Data Set Information
DATA_SET_NAME MGS ALTITUDE DATA RECORDS V1.1
DATA_SET_ID MGS-M-ACCEL-5-ALTITUDE-V1.1
NSSDC_DATA_SET_ID
DATA_SET_TERSE_DESCRIPTION
DATA_SET_DESCRIPTION Data Set Overview : All ALTITUDE data are packaged by periapsis number for each aerobraking orbit. ALTITUDE data are provided in a table labeled Pyyyy.tab where 'yyyy' is the four digit periapsis number. Parameters : Altitude: Units : km Latitude: Units : degrees Longitude: Units : degrees Local Solar Time: Units : N/A Longitude of the Sun: Units : degrees Solar Zenith Angle: Units : degrees Density: Units : kg/km**3 Sigma Density: Units : kg/km**3 Scale Height: Units : km Sigma Scale Height: Units : km Data : For each orbit, ALTITUDE data consist of an 11 by 10 array in the file folder Pyyyy. Each row gives atmospheric characteristics at a constant altitude. When applicable, inbound and outbound legs are in separate rows. The altitude levels going from row 1 to row 11 are: periapsis, 1.26 nbar inbound, 1.26 nbar outbound, 130 km inbound, 130 km outbound, 140 km inbound, 140 km outbound, 150 km inbound, 150 km outbound, 160 km inbound, 160 km outbound. The columns from one to ten are separated as follows: altitude, latitude, longitude, local solar time, longitude of the sun, solar zenith angle, density, sigma density, scale height, and sigma scale height. Processing : Density and density scale heights are provided at reference altitudes of periapsis, 1.26 nbar, 130, 140, 150, and 160 km. The latter 4 are obtained by a least squares fit to the 40 point running mean data sets that span 5 km on either side of a reference altitude for both the inbound and outbound portions of the orbit. The values at periapsis are obtained by a similar fit to all data within 10km of the periapsis altitude. See [TOLSONETAL1999B]. Coordinate System : Latitude and longitude are in the IAU Mars Centered Mars Equatorial System. Altitude is above the IAU reference ellipsoid, with a:3393.4 km and f:0.0052083 and including corrections for (4,4) gravitational potential.
DATA_SET_RELEASE_DATE 2000-08-09T00:00:00.000Z
START_TIME 1997-11-13T12:58:24.680Z
STOP_TIME 1999-02-04T09:12:48.010Z
MISSION_NAME MARS GLOBAL SURVEYOR
MISSION_START_DATE 1994-10-12T12:00:00.000Z
MISSION_STOP_DATE 2007-09-30T12:00:00.000Z
TARGET_NAME MARS
TARGET_TYPE PLANET
INSTRUMENT_HOST_ID MGS
INSTRUMENT_NAME ACCELEROMETER
INSTRUMENT_ID ACCEL
INSTRUMENT_TYPE ACCELEROMETER
NODE_NAME Planetary Atmospheres
ARCHIVE_STATUS ARCHIVED
CONFIDENCE_LEVEL_NOTE Confidence Level Overview : Standard deviations on density and scale height are based on the formal covariance matrix for the linear regression of log density and altitude. Data noise is assumed to be the standard deviation of the fit. Review : Comparisons were made with operational data sets. Deviations were within expectations founded on archiving analysis that is based on (4,4) gravitational potential and numerically integrated precision trajectories that were not included in operational software. Data Coverage and Quality : Data coverage during an aerobraking pass has varied throughout the mission. Early in the mission, data were received for 500 seconds on either side of periapsis. Later, the data started between 200 and 250 seconds before periapsis. This change was made to reduce propulsion usage. Though this change somewhat reduced the accuracy of determining the accelerometer bias, it had the advantage of reducing the corruption of the data set with thruster firings while still inside the detectable atmosphere. Not all orbits have yet been included in current archiving data sets. Omitted orbits include orbits where automatic data processing procedures did not produce realistic answers. If required, many of these orbits can be recovered by manual manipulation of data and data analysis procedures.
CITATION_DESCRIPTION Citation TBD
ABSTRACT_TEXT All ALTITUDE data are packaged by periapsis number for each aerobraking orbit. ALTITUDE data are provided in a table labeled Pyyyy.tab where 'yyyy' is the four digit periapsis number.
PRODUCER_FULL_NAME GERALD M. KEATING
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