1,721,281 research outputs found
COLDEX Unfocused Airborne VHF Radar Transects: 2023-2024 South Pole Field Season
No full textThese 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. <p
Radar Classification of the Antarctic Ice-Bed Interface: Version 2
No full textThis classified_bed data product represents the radar bed classification shown in Young et al., 2016. Values of 0 represent specularity content below 20%; values of 3.3 represent specularity content above 20% and energy 1 microsecond below the bed 15 dB lower than the bed echo, and values of 6.7 represent specularity content above 20% and energy 1 microsecond below the bed 15 dB within than the bed echo. Grids for specularity content and post bed echo are also available. Data is available as COARDS-compliant netCDF-4/HDF5 grids (.grd) and GeoTiffs (.tiff), both in EPSG 3031 (Antarctic Polar Stereographic) projection.
Data were gridded using GMT6.1 and the nnbathy natural neighbor interpolator. Cell size was 1 km, gaussian filter distance was 5 km, and mask radius was 2 km.
Browse images, with Bedmap3 (Pritchard et al., 2025) surface elevation contours and MEASURES phase derived surface velocities (Mouginot et al. 2019) are available for each dataset.
An interpretation of the values in the classified_bed product is that low values are rough bed, intermediate values are isotropic wet bed, and high values are anisotropic wet bed.
Version 1 includes data from the 2016 paper, including AGASEA over Thwaites Glacier (Holt et al., 2006), ATRS over West Antarctica (Peters et al., 2005), GIMBLE over Marie Byrd Land (Young et al, 2013) and parts of ICECAP over Wilkes Subglacial Basin, Dome C, Highland B and Totten Glacier. (Young et al, 2011, Young et al., 2016). We expect updates to the coverage as part of work funded by the Arête Glaciers Initiative.
References
Holt, J. W., Blankenship, D. D., Morse, D. L., Young, D. A., Peters, M. E., Kempf, S. D., Richter, T. G., Vaughan, D. G., and Corr, H., New boundary conditions for the West Antarctic ice sheet: subglacial topography of the Thwaites and Smith Glacier catchments, 2006, Geophysical Research Letters, 33 (L09502), pp., https://doi.org/10.1029/2005GL025561
Mouginot, J., Rignot, E., and Scheuchl, B., Continent-wide, interferometric SAR phase, mapping of Antarctic ice velocity, 2019, Geophysical Research Letters, 46(16), pp.9710-9718, https://doi.org/10.1029/2019GL083826
Peters, M. E., Blankenship, D. D., and Morse, D. L., Analysis techniques for coherent airborne radar sounding: Application to West Antarctic ice streams, 2005 ,Journal of Geophysical Research, 110(B06303), pp.,https://doi.org/10.1029/2004JB003222
Pritchard, H. D., and others.,Bedmap3 updated ice bed, surface and thickness gridded datasets for Antarctica,2025,Scientific Data,12(1), pp.414,https://doi.org/10.1038/s41597-025-04672-y
Young, D. A., D. D. Blankenship, J. S. Greenbaum, E. Quartini, G. L. Muldoon, F. Habbal, L. E. Lindzey, C. A. Greene, E. M. Powell, G. C. Ng, T. G. Richter, G. Echeverry, and S. Kempf, 2024, Geophysical Investigations of Marie Byrd Land Lithospheric Evolution (GIMBLE) Airborne VHF Radar Transects: 2012/2013 and 2014/2015, https://doi.org/10.18738/T8/BMXUHX, Texas Data Repository
Young, D. A., Wright, A. P., Roberts, J. L., Warner, R. C., Young, N. W., Greenbaum, J. S., Schroeder, D. M., Holt, J. W., Sugden, D. E., Blankenship, D. D., van Ommen, T. D., and Siegert, M. J.,A dynamic early East Antarctic Ice Sheet suggested by ice covered fjord landscapes, 2011, Nature, 474, pp.72-75, https://doi.org/10.1038/nature10114
Young, D. A., Schroeder, D. M., Blankenship, D. D., Kempf, S. D., and Quartini, E.,The distribution of basal water between Antarctic subglacial lakes from radar sounding,2016,Philosophical Transactions of the Royal Society A, 374 (20140297), pp.1-21, https://doi.org/10.1098/rsta.2014.0297
Change Log
Changes from V1: changes to gridding parameters to more closely match the figures from Young 2016; updated metadata gridding descriptio
NSF COLDEX Delay Doppler Radar Profiles of Southern Dome A, Antarctica
No full text
Underway coherent radar data, transformed from the along track space domain to the wavenumber domain to reveal the Doppler response of signals, indicates the direction of returning echoes. This delay-Doppler processing can be used to constrain the degree of scattering or specularity of the target surfaces (Tyler et al. 1992, Michaelides and Schroeder, 2019).
