NASA's Android-powered mini-satellites
What could you do with $3500 and an old smartphone? You could toss the phone, take the cash, and buy yourself the next best smartphone. Or, with a bit of a DIY attitude, you could push the limits of this hefty piece of technology and use it to power something else.
That's the initial idea of the PhoneSat project, a small satellite project run by a team of engineers at NASA's Ames Research Center. The PhoneSat team has built and developed two small satellite models powered by Android smartphones, with the rest of the body constructed mostly of things you could buy at your nearest hardware store.
At a 2009 meeting of the International Space University's Space Studies Program, a group of young engineering students had a big idea: Why not try to develop a cheap satellite-control system using mostly off-the-shelf consumer technology items? They wanted to see if they could create something that could survive in space using existing technology, rather than spending resources to invest in building items from the ground up.
The idea is relatively simple. “Here’s what you have in your pocket, and it can fly in space,” says Oriol Tintore, a software and mechanical engineer for NASA’s PhoneSat project.
After we reported on these microsatellites earlier this summer, the PhoneSat team invited us to visit their lab at NASA’s Ames Research center in Moffett Field, California, in the heart of Silicon Valley. They showed off the two current PhoneSat models, PhoneSat 1.0 and PhoneSat 2.0, and further explained their upcoming mission, now scheduled for November 11, 2012.
PhoneSat: Meet the team, and the units
At a 2009 meeting of the International Space University's Space Studies Program, a group of young engineering students had a big idea: Why not try to develop a cheap satellite-control system using mostly off-the-shelf consumer technology items? They wanted to see if they could create something that could survive in space using existing technology, rather than spending resources to invest in building items from the ground up. This big idea put the PhoneSat project into motion.
Today, team PhoneSat is a small group of about ten engineers, led by Small Spacecraft Technology program manager Bruce Yost and PhoneSat project manager Jim Cockrell.
"[PhoneSat] gives young engineers a chance to work on something that’s actually going to fly in space early on in their careers," said Cockrell.
Although the project idea emerged in 2009, the building, designing, and testing of the parts that would make up the PhoneSat 1.0 model began in 2010. To power the satellite units, the PhoneSat team turned to small phones with large processors.
“This phone has a very powerful processor of [1GHz], which is more powerful than most processors out there in space,” says Jasper Wolfe, who handles altitude control for the project. “It has just about everything we need, so why not use it? It’s a few hundred dollars compared to tens of thousands of dollars.”
The units themselves are small—compact enough to fit in your hand. At 10cm by 10cm by 10cm, each device is barely larger than a coffee cup. And the cost of each of these units is relatively cheap: PhoneSat 1.0 costs roughly $3500, while PhoneSat 2.0 is about $7800 due to its more advanced hardware.
PhoneSat 1.0 houses a Google Nexus One smartphone, which runs a single Android application that the team developed themselves. All of the Nexus's phone capabilities have been disabled—Wolfe jokes that they have to set the phones to "airplane mode" before launch—and instead the device relies on the PhoneSat app for communication and data recording.
The PhoneSat team was initially attracted to the Nexus One because, at the time, it was one of the best smartphones available. Plus, they liked the open-source nature of developing for the Android platform.
“We talked about whether we should use an Android phone versus something else, like an iPhone, and the consensus was that the iPhone was a great phone, but an Android phone was a great satellite,” says Tintore, the team’s mechanical and software engineer.
Besides the Nexus One, the main pieces of the satellite include external batteries and an external radio beacon. A watchdog circuit will monitor the system and reboot the Nexus if necessary.
The team plans to evolve the satellites as technology evolves, which is why PhoneSat 2.0 uses a Samsung Nexus S instead of a Nexus One. In fact, the Nexus S has an added gyroscope already built in, which has been “extraordinarily helpful” in building a next-gen satellite, according to Wolfe. “It’s just a tiny little chip, but very useful,” he says. The gyroscope helps the phone measure and maintain orientation, so it assists with navigation as well as with the motion and rotation of the phone itself.
PhoneSat 2.0’s design includes a two-way S-band radio, solar arrays for unlimited battery regeneration (“Well, for as long as there is sun,” says Yost), and a GPS receiver. The radio will command the satellite from the ground, while the solar panels will enable the unit to embark on a mission with a long duration. Also built into the PhoneSat 2.0 design are magnetorquer coils (electromagnets that interact with Earth’s magnetic field) and reaction wheels to control the unit’s orientation in space.
Each model has been tested in environments that closely resemble what they could encounter while in space. Two Nexus One phones were launched on smaller rockets in 2010 as a preliminary test of how the phones will handle high speeds and high altitude. One rocket crashed and destroyed the smartphone; the other landed with the Nexus One perfectly intact. Both PhoneSat 1.0 and 2.0 models have also been tested in a thermal-vacuum chamber, on vibration and shock tables, and on high-altitude balloons, all with great success.