Feature

NASA Ames Plays Key Role in Proposed Space Missions
01.19.10
 
Computer Simulated Global View of Venus. Image: NASA/JPLComputer simulated global view of Venus.
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Image credit: NASA/JPL

Asteroid 951 Gaspra. Image credit: NASA.Asteroid 951 Gaspra.
Click image for full-resolution.Image credit: NASA
Scientists at NASA’s Ames Research Center, Moffett Field, Calif., are contributing to proposed missions to probe the atmosphere and crust of Venus and return a piece of a near-Earth asteroid for analysis on Earth.

Ames has a role in two of the winning proposals NASA selected as candidates for the agency's next space venture to another celestial body in our solar system. NASA will select one proposal for full development in mid-2011 after detailed mission concept studies are completed and reviewed. The final project may provide a better understanding of Earth's formation or perhaps the origin of life on our planet.

Each winning proposal team initially will receive approximately $3.3 million in 2010 to conduct a 12-month mission concept study that focuses on implementation feasibility, cost, management and technical plans. Studies also will include plans for educational outreach and small business opportunities. The studies will begin this year, and the selected mission must be ready for launch no later than Dec. 30, 2018. Mission cost, excluding the launch vehicle, is limited to $650 million.

"These are projects that inspire and excite young scientists, engineers and the public," said Ed Weiler, associate administrator for the Science Mission Directorate at NASA Headquarters in Washington. "These three proposals provide the best science value among eight submitted to NASA."

The Surface and Atmosphere Geochemical Explorer, or SAGE, mission to Venus would release a probe to descend through the planet's atmosphere. During descent, instruments would conduct extensive measurements of the atmosphere's composition and obtain meteorological data. The probe then would land on the surface of Venus, where its abrading tool would expose both a weathered and a pristine surface area to measure its composition and mineralogy. Scientists hope to understand the origin of Venus and why it is so different from Earth. Larry Esposito of the University of Colorado, Boulder, is the principal investigator.

Tony Colaprete and Kevin Zahnle, both research scientists at NASA Ames, are SAGE science team co-investigators. Colaprete also is the principal investigator of the SAGE Atmospheric Structure Investigation (ASI) and instrument package. The ASI instrument package will measure pressure, temperature and wind as the probe descends from the top of its atmosphere, approximately 93 miles high, to the surface. NASA Ames also is responsible for the SAGE Instrument Control Module, which interfaces with each module and the lander. The instrument package will determine Venus's atmospheric structure, stability and composition, using sensors, including an Inertial Measurement Unit. The unit includes accelerometers and gyroscopes; a temperature and pressure measuring assembly, to measure temperature, dynamic and static pressure and determine the spacecraft's descent speed; and an anemometer to measure surface wind speed.

“We can build a coherent picture of Venus's atmospheric profile by taking direct measurements in unprecedented accuracy and resolution with a unique set of sensors as SAGE flies through the atmosphere,” Colaprete said. “Wind speed, direction and the rate at which the atmosphere overturns are critical to understanding the chemistry of the atmosphere and how it interacts with the surface.”

Zahnle is part of a team that will interpret the abundances of gases in Venus's atmosphere measured by SAGE as it descends to the planet's surface. Zahnle will focus on the presence of noble gases, such as helium and neon, but particularly xenon.

"Noble gases are both rare on planets like Earth and Venus and chemically inert, but they accumulate in the atmosphere," Zahnle said. "This makes them accessible to a probe like SAGE."

Some of the noble gases are made by radioactive decay of rock-forming elements like potassium and uranium, which enter the atmosphere through volcanic eruptions.

"Some noble gases can be used to determine the geologic history of Venus because radioactive decay acts as a kind of clock," Zahnle explained. "Other noble gases are primordial, in the sense that they formed before the planets, and can be used to determine the origin and earliest evolution of planets and their atmospheres."

The Origins Spectral Interpretation Resource Identification Security Regolith Explorer spacecraft, called OSIRIS-REx, would rendezvous and orbit a primitive asteroid. After extensive measurements, instruments would collect more than two ounces of material from the asteroid's surface for analysis on Earth. The returned samples would help scientists better understand and answer long-held questions about the formation of our solar system and the origin of complex molecules necessary for life. Michael Drake of the University of Arizona in Tucson, is the principal investigator.

Scott Sandford, research scientist at NASA Ames, an OSIRIS-REx science team co-investigator, will assess and control spacecraft contamination, particularly for organic particles that may appear during the design, construction, flight or recovery of the spacecraft.

While at the asteroid, the OSIRIS-REx will study the asteroid's shape, rotation and other features. Scientists then will analyze the sample to identify the minerals and organics that comprise the asteroid.

"We are hoping to find out what the true composition of organic-rich asteroids are and find out what sort of impact hazards and potential space resources they represent," said Sandford.

Sandford also will help organize and lead a portion of the Preliminary Examination Team that will study and analyze the organic particles present in the returned samples, as well as assess the cleanliness of the sample return capsule (SRC).

"When the SRC re-enters Earth's atmosphere, the spacecraft lets atmospheric air into the capsule," explained Sandford. "However, we don't want that air to also suck in contamination that will ruin the samples."

To prevent contamination, the SRC will be equipped with an air filter to protect the sample. Sandford brings his experience testing filter designs from his work on NASA's Stardust mission to collect comet dust and NASA's Genesis mission to collect solar wind particles.

Sandford also is part of another science team that will study a force that acts on rotating bodies in space, known as the Yarkovsky effect, which can cause asteroids to change their orbits. Data from the mission science instruments can also be compared with data from Earth-based telescopes. These comparisons will help scientists understand the nature of asteroids in our solar system.

"This is a key issue for being able to predict the orbits of asteroids and determine their dangers as impact hazards," said Sandford. "The science instruments also will measure the composition of the asteroid even before we get samples back."

After the samples have been analyzed, Sandford will work with the Astromaterials Research and Exploration Science Directorate at NASA's Johnson Space Center, Houston, to organize their distribution to various organizations and researchers.

In addition to science team support, the Human-Computer Interaction Group at NASA Ames is developing software for the science processing and operations center at the University of Arizona, Tuscon.

If OSIRIS-REx is selected as a mission, NASA Ames also will provide thermal protection systems support by completing heat shield and design testing and verification in the NASA Ames arc jet facilities.

The proposals were submitted to NASA on July 31, 2009, in response to the New Frontiers Program 2009 Announcement of Opportunity. New Frontiers seeks to explore the solar system with frequent, medium-class spacecraft missions that will conduct high-quality, focused scientific investigations designed to enhance our understanding of the solar system. The New Frontiers Program is managed by NASA's Marshall Space Flight Center, Huntsville, Ala., for NASA Headquarters.

The final selection will become the third mission in the program. New Horizons, NASA’s first New Frontiers mission, launched in 2006, will fly by the Pluto-Charon system in 2015, then target another Kuiper Belt object for study. The second mission, called Juno, is designed to orbit Jupiter from pole to pole for the first time, conducting an in-depth study of the giant planet's atmosphere and interior. It is slated for launch in August 2011.

For more information about the New Frontiers Program, visit the New Frontiers program site.
 
 
Rachel Prucey
Ames Research Center, Moffett Field, Calif.