SAN FRANCISCO — When the U.S. National Science Foundation (NSF) began laying the groundwork five years ago to use cubesats to investigate space weather, few people believed the miniature satellites would prove to be a useful scientific tool. “When I mentioned cubesats, everyone snickered,” said Therese Moretto Jorgensen, NSF program director for space weather research and instrumentation. “No one is snickering anymore.”
In fact, cubesats — 1-kilogram satellites measuring 10 centimeters on a side — have become a popular research tool. During the annual conference of the American Geophysical Union (AGU) here Dec. 3-7, government and university researchers described dozens of efforts to use cubesats to study the sun, observe Earth, gather climate data and search for exoplanets.
The growing interest in cubesats is due, in part, to the increasing capabilities of small satellites. For nearly 20 years, cubesats could do little more than Sputnik, said Tony Freeman, Earth system science formulation manager for NASA’s Jet Propulsion Laboratory (JPL) in Pasadena, Calif. “All they did was go up and beep. We are now at an Explorer 1 moment.”
Like Explorer 1, which measured radiation in Earth’s orbit, cubesats are proving their ability to gather useful scientific data. While the tasks these small satellites can perform still are limited, Freeman expects their capabilities to grow enormously during the next decade in the same way the capabilities of larger spacecraft spiked between the 1958 Explorer 1 mission and the 1969 Apollo Moon landing. “We are poised for something like that,” Freeman said.
Freeman was not always a cubesat advocate. Young researchers were clamoring for the chance to build the tiny satellites for approximately three years before he gave the topic serious consideration. In November 2011, Freeman called a meeting at JPL to evaluate whether cubesats could make valuable contributions to Earth science. “The answer was yes,” he said. “You can do compelling science.”
Miniature satellites cannot perform the same type of work as complex, billion-dollar spacecraft. “They will never replace NASA’s marquee missions, but they have a place in the complete space portfolio,” said Glenn Lightsey, an aerospace engineering professor at the University of Texas in Austin. Cubesats are not suited for missions that require active sensors, such as radars and lidars, due to limited onboard power, Freeman said. They also lack room for large-aperture antennas, Lightsey said.
Instead of trying to design cubesats to perform the same missions as their larger counterparts, leaders in the field are focusing on the unique jobs little spacecraft can perform. “There are measurements that can be made with small satellites that we could not afford to do with larger missions,” Freeman said. For example, a cubesat could carry a small sensor to detect sulfur dioxide. While researchers would like to obtain data on sulfur dioxide produced by volcanoes, the mission is not important enough to warrant development of a large satellite. “We wouldn’t fly a $400 million mission to make that measurement,” Freeman added. The mission might be worthwhile, however, if scientists could do it for a fraction of the cost.
Cubesats vary widely in price and complexity. If researchers can acquire the hardware to build a cubesat for $20,000 and obtain free rides into orbit on a NASA rocket or pay $300,000 to fly on a commercial launch vehicle, they can test new sensors and new observation techniques, Freeman said. Scientists can also begin developing constellations of tiny satellites.
For now, it is difficult for engineers to establish cubesat constellations because the miniature spacecraft lack the onboard propulsion they would need to move into different orbital slots. That propulsion is being developed, however. In addition, researchers are testing innovative methods for creating cubesat constellations such as adjusting the angle of the solar panels to vary the amount of drag on each satellite in a group.
More innovation is needed to enable cubesats to reach their full potential. “We are just starting to see what cubesats can do,” Lightsey said. In the years ahead, the tiny satellites are likely to include propulsion, networking capabilities and higher data rate communications.
Increasingly capable cubesats also will rely on new sensors. “We need small instruments,” Freeman said. “We don’t have enough of those because for many years we have been designing instruments for large spacecraft.”
Instrument development is improving. Scientists attending the AGU conference described a growing array of cubesat sensors being designed, built, tested and flown. NSF, which was one of the first government agencies to endorse the idea of cubesats, has provided funding for eight cubesat missions. The first four to launch are currently in orbit, obtaining “valuable scientific data,” Jorgensen said.