An illustration of the double Mars Cube One (MarCO) CubeSats that fly past Mars. The spacecraft is a technology demonstration for future deepspace CubeSats and also provides a data relay for the InSight lander. (credit: NASA / JPL-Caltech)
by Jeff Foust
Monday, August 20, 2018
The debate about whether smallsats in general, and CubeSats in particular, have any usefulness that goes beyond the experience gained in building them, has ended a long time ago. A growing number of companies have shown that they can create profitable companies by building large numbers of such satellites for imaging, asset tracking and other applications. This has generated ripple effects from growing private investments in such companies into a wave of companies developing small launchers to launch those satellites.
The idea of using CubeSats and other smallsats for scientific missions has recently gained traction, even if the idea is not so new. "CubeSats can do science with high priority, they have already," said one speaker at the 2016 edition of the conference on small satellites, held by AIAA and Utah State University two August ago.
|"We are going to realize the importance of small satellites, not just as a platform, but also as a way of doing science that would otherwise not be feasible," Zurbuchen said.|
That speaker had just completed a study that was published earlier that year by the National Academies on the scientific usefulness of CubeSats, a conclusion that concluded that such a spacecraft could play an important role in various aspects of Earth and space sciences. At the end of his lecture someone asked how the results would be implemented. "I think we should look at the whole set of recommendations," he replied after discussing the briefings of the report in the White House and with members of Congress. "I think there is a lot of potential there."
That speaker was Thomas Zurbuchen, then a professor at the University of Michigan. Two months later, however, he was with NASA as the new associate administrator of the science bureau. In that position he was able to shape the scientific program of NASA to make more use of small satellites.
Earlier this month, he returned to the state of Utah for this year's smallsat conference, an event that continues to attract new entrants and new entrants (the attendance of about 3,060 has set a new record.) As a keynote speaker for the conference, Zurbuchen explained what NASA was doing to make more use of it and to implement the recommendations from the report that it helped to produce.
"We are active for small satellites and CubeSats," he said in his speech. "We are going to realize the importance of small satellites, not just as a platform, but also as a way of doing science that would otherwise not be feasible."
Zurbuchen used his keynote to announce a new smallsat initiative in NASA's Directorate for Science Mission. "This was the first initiative I introduced when I joined two years ago," he said, but it was only in the last month, after NASA finalized the operational work plan for the 2018 financial year, funding now set at $ 100 million. per year, from 2018, for smallsat-related science projects.
"I felt, because of those Academies study, that it is absolutely essential that we do this," he said. That includes "totally new opportunities that have been coming out lately 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 occasion, released the same day as his speech, sought proposals for small moves that could fly on the Interstellar Mapping and Acceleration Probe, which will launch to the Earth-Sun L-1 Lagrange point in 2024. NASA offers up to $ 65 million for one or more such ressourism missions.
"This is really a new type of application due to the fact that it is deliberately aimed at improving the technological possibilities in that area," he said. "If this succeeds, this not only teaches new science, but also protects the technological infrastructure that is sensitive to space weather."
Another new aspect of this initiative is offering more such opportunities for small competitions. Zurbuchen said that when NASA launches for future larger missions, it will automatically include a so-called EELV Secondary Payload Adapter (ESPA), also called an "ESPA ring" due to its ring-shaped appearance, to which smallsats can be attached.
"We are not going to ask if we need it," he said. "You will have to convince us that we do not need it."
Some other elements of the NASA small science science initiative are in progress, such as streamlined documentation and assessment processes for such missions. He also announced awards to three companies, DigitalGlobe, Planet and Spire, for the purchase of commercial earth science satellite data for research applications.
|"Astrophysics CubeSats have unique challenges and that is why you do not hear too much about them", said Ardila.|
Zurbuchen suggested that NASA could be a good secondary customer for such data after companies exhausted their first customers who were interested in immediate access. "If you have data of value to the scientific community, if you have earned the value that comes from latency and so on, and you want a secondary market, we are in the market," he said.
While the specific companies announced in his speech were new, the initiative goes back at least two years. "Thank you for your patience, thank you for maintaining it," he said. (And even then, a NASA spokesperson said later, the prices for those three companies were not yet definitive, hence Zurbuchen the value of the awards not announced.)
Zurbuchen also used his speech to emphasize the wide range of small science missions that was underway at NASA. An example he mentioned was a RainCube, which is intended to test a small Ka band radar to perform rainfall measurements. That spacecraft recently achieved "first light", which in this case meant the successful transmission and reception of radar signals.
