NASA’s Android-powered mini-satellites

September 19, 2012 § 4 Comments

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

From left to right: Jasper Wolfe, Jim Cockrell, Oriol Tintore, Alberto Guillen Salas, and Watson Attai. Photo by Robert Cardin.

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 2.4MHz, 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.”

A PhoneSat 1.0 model. Photo by Robert Cardin.

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 first PhoneSat 1.0 model crashed during a speed test when its parachute deployed early, ruining the Nexus One inside. Photo by Robert Cardin.

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.

PhoneSat 1.0 (left) and PhoneSat 2.0 (right). Photo by Robert Cardin.

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.

PhoneSat’s first mission: survival

Three of the PhoneSat units—two PhoneSat 1.0 models and one PhoneSat 2.0—are gearing up for their first mission. They’ll be hitching a ride on the first test flight of the orbital Antares rocket, which is scheduled to launch on November 11. Because the satellites are “hitchhikers,” according to the team, their status is entirely dependent upon when the Antares is ready to fly. The Antares’s first test flight was originally supposed to occur in August of this year, but that was delayed due to complications with the launch facility.

A scene from the PhoneSat lab. Most of these parts are common items anyone can purchase. Photo by Robert Cardin.

The delay of the launch was somewhat beneficial to the PhoneSat team, because it gave them more time to improve PhoneSat 1.0 and test PhoneSat 2.0. Originally, only PhoneSat 1.0 models were scheduled to fly on the Antares, but the delay allowed for a PhoneSat 2.0 model to go for a ride as well.

Each PhoneSat unit has its own role in the mission, which is more of a tech demonstration to show off what the team has accomplished with these microsatellites. The team jokes that PhoneSat 1.0 has a simple Sputnik-like goal of broadcasting status data back to Earth and taking photos. PhoneSat 2.0 will test the subsystems on the satellites themselves—features such as desaturation, location control, and the power-regeneration system.

The satellites will be in orbit for about 10 to 14 days before they reenter our atmosphere. According to Cockrell, mission duration isn’t limited by battery life and power, bur rather by atmospheric drag: The higher the satellites go, the longer they will stay in orbit. Although the PhoneSat 1.0’s batteries are expected to run out after ten days, PhoneSat 2.0 is solar powered, so it could, in theory, live longer. But it will still come back at around the same time as the two PhoneSat 1.0 models will, because they all have roughly the same mass.

The future of PhoneSat

Photo by Robert Cardin.

The team has plenty of ideas on things they’d like to try in the next PhoneSat rebuilds. Because their projects aren’t specific missions and are more about tech demonstrations, the team can always develop further by adding new subsystems. They definitely envision building a PhoneSat 3.0, a 4.0, and even more, because the team views the project as never being fully complete.

“We don’t have a defined level of when it’s completed,” Wolfe explains. “[It’s more about] however much you can make in a bit of time, how much can you get out of three months, then six months, and so on.”

According to Alberto Guillen Salas, the team’s hardware engineer, using materials that are mostly already built and ready to go gives the team the ability to develop satellites in a very short time. That way, they can test the units often to keep improving them.

As for smartphone models to try next, Wolfe suggested the Samsung Nexus Galaxy “because of the name” and to stick with using phones from the Google family. The team would also like to use a smartphone with a high-resolution camera to capture good quality photos from space.

PhoneSat’s next expected launch will be in the summer of 2013, when the team will be advancing the development of the PhoneSat 2.0 unit. The primary focus of this next tech demo is to push the 2.0 system and see what the group can do with it. Plus, the team can use information gathered from the first PhoneSat 2.0 launch this year to make improvements on the model. Radiation testing is extremely difficult to perform, so Cockrell anticipates that the team may have to update PhoneSat 2.0’s design to protect it from radiation for future launches. Only one unit will participate in the 2013 launch.

The part of the PhoneSat project that really excites the team is the possibility of involving the public in future PhoneSat developments, mainly through Android application development. The group would like to open the project up to allow people to write apps for the PhoneSats, and then send the units into space. The PhoneSat project has gathered interest through its public appearance at Maker Faire, through Random Hacks of Kindness, and through the International Space Apps Challenge.

“We’re getting a whole new crowd of people involved in space, people that didn’t have the money to get involved before,” says Wolfe, “though the leveraging of the open-source community around Android is also opening up a whole new market of people who want to get involved in space.”


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