the course of the Cenozoic, with significant implications for the origin and evolution of the ice sheet. Two seasons were flown. ICP5 operated from Byrd Camp using Basler C-GJKB and the HiCARS2 radar in January 2013, and ICP6 operated from WAIS Divide Camp using Basler C-FMKB and the MARFA radar in late 2014, both supported by the US Antarctic Program and Kenn Borek Air. ICP6 experienced issues with data overflow on the MARFA system, with resulted in missing radar records and timing ambiguities. GIMBLE data can be found at https://www.usap-dc.org/view/project/p0000435. Dataset organization Transects are provided a P/S/T nomenclature, organized by the Project they are flying in, the acquisition System (typically named after the aircraft) and the Transect within the Project. Transects were collected in preplanned systems with the following parameters: MBL corridor (MBL/MKB##/X|Y###) rotated from the EPSG:3031 polar stereographic projection at 61.75 degrees and separated by 7.5 km in the Y direction and 5 km in the X direction, with an origin of X -579.6 km and Y -803.3 km Untargeted transit lines used the name of the expedition (ICP5|ICP6) as the project, and used the flight and the increment within the flight to name the Transect (eg (ICP6/MKB2l/F19T01a). Processing These data represent focused VHF radargrams. The data are from the HiCARS2/MARFA radar system, a 60 MHz ice penetrating radar system that has operated in several different guises over the years. HiCARS2/MARFA operates with a 1 microsecond chirp with a design bandwidth of 15 MHz, allowing for ~8 range resolution. The record rate after onboard stacking is 200 Hz. High and low gain channels are collected from antennas on each side of the aircraft, for MARFA the antennas are recorded separately. In ground processing, the data was processed using focusing SAR over a range delay of 100 nsec following Peters et al, 2007 (doi:10.1109/TGRS.2007.897416). Where data loss in ICP6 prevented the generating of focused data, simpler unfocused 'pik1' data was substituted, with 10 coherent stakes and 5 incoherent stacks. Data format These data collection represents georeferenced, time registered instrument measurements (L1B data) converted to SI units. The data format are netCDF3 files, following the formats used for NASA/AAD/UTIG's ICECAP/OIB project at NASA's NSIDC DAAC (10.5067/0I7PFBVQOGO5). Metadata fields can be accessed using the open source ncdump tool, or c, python or matlab modules. A Keyhole Metadata Language (KML) file with geolocation for all transects is also provided. 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. Acknowledgements This field work was supported by NSF grant 1043761 to Young; ICP5 aircraft lease costs were supported by NASA Operation Ice Bridge grant NNX11AD33G. Data processing costs were supported by a gift from the G. Unger Vetlesen Foundation and the Open Polar Radar project (NSF grant 2127606) 

These transect organized radargrams were collected as part of the Center for Oldest Ice Exploration (COLDEX) Science and Technology Center (https://www.coldex.org) in the 2023/24 (CXA2) airborne reconnaissance field season. The raw 3 TB data is deposited at the USAP data center at https://doi.org/10.15784/601768. Flight organized data with additional processing by the University of Kansas to remove electromagnetic interference can be found at the Open Polar Radar server (https://www.openpolarradar.org). The science goal was to characterize the ice sheet between Antarctica's Dome A and Amundsen Scott South Pole Station, to locate sites of interest for the drilling of an ice core with ages spanning the mid-Pleistocene. The radar was deployed on Balser C-FMKB, and flown at ranges of up to 800 km from South Pole Station at velocities of 90 m/s and typical altitude above ground of 600 m. Other instruments included a UHF array system provided by the University of Kansas, a gravity meter, a magnetometer, a laser altimeter, and multiple global navigation satellite systems receivers. The radar data is used for finding ice thickness, bed character, englacial structure and surface assessment. Dataset organization Transects are provided a P/S/T nomenclature, organized by the Project they are flying in, the acquisition System (typically named after the aircraft) and the Transect within the Project. Transects were collected in preplanned systems with the following parameters: