CubeSats get bigby Jeff Foust
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| “We’re on the verge of doing some really neat science with CubeSats,” said Malphrus. |
Yet, while the conference has gotten larger, the topic of the conference has gotten smaller. It’s not that interest in smallsats is waning, but instead the satellites themselves are getting smaller. In the last several years, there’s been a surge in interest in very small satellites, called CubeSats, that are ten centimeters on a side and weigh one kilogram. While the CubeSat concept has been around for over a decade, it had originally been considered by most in the industry as little more than a novelty: good engineering projects for students, but of little use otherwise—and possible, in large numbers, an orbital debris nuisance. At this year’s conference, though, CubeSat-class missions dominated the conference presentations and other discussions during the four-day event.
One reason for the change has been the evolution of the CubeSat from a standalone satellite to a building block for larger—but still very small—spacecraft. A common example is the “3U” CubeSat, consisting of three CubeSats combined into a single spacecraft approximately 30 centimeters long. Others are examining 6U, 12U, and even larger spacecraft, as well as smaller 1.5U spacecraft. Such spacecraft create a form of standardization that make it easier to both develop such spacecraft and to find rides for them as secondary payloads.
Meanwhile, advances in technology make it possible to put increasingly capable payloads into such small spacecraft. “We’re on the verge of doing some really neat science with CubeSats,” said Ben Malphrus of Morehead State University in a conference presentation on the Cosmic X-ray Background Nanosat. The spacecraft, slated for launch this week as a secondary payload on an Atlas V out of Vandenberg Air Force Base in California, is a 2U CubeSat designed to measure the cosmic x-ray background at energies of 30 to 50 KeV. That radiation is neither well measured nor understood, with competing models for its origin, he said. “That’s what we’re hoping to solve with our little x-ray satellite.”
Other CubeSats are already providing good scientific data for researchers. The University of Michigan’s Radio Aurora Explorer 2 (RAX-2) spacecraft, a 3U CubeSat launched last October as a secondary payload on a Delta II, is helping space scientists understand the development of plasma instabilities in the ionosphere that can disrupt radio communications. “It’s provided the highest resolution mapping of ionospheric irregularities ever,” said John Springmann of Michigan in a presentation on RAX. Initial results from the RAX-2 satellite were published in the journal Geophysical Research Letters this summer. That project is one of several supported in part by grants from a National Science Foundation program for funding CubeSat missions to carry atmospheric and space science research.
The low cost of CubeSats, which makes it easier to fly large numbers of such spacecraft, is opening up potential new applications as well. Craig Clark, CEO of Scottish smallsat company Clyde Space, discussed at the conference a concept for a network of 3U CubeSats to provide realtime imagery of the globe. Advanced technologies such as deployable optics would allow such spacecraft to take images with resolutions as sharp as 0.7 meters, he said. “This is all leading to having live images of the Earth for people to view, initially with medium-resolution images” and later moving to higher-resolution images—in effect, he said, a live version of Google Earth.
NASA is also studying the use of clusters of CubeSats with its Edison Demonstration of Smallsat Networks (EDSN) mission under development. EDSN will fly ten 1.5U CubeSats to test technologies that could be used by future swarms of such spacecraft. “You can do things with a swarm that you can’t do with a single, traditional, monolithic satellite,” said Jim Cockrell of NASA Ames Research Center. That includes studying geographically dispersed phenomena simultaneously and increasing revisit rates over the same point on the Earth, as well as spreading functions—and risks—over multiple spacecraft. EDSN will build upon NASA’s PhoneSat program, which is developing CubeSats that use Android smartphones as the flight avionics system. The initial PhoneSats are slated for launch as secondary payloads later this year as secondary payloads on the first Orbital Sciences Corporation Antares launch.
| “The community knows that if I build my CubeSat, if I get the money to go build it, there are going to be rides there for me,” Skrobot said of NASA’s ELaNa program. |
CubeSats don’t need the brains of a Google-powered smartphone to carry out useful missions, though. Smallsat pioneer Gil Moore discussed at the conference a mission called the Polar Orbiting Passive Atmospheric Calibration Sphere (POPACS). The spacecraft in this case are six 10-centimeter spheres filled with sand to masses of 1, 1.5, and 2 kilograms; three are painted white while three will have shiny metallic surfaces. The spheres will fly within 3U CubeSat frames as secondary payloads on the first Falcon 9 launch from Vandenberg in early 2013, and released once in polar orbit. Air Force radars as well as ground observers—including, Moore hopes, college students—will track the orbits of these objects as they decay over 10 to 15 years to measure atmospheric density.
