POTENTIAL ENTRY GUIDANCE MODIFICATIONS TO IMPROVE LANDING ACCURACY FOR THE 2007 PHOENIX MARS MISSION

摘要

The robotic Mars Mission slated for 2007, known as Phoenix, will demonstrate the use of guidance to control range during entry. The current Phoenix guidance design has heritage to the 2001 Precision Lander guidance and gets its origins from the Apollo Program. The Phoenix entry guidance is essentially the same design as that used for the final phase guidance during Apollo Earth re-entry. Modifications to the final phase guidance scheme have been introduced since the Apollo and Precision Lander programs that further improve the landing accuracy that can be achieved. Those modifications include the use of smart parachute logic that allows the guidance to determine when the parachute should be deployed, within parachute constraints. By allowing the guidance to determine when to deploy the parachute, this logic essentially performs as a downrange controller. The other addition is the use of an azimuth or heading controller near the end of the trajectory. This software switches primary control of the lift vector from downrange to crossrange control, eliminating any existing crossrange error. This paper reports the landing accuracy improvement that can be achieved by applying the smart parachute and azimuth controller guidance modifications to the Phoenix Mission.