CLX radials (CLX/MKB##/R###), attempting to emulate flow lines from Dome A and radiating (in the EPSG:3031 polar stereographic projection) from easting 965 km northing 385 km, with a separation of 0.25 degrees. CLX corridor (CLX/MKB##/X###) rotated from the EPSG:3031 polar stereographic projection at -150 degrees and separated by 10 km in the Y direction and 3.75 km in the X direction CLX2 corridor (CLX2/MKB##/X###) rotated from the EPSG:3031 polar stereographic projection at -150 degrees and separated by 2.5 km in its Y direction and 2.5 km in its X direction NPXE radials (NPXE/MKB##/R####) primarily designed to survey the Upper Byrd Glacier Catchment, constitute spokes radiating from South Pole separated by 2 degrees, in the EPSG:3031 polar stereographic projection Untargeted transit lines used the name of the expedition (CXA2) as the project, and used the flight and the increment within the flight to name the Transect (eg (CXA2/MKB2n/F10T02a). Processing These data represent range compressed VHF radargrams as collected and analyzed in the field. The data are from the MARFA radar system, a 60 MHz ice penetrating radar system that has operated in several different guises over the years. MARFA operates with a 1 microsecond chirp with a design bandwidth of 15 MHz, allowing for ~8 meter range resolution. The record rate after onboard stacking is 200 Hz. High and low gain channels are collected from antennas on each side of the aircraft. In ground processing, the data were stacked 10x coherently to reduce range delayed incoherent surface scattering, and then stacked 5 times incoherently to improve image quality. In this preliminary processing, the effective resolution of deep scattering is several hundred meters due to range ambiguities at depth. Data format These data collection represents georeferenced, time registered instrument measurements (L1B data) converted to SI units. The data format are netCDF3 files, following the formats used for NASA/AAD/UTIG's ICECAP/OIB project at NASA's NSIDC DAAC (10.5067/0I7PFBVQOGO5). Metadata fields can be accessed using the open source ncdump tool, or c, python or matlab modules. A Keyhole Metadata Language (KML) file with geolocation for all transects is also provided. 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. Acknowledgements This work was supported by the Center for Oldest Ice Exploration, an NSF Science and Technology Center (NSF 2019719). We thank the NSF Office of Polar Programs, the NSF Office of Integrative Activities, and Oregon State University for financial and infrastructure support, and the NSF Antarctic Infrastructure and Logistics Program, and the Antarctic Support Contractor for logistical support. Additional support was provided by the G. Unger Vetlesen Foundation. 

These transect organized radargrams were collected as part of the Center for Oldest Ice Exploration (COLDEX) Science and Technology Center (https://www.coldex.org) in the 2022/23 (CXA1) airborne reconnaissance field season. The raw 3 TB data is deposited at the USAP data center at https://doi.org/10.15784/601768. Flight organized data with additional processing by the University of Kansas to remove electromagnetic interference can be found at the Open Polar Radar server (https://www.openpolarradar.org). The science goal was to characterize the ice sheet between Antarctica's Dome A and Amundsen Scott South Pole Station, to locate sites of interest for the drilling of an ice core with ages spanning the mid-Pleistocene. The radar was deployed on Balser C-FMKB, and flown at ranges of up to 800 km from South Pole Station at velocities of 90 m/s and typical altitude above ground of 600 m. Other instruments included a UHF array system provided by the University of Kansas, a gravity meter, a magnetometer, a laser altimeter, and multiple global navigation satellite systems receivers. The radar data is used for finding ice thickness, bed character, englacial structure and surface assessment. Dataset organization Transects are provided a P/S/T nomenclature, organized by the Project they are flying in, the acquisition System (typically named after the aircraft) and the Transect within the Project. Transects were collected in preplanned systems with the following parameters: CLX radials (CLX/MKB##/R###), attempting to emulate flow lines from Dome A and radiating (in the EPSG:3031 polar stereographic projection) from easting 965 