Another development enabling greater use of CubeSats has been an increase in launch opportunities. Even with the development of standardized CubeSat payload dispensers, like the Poly-PicoSatellite Orbital Deployer, or P-POD, finding rides for CuebSats as secondary payloads has been a challenge, and often required flying on Russian vehicles. However, there are now increasing opportunities for CubeSat launches on American vehicles; at the conference representatives of Orbital Sciences, SpaceX, and United Launch Alliance all affirmed their commitment to flying CubeSats and other smallsats on their vehicles.
NASA has helped prime the pump for these launch opportunities through its Educational Launch of Nanosatellites (ELaNa) program, which offers rides for university-built CubeSats. NASA has selected 68 CubeSats in the first three rounds of the program, with a fourth call for proposals currently open. Those missions are flown on a variety of NASA missions, including upcoming commercial cargo missions to the ISS.
NASA’s Garrett Skrobot said ELaNa helps provide sustainability to university CubeSat developers. “The community knows that if I build my CubeSat, if I get the money to go build it, there are going to be rides there for me,” he said.
Key to these enhanced launch opportunities is standardization in payloads, to make it easier for launch providers to integrate them onto their missions. “For us, labor is actually the driving cost for secondary payloads,” said SpaceX’s Dustin Doud. “The more easily you are integrated, the better chance you have of being manifested.”
An alternative to secondary payloads is to fly a dedicated mission of CubeSats or other small satellites, as has been done from time to time, again primarily with Russian vehicles. The QB50 project plans to fly 50 university-built CubeSats on a single Russian sub-launched Shtil rocket in 2014 or 2015 for technology demonstration and studies of the Earth’s thermosphere. Dutch company Innovative Solutions In Space (ISIS) is working on the payload dispenser than can accommodate all 50 in a rocket whose total payload capacity to LEO is only 220–230 kilograms. Jeroen Rotteveel of ISIS said at the conference they hope this dispenser system can be used for future missions as well.
| “I’ll be the first one to extol the virtues of CubeSats,” said Voss. “However, I think many of us have drunk the CubeSat Kool-Aid, so to speak, and have gone straight from a TacSat-sized bus to a CubeSat.” |
Dedicated launches of perhaps single CubeSats is the goal of NASA’s Nanosatellite Launch Challenge, a competition part of its Centennial Challenges prize program and run by Space Florida. The public comment period on the draft rules closed this summer, although the final rules for the competition have not been released. Last month NASA issued a request for information (RFI) about user needs for a nanosat launcher. That RFI, which closes today, suggests that NASA may be looking at somewhat larger satellites—up to 10 kilograms from the original 1 kilogram—than originally planned.
The increased attention CubeSats, in their various configurations, are getting has raised concerns from some in the field who believe somewhat larger smallsats—those weighing tens of kilograms—are being overlooked. “I’ll be the first one to extol the virtues of CubeSats,” said David Voss of the Air Force Research Laboratory. “However, I think many of us have drunk the CubeSat Kool-Aid, so to speak, and have gone straight from a TacSat-sized bus”—weighing over 100 kilograms—“to a CubeSat.”
That approach, he said, results in “jumping over one of the most capable classes of satellites, the 20–50 kilogram class.” Voss is involved with the Air Force’s University Nanosatellite Program, which has supported the development of spacecraft in that class by various universities, although the latest rounds of the competition have now included CubeSat-class spacecraft as well. “Let the mission drive you to the class” of spacecraft, he advised.
For now, while there is strong interest in CubeSats, many of their capabilities have yet to be demonstrated in space. “There’s a really pivotal year going on” for CubeSats, said Michael Swartwout of Saint Louis University. There are as many as 50 to 70 CubeSats planned for launch in the next year, far more than ever before, which he thinks will go a long ways towards demonstrating what utility—if any—such spacecraft offer. “We’re going to address this question of toy, tool, or debris cloud.”