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Launched on August 3, 2004, MESSENGER (MErcury Surface, Space ENvironment, GEochemistry, and Ranging) will be the first spacecraft to orbit the planet Mercury. Designed and built by The Johns Hopkins University Applied Physics Laboratory in conjunction with the Carnegie Institution of Washington, MESSENGER will study Mercury during a 1-year orbital phase that will begin in March 2011. Currently the spacecraft is in the middle of a 7-year cruise phase that so far has included a flyby of the Earth (August 2005), two flybys of Venus (October 2006 and June 2007), and the first of three flybys of Mercury (January 2008). The January 2008 Mercury flyby marked the first spacecraft visit since Mariner 10 (1975) and made MESSENGER the first spacecraft to encounter Mercury when near the planet's perihelion.

Due to the elliptical shape of Mercury’s orbit and the slow planetary spin rate, Mercury has a large surface temperature difference that creates highly variable spacecraft thermal environments that are a function of both planet solar distance and spacecraft orbit plane position. Being able to analytically simulate the severe thermal environments experienced by a spacecraft over the lifetime of a Mercury orbiting mission make it possible to realize a feasiable spacecraft thermal design. The analysis described throughout this paper was used to characterize the temperature response as a function of initial phase angle conditions (αρ) when referenced at Mercury perihelion for a 3-axis stabilized spacecraft. Variables in the analysis include solar distance, argument of periapsis, and αρ. The selected orbit is highly elliptical, with a 720-minute period and a near polar inclination.

Increasingly complex missions with reduced budgets has placed a premium on “better, cheaper, faster” system approaches for producing spacecraft. The natural consequence of this pressure to improve quality while reducing process time and expense is that activities once considered essential to design and development are now viewed as luxuries. To produce timely inputs during the condensed design phase, the spacecraft subsystem architect must continually improve the efficiency of analysis activities. This type of improvement is particularly necessary in the area of thermal analysis, which is often viewed as a peripheral activity. However, through the use of enhanced software analysis tools, the thermal engineer can ensure a comprehensive spacecraft thermal analysis that yields timely system design inputs in a cost-effective manner.