Mars Exploration Rover Six-Degree-of-Freedom Entry Trajectory Analysis

Abstract

The Mars Exploration Rover mission will be the next opportunity for surface exploration of Mars in January 2004. Two rovers will be delivered to the surface of Mars using the same entry, descent, and landing scenario that was developed and successfully implemented by Mars Pathfinder. This investigation describes the trajectory analysis that was performed for the hypersonic portion of the MER entry. In this analysis, a six-degree-of-freedom trajectory simulation of the entry is performed to determine the entry characteristics of the capsules. In addition, a Monte Carlo analysis is also performed to statistically assess the robustness of the entry design to off-nominal conditions to assure that all entry requirements are satisfied. The results show that the attitude at peak heating and parachute deployment are well within entry limits. In addition, the parachute deployment dynamics pressure and Mach number are also well within the design requirements.

Aerodynamics for Mars Phoenix Entry Capsule

“…The uncertainty increases at supersonic Mach numbers where afterbody effects are not well modeled and the Viking base pressure correction was used. Other uncertainty magnitudes were changed slightly from values used for MER 21 . First, pitching (and yawing) moment uncertainty was modeled both as an adder (trim angle shift) and a multiplier (pitching moment slope change).…”

Aerothermodynamic Design of the Mars Science Laboratory Backshell and Parachute Cone

“…The entry system will land the rover using an aeroshell and parachute architecture that has successfully delivered payloads on Mars starting with Viking 2 and continuing with Pathfinder, 3 the Mars Exploration Rovers, 4 and Phoenix. 5 Prior to supersonic parachute deployment, the MSL entry capsule will fly with a hypersonic lift-to-drag ratio (L/D) of 0.24 at a trim angle-of-attack of 16 deg using active guidance and reaction control system (RCS) thruster to control lift vector direction.…”

On the use of a range trigger for the Mars Science Laboratory Entry, Descent, and Landing

“…Viking used a radar altimeter measurement to trigger this critical event [6]. Mars Pathfinder [8] and MER [4] both used triggers based on sensed-acceleration measurements, provided by the on-board Inertial Measurement Unit (IMU), to proxy dynamic pressure, though their algorithms differed. Mars Phoenix Lander, on the other hand, used a navigated velocity trigger to proxy Mach number.…”