A Low-Cost Mercury Orbiter Mission - Abstract
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A LOW-COST MERCURY ORBITER MISSION

Kenneth J. Ely
Wallace T. Fowler
Byron D. Tapley


Center for Space Research
The University of Texas at Austin




Due to Mercury's small mass and position deep within the solar gravitational well, an orbiter mission poses difficult performance requirements (i.e. DV, thermal extremes). However, Yen (JPL) showed that with extended trip times, substantial Mercury missions are feasible. Low cost, quick concept-to-launch, high quality, and reliability are balanced in constraining a small spacecraft mission to Mercury. The primary science objective is high quality multispectral imagery and altimetry. The spacecraft is based on the Clementine spacecraft and sensors. UV/Visual/infrared cameras, star trackers, and a laser altimeter are proposed to determine mineralogical composition, surface structure/morphology, spectral/compositional mapping, and topography. Clementine sensors would require upgrades to enhance thermal dissipation and to increase radiation protection. The first available launch opportunity is in August 1996 and the target orbit is a 300 km polar Mercury orbit. Launch vehicle options are discussed. Options for companion or follow-on spacecraft are presented.


INTRODUCTION

This study was completed as an exercise in preparation for more detailed anaylses of Mercury mission planning. The purpose of this study is threefold: to suggest that Mercury, the only inner planet not orbitted by a spacecraft, be considered for near term spacecraft missions- , to promote the use of small satellites with focused scientific goals for planetary missions, and to present a conceptual design for a Mercury orbiter mission.

Mercury's known and unknown characteristics are examined and used as justification for observation through use of a Mercury orbiter. A general discussion of mission constraints and objectives defines the design metodology. A number of science objectives have been identified by the Terestrial Bodies Science Working Group [1] for furture Mercury missions. For the purposes of this study these science objectives were grouped to define smaller payload sets for separate spacecraft with focused science goals, rather than a single all inclusive mission.

The selected mission scenarios are presented, followed by the spacecraft conceptual design including DV requirements, estimated mass and power budgets and chosen sensors. Until Yen developed a series of reverse multiple gravity assist trajectories in 1985 a Mercury orbiter was not believed feasible with current propulsion technology, due to the high orbit energy requirements. A discussion of the selected trajectory along with launch vehicle options is presented. Recommendations and intent for further study are discussed.



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