Mission Design for the 2020 Mercury Lander Decadal Survey

This paper presents the mission design for a Mercury Lander concept in support of NASA’s 2020 Planetary Science Decadal Survey. We evaluated both chemical and solar electric propulsion trajectory options for the interplanetary and orbital phases. Like previous missions, our solution uses a series of Venus and Mercury gravity assists to reduce the total delta-V needed to capture at Mercury. Solar electric propulsion offers significant propellant savings for the interplanetary phases, but results in unreasonably long flight times during the orbital lowering phase. Based on these trades, we selected a trajectory that uses a NEXT-C electric propulsion system with a baseline power of 9 kW to orbit match with Mercury. Upon arrival at Mercury, the electric propulsion stage is jettisoned, and a chemical system performs orbit insertion and lowering to the final orbit. Descent and landing are performed using a solid rocket motor and liquid propulsion system, respectively. The arrival is phased so that the lander can operate in local nighttime for up to 13 weeks, with direct-to-Earth communication availability for up to 7 weeks.