Tiny satellites could revolutionize earth, space science research

The first U.S.-launched satellite, Explorer I, was 6 feet long and weighed 30 pounds, and it led to the discovery of the Van Allen radiation belt that surrounds Earth. More than 50 years later, scientists could do a lot more with far less.

Scientists in Maryland are helping to design satellites that could fit in a shoebox yet provide the same — or better — capabilities as NASA spacecraft that are far larger and more costly. The devices, composed of one or more 10-centimeter cubes, have been used over the past decade for affordable yet relatively low-tech experiments for university students, but a pair recently launched could advance the technology.

The Johns Hopkins Applied Physics Laboratory and NASA sent a pair of "cubesats" into orbit in November that could prove that the devices can be nearly as sophisticated, and in some cases, more useful, than traditional satellites at a fraction of the cost. Scientists are making plans to use them for earth and space science research, including a look at the radiation surrounding Earth in more detail than Explorer I or any satellite since has been capable of.

"This has the potential of being disruptive," said Ann Darrin, managing executive of the space sector at the Howard County lab.

Most satellites used for sophisticated research require significant investment and oversight by government agencies or large companies, she said. With cubesats, she said, "smaller groups could schedule and manage their own assets."

Cubesats have typically been used for university projects focusing on radio and communications, earthquake detection and imaging. The spacecraft often carry simple scientific equipment, with data communicated back to Earth over amateur radio frequencies. They can be composed of a single cube "unit" or several stacked together, piggybacking on launches of larger spacecraft.

But the pair launched last fall are unlike the others. Their features include more robust power systems using solar panels, GPS navigation technology and other mechanisms that enable the cubesats to maintain their orientation toward Earth and space, and better ability to communicate data. Their solar panels had to be designed to spread without the use of pyrotechnics; cubesats are not allowed to contain explosives, because they are essentially cargo riding along for launch.

All that is contained within three units, measuring 34 by 10 by 10 centimeters, or about 13 by 4 by 4 inches. There also must be room for a payload — the scientific equipment for any particular mission. In this case, the cubesats are being used for Department of Defense communications experiments as well as to demonstrate the capabilities of the physics lab's cubesat design.

Scientists at the Applied Physics Lab have been working on the cubesats for three years, collaborating with others at NASA Goddard Space Flight Center in Greenbelt, though Darrin said they can be built faster. They also cost in the realm of a few million dollars, compared with tens or hundreds of millions for larger orbiters.

"We have a lot of experience with making reliable spacecraft, so the idea is to have these small cubesats that are inexpensive but also still reliable, very robust and can do a lot of science," said Bill Swartz, an atmospheric research scientist at the Hopkins lab.

Swartz is working on one mission that cubesats have made possible, scheduled for a pilot launch next year. The mission, known as Radiometer Assessment using Vertically Aligned Nanotubes, or RAVAN, would deploy 30 to 40 cubesats for a precise measurement of radiation going into and coming out of Earth's atmosphere. Past observations show that slightly more radiation comes in than goes out, but a fleet of cubesats around the world measuring the radiation simultaneously would offer a more detailed picture, including how it differs depending on geography, weather or time of day, information that could better inform climate forecasting models, Swartz said.

That potential for data collection is exciting for all types of earth, atmospheric and space scientists, said Tom Flatley, head of the science data processing branch at NASA Goddard.

"Taking measurements from multiple locations at the same time buys them some capability they didn't have before," he said. "They're able to do missions they weren't really able to do before because they just cost too much."

As development of more advanced cubesats proceeds, it is bounded by limits on space junk. Cubesats must be designed to degrade within 25 years, and some designs include sails or other elements that can increase drag and eventually cause the devices to burn up in the atmosphere, Flatley said. Designs are also reviewed to ensure that they don't include materials that could survive a fall through the atmosphere and harm anything on the Earth's surface.

Still, they are expected to grow in number. There are about two dozen active around the globe, with dozens more floating as space junk, Flatley said.

"If you can put more of them up there, you can get better mapping and better science," said Gary Crum, cubesat systems lead for the science data processing branch at Goddard. "You get better science in a smaller package."

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