P34A-02
Navigating the MESSENGER Spacecraft through End of Mission

Wednesday, 16 December 2015: 16:15
2011 (Moscone West)
Christopher George Bryan1, Bobby Gene Williams1, Kenneth E. Williams1, Anthony H. Taylor1, Eric Carranza1, Brian R. Page1, Dale R. Stanbridge1, Erwan Mazarico2, Gregory A Neumann3, Daniel J. O’Shaughnessy4, James V. McAdams4 and Andrew B. Calloway4, (1)KinetX Inc, Tempe, AZ, United States, (2)NASA Goddard Space Flight Center, Greenbelt, MD, United States, (3)NASA, Baltimore, MD, United States, (4)Applied Physics Laboratory Johns Hopkins, Laurel, MD, United States
Abstract:
The MErcury Surface, Space ENvironment, GEochemistry, and Ranging (MESSENGER) spacecraft orbited the planet Mercury from March 2011 until the end of April 2015, when it impacted the planetary surface after propellant reserves used to maintain the orbit were depleted. This highly successful mission was led by the principal investigator, Sean C. Solomon, of Columbia University. The Johns Hopkins University Applied Physics Laboratory (JHU/APL) designed and assembled the spacecraft and served as the home for spacecraft operations. Spacecraft navigation for the entirety of the mission was provided by the Space Navigation and Flight Dynamics Practice (SNAFD) of KinetX Aerospace. Orbit determination (OD) solutions were generated through processing of radiometric tracking data provided by NASA’s Deep Space Network (DSN) using the MIRAGE suite of orbital analysis tools.

The MESSENGER orbit was highly eccentric, with periapsis at a high northern latitude and periapsis altitude in the range 200–500 km for most of the orbital mission phase. In a low-altitude “hover campaign” during the final two months of the mission, periapsis altitudes were maintained within a narrow range between about 35 km and 5 km. Navigating a spacecraft so near a planetary surface presented special challenges.

Tasks required to meet those challenges included the modeling and estimation of Mercury’s gravity field and of solar and planetary radiation pressure, and the design of frequent orbit-correction maneuvers. Superior solar conjunction also presented observational modeling issues. One key to the overall success of the low-altitude hover campaign was a strategy to utilize data from an onboard laser altimeter as a cross-check on the navigation team’s reconstructed and predicted estimates of periapsis altitude. Data obtained from the Mercury Laser Altimeter (MLA) on a daily basis provided near-real-time feedback that proved invaluable in evaluating alternative orbit estimation strategies, and eventually allowed the navigation team to settle on an approach that gave consistently accurate predictions. Thus, final mission success was truly the result of a collaborative effort between members of the science, mission operations, mission design, and navigation teams.

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