Mars Exploration Rovers Propulsive Maneuver Design

Abstract

The Mars Exploration Rovers Spirit and Opportunity successfully landed respectively at Gusev Crater and Meridiani Planum in January 2004. The rovers are essentially robotic geologists, sent on a mission to search for evidence in the rocks and soil pertaining to the historical presence of water and the ability to possibly sustain life. In order to conduct NASA's "follow the water" strategy on opposite sides of the planet Mars, an interplanetary journey of over 300 million miles culminated with historic navigation precision. Rigorous trajectory targeting and control was necessary to achieve the atmospheric entry requirements for the selected landing sites. The propulsive maneuver design challenge was to meet or exceed these requirements while preserving the necessary design margin to accommodate additional project concerns. Landing site flexibility was maintained for both missions after launch, and even after the first trajectory correction maneuver for Spirit. The final targeting strategy was modified to improve delivery performance and reduce risk after revealing constraining trajectory control characteristics. Flight results are examined and summarized for the six trajectory correction maneuvers that were planned for each mission.

High Mass Mars Entry, Descent, and Landing Architecture Assessment

“…An additional investigation into the sensitivity of the entry system delivery accuracy was performed by analyzing the impact of a ±0.14 • variation in entry flight path angle, commiserate with that required by the MER system. 27 This analysis used the 20 t direct entry vehicle with a 20 m diameter IAD. The flight path angle obtained during the original optimization was perturbed by the desired ±0.14 • and the design was reconverged with flight path angle removed as a design variable.…”

Mars Exploration Rovers Landing Dispersion Analysis

“…These probability values were the primary landing site requirements the navigation team used, as part of the maneuver design process. 16 In this way, landing in-spec probability values (within well-characterized areas of the surface) were being targeted, more than a formal "target ellipse". Prior to launch and periodically throughout cruise, however, covariance studies were used to benchmark landing ellipse estimates for planning purposes.…”

Mars Exploration Rovers Launch Performance and TCM-1 Maneuver Design

“…Subsequent maneuvers, which are addressed in an accompanying paper (Ref. 2), correct for maneuver execution errors and orbit determination errors.…”