Strategy to Rotate the Mars Observer Orbit Node Line to Advance the Mapping Schedule


The Mars Observer (MO) spacecraft was successfully launched on September 25, 1992 and will arrive at Mars on August 24, 1993. At Mars, the spacecraft will study the planet's surface, atmosphere, and gravitational and magnetic fields. In order to achieve these scientific objectives, MO will be placed in a 2 PM (descending node) sun-synchronous orbit. Upon arrival at Mars, however, the longitude of the descending node will be approximately 15° greater than the desired value. The baseline plan requires a 59 day `waiting' period for the correct solar orientation to occur. During this period, 28 days are required for scientific experimentation but the remaining 30.6 days potentially could be eliminated. The strategy developed in this study examined the possibility of using any `excess' ?V available at Mars arrival to rotate the node line to the desired value and thus allow mapping to begin earlier. A preliminary analysis completed prior to launch is described that examined the entire launch period including the required ?V to perform the needed nodal rotation. A more detailed study performed after launch is also summarized.

Meeting Name

3rd Annual Spaceflight Mechanics Meeting


Mechanical and Aerospace Engineering

Keywords and Phrases

Extraterrestrial Atmospheres; Gravitation; Magnetic Fields; Orbits; Planets; Spacecraft Observatories; Surfaces

Document Type

Article - Conference proceedings

Document Version


File Type





© 1993 Univelt Inc., All rights reserved.

Publication Date

01 Jan 1993

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