These MARFA 60 MHz radar data have been processed using a delay-Doppler approach to obtain three views of the echo data: one pointing 11° ahead of the aircraft, one pointing 11° behind the aircraft, and one directly below the aircraft. The data is organized with individual transects as separate netCDF4 files. Delay Doppler processing operated on a 1 m sampled version of the raw data, using a 1000 m aperture. The fast time sampling of the product is 0.2 µsec, and the along track sampling is 500 m.
The maximum value in each delay doppler bin was found. The channels were scaled using the noise floor. The data are processed using only the right aircraft wing high gain channel (MARFA channel 6) to widen the across track beam pattern and reduce the effect of aircraft roll.
X and Y GPS locations of the aircraft in EPSG 3031 (Antarctic Polar Stereographic) coordinates are included.
Browse images in PNG format (*_specularity.gmt) show the following:
An RGB version with the nadir view loaded into blue, and the sum of the fore and aft views loaded into the red and green channels, with the tracked surface and the bottom of the stratigraphic unit traced.
A grayscale view of the sum of the fore and aft views.
A grayscale view of the nadir view.
A tab delimited ASCII table (*_specularity.gmt) is included for each transect with the following columns:
x: easting coordinate in EPSG 3031 projection [meters]
y: northing coordinate in EPSG 3031 projection [meters]
surface[s]: time delay to the surface [microseconds]
base_specular[s]: time delay to base of the specular englacial unit [microseconds]
deep_scattering_zone[s]: time delay to 1 microsecond into scattering basal unit in [microseconds]
slope: slope of the transition the base of the specular englacial unit
slope: srf_spec: signal to noise ratio of the detected surface return [dB]. Note for the high gain channel this will be usually saturated
dsz_power: signal to noise ratio of the echos in the basal unit [dB]
The netCDF4 files are structured as follows:
netcdf TRANSECTNAME_dd_analysis.nc {
group: channels {
dimensions:
fast_time = 320;
direction = 3;
aperture = UNLIMITED;
variables:
double fast_time(fast_time=XXX);
double direction(direction=3);
float normalized_max_in_bin(aperture=XXX, fast_time=320, direction=3);
:_ChunkSizes = 1U, 320U, 3U; // uint
double X(aperture=XXX);
:units = "m";
:_ChunkSizes = XXXU; // uint
double Y(aperture=XXX);
:units = "m";
:_ChunkSizes = XXXU; // uint
}
// global attributes:
:increment = 500L; // long
:aperture = 1000L; // long
:transect = "TRANSECTNAME";
:processor = "denoise1";
:channel = 6L; // long
}
</div
NSF COLDEX Basal Unit maps derived from delay Doppler proccessing
No full text
The geotiff files in this dataset are maps of the transect based data included as *.gmt files with the delay Doppler profiles in “NSF COLDEX Delay Doppler Radar Profiles of Southern Dome A, Antarctica”. . Ice thicknesses from the [NSF COLDEX compilation](https://doi.org/10.18738/T8/M77ANK) were used for reference, and a two-way speed of light in ice used was 84.5 m/microsecond. GMT 6.2 was used to generate these files with the following steps:
gmt blockmedian with a cell size of 5000 meters
gmt surface with a cell size of 1000 meters and a tension factor of 0.35
gmt grdmask with a search radius of 10000 meters
The files include:
srf.xyz_val.tiff: time delay to the surface [microseconds]
basal_depth.xyz_val.tiff: thickness to the base of the specular englacial unit [m]
basal_thk.xyz_val.tiff: thickness of the basal unit [m]
dsz_delay.xyz_val.tiff: time delay to 1 microsecond into scattering basal unit [microseconds]
dsz_power: signal to noise ratio of the echos in the basal unit [dB]
gradient.xyz_val.tiff: slope of the transition at the base of the specular englacial unit [dB/microsec]
Files are in the Antarctic Polar Stereographic projection (ESPG 3031) with X and Y units of meters.
Browse PNG files are also included.
