Photograph courtesy Chris Boshuizen

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NASA PhoneSat is seen a hundred thousand feet above Earth.

Photograph courtesy Chris Boshuizen

Bread-Loaf Size Satellites to Probe Atmosphere, Deep Space

"Watershed" moment seen for little low-cost CubeSats.

Formerly the domain of student projects, CubeSats—low-cost satellites no bigger than loaves of bread—are coming into their own, performing high-level scientific research.

Developed at California Polytechnic State University and Stanford University beginning in 1999, the satellites typically use off-the-shelf components and are built to uniform sizes, the smallest being a four-inch (ten-centimeter) cube. The cubes can be linked to fit more instruments into a single satellite.

Stacked in bulk in a special container, CubeSats hitchhike as secondary cargo on launch vehicles—adding to their considerable economic advantage over conventional satellites, which can run $50 to $100 million at the low end.

At the same time, computer chips are getting smaller, allowing researchers to fit more and more into these Rubik's Cube-size boxes.

It all adds up to increasing popularity for the tiny satellites, as evidenced by the growing industry around them. Aerospace companies, for instance, have begun producing standardized parts specifically for CubeSats.

Firefly Cleared for Flight

Among this growing breed of nanosatellite is Firefly, made up of three stacked CubeSats.

Firefly will study bursts in Earth's atmosphere known as terrestrial gamma-ray flashes (TGFs). TGFs are poorly understood but are thought to be created when electric fields above a thunderstorm accelerate electrons to speeds nearing the speed of light—like a natural particle collider. (See "Lightning Created Particle Colliders Above Earth.")

"Nowhere in the theory of lightning were you able to say there should be these gamma rays," said Allan Weatherwax, lead scientist on the Firefly project.

Firefly—the first satellite to simultaneously measure TGFs and lightning—aims to shed light on the mystery.

To do so, the 12-inch-long (31-centimeter-long) satellite has been packed with just a few instruments: a gamma ray detector, an optical sensor to seek out lightning, and a radio sensor, since lightning also produces low-frequency radio waves.

CubeSats Cheap and Efficient

Firefly's total cost will be about a million U.S. dollars—an affordable level for many universities—said Weatherwax, a physicist at Siena College in New York State.

"Would we have been funded to study just TGFs at a hundred million dollars?" he said. "Maybe not. But for a million dollars, it's exciting science.

"If we can understand this acceleration process, we can start applying that to solar flares, cosmic shock waves, black holes. Any place you have these electric fields accelerating particles to high energies." (See "Higgs Boson Found? Without 'God Particle,' No Galaxies—And No Life.")

The mission may even explain lightning itself, as TGFs are hypothesized to be the way a visible lightning strike gets started.

CubeSats Also Out of This World

Aiming its "eyes" farther out in space, a Lawrence Livermore National Laboratory CubeSat will soon be tracking space junk. Likewise Morehead State University in Kentucky will soon launch a CubeSat to examine the cosmic microwave background—the "echoes" of the big bang. (Related: "Other Universes Finally Detectable?")

And at MIT a team of astronomers is planning a CubeSat to hunt down new planets outside our solar system.

Called ExoplanetSat, the instrument will follow up on known exoplanets that were discovered via the wobble they induce in their host stars' gravity. The CubeSat is intended to learn whether those planets also cross in front of, or transit, their stars, as seen from Earth.

That knowledge would allow for further observations by other instruments, for example to analyze the planets' atmospheres. (See "Smallest Exoplanets Found—Each Tinier Than Earth.")

If the project is successful, MIT would like to have several dozen ExoplanetSats zipping through the sky, each pointing at a different star that might host a planet that could be harboring life, MIT astrophysicist Sara Seager said.

"I would say we're on a watershed for how science gets done," Seager said. "[CubeSats] could very well take off for science."