MSL Readings Could Improve Safety for Human Mars Missions
WASHINGTON — Although the Mars Science Laboratory (MSL) rover has yet to begin its primary science investigations, the mission has already gathered data that could prove useful for future human spaceflight missions, scientists said.
NASA’s Human Exploration and Operations Mission Directorate, which operates the international space station and is developing the hardware needed to send humans beyond low Earth orbit, contributed about $40 million to the $2.5 billion MSL mission. That paid for the MSL Entry, Descent and Landing Instrument (MEDLI), which recorded the thermal and aerodynamic forces on the rover’s heatshield and aeroshell during descent into the martian atmosphere, and the Radiation Assessment Detector, which monitored radiation levels during MSL’s nearly nine-month cruise to Mars.
The data gathered by these systems were among the first to be returned by MSL. The measurements could influence future NASA designs for larger martian landing craft, and help engineers better protect astronauts from solar and cosmic radiation during the long trip to Mars or other faraway destinations.
NASA’s human spaceflight division put $22 million into the MSL Entry, Descent and Landing Instrument, which was built at the Langley Research Center in Hampton, Va. The sensor suite completed its mission Aug. 6 and was discarded on Mars along with the rest of the Curiosity rover’s entry, descent and landing hardware. However, the Radiation Assessment Detector, a collaboration between NASA and the German Aerospace Center, DLR, will continue to monitor radiation levels on the martian surface throughout the rover’s 98-week primary mission.
The Radiation Assessment Detector was switched on Dec. 6, 2011 — just 10 days after the rover launched from Cape Canaveral Air Force Station, Fla., aboard aAtlas 5 rocket. It was the first MSL instrument activated and has already logged about seven months worth of data, said principal investigator Don Hassler, a physicist at the Boulder, Colo.-based Southwest Research Institute. The instrument also was briefly activated Aug. 6, the day Curiosity touched down on Mars. Hassler expected the detector to rake in about eight-and-a-half hours worth of data during the rover’s first week on the surface.
DLR spokeswoman Manuela Braun said Aug. 8 that Germany’s financial contribution to the Radiation Assessment Detector instrument was 2.5 million euros ($3.1 million).
The Radiation Assessment Detector measures three types of radiation. During the cruise phase, the instrument measured galactic cosmic radiation, which originates from outside the solar system, and solar energy particles, which come from the sun. On Mars, the detector will look for signs of albedo neutrons, “which would be the result of galactic cosmic rays and solar energetic particles having nuclear interactions in the atmosphere and also in the regolith on the surface of Mars,” Hassler said in an Aug. 7 interview.
While this energy is harmless to the Curiosity rover — which itself is nuclear powered — it could be hazardous to humans that visit Mars.
Already, the Radiation Assessment Detector team has gleaned some insight from the data gathered during MSL’s long trip to Mars, during which the craft was bombarded by energy from five large solar particle events that occurred this year, Hassler said. During the cruise phase, the instrument was shielded about as well as an astronaut would be on the international space station, Hassler said. Nevertheless, the detector received a nontrivial dose of solar particles, “even with the amount of shielding we have around MSL.”
Hassler said that his team aims to publish results in the next several months.
Meanwhile, scientists at NASA’s Langley Research Center will shortly begin pouring over the data gathered by the MSL Entry, Descent and Landing Instrument. Michelle Munk, deputy principal investigator for the instrument at Langley, said that by Aug. 10, NASA had received the full data set gathered during MSL’s descent into the martian atmosphere.
“We’ll use the data for a few different purposes: one is to validate our computer models and compare our predictions of both the environment during Mars entry and the behavior of the spacecraft, in particular the heatshield material,” Munk said in an interview.
The hope, Munk said, is that by analyzing the performance of MSL’s heat shield and aeroshell, engineers will be able to understand whether the wide margins of error they included in their designs could be safely reduced. If they can, future entry, descent and landing systems could be reduced in mass, allowing future Mars landers to carry “more scientific instruments, or extra fuel, or other systems that will improve the science returns on future missions,” Munk said.
The Human Exploration and Operations Directorate footed the bill for building MEDLI. Munk said NASA’s Aeronautics Research Mission Directorate kicked in $8 million to cover analysis of the data gathered during Curiosity’s descent. The Space Technology division, which oversees development of potential cross-agency technology, contributed $4.4 million. MEDLI was a relatively late edition to MSL’s design. It was added to the mission in 2006, after the MSL aeroshell had undergone its preliminary design review. The instrument package was added at the insistence of Mike Griffin, then the NASA administrator. During his tenure, Griffin “made a statement that we should be instrumenting every entry vehicle,” Munk said.
About 120 people worked on MEDLI, 85 of whom were based at Langley, Munk said. The remainder of the team works out of the Ames Research Center in Mountain View, Calif.