NSF 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.
