NASA is primed to provide a U.S.-led multinational research team with an intimate near Earth object (NEO) encounter in the hopes of information that a decade ago would have seemed more sci-fi than scientific. Over a seven-year roundtrip to the asteroid Bennu, the Osiris-REx spaceraft is to carry out a lengthy orbital reconnaissance prior to a novel touch-and-go soil-sample collection session, while at the same time conducting a long-term assessment of the subtle non-gravitational forces that influence the course of thousands of NEOs that could pose an impact threat to Earth—ideally supplying information for a kind of detect-and-deflect primer. 


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This story is a selection from the April 25, 2016 issue of Aviation Week & Space Technology. New content posted daily online.

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Bennu, measuring 575 meters (1,186 ft.) across, orbits the Sun every 1.2 years. An early candidate destination for the robotic phase of NASA’s Asteroid Redirect Mission, Bennu skirts near to Earth every six years.

While promising to deliver planetary scientists with the first sizeable pristine samples of the carbon-rich surface material left over from the formation of the Solar System’s inner planets—that perhaps delivered water and the building blocks of life as well—Osiris will furnish the planetary protection community with a preview of an object believed to have a relatively high probability—one in 1,800—of impacting the Earth in 2182.

The spacecraft is wrapping up the ground systems integration and test phase of its five-year development at Lockheed Martin Space Systems Littleton, Colorado, assembly, test and operations facilities on May 20 for NASA’s Kennedy Space Center

In Florida, the spacecraft will undergo prelaunch testing for a liftoff from Cape Canaveral AFS atop an Atlas 5 on Sept. 8 (at 7:05 p.m. EST), early in a launch period lasting another 34 days. If all goes well, the spacecraft’s sample-return capsule, toting 60 grams (2.11 oz.) to 2 kg (4.4 lb.) of soil from Bennu, will reenter the Earth’s atmosphere at high velocity in late 2023, parachuting to a landing on the U. S. Air Force Utah Test and Training Range west of Salt Lake.

The long, $1 billion mission, led by University of Arizona principal investigator Dante Lauretta and managed by NASA’s Goddard Space Flight Center, will afford experts an opportunity to refine measurements of the “Yarkovsky effect,” a small force attributed to sunlight absorbed by NEOs and reemitted as heat energy that builds up over time. The push on asteroids is uneven because of their shape, rotations and surface composition, yet significant if experts are to learn to predict the course of potential impactors and devise strategies to fend them off.

The challenge was clear when NASA’s New Frontiers Program selected Osiris-REx (Origins, Spectral Interpretation Resource, Identification Security-Regolith Explorer) as its third mission on May 25, 2011, behind the Jupiter-bound Juno and already successful New Horizons Pluto flyby missions.

Japan’s troubled 2003-10 Hayabusa 1 asteroid sample-return mission was testament. The Japan Aerospace Exploration Agency managed to overcome solar array damage, multiple reaction-wheel failures and periodic losses in communication to reach the surface of asteroid 25143 Itokawa for the world’s first asteroid sample-return attempt. Hayabusa managed to return with several hundred grains of extraterrestrial material, a hard-won consolation prize.

“We basically try to leverage as much technology as we can from previous missions,” says Tim Linn, Lockheed Martin’s chief systems engineer for the spacecraft. “Osiris-REx is no different.”

The spacecraft shares an open main bus and avionics heritage with NASA’s Lockheed-developed and operated Maven and Mars Reconnaissance Orbiter (MRO), which have been circling Mars since September 2014 and March 2006, respectively. Maven is studying Martian atmosphere, while MRO maps and gathers high-definition imagery. Osiris-REx’s high-gain communications antenna is a match for Maven’s.

The heritage strategy, however, draws especially from lessons from Genesis and Stardust, two pioneering NASA deep-space sample-return missions that landed at the Utah Test and Training Range in September 2004 and January 2006, bearing solar wind particles and pieces of Comet Wild 2, respectively. 

Like Stardust’s circular 18-in. sample-return capsule, Osiris-REx’s Earth-return hardware is shielded from the high temperature of atmospheric reentry with a phenolic impregnated carbon ablative material and a back shell housing drogue and main parachutes. The parachutes are designed to slow the return capsule from supersonic to subsonic velocities to an ultimate gentle, intact landing.

Genesis plummeted to the desert floor, a mishap blamed on an inverted gravity sensor critical to the parachute deployment mechanisms. Scientists managed to recover valuable samples from the wreckage. An investigation board blamed the crash on the agency’s rush to embrace a “faster, better, cheaper” culture over a test-as-you-fly ethic.

That is not the case with Osiris-REx, which will feature a new technology for collecting samples from Bennu, Linn says. “We are doing even more to ensure we really understand the end-to-end testing and make sure that everything from the smallest G switch we use to trigger the different parachute events as we reenter have been tested better than they ever were, even in the past,” he says. “We continue to develop better parts, better design techniques.”

Although it is a new feature and critical to the success of Osiris-REx, the articulating 3-meter-long touch-and-go sample-acquisition mechanism (Tagsam) has been under Lockheed internal research and development for more than a decade as a means of gathering loose regolith from small planetary bodies.

Osiris-REx should reach Bennu in October 2019, subsequently initiating a 505-day global mapping campaign at altitudes of 5-0.7-km (3-0.43 mi.), with a suite of cameras and spectrometers contributed by the Canadian and French space agencies. Under current scheduling, Osiris-REx will descend to a site on the surface of the asteroid selected through the survey campaign around July 4, 2021.

“That will be when we have already picked a site on the asteroid and we understand its rotation and its orbital dance. The actual touch-and-go is about a 5-sec. event,” says Linn. “We depart a safe home orbit, come around and do a couple of small maneuvers that basically get us on approach to the surface at about 10 cm [3.9 in.] per sec. and match the rotation period.”

With Tagsam extended, the sampler head will make contact. A burst of nitrogen gas sweeps a fluidized regolith into a chamber in the sampler head. A filter allows the nitrogen to escape, while confining the regolith. Contact pads on the outside of Tagsam will collect additional fine-grained material as they make surface contact.

The Tagsam strategy avoids the pitfalls of the European Space Agency’s Rosetta mission lander, Philae, which crashed onto the surface during an otherwise successful exploration of the comet 67P/Churyumov–Gerasimenko in late 2014.

Lockheed’s integration and test activities with Tagsam used a small blimp-like balloon to off-load gravitational forces. The sample-collecting extension functions like a pogo stick that triggers the nitrogen release as it makes contact with the surface.

Tagsam, equipped with enough nitrogen for three sample acquisitions, will place and secure the sampler head into the Stardust heritage sample-return capsule whose provisional Earth return date is Sept. 24, 2023.