"Honestly, it's a small miracle," he said about RainCube's ability to incorporate that radar system into a 6U CubeSat.
Earth sciences and heliophysics, however, are particularly early adopters of CubeSats in particular: their missions can in most cases be carried out from Earth's orbit, and their instruments can more easily fit into CubeSat form factors. NASA's other two scientific divisions, astrophysics and planetary science, are slower to adopt CubeSats. Planetary missions beyond the earth's orbit involve technical challenges such as power and communication, while astrophysical missions often require larger openings that make them unsuitable for CubeSats.
"Astrophysics CubeSats have unique challenges and that is why you do not hear too much about them", said David Ardila of JPL during a pre-conference workshop at the small conference on 4 August. "First of all, astrophysics is a signal hunger.What you observe are point sources, so the way to get more signal is to have a larger aperture, which does not work very well in a CubeSat."
Additional challenges, he said, are the need for long-term exposure, which creates the need for stability and a desire for long missions, for which more robust components are needed. There is also, according to him, a view that CubeSats can only do things that larger satellites have earlier, only at a lower cost. "But in the context of scientific 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 on finding such unique niches with a mission concept called Star-Planet Activity Research CubeSat (SPARCS). That spacecraft would have a 6U CubeSat equipped with a telescope nine centimeters in diameter and an ultraviolet camera. It will carry out special monitoring of a dozen stars with a low mass to measure their stellar variability, which may give clues to their habitability: stars with significant UV variability can be subject to violent storms that can make planets around them inhospitable, even if they are in a job. in the so-called "habitable zone" of that star.
A CubeSat is suitable for this mission, he reasoned, because it is relatively affordable to dedicate a single spacecraft to studying a handful of stars. "We need long looks to be able to characterize the stars," he said. "If you want to observe a star for 30 days, you need your own satellite."
That ability to perform special long-term observations is behind another astrophysical CubeSat mission called Monitoring Spectroscopic Telescope for Energetic Radiation, or MonSTER. That spacecraft would perform observations of known X-ray beacons in order to be able to absorb an eruption from one of those systems from the outset.
"There are about a dozen of these systems going eruption every year," said Brian Grefenstette of Caltech at the pre-conference workshop on 5 August. "We want to continuously observe these bright X-ray double stars when they go into eruption." That can help coordinate timely optical and radio observations of the eruptions as well.
In the area of planetary science, NASA & # 39; s first interplanetary CubeSat mission is already under way, although strictly speaking it is not a scientific mission. The two Mars Cube One or MarCO, CubeSats were launched in May together with NASS mission InSight Mars Lander. The two are designed to serve as communication relays during InSight's entry, descent and landing (EDL) phase in late November, when InSight itself is not in direct contact with the earth.
"MarCO, in essence, is a technology demonstration, the first time that much of this technology has flown into a deep space environment," said Anne Marinan of JPL at the August 5 workshop. The two CubeSats, MarCO-A and -B, perform more than three months after the launch, she noted.
|"Just because a spaceship is small does not make it easy," Zurbuchen said.|
The MarCO CubeSats will fly by Mars, but Marinan said that there might be an option for an extensive mission to further study how such satellites work in deep space. "At the moment the focus is on EDL," she said. "But if budget and staff and interests are all aligned, we would like to keep the MarCO mission flying for as long as possible, collecting more data and seeing when they fail and what causes them."
MarCO can enable future planetary science CubeSat-class missions. A concept mentioned at the conference was a larger CubeSat mission that could fly as a secondary load on NASA's Psyche mission to the main belt asteroid of the same name, but would be dropped off in the orbit of Mars when it head spacecraft a flyby from the planet.
The new emphasis on small science missions in general, regardless of discipline, does not mean that NASA is leaving larger missions. "Is everything we're going to do little things?" "No," Zurbuchen said. "What we want is a balanced mission portfolio, where part of our portfolio are missions that are really very difficult." That includes things like the James Webb Space Telescope, Mars landers and the recently launched Parker Solar Probe.
That is not to say that petty missions are simple, something that developers probably agree with. "Just because a spaceship is small does not make it easy," Zurbuchen said. "I think that a very limited spacecraft pushes the technique a bit and pushes the resourcefulness of the team in a way that is, in all respects, similar to some of these great missions we do."
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