km northing 385 km, with a separation of 0.25 degrees. CLX corridor (CLX/MKB##/X###) rotated from the EPSG:3031 polar stereographic projection at -150 degrees and separated by 10 km in the Y direction and 3.75 km in the X direction CLX2 corridor (CLX2/MKB##/X###) rotated from the EPSG:3031 polar stereographic projection at -150 degrees and separated by 2.5 km in its Y direction and 2.5 km in its X direction SAD corridor (SAD/MKB##/X###|Y####) designed to characterize the Saddle region near South Pole approximately perpendicular to the flow lines, rooted from the EPSG:3031 polar stereographic projection at -73.8 degrees and separated by 2.5 km in its Y direction and 2.5 km in the its X direction Untargeted transit lines used the name of the expedition (CXA1) as the project, and used the flight and the increment within the flight to name the Transect (eg (CXA1/MKB2n/F10T02a). Processing These data represent range compressed VHF radargrams as collected and analyzed in the field. The data are from the MARFA radar system, a 60 MHz ice penetrating radar system that has operated in several different guises over the years. MARFA operates with a 1 microsecond chirp with a design bandwidth of 15 MHz, allowing for ~8 range resolution. The record rate after onboard stacking is 200 Hz. High and low gain channels are collected from antennas on each side of the aircraft. In ground processing, the data were stacked 10x coherently to reduce range delayed incoherent surface scattering, and then stacked 5 times incoherently to improve image quality. In this preliminary processing, the effective resolution of deep scattering is several hundred meters due to range ambiguities at depth. Data format These data collection represents georeferenced, time registered instrument measurements (L1B data) converted to SI units. The data format are netCDF3 files, following the formats used for NASA/AAD/UTIG's ICECAP/OIB project at NASA's NSIDC DAAC (10.5067/0I7PFBVQOGO5). Metadata fields can be accessed using the open source ncdump tool, or c, python or matlab modules. A Keyhole Metadata Language (KML) file with geolocation for all transects is also provided. 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. Acknowledgements This work was supported by the Center for Oldest Ice Exploration, an NSF Science and Technology Center (NSF 2019719). We thank the NSF Office of Polar Programs, the NSF Office of Integrative Activities, and Oregon State University for financial and infrastructure support, and the NSF Antarctic Infrastructure and Logistics Program, and the Antarctic Support Contractor for logistical support. Additional support was provided by the G. Unger Vetlesen Foundation. 

Abstract. One of the key components of this research has been the mapping of Antarctic bed topography and ice thickness parameters that are crucial for modelling ice flow and hence for predicting future ice loss andthe ensuing sea level rise. Supported by the Scientific Committee on Antarctic Research (SCAR), the Bedmap3 Action Group aims not only to produce newgridded maps of ice thickness and bed topography for the internationalscientific community, but also to standardize and make available all thegeophysical survey data points used in producing the Bedmap griddedproducts. Here, we document the survey data used in the latest iteration,Bedmap3, incorporating and adding to all of the datasets previously used forBedmap1 and Bedmap2, including ice bed, surface and thickness point data from all Antarctic geophysical campaigns since the 1950s. More specifically,we describe the processes used to standardize and make these and futuresurveys and gridded datasets accessible under the Findable, Accessible, Interoperable, and Reusable (FAIR) data principles. With the goals of making the gridding process reproducible and allowing scientists to re-use the data freely for their own analysis, we introduce the new SCAR Bedmap Data Portal(https://bedmap.scar.org, last access: 1 March 2023) created to provideunprecedented open access to these important datasets through a web-map interface. We believe that this data release will be a valuable asset to Antarctic research and will greatly extend the life cycle of the data heldwithin it. Data are available from the UK Polar Data Centre: https://data.bas.ac.uk (last access: 5 May 2023​​​​​​​). See the Data availability section for the complete list of datasets.