A big push for small satellites for NASA science
by Jeff Foust
|“We’re going to realize the importance of small satellites not just as a platform but as an enabler to do science that is otherwise not achievable,” said Zurbuchen.|
That speaker had just wrapped up a study published earlier that year by the National Academies on the scientific utility of CubeSats, one that concluded that such spacecraft could play significant roles in various aspects of Earth and space sciences. At the end of his talk, someone asked how the results would be implemented. “I think what we need to do is look at the entire set of recommendations,” he answered, after discussing briefings of the report at the White House and with members of Congress. “I think there’s a lot of potential there.”
That speaker was Thomas Zurbuchen, at the time a professor at the University of Michigan. Two months later, though, he was at NASA as the agency’s new associate administrator for science. In that position, he has had the ability to shape NASA’s science program to make greater use of small satellites.
Earlier this month, he returned to Utah State for this year’s smallsat conference, an event that continues to attract new interest and new attendees (the attendance of about 3,060 set a new record.) As the conference’s keynote speaker, Zurbuchen outlined what NASA was doing to make greater use of them, and to carry out the recommendations of the report he helped produce.
“We’re in business for small satellites and CubeSats,” he said in his speech. “We’re going to realize the importance of small satellites not just as a platform but as an enabler to do science that is otherwise not achievable.”
Zurbuchen used his keynote to announce a new smallsat initiative in NASA’s Science Mission Directorate. “This was the first initiative I put in place when I joined two years ago,” he said, but it was only in the last month, after NASA finalized its fiscal year 2018 operating plan, was the funding now set: $100 million a year, starting in 2018, for smallsat-related science projects.
“I felt, because of that Academies study, that it’s absolutely critical that we’re doing this,” he said. That includes “totally new opportunities that are coming out recently or in the near future.”
One of those new opportunities he discussed was an opportunity to fly smallsats as secondary payloads on a future NASA heliophysics mission. An announcement of opportunity, released the same day as his speech, sought proposals for smallsats that could fly on the Interstellar Mapping and Acceleration Probe, which will launch in 2024 to the Earth-Sun L-1 Lagrange point. NASA will offer up to $65 million for one or more such rideshare missions.
“This is really a novel type of application because of the fact that it deliberately focuses on enhancing the technological capabilities in that area,” he said. “If successful, this will not only teach us new science but will protect technological infrastructure that is sensitive to space weather.”
Another new aspect of this initiative is providing more such rideshare opportunities for smallsats. Zurbuchen said that, when NASA buys launches for future larger missions, it will automatically include what’s known as an EELV Secondary Payload Adapter (ESPA), sometimes called an “ESPA ring” because of its ring-shaped appearance, to which smallsats can be attached.
“We’re not going to ask whether we need it,” he said. “You’re going to have to convince us that we don’t need it.”
Some other elements of NASA’s smallsat science initiative are ongoing, like streamlined documentation and review processes for such missions. He also announced awards to three companies—DigitalGlobe, Planet, and Spire—for purchases of commercial Earth science satellite data for research applications.
|“Astrophysics CubeSats have particularly unique challenges, and that’s why you don’t hear too much about them,” said Ardila.|
Zurbuchen suggested NASA might be a good secondary customer for such data after companies exhausted initial customers who were interested in immediate access. “If you have data that is of value to the science community, if you’ve expended the value that comes from latency and so forth, and you want a secondary market, we’re in business,” he said.
While the specific companies announced in his speech were new, the initiative goes back at least two years. “Thanks for your patience. Thanks for sticking with it,” he said. (And even then, a NASA spokesperson later said, the awards to those three companies had yet to be finalized, which is why Zurbuchen didn’t announce the value of the awards.)
Zurbuchen also used his speech to highlight the wide range of smallsat science missions underway at NASA. One example he cited was one called RainCube, which is intended to test a small Ka-band radar to make precipitation measurements. That spacecraft recently achieved “first light,” which in this case meant the successful transmission and reception of radar signals.
“Frankly, it’s a small miracle,” he said of RainCube’s ability to incorporate that radar system into a 6U CubeSat.
