Pointing Platform Enables Earth Imaging from Space Station
Most people think of the International Space Station (ISS) as a place to learn about space, but in recent years the modules of humanity’s only outpost in space are also becoming halls of commerce, where companies experiment with materials in the space environment or 3D print nanosatellite parts.
A less obvious commercial use taking shape is Earth imaging. While low-Earth orbit is increasingly populated with downward-looking satellites, the space station can present a more affordable option for anyone looking to fly or at least try out science-grade imaging instruments. Since the station is already a satellite in orbit, a client only needs to send up the instrument itself.
Until recently, though, there was nowhere to put such an imager, and even if there were, there would have been no way to point it precisely: the space station only calculates its orientation to within about a degree of accuracy, but for a camera looking down on Earth from that 250-mile-high perch, turning just a hundredth of a degree means a difference of almost 200 feet on the ground.
“Before, you couldn’t track a spot on the ground or hold on a spot as you passed over it,” says Mike Read, who manages the ISS’s National Laboratory from Johnson Space Center.
To overcome this deficiency, Read’s office partnered with Huntsville, Alabama-based Teledyne Brown Engineering to outfit the station with its new Multi-User System for Earth Sensing (MUSES), which flew to the ISS in June of 2017 and went into full operation that September.
“We thought there was probably a market out there for various types of instruments that could be Earth-pointing,” he says, noting that the facility also fills a gap in NASA’s research capabilities.
This sort of thinking arises in part from a 2010 mandate from Congress that half of the National Lab’s resources be used by entities outside NASA, including commercial, academic, and governmental organizations.
Teledyne Brown was one of the first companies to enter into a cooperative agreement with the Space Agency to carry out commercial activities on the space station, signing the MUSES contract in 2012.
The company was accustomed to working with NASA but found as it was developing MUSES that if it wanted to turn a profit it had to reduce some of the redundancies and complexities the Agency had normally required, says Jack Ickes, vice president of geospatial solutions for Teledyne Brown. “Our challenge was to be able to make that product in space at such a cost that we would have a shot at return on investment.”
He says the agreement worked because NASA was willing to leave the system’s success up to the company, writing requirements only for crucial factors like safety. At first, he says, the Agency’s engineers often had to be reminded of that new approach, but it’s now become the National Laboratory’s standard practice for partnering with companies.
“We’re trying to make sure we only levy those requirements that are necessary,” says Read. “We’ve got a major undertaking going on to shift our culture to be more responsive to commercial best practices.”
Designed to fit on one of the space station’s four external ExPRESS (that’s Expedite the Processing of Experiments to the Space Station) Logistics Carriers, MUSES consists of two 18-by-36-inch canisters and two that are 10 by 36 inches. All four can house multiple payloads, depending on customers’ needs.
To enable precision pointing, it uses a star tracker that orients itself by the stars, as well as enhanced GPS and miniaturized inertial measurement devices. It’s accurate down to less than a thousandth of a degree.
Randy Miller, operations manager for geospatial solutions at Teledyne Brown, says the system is so sensitive it can detect the vibrations caused by an astronaut exercising inside the space station. By sensing such disturbances, the system can correct for them on a pixel-by-pixel basis.
MUSES has deep roots in the Space Agency, well beyond the cooperative agreement and the know-how Teledyne Brown has accumulated over decades as a NASA contractor. The company’s chief technologist and “father of the MUSES design,” Mark Whorton, was a 20-year NASA veteran who had retired as chief of the Guidance, Navigation, and Mission Analysis Branch at Marshall Space Flight Center, notes Ray Perkins, Teledyne Brown’s business development manager for geospatial solutions. “So he had a very extensive background in space-based control and pointing systems.”
The company also spent about a week at Marshall, running the hardware through the temperature extremes and electromagnetic interference it would face in space to qualify it and characterize its performance. Meanwhile, Johnson engineers helped test the communications interfaces that let MUSES downlink as much as 225 gigabits per day over the space station’s wireless communications system. And the payload rack checkout unit testing that’s required for external payloads on the space station was carried out at Kennedy Space Center. “When we had a challenge, we worked with NASA at all three of these Centers to overcome it,” Perkins says.
