SAN FRANCISCO — Cubesats, once largely regarded as university teaching tools, are attracting the attention of U.S. military officials eager to use the miniature satellites to improve battlefield communications, monitor space weather and gather data from unattended sensors.
Before cubesats can be widely used for those jobs, however, government and industry teams must devise ways to cram additional power and capability into the small satellites, government and industry officials said.
Current U.S. Army, Navy and Air Force cubesat initiatives focus primarily on using the small satellites, which measure 10 centimeters on a side and weigh approximately 1 kilogram, to conduct research and test new technologies. Within a few years, however, cubesats are likely to play a role in supporting military operations. “That’s coming along a lot faster than people think,” said U.S. Air Force 1st Lt. Chalie Galliand, spaceflight mission design manager for the Space Development and Test Directorate at Kirtland Air Force Base in New Mexico.
On Dec. 8, the Falcon 9 rocket launched by Space Exploration Technologies (SpaceX) of Hawthorne, Calif., to send its Dragon spacecraft into low Earth orbit also sent aloft six cubesats. SpaceX officials declined to identify all the payloads, but three customers announced the successful launch of their cubesats on the Dec. 8 flight: the University of Southern California, the U.S. Army Space and Missile Defense Command in Huntsville, Ala., and the U.S. Naval Research Laboratory (NRL) in Washington.
The U.S. Army used that flight to launch a triple-unit cubesat, a popular configuration that joins together three of the miniature cubes to create a satellite roughly the size of a can of tennis balls, to prove the ability of small satellites to transfer data to and from unattended ground sensors.
The NRL’s Center for Space Technology launched two triple-unit cubesats on the same rocket to determine whether the small satellites could be used as platforms for future experiments. The two cubesats, known as CubeSat Experiment or QbX, were built by Pumpkin Inc. of San Francisco, and provided to the NRL by the U.S. National Reconnaissance Office.
NRL researchers used QbX to evaluate the spacecraft bus as well as “a ground operations network suitable for low-cost constellation operations,” Mark Johnson, electronics engineer with the NRL’s space electronics branch, said in an e-mail.
While university researchers often rely on individual satellites to conduct experiments or test new technologies, military cubesats are likely to operate in constellations or swarms, government and industry officials said. Those constellations can be composed of identical satellites operating in low Earth orbit to offer broad geographic coverage, or various mission components may be divided among a swarm of small satellites.
Both approaches are designed to take advantage of the relatively low price and ease of launch of cubesats. In contrast to multibillion-dollar U.S. Defense Department satellites, military cubesats cost roughly $250,000 apiece and can be launched as secondary payloads on commercial, military or NASA rockets.
Before the small satellites can fulfill their promise of providing responsive, low-cost access to orbit, however, key technologies need to be improved. NRL engineers are developing specialized radios, antenna and space weather sensors for cubesats. “The CubeSat may be limited by physics in many ways; however as miniaturization and nanotechnology advances, new capabilities can be achieved,” Johnson said.
Government and industry groups also are striving to increase the amount of power available for on-board devices. “If you can increase the energy density, you can pack more power generation into a smaller volume,” said Alex Lopez, vice president of the Advanced Network & Space Systems business unit of Boeing Phantom Works in El Segundo, Calif.
Most cubesats generate power for payloads with solar panels mounted on exterior walls. To boost available power, companies, university researcher organizations and government laboratories are developing solar arrays that extent from the satellite’s frame. Boeing is working to develop new, high-efficiency solar cells to boost power for cubesats and other small satellites, Lopez said.
Boeing engineers also are focused on reducing the size of antennas, or apertures, used to gather data. “If you can fold an aperture up like an umbrella, you can stuff it into a very small space,” Lopez said.
Packing electronics in a tight space, however, means more heat is being generated inside the satellite. “Cubesats get very dense and electronics are heat-sensitive,” Galliand said. One approach being explored by Boeing is to dissipate the heat inside the satellite by designing deployable radiators, Lopez said.
In addition, military cubesat customers are anxious to protect data transmitted. NRL is helping to develop secure communications equipment for cubesats and their larger cousins, nanosatellites, which weigh between 1 and 10 kilograms. Many of the satellite components currently used to encrypt data are too large to fit in cubesats and will have to shrink. “In order for cubesats to be operationally relevant to the military, you have to protect the data,” Galliand said.
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