The following transects were excluded due to electromagnetic interference issues:
CLX/MKB2m/X48a
CLX/MKB2m/X53a
CLX/MKB2n/R40a
CLX/MKB2n/R48a
CLX/MKB2n/R52a
CLX/MKB2n/R54a
CLX/MKB2n/R54b
CLX/MKB2n/R68a
CLX/MKB2n/R70a
CLX/MKB2n/R72a
CLX/MKB2n/X33a
CLX/MKB2n/X38a
CLX/MKB2n/X43a
CLX/MKB2n/X53b
CLX/MKB2n/X58a
CLX/MKB2n/X63a
CLX/MKB2o/R77a
NPXE/MKB2o/R55a
</div
NSF COLDEX 2023-2024 Airborne Season (CXA2): Level 1B Serial Instrument Measurements
No full textNSF COLDEX CXA2 laser ranging, magnetic field strength and orientation, and positioning
This data collection represents georeferenced, time registered instrument measurements (Level 1B data) converted to SI units, and is of most interest to users who wish to reprocess the data. Users interested in geophysical observables (eg magnetic anomalies and surface elevation) should used the derived Level 2 datasets. The data format are space delimited ASCII files, following the formats used for UTIG predecessor ICECAP/OIB project at NASA's NSIDC DAAC. Fields are described in the # delimited detailed header for each granule.
DATASET ORGANIZATION
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).
POSITIONING
GPS provides the positioning (and timing) for all other data streams:
IPUTG1B (ICECAP Positioning/UTIG GPS Level 1B): real time CA-code 1 Hz GPS position data
MAGNETICS
Magnetic data provides constraints on the depth to crystalline rock, the temperature structure of the crust, and the underlying tectonics
IMGEO1B (ICECAP Magnetics: Geometrics Level 1B): georeferenced total magnetic field data; 10 Hz ASCII
IMFGM1B (ICECAP Magnetics/Flux Gate Magnetometer Level 1B): georeferenced aircraft referenced magnetic field vectors; 10 Hz ASCII
ALTIMETRY
Laser altimetry provides for surface shape and altimetry validation. See COLDEX 2023-24 Riegl Laser Altimeter Level 2 Geolocated Surface Elevation Triplets for derived surface elevation data.
ILUTP1B (ICECAP Lidar/UTIG Profiler Level 1B): georeferenced laser range data, no orientation corrections; 3.5 Hz ASCII
This work was supported by the U.S. National Science Foundation Center for Oldest Ice Exploration (NSF COLDEX), an NSF Science and Technology Center (NSF 2019719). We thank the NSF Office of Polar Programs, the NSF Office of Integrative Activities and the NSF Antarctic Infrastructure and Logistics Program, Kenn Borek Airlines and the Antarctic Support Contractor for logistical support. Additional support came from the Open Polar Radar project (NSF grant 2127606) award to the University of Texas at Austin and a gift to UTIG from the G. Unger Vetlesen foundation
NSF COLDEX 2022-2023 Airborne Season (CXA1): Level 1B Serial Instrument Measurements
No full textNSF COLDEX CXA1 laser ranging, magnetic field strength and orientation, and positioning
This data collection represents georeferenced, time registered instrument measurements (Level 1B data) converted to SI units, and is of most interest to users who wish to reprocess the data. Users interested in geophysical observables (eg magnetic anomalies and surface elevation) should used the derived Level 2 datasets. The data format are space delimited ASCII files, following the formats used for UTIG predecessor ICECAP/OIB project at NASA's NSIDC DAAC. Fields are described in the # delimited detailed header for each granule.
DATASET ORGANIZATION
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).
POSITIONING
GPS provides the positioning (and timing) for all other data streams:
IPUTG1B (ICECAP Positioning/UTIG GPS Level 1B): real time CA-code 1 Hz GPS position data
MAGNETICS
Magnetic data provides constraints on the depth to crystalline rock, the temperature structure of the crust, and the underlying tectonics
IMGEO1B (ICECAP Magnetics: Geometrics Level 1B): georeferenced total magnetic field data; 10 Hz ASCII
IMFGM1B (ICECAP Magnetics/Flux Gate Magnetometer Level 1B): georeferenced aircraft referenced magnetic field vectors; 10 Hz ASCII
ALTIMETRY
Laser altimetry provides for surface shape and altimetry validation. See COLDEX 2022-23 Riegl Laser Altimeter Level 2 Geolocated Surface Elevation Triplets for derived surface elevation data.
