PDS_VERSION_ID = PDS3 RECORD_TYPE = FIXED_LENGTH RECORD_BYTES = 720 FILE_RECORDS = 180 ^IMAGE = "GGM0890A.IMG" INSTRUMENT_HOST_NAME = "MARS GLOBAL SURVEYOR" TARGET_NAME = MARS INSTRUMENT_NAME = "RADIO SCIENCE SUBSYSTEM" DATA_SET_ID = "MGS-M-RSS-5-SDP-V1.0" ORIGINAL_PRODUCT_ID = "anom.mgm0890.xyz" PRODUCT_ID = "GGM0890A.IMG" PRODUCT_RELEASE_DATE = 1999-05-31 DESCRIPTION = " This file contains a digital map of Mars gravity accelerations derived from radio tracking of the Mariner 9, Viking, and Mars Global Surveyor spacecraft. The map is vertical gravity in milligals (1 milligal = 0.01 mm/s/s) at the surface referenced to a sphere of 3397 km radius. The model was constructed from 515,878 observations, summarized in the table below. MGS data are limited to tracking from the Aerobraking Hiatus and Science Phasing Orbit (SPO) subphases of the Orbit Insertion phase. Spacecraft Total Observations -------------------- ------------ Mariner 9 69992 Viking 1 109176 Viking 2 79545 Mars Global Surveyor 257165 -------------------- ------------ Total 515878 Performance of the gravity model can be evaluated by computing the orbit position discrepancy between overlapping arcs. The set of overlapping arcs included nine 4.5 day arcs between March 27 and May 1, 1998 (SPO-1), and 23 4.5 day arcs between May 31 and September 8, 1998 (SPO-2). Results are summarized in the table below: Average RMS Overlaps for Gravity Model MGM0890 Time Interval Radial Cross-Track Along-Track Total (m) (m) (m) (m) ------------- ------ ----------- ----------- ------ SPO-1 35.9 934.1 424.0 1034.1 SPO-2 29.1 116.5 491.2 510.5 Details of the analysis and results can be found in the DOCUMENT directory of this archival volume (see AAS99147.LBL). Or, see [LEMOINEETAL1999]." START_TIME = 1997-09-12T00:00:00 STOP_TIME = 1998-09-17T23:59:59 SOFTWARE_NAME = "SOLVE.SPECIAL;9603.02" PRODUCT_CREATION_TIME = 1998-12-31T23:10:47 PRODUCER_ID = "MGS RST" OBJECT = IMAGE LINES = 180 LINE_SAMPLES = 360 SAMPLE_TYPE = MSB_INTEGER SAMPLE_BITS = 16 OFFSET = 0. SCALING_FACTOR = 0.1 DESCRIPTION = "The Digital Map contains values of vertical gravity in milligals (1 milligal = 0.01 mm/s/s). The true values can be obtained by multiplying the sample in the map by SCALING_FACTOR and then adding OFFSET. " END_OBJECT = IMAGE OBJECT = IMAGE_MAP_PROJECTION ^DATA_SET_MAP_PROJECTION = "DSMAP2.CAT" COORDINATE_SYSTEM_TYPE = "BODY-FIXED ROTATING" COORDINATE_SYSTEM_NAME = PLANETOCENTRIC MAP_PROJECTION_TYPE = "SIMPLE CYLINDRICAL" A_AXIS_RADIUS = 3397.00 B_AXIS_RADIUS = 3397.00 C_AXIS_RADIUS = 3397.00 FIRST_STANDARD_PARALLEL = "N/A" SECOND_STANDARD_PARALLEL = "N/A" POSITIVE_LONGITUDE_DIRECTION = "EAST" CENTER_LATITUDE = 0.0 CENTER_LONGITUDE = 0.0 REFERENCE_LATITUDE = 0.0 REFERENCE_LONGITUDE = 0.0 LINE_FIRST_PIXEL = 1 LINE_LAST_PIXEL = 180 SAMPLE_FIRST_PIXEL = 1 SAMPLE_LAST_PIXEL = 360 MAP_PROJECTION_ROTATION = 0.0 MAP_RESOLUTION = 1.0E+00 MAP_SCALE = "N/A" MAXIMUM_LATITUDE = 89.5 MINIMUM_LATITUDE = -89.5 EASTERNMOST_LONGITUDE = 179.5 WESTERNMOST_LONGITUDE = -179.5 LINE_PROJECTION_OFFSET = 89.5 SAMPLE_PROJECTION_OFFSET = 179.5 END_OBJECT = IMAGE_MAP_PROJECTION END