The first customer for MUSES was the German Aerospace Center, Deutsches Zentrum für Luft- und Raumfahrt (DLR), which signed on in 2014 to place its DLR Earth Sensing Imaging Spectrometer (DESIS) onto the platform. The hyperspectral imager, installed in early 2018, has a 30-meter resolution and “sees” Earth through 235 channels in the visible and near-infrared wavelengths. It can sense changes in surface coverage, oceans, and the atmosphere and is intended to help inform Germany’s decisions around problems like environmental and climate protection and food security.
Teledyne Brown expects that a major customer base for MUSES will include entities that want to try out their technology in space before putting it on a satellite. The DESIS spectrometer, for example, is planned for the German Environmental Mapping and Analysis Program satellite that’s supposed to fly in 2019. But the one on MUSES required a lot less engineering and reinforcement than the satellite version will.
Satellites being sent to space are attached to the frame of the spacecraft carrying them and experience all the jarring vibrations of liftoff, so it takes a lot of engineering to ensure all their components will survive launch, Perkins says. But smaller components being sent to the space station can be packed away and insulated from vibration. “It’s the difference between driving a dump truck and driving a Cadillac.”
Without the need to withstand violent shaking, builders can use more inexpensive, off-the-shelf components. Test articles are sent up with resupply missions and installed on the MUSES platform via robotic arm, cutting down on expenses, and they can later be returned to Earth.
Jessica Sanders, director of marketing and communications for Teledyne Brown, says 30-40 percent of CubeSats that go into orbit don’t perform as expected—succumbing to glitches that might be discovered on a test flight on MUSES. “To be able to do an incremental test flight of your prototype, that’s a significant cost saving.”
Other clients might send a final product to carry out a mission—imaging or otherwise—on the platform. “Whether it’s a test flight or a mission, MUSES is more cost-effective than a dedicated satellite launch,” Sanders says. “It’s almost like a payload hotel, and you can check in and check out when you want.”
Secondary customers, meanwhile, can simply buy imagery from Teledyne Brown, which retains commercial rights to the data DESIS gathers. NASA is among these customers: its Earth Science Division paid for access to any data the Space Agency or a university has a use for.
In preparation for multiple data streams coming from MUSES, Teledyne Brown created what it calls the Teledyne Cloud, to store image archives, process data, and support collaboration between users. It already holds data from the U.S. Department of Agriculture’s National Agriculture Imaging Program and will soon incorporate a growing DESIS archive.
“If you place an order for images of a particular area, and that imagery already exists, you can get it right away,” says Johnny Miller, director of media services for Teledyne Brown. Otherwise, it will be captured on the space station’s next pass.
Perkins says state and local natural resource managers have expressed interest in using the hyperspectral data to calculate the area, type, and health of forest cover. Even some state budget offices could benefit from such data, depending on how much of a state’s tax revenue comes from lumber sales. Others are interested in monitoring water quality or pollutants in the atmosphere. One application likely to find government and commercial applications is taking inventory of crops and forecasting their yields.
Different wavelengths are useful for identifying different characteristics and features, and with DESIS differentiating between 235 spectral bands, Perkins says, a wealth of information can be extracted from the data it generates. “No instrument has flown in space with that level of spectral resolution before,” he says. “This is designed for government and commercial users to make significant decisions based on information extracted from data.”
And the DESIS imager is just the first of many potential tenants aboard MUSES, Read emphasizes. “Our hope is that there will be multiple instruments using different ends of the spectrum that can be turned into commercial products to be sold on the ground,” he says.
MUSES, in turn, is just one of several commercial partnerships taking shape on the ISS in recent years. “We want to see a viable economy in low-Earth orbit, and we want to be a customer,” Read says. “Helping companies learn they can make money in orbit is critical to growing that economy.”