ILUTP1B (ICECAP Lidar/UTIG Profiler Level 1B): georeferenced laser range data, no orientation corrections; 3.5 Hz ASCII
This work was supported by the U.S. National Science Foundation Center for Oldest Ice Exploration (NSF COLDEX), an NSF Science and Technology Center (NSF 2019719). We thank the NSF Office of Polar Programs, the NSF Office of Integrative Activities and the NSF Antarctic Infrastructure and Logistics Program, Kenn Borek Airlines and the Antarctic Support Contractor for logistical support. Additional support came from the Open Polar Radar project (NSF grant 2127606) award to the University of Texas at Austin and a gift to UTIG from the G. Unger Vetlesen foundation
NSF COLDEX/Open Polar Radar Example Delay Doppler Classification of Englacial Reflectors
No full textThis 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
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.
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; the idea for using this approach for looking at englacial structure was discussed by Arenas-Pingarrón, Á. et al.,
2023. Details of HiCARs/MARFA focused processing can be found in Peters et al., 2007.</p
NSF COLDEX Level1B GPS/IMU derived post processed aircraft trajectories
No full text
NSF COLDEX GPS/IMU Level 1B Airborne Position and Attitude Solutions
These data are results processed using Hexagon | NovAtel's Waypoint Inertial Explorer, a GUI
environment for performing joint Inertial Measurement Unit (IMU) / Global Positioning System (GPS)
kinematic position and attitude solutions. The raw data used for creating these solutions is at Young et al., 2025 [USAP-DC] . Manual steps included cutting out bad portions of data and removing bad GPS satellite range information. Only the US GPS constellation of satellites was used.
Two types of solution are provided.
wpt1 solutions are produced by jointly processed IMU rotation rate and acceleration data with GPS
data using a Kalman filter to produce an internally consistent position and aircraft attitude solution at the
center of the IMU unit at a rate of 50 Hz. Loosely coupled solutions first perform kinematic precise point
positioning (PPP) solving the GPS range data for 1 Hz positions, and then fit the IMU data to interpolate
positions and find attitude. Tightly coupled solutions incorporate the IMU data into the position solutions.
Accuracies are typically on the order of a few cm.
wpt2 solutions only have the PPP position solution, and provide redundancy in the case of an IMU issue.
These produce data at the rate of the GNSS receiver (typically 1–2 Hz).
Files have the following name convention:
SEASON_PLATFORM_FLIGHT_PROCESSING.wpt#
Here the SEASON is either CXA1 (the 2022–23 NSF COLDEX airborne season) or
CXA2 (the 2023–24 NSF COLDEX airborne season); the PLATFORM is the GNSS
antenna/receiver combination; the FLIGHT is the flight number within the season; and the
PROCESSING is either LCPPP (loosely coupled with PPP), TCPPP (tightly
coupled with PPP), or PPP (PPP only). Some flights have multiple files due to system restarts;
other files span multiple flights due to short turn around between flights.
A file called POS_timelimits.csv contains the start and end time of each file in seconds with respect to the UNIX epoch.
The files are in the form of tables with headers and footers delimited with the # character.
Column names are internally defined.
</article
NSF COLDEX 2023-24 Level 2 Basal Specularity Content Profiles
No full text Introduction
The National Science Foundations Center for Oldest Ice Exploration (NSF COLDEX) is a Science and Technology Center working to extend the record of atmospheric gases, temperature and ice sheet history to greater than 1 million years. As part of this effort, NSF COLDEX has been searching for a site for a continuous ice core extending through the mid-Pleistocene transition. Two seasons of airborne survey were conducted from South Pole Station across the southern flank of Dome A.
2023-2024 Field Season
In the 2023-2024 field season (CXA2), and using a BT-67 Basler, NSF COLDEX conducted 17 flights from South Pole Station toward the southern flank of Dome C. Three test flights were conducted from McMurdo Station. Instrumentation included the 60 MHz MARFA ice penetrating radar from the University of Texas Institute for Geophysics, a UHF ice penetrating radar from the Center for Remote Sensing and Integrated Systems; an GT-2 Gravimeter, and LD-90 laser altimeter and an G-823 Magnetometer.