Earth science and heliophysics, though, have been early adopters of CubeSats in particular: their missions could be carried out from Earth orbit in most cases, and their instruments could more easily fit into CubeSat form factors. NASA’s other two science divisions, astrophysics and planetary science, have been slower to adopt CubeSats. Planetary missions beyond Earth orbit impose technical challenges, like power and communications, while astrophysics missions often require larger apertures that make them ill-suited for CubeSats.
“Astrophysics CubeSats have particularly unique challenges, and that’s why you don’t hear too much about them,” said David Ardila of JPL in a pre-conference workshop at the smallsat conference August 4. “First of all, astrophysics is signal-starved. What you are observing are point sources, so the way to get more signal is to have a larger aperture, which doesn’t work very well in a CubeSat.”
Additional challenges, he said, is the need for long exposures, which drives the need for stability, and a desire for long mission lives which requires more robust components. There’s also, he argued, a view that CubeSats can only do things that larger satellites have previously, just at a lower cost. “But in the context of science missions in astrophysics, you have to show that your CubeSat or smallsat can compete in the current landscape,” he said. “You have to find unique niches.”
Ardila is working to find such unique niches with a mission concept called Star-Planet Activity Research CubeSat (SPARCS). That spacecraft would be a 6U CubeSat equipped with a telescope nine centimeters in diameter and an ultraviolet camera. It will perform dedicated monitoring of a dozen low-mass stars to measure their stellar variability, which could provide clues to their habitability: stars with significant ultraviolet variability may be subject to intense storms that could render any planets orbiting them inhospitable, even if they orbit in the so-called “habitable zone” of that star.
A CubeSat is well-suited for this mission, he argued, since it’s relatively affordable to devote a single spacecraft to studying a handful of stars. “We require long stares to be able to characterize the stars,” he said. “If you want to observe a star for 30 days, you’re going to need your own satellite.”
That ability to perform dedicated long-term observations is behind another astrophysics CubeSat mission called Monitoring Spectroscopic Telescope for Energetic Radiation, or MonSTER. That spacecraft would carry out observations of known x-ray binaries to be able to catch an outburst from one of those systems from the beginning.
“There are about a dozen of these systems that go into outburst every year,” said Brian Grefenstette of Caltech at the pre-conference workshop August 5. “We want to continuously observe these bright x-ray binaries when they go into outburst.” That can help coordinate timely optical and radio observations of the outbursts as well.
On the planetary science side, NASA’s first interplanetary CubeSat mission is already underway, although not strictly speaking a science mission. The two Mars Cube One, or MarCO, CubeSats launched in May along with NASA’s InSight Mars Lander mission. The two are designed to serve as communications relays during InSight’s entry, descent, and landing (EDL) phase in late November, when InSight itself will not be in direct contact with the Earth.
“MarCO, at its heart, is a technology demonstration. It’s the first time a lot of this technology has flown in a deep space environment,” said Anne Marinan of JPL at the workshop August 5. The two CubeSats, MarCO-A and -B, are performing well more than three months after launch, she noted.
|“Just because a spacecraft is small doesn’t make it easy,” Zurbuchen said.|
The MarCO CubeSats will fly past Mars, but Marinan said there may be an option for an extended mission to further study how such satellites work in deep space. “Right now the focus is getting to EDL,” she said. “But if budget and personnel and interests all align, then we would definitively love to keep flying the MarCO mission as long as possible, to gather more data and see when they fail and what causes it.”
MarCO could enable future planetary science CubeSat-class missions. One concept under study mentioned at the conference was a larger CubeSat mission that could fly as a secondary payload on NASA’s Psyche mission to the main belt asteroid of the same name, but be dropped off in Mars orbit when the main spacecraft does a flyby of the planet.
The new emphasis on smallsat science missions in general, regardless of discipline, doesn’t mean NASA is abandoning larger missions. “Is everything we’re going to be doing smallsats? No,” Zurbuchen said. “What we want is a balanced mission portfolio, in which some part of our portfolio are missions that are really, really super hard.” That includes things like the James Webb Space Telescope, Mars landers, and the recently launched Parker Solar Probe.
That’s not to say, though, that smallsat missions are easy, something smallsat developers would likely agree with. “Just because a spacecraft is small doesn’t make it easy,” Zurbuchen said. “I think a highly constrained spacecraft kind of pushes the engineering and pushes the ingenuity of the team in a way that, in every way, is comparable to some of these big missions that we’re doing.”
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