Data Set Overview : This data set contains 243 Archival Tracking Data Files (ATDFs) and 6 Orbit Data Files (ODFs) from the MAGELLAN mission to Venus. The ATDFs were collected at Earth stations of the NASA Deep Space Network (DSN) from May 1989 (as MAGELLAN began its cruise to Venus) until October 1994 (after the MAGELLAN 'termination experiment'). ODF coverage is only from April 1992 to end of mission; ODFs were reconstructed from NAVIO files (an in-house format at the NASA Jet Propulsion Laboratory, JPL). The data have been used to derive spherical harmonic models of the Venus gravity field [KONOPLIVETAL1999][KONOPLIV&SJOGREN1996]. The models can be obtained from the NASA Planetary Data System (PDS), where they are part of data set MGN-V-RSS-5-GRAVITY-L2-V1.0. Parameters : ATDFs and ODFs contain measurements of range between the Earth station and MAGELLAN spacecraft, Doppler shift of the carrier frequency, carrier signal strength, and ground station azimuth and elevation angles. They also contain many ground station configuration parameters. The ODF is an edited and compressed (time integration) version of the ATDF. The ODFs in this archive are aggregations covering about one year each (1992, 1993, and 1994). Processing : ATDF data were collected using one or more DSN closed-loop receivers, which reported frequency and amplitude of the MAGELLAN carrier signal at a rate (typically) of 10 times per second. When a coded (ranging) subcarrier was used, a correlator estimated round-trip time between Earth and spacecraft, which can be interpreted as two-way distance. The file of measured values was screened manually, and 'bad' measurements were removed. There has been no other ATDF processing. ODF files are usually derived from one or more ATDFs. The MAGELLAN ODFs were reconstructed from NAVIO files (an internal JPL format). In addition to being edited versions of ATDFs, these ODFs contain averaged values of observation parameters -- both 2- and 10-second averages are available (in separate files). Data : The archive comprises 243 ATDFs, 6 ODFs, and supporting documentation on the structure and content of the ATDF and ODF. Ancillary Data : Also included in the data set are four data types that may be used to calibrate the radio tracking measurements. Angular Momentum Desaturation (AMD) files -- also known as Small Forces Files -- are included in the AMD directory. Media calibration files for ionospheric and tropospheric effects are in the ION and TRO directories, respectively. Local weather conditions at the NASA DSN complexes are stored in the WEA directory. Coordinate System : The radio data are not strongly dependent on coordinate systems. Ground antenna azimuth and elevation are in an unknown local frame; but it is the range and Doppler measurements which are most important and those are independent of the coordinate system chosen. Software : No software is included with this archive. Media/Format : This archival data set were delivered to the PDS Geosciences (GEO) Node on three DVD+R discs. They will be distributed electronically.

Overview : These data have not been reviewed for quality. Five original files were not included in the archive for the reasons noted below: Coverage (YYYY/DDD) Reason for Omission from Archive ------------------- ---------------------------------- 1990/166-1990/193 Lost before GEO collection in 1997 1991/084-1991/112 Corrupted 1992/034-1992/050 Duplicate 1993/313-1993/313 Duplicate 1994/162-1994/164 Corrupted The NAVIO files (parents of the ODFs) have been used to compute a 180x180 spherical harmonic model of the Venus gravity field [KONOPLIVETAL1999]. Additional information on data quality may be found in the Venus Gravity Handbook [KONOPLIV&SJOGREN1996]. Review : This archival data set was reviewed by a peer review panel prior to its acceptance by the Planetary Data System (PDS). The peer review was conducted by the PDS Geosciences Node in accordance with PDS procedures. Data Coverage and Quality : The ATDF tracking data began on 1989-05-04, as MAGELLAN started its cruise to Venus. The last ATDF ends on 1994-10-12, the day after the MAGELLAN 'termination' experiment. ODF coverage began on 1992-04-22 and ended on 1994-10-12. The coverage and quality are variable, but were sufficiently good that [KONOPLIVETAL1999] derived a 180x180 spherical harmonic model of the gravity field from the tracking data. Corrupted and lost data are listed above under Overview. There are five angular momentum desaturation (AMD) files covering the years 1990 (days 215-365), 1991, 1992, 1993, and 1994 (to end of mission). Fifty-six (56) ION files cover 1990 to end of mission except that June and July 1993 are missing. Forty-four (44) TRO files cover 1990 (days 091-365), 1991 (except that February - April are missing), 1992 (January - August are missing), 1993, and 1994 (through end of mission). Fifteen (15) WEA files are included, covering 1989 through 1994 except that 1991 files are missing for all DSN complexes. Limitations : No limitations are known other than those which would apply when working with data of this quality.