Instrument provides opportunities and challenges

MIT graduate students Pronoy Biswas (left) and Mark Chodas prepare the Regolith X-Ray Imaging Spectrometer (REXIS) instrument for flight. Photo by William Litant/MIT
MIT graduate students Pronoy Biswas (left) and Mark Chodas prepare the Regolith X-Ray Imaging Spectrometer (REXIS) instrument for flight. Photo by William Litant/MIT

A student-built instrument launching with an upcoming space mission to an asteroid will provide not only valuable training and experience for future aeronautical engineers, but also vital scientific data for later research.

The mission, sponsored by NASA and the University of Arizona, will launch in late 2016 and rendezvous with the asteroid two years later.

The Regolith X-Ray Imaging Spectrometer, known as REXIS, will be attached to OSIRIS-REx as it attempts to study and return a sample from Bennu, an asteroid with a close orbit to Earth that brings it within about 18,591 miles once every six years.

Students in a cooperative effort at the Massachusetts Institute of Technology and Harvard designed the instrument.

REXIS uses X-rays to create a type of image that can tell researchers what kind of elements, and their quantities, are present in the loose surface material of Bennu. It does this by detecting the X-ray light from the sun that has interacted with the elements and then reflects back into space where REXIS can capture and image them.

Although the REXIS instrument is simpler in design and less expensive, it still has a high level of sophistication, said Ed Beshore, deputy principal investigator for OSIRIS-REx at the UA.

“It still uses a sophisticated technique for detecting X-rays on the surface and effectively developing a kind of an image, if you will, of the abundance of elements in the material on the surface of Bennu,” Beshore said. “So, I’d say that it’s still a pretty darn sophisticated instrument.

“Even though it’s relatively low cost and certainly not as sophisticated as the other instruments that we’re flying on the spacecraft, but nevertheless, it represents a pretty serious effort,” he said. “Any spacecraft would be proud to have this instrument.”

For Rebecca Masterson, project manager of REXIS and research scientist at MIT, the instrument is as unique as it is beneficial to educating the next generation of aeronautical engineers.

“We’re going to be able to tell what the elements are on the surface of the asteroid,” Masterson said. “And there’s no other instrument that will be looking at the asteroid in the X-ray spectrum.”

The project was awarded to the students at MIT and Harvard in 2011 during a UA-sponsored competition during the early stages of the OSIRIS-REx proposals to NASA.

NASA funding for student-led projects gives future engineers and researchers hands-on skills.

“What the intent of this experiment is to prepare the next generation of scientist and engineers to be able to go build even more sophisticated spacecraft instruments for future missions,” Beshore said. “If REXIS wasn’t flying on the spacecraft, but it is, it would have still accomplished that goal.”

Masterson also spoke about the benefits these type of projects offer in promoting educational opportunities not typically found in the classroom.

“All these students have been exposed to hardware in a way most students have not been,” she said.

One student from MIT, Mark Chodas, was present through the entire process. Having been the only student involved since the proposal was won, gives Chodas a unique perspective.

“Being here for the entire length of the project, or at least from the start until now, has been an advantage for me,” Chodas said. “Because I’ve seen how we have evolved, how our design has evolved.

“Other students may have only seen one or two years of that process,” he said.

Student-led projects do not come without risk, however. The tight budgets leaves less security than is found with non-student funded projects, should something be damaged during the construction of the instrument.

REXIS is a student-built instrument that will study the elemental abundances on the surface of Bennu. Photo courtesy of Lockheed Martin
REXIS is a student-built instrument that will study the elemental abundances on the surface of Bennu. Photo courtesy of Lockheed Martin

During construction, the REXIS instrument almost came to a sudden end when a detector was damaged by accident. The mishap could have happened on any project, whether involving professional or student engineers, but without the funds to build back-up components, REXIS faced being unable to launch with the mission.

The normal process during construction is to have backup components built and ready should something become damaged or unusable, Beshore said.

The damage occurred when a NASA inspector accidentally pressed against two cables, tearing them and damaging one of four detectors, Masterson said. Each detector has four nodes, providing 16 to do the necessary imaging.

“It was an interesting day,” Chodas said. “It certainly was one of those things that when (it) happens and you see it, it kind of makes you think about all the possible ramifications of what happened.

“My thoughts went kind of based on, ‘Does this mean it’s the end of the project,’ to ‘How can we fix this,'” he said. “My immediate reactions was, ‘I really hope the damage isn’t significant and I hope that REXIS can actually continue.'”

With one detector damaged, the instrument was left with 12 nodes to do its imaging.

“It was pretty devastating,” Masterson said. “And we had to sort of recover from that and try to repair what was left.

“We’re still able to do good science with the nodes that we have,” she said. “We just have to  integrate in the field longer to make up for the area we’re actually missing.”

While the damage reduced the imaging capability on REXIS, requiring more time to collect its image, it will still be able to image the surface of Bennu.

“They had to overcome some serious hurtles,” Beshore said. “They had some instrument failures. They had some component failures that for a while we were concerned was going to end it.

“And they came back and managed to get it done,” he said. “It’s been a really impressive process, and we’re just delighted that they are going to be able to return some science from that.”

Engineers install the REXIS instrument onto the OSIRIS-REx spacecraft in a Lockheed Martin clean room in Denver, Colorado. Photo courtesy of Lockheed Martin
Engineers install the REXIS instrument onto the OSIRIS-REx spacecraft in a Lockheed Martin clean room in Denver, Colorado. Photo courtesy of Lockheed Martin

Jorge Encinas is a reporter of Arizona Sonora News, a service from the School of Journalism with the University of Arizona. Contact him at jencinas9@email.arizona.edu.

Click here for high-resolution photos.

Leave a Reply

Your email address will not be published.