2016.A.1.3. Sampling Venus’ atmosphere with a low-cost probe mission
Anthony Freeman (1)
Christophe Sotin (1)
Murray Darrach (1)
John Baker (1)
- JPL/Caltech, United States of America
Venus science probe
Measuring the relative abundances of Neon, Argon, Helium, Krypton and other noble gases have been emphasized as high priorities in the planetary science community’s efforts to understand how Venus’ atmosphere formed and has evolved. The Venus Exploration Advisory Group (VEXAG), for example, has stressed the significance of these measurements. The underlying objectives are to determine if Venus and Earth formed from the same mix of solar nebular ingredients, and whether comets played a substantial role in delivering volatiles. To be truly representative of the noble gases and their isotopic ratios, a sample of the atmosphere has to be acquired where the atmosphere is well-mixed: at an altitude below the homopause, which for Venus is around 120 km.
This paper contrasts two architectures for a low-cost mission concept that would make use of cubesat developments to sample the noble gases and their isotopic ratios at Venus. Sampling is achieved by a compact, ion-trap mass spectrometer of volume ~ 4U incorporated into a small probe that skims through the atmosphere, targeting a closest approach altitude above the surface below the nominal 120 km. Following acquisition, the gas sample is analyzed over a period of ~100 minutes, then results are relayed via a UHF comm link to the carrier spacecraft that escorted the atmospheric entry probe to Venus. Data is then relayed back to Earth via an X-Band downlink.
The two architectures studied in this paper are: a mother-daughter configuration, in which the probe is escorted to Venus by a larger orbiter that then drops the probe off once Venus orbit is achieved; and a free-flying Venus probe + carrier spacecraft that is launched together on a Type II trajectory towards Venus, on a dedicated Pegasus launch vehicle. In both cases the estimated mass of the atmospheric entry probe mass is less than 30 kg, assuming a compact mass spectrometer instrument mass of 8 kg. Following the probe skim-through and data analysis, results are returned to Earth via a UHF/X-Band relay, via either the primary spacecraft in orbit around Venus or the smaller carrier spacecraft on a flyby trajectory.
Carrier spacecraft and probe costs are constricted by using avionics, telecom and other subsystems developed for other NASA/JPL planetary cubesat missions, including INSPIRE and MarCO. Since the entry probe does not penetrate deep into the atmosphere of Venus, it does not need a pressure vessel, which should significantly lower both mass and cost.
The work described here was performed at the Jet Propulsion Laboratory, California Institute of Technology, under contract with the National Aeronautics and Space Administration.
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