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Builders Packing More Capability into Small Satellites
SAN FRANCISCO — Although small satellites come in a wide range of sizes and perform an impressive array of missions, customers share a common wish list for future spacecraft. They want additional power, faster communications and improved pointing accuracy. Often, government and industry customers are even willing to buy slightly larger satellites to acquire higher performance.
“People want to put additional capability on small satellites,” said Jim Armor, a retired U.S. Air Force major general who now serves as vice president of strategy and business development for ATK Space Systems and Services of Beltsville, Md. “Once you engage with customers and find out their real requirements, they often end up wanting satellites that are a little larger” than they initially expected.
To show customers that it can meet their demand for spacecraft of various sizes, ATK has collected its small satellite buses into a family that includes: the ATK 100, which is designed to carry payloads weighing 15 kilograms or less; the ATK 200, for payloads of 200 kilograms or less; the ATK 500, for 200-kilogram to 500-kilogram payloads; and the ATK 700, for payloads weighing as much as 1,700 kilograms. ATK has sold each of those satellite platforms for years although some were known by other names. The ATK 200, previously known as the Responsive Space Modular Bus, was used for NASA’s Earth Observing-1 satellite and the Defense Department’s Operational Responsive Space (ORS)-1 satellite. The ATK 500, previously known as the High End Modular Bus, was selected by the Defense Advanced Research Projects Agency for its Phoenix program, an effort designed to take valuable components from satellites in geosynchronous orbit that are no longer working and reuse them on new, small spacecraft.
While NASA and U.S. national security agencies continue to express interest in the ATK 100, ATK sees a growing market for the ATK 500 and the ATK 700 because satellites of that size are beginning to take on missions previously performed by much larger spacecraft, Armor said. Advances in electronics and sensor technologies are leading to dramatic reductions in the size of instruments. ORS-1, a satellite launched in June 2011, for example, carries an electro-optical and infrared sensor with capabilities similar to sensors built in the late 1990s that were nearly ten times the size of ORS-1.
Even for the smallest satellites, the desire for additional capability is prompting developers to adopt slightly larger platforms. When cubesats were introduced more than a decade ago, engineers focused on missions that could be performed in a single 10-centimeter cubesat or a triple cubesat. Increasingly, developers are eager to fly six-unit or 12-unit cubesats, which can accommodate a new class of payload, said Jordi Puig-Suari, the aerospace engineering professor at the California Polytechnic State University who worked with Stanford University professor Bob Twiggs to invent the cubesat standard in the late 1990s.
In 2011 Puig-Suari and Scott MacGillivray, former manager of nanosatellite programs for Boeing Phantom Works, established Tyvak Nano-Satellite Systems LLC in San Luis Obispo, Calif., to sell miniature avionics packages for cubesats. “There’s a huge benefit to the small component development because it increases the volume available for payloads,” Puig-Suari said.
Cubesat mission planners also are seeking to add propulsion to their spacecraft without jeopardizing the primary missions that give them rides into orbit. “The emerging, third-generation of cubesats has some operational utility,” said Andrew Kalman, Stanford University professor and president of San Francisco-based Pumpkin Inc., manufacturer of the CubeSat Kit. That utility will increase when cubesats offer higher power for onboard systems, improved communications and propulsion. Onboard propulsion will enable cubesats to move to higher orbits, conduct proximity operations and form constellations, Kalman said.
Honeybee Robotics is working with MMA Design LLC on new solar energy system to provide cubesats with additional power. Honeybee developed a solar array drive assembly for MMA’s High Watts per Kilogram power system, a two-wing solar array designed to more than double the average orbital power of a cubesat by turning toward the sun, said Mitchell Wiens, president of Boulder, Colo.-based MMA Design. MMA is developing the solar-tracking cubesat array under a Small Business Innovative Research grant from the Air Force Research Laboratory. The company also has signed a Space Act Agreement to apply the technology to future NASA missions.
The MMA solar array is designed to fit in a 6.5-millimeter space between the cubesat and the Poly Pico Satellite Orbital Deployer (PPOD), which houses the small satellite in a launch vehicle and ejects it into space. The thin solar panels are designed to spread out when the cubesat is released from the PPOD, Wiens said.
Honeybee also is developing an attitude control actuator designed to enable large satellites, in the 20-kilogram to 100-kilogram range, to reorient frequently in space. Instead of turning toward two focal points during a single orbit, Honeybee is developing a control moment gyroscope to enable a satellite to fix its sights on four, five or even ten different targets, said Erik Mumm, vice president and director of flight systems for Honeybee Robotics of New York. The company hopes to demonstrate that capability in space in early 2013, Mumm added.