The full text of the 11 mission concept studies that did not undergo CATE analysis (as well as the full text of the 13 mission concepts that did), plus the full text of the four technology studies, is provided in the CD accompanying Appendix G and included with the printed report.

The design centers conducted two types of mission study: rapid mission architecture (RMA) studies and full mission studies (FMSs) of mission point designs. RMA studies considered a broad array of mission architectures to find a promising approach. The resulting “point design” could then, as an option, be subjected to a full mission study.

MERCURY LANDER

The Mercury Lander mission concept study was performed by the Space Department of the Johns Hopkins University Applied Physics Laboratory in partnership with NASA’s Marshall Space Flight Center and Glenn Research Center.

Overview

The purpose of this RMA study was to determine the feasibility of a landed mission to Mercury. This mission concerned fundamental science questions that can be best, or only, addressed by conducting surface operations such as those for determining Mercury’s bulk composition, the nature of the planet’s magnetic field, surface history, internal structure, and surface-solar wind interactions.

Science Objectives

• Characterize major and minor elements of the chemical composition of Mercury’s surface.

• Characterize the mineralogy and structural state of the materials at Mercury’s surface.

• Investigate the magnitude and time dependence of Mercury’s magnetic field, for at least one location on the surface.

• Characterize geologic activity (e.g., volcanism, tectonism, impact cratering) at scales ranging from regional to local.

• Determine the rotational state of Mercury.

Mission Design

The architecture for the flight system of the Mercury Lander was based on a three-stage concept consisting of a cruise stage, a braking stage, and a final descent and soft-landing stage. Because of the complexities associated with a landed mission to Mercury, analysis of scientific instrumentation was not included in this study, which focused instead on the viability of flight-system and landing elements.

The 2018-2023 time frame was chosen for launch, with landings planned approximately 5 years after launch; specific dates would be dependent on trajectory type. Landed operations would be modest in scope, with 22 contiguous days planned for science operations and a possible extension of 68 more days, depending on mission success.

Mission Challenges

Because a landed mission to Mercury is extremely challenging with respect to a launch energy and relative velocity, two trajectory approaches were considered:

• A ballistic/chemical approach fitting on the edge of Atlas V 551 constraints; and

• A low-thrust option using a solar-electric propulsion (SEP) cruise stage that would be dependent on high- temperature solar cell technology that has yet to be developed beyond the cell level.



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