Abstract:
The Mars Exploration Rover (MER) flight system had the ability to update EDL parameters during Approach, and the mission design furnished an operational plan, process, and tools for performing the updates. These capabilities permitted JPL to respond to new data on the Mars atmospheric density by modifying the timing of the MER parachute release, assuring mission success. Maintain an operational capability to code critical parameters in flight software and to update them during the latter stages of encounter/EDL.
Description of Driving Event:
Both the Mars Exploration Rover (MER) flight system and mission designs had the flexibility to react to unexpected events. The MER flight system provided an in-flight capability to revise Entry, Descent and Landing (EDL) parameters by coding them in flight software. The MER mission design provided an operational plan, process, and tools permitting JPL to perform EDL parameter updates over a span of several days during final approach to Mars and up to six hours before landing.  [D]
The ability to update EDL parameters was critical to the success of the MER mission. Updated data on Martian atmospheric pressure received from the Thermal Emission Spectrometer (TES) instrument on the Mars Global Surveyor (MGS) spacecraft during final approach (see figure) indicated a lesser atmospheric density than expected. Left uncorrected, the actual lesser atmospheric density could have caused MER to sense its dynamic pressure target at a lower altitude than planned, and to trigger its parachute deployment too near the ground. Because the flight team had the processes for changing EDL parameters, and the ability to modify these parameters after launch, the timing of the MER parachute release was successfully accomplished. References:
- “Mars Exploration Rover (MER) Flight Operations Report,” NASA Engineering and Safety Center Report No. RP-04-04/03-004-I
- 2003 Mars Exploration Rover Final Navigation Peer Review, February 3, 2003
Additional Key Words: Mars lander, Mars probe, mission failure, signal loss, flight constraints, communications lag, continuous telemetry
Lesson(s) Learned:
Critical parameters coded in flight software and the ability to alter them within hours of critical events in response to unexpected data on flight characteristics can save a planetary mission or deep space encounter.
Recommendation(s):
For spaceflight missions-- particularly landers-- ensure that the flight system and mission designs have flexibility to react to unexpected events:
- Code critical parameters in flight software.
- Maintain an operational capability to update these parameters during the latter stages of encounter/EDL.
Evidence of Recurrence Control Effectiveness:
JPL will reference this lesson learned as additional rationale and guidance supporting Paragraph 4.5.1.4 (Telecommunications capability for special mission events) and 4.9.3.1 (Flight-Ground Interface) in the JPL standard ?Design, Verification/Validation and Operations Principles for Flight Systems (Design Principles),? JPL Document D-17868, Rev. 3, December 11, 2006.
Documents Related to Lesson:
- JPL Procedure: Mission Planning-Operations, JPL Document 31912, March 05, 1999.
- NPR 7120.5B, NASA Program and Project Management Processes and Requirements, November 21, 2002.
Mission Directorate(s):
- Exploration Systems
- Aeronautics Research
Additional Key Phrase(s):
- Communication Systems
- Environment
- Flight Equipment
- Flight Operations
- Hardware
- Payloads
- Risk Management/Assessment
- Safety & Mission Assurance
- Spacecraft
Additional Info:
|
