Magellan Free-air gravity

Magellan line of sight acceleration profile data record (LOSAPDR)

The Magellan LOSAPDR files contain results from processing of radio tracking data. The Doppler shift of radio transmissions along the line-of-sight from the spacecraft to the receiver on the Earth is measured, and splines are fitted to the Doppler residual values resulting from spacecraft orbit solutions. Analytical differentiation of spline results is then interpreted as local accelerations, from which the size and location of mass anomalies can be inferred. The image above shows the free-air gravity field of Venus as determined from cycle 4 and 5 Doppler data. More information about this image is available in the caption. Note that this image is NOT on the CD-ROM, which contains LOSAPDRs stored as ASCII tables, one file per orbit. Each row in the table contains times, Doppler residuals, spacecraft position and velocity information, and inferred spacecraft acceleration.

The Planetary Data System (PDS) has written the LOSAPDR products onto CD. One CD-ROM volume has been produced for cycle 4 and 2 CD-WO volumes have been produced covering cycles 4-6. These are available from NSSDCA. These data are also available on-line at the PDS Geophysics Subnode.

Ordering the LOSAPDR CD-ROM - NSSDCA CD-ROM Catalog
More information on the LOSAPDR CD-ROM - NSSDCA Master Catalog
Detailed information on the Cycle 4 LOSAPDR CD
PDS Geosciences Node
PDS Geophysics Subnode

NSSDCA Planetary Sciences Home Page

Dr. David R. Williams,
NSSDCA, Mail Code 690.1
NASA Goddard Space Flight Center
Greenbelt, MD 20771

NASA Official: Ed Grayzeck,
Last Updated: 30 December 2004, DRW