Basal specularity content
These basal specularity content were derived from comparing 1D and 2D focused MARFA data (Peters et al., 2007). By comparing bed echo strengths for different focusing apertures, and accounting for the ranges and angles involved, we can derive the "specularity content" of the bed echo, a proxy for small scale bed roughness and a good indicator for subglacial water pressure in regions of distributed subglacial water (Schroeder et al., 2014, IEEE GRSL , Dow et al., 2019, EPSL ) and smooth deforming bed material (Schroeder et al., 2014, GRL, Young et al., 2016, PTRS. Specularity data are inherently noisy, so these products have been smoothed with a 1 km filter.</p
NSF COLDEX 2022-2023 Airborne Season (CXA1): Level 1 gravimeter instrument measurements
No full textNSF COLDEX CXA1 raw gravity measurements
These are the raw acceleration and gravity measurements from the GT-2A gravity meter SN018, formatted as ASCII text files, and organized by flight. They are not georeferenced. For processing for gravity anomalies, precise GPS trajectories are required to remove aircraft accelerations. Raw GNSS data is available at the USAP-DC . For each flight, measurements were taken before and after takeoff for reference, and then during the flight.
The absolute value of gravity at the aircraft parking place used in processing of the airborne data was determined to be 982316.4 mGal, via a tie to the Thiel gravity monument at McMurdo Station obtained using Lacoste & Romberg Gravity meter G-399 carried between the locations.
There are three types of GT-2A files:
“G” files - data from the gravity sensor
“S” files - data from the gravity meter 3-axes platform
“H” files - header file describing parameters set for each flight
Gravity Sensor Files
These files are formatted with a header line with flight information, and 18 columns:
Message Identifier
Time in seconds the gravimeter has been operational
UTC time (hhmmss.ss)
Subsecond time
fine channel Z acceleration (m/s2) first interval
fine channel Z acceleration (m/s2) second interval
coarse channel Z acceleration (m/s2) first interval
coarse channel Z acceleration (m/s2) second interval
X acceleration (m/s2) first interval
X acceleration (m/s2) second interval
Y acceleration (m/s2) first interval
Y acceleration (m/s2) second interval
Normalized temperature
Y * X Cross Coupling term (m/s2)
X * Y Cross Coupling term (m/s2)
Proof mass vertical displacement (m)
Saturation indicator
checksum
Platform Files
These files are formatted with a header line with flight information, and 18 columns:
Message Identifier
Time in seconds the gravimeter has been operational
UTC time (hhmmss.ss)
Subsecond time
Normalized relative angular velocity around the x axis (1/s)
Normalized relative angular velocity around the y axis (1/s)
Normalized relative angular velocity north component (1/s)
Heading (radians)
Instrument twist within platform (radians)
X damping (1/s)
Y damping (1/s)
X damping algorithm estimate (1/s2)
Y damping algorithm estimate (1/s2)
Platform pitch (radians)
Platform roll (radians)
Platform yaw (radians)
Equipment Status
checksum
Header Files
This file is a sequence of value settings:
F = Latitude of starting point (ddd°mm’sec.sec”)
L = Longitude of starting point (ddd°mm’sec.sec”)
H = Height of starting point (m)
G = gravity of starting point (m/s2)
D = Date of flight
VarGPS = zero
Fcheb = zero
Xant = X coordinate of GPS antenna (m)
Yant = Y coordinate of GPS antenna (m)
Zant = Z coordinate of GPS antenna (m)
Kwx = Scale correction for the X accelerometer
Kwy = Scale correction for the Y accelerometer
Kwzm = Correction to the GSE scale factor, small range
Kwzb = Correction to the GSE scale factor, large range
Kp = Scale correction to gyro X
Kq = Scale correction to gyro Y
Kr = Scale correction to the Fibro Optic Gyro (FOG)
dp = Gyro Drift along X axis
dq = Gyro Drift along Y axis
dr = FOG along Z axis
dWx = Zero drift of X accelerometer
dWy = Zero drift of Y accelerometer
Awx = Misalignment of X accelerometer
Awy = Misalignment of Y accelerometer
Ay = Non-orthogonality gyro axis
Betz = Misalignment of GSE about X axis
Gamz = Misalignment of GSE about Y axis
dASx = Zero point of X angular-data transmitter
dASy = Zero point of Y angular-data transmitter
dASz = Zero point of Z angular-data transmitter
Kwxq = Scale factor of GSE X RMS correction
Kwyq = Scale factor of GSE Y RMS correction
This work was supported by the U.S. National Science Foundation Center for Oldest Ice Exploration (NSF COLDEX), an NSF Science and Technology Center (NSF 2019719). We thank the NSF Office of Polar Programs, the NSF Office of Integrative Activities and the NSF Antarctic Infrastructure and Logistics Program, Kenn Borek Airlines, Transparent Earth Geophysics, and the Antarctic Support Contractor for logistical support. Additional support was provided by a gift to UTIG from the G. Unger Vetlesen foundation
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