Apollo 15 gravity analysis from theS-band transponder experiment
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TheS-Band Transponder experiment used precision doppler tracking data of the command and service module, the lunar module and the subsatellite to provide detailed information about the near side gravity field. No special instruments are required other than the existingS-Band transponder used for real time navigation. The data consists of variations in the spacecraft speed as measured by the earth-based radio tracking system, which has a resolution of 0.65 mm/s.
Initial data reduction has been concentrated on the low altitude CSM data (≈ 20 km) which provides new detailed gravity profiles of the Serenitatis and Crisium mascons. The results are in good agreement with Apollo 14 analysis and strongly suggest that the mascons are near surface features with a mass distribution per unit area of approximately 800 kg/cm2. The Apennines reveal themselves as a local gravity high of 85 mgal and Marius Hills likewise have a gravity high of 62 mgal.
The subsatellite data is too sparse at present to definitely determine new gravity anomaly locations. The spacecraft is functioning well and a dense data block is being obtained, which will provide a new gravity map from ±95° longitude to ±30 latitude. Since periapsis altitudes are following relatively close to predicted altitudes, it seems fairly safe at this point to believe the subsatellite lifetime will be at least one year.
KeywordsGravity Anomaly Data Block Side Gravity Local Gravity Anomaly Location
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