With such tiny satellites, NASA can pack in a bunch for every launch
Ever since NASA launched a new group of tiny, phone-powered satellites into space a few weeks ago, we've been waiting for one of the little PhoneSats to phone home. Now, one of the nano-satellites has successfully communicated with Earth, an important test of a much-needed capability.
Engineers at NASA’s Ames Research Center are currently in the middle of testing two-way communications technology on one of the PhoneSat experimental satellites they shot into space a couple weeks ago. On Wednesday, the tiny satellite—weighing only about 2.2 pounds, or the size of 20 CDs stacked into a cube—used its S-band radio to make a call the ground monitoring station at Santa Clara University, in California, signaling to the engineers that it was ready to receive commands.
The satellite is called a PhoneSat because the satellite’s brain is basically built around a heavily modified Samsung Nexus S, running off the shelf Android software.
Two way communications are really important to NASA’s long term objective of building satellites on the cheap, because they’ll enable teams on the ground to control PhoneSat—eventually including things like navigation and instrument readings.
During the two-way radio tests, the most critical system the engineers on the ground will send commands to is the attitude control. That system uses a smartphone’s magnetometer to sense the earth’s field, creating an aligning force with magnetorquers, or printed-circuit electromagnetic coils commanded by the phone. With its attitude control functioning, the PhoneSat can align itself with Earth’s horizon, something that’s pretty useful for satellites, according to NASA engineer Jim Cockrell.
But the attitude control system uses a lot of power, so the teams on the ground want to be able to shut it on and off—hence the importance of the new two-way S-band radio.
This new version of the PhoneSat—the first version went to space earlier this year—uses more heavily modified Nexus phones than previously. NASA has stripped away or disable many of the components they don’t need—for example, the engineers removed the screen and enclosure, as neither are necessary to operate a satellite. Basically, the only thing left over is whatever’s attached to the circuit board, said Cockrell.
The engineering team also replaced the standard Nexus battery with a much more powerful Lithium Ion battery pack that’s charged via solar cells—also bought off-the-shelf—custom fitted to the PhoneSat’s outer hull. Interestingly enough, the engineers chose to use factory second solar cells, or remnants from older solar arrays in order to, you guessed it, build panels on the cheap. The engineering team then had to construct custom mounts and boards, Cockrell said.
The whole point of the PhoneSat program is twofold: to first determine if it’s even possible to operate space faring vehicles with off-the-shelf consumer technology. And so far, it looks like it is. The second reason NASA is interested in building satellites out of smartphones is discover the cheapest possible way to build a useful spacefaring satellite. Versus traditional satellites, smartphones—and so too the PhoneSats—have thousands of times faster computational speeds, and many times more memory, said Cockrell.
Phonesat 2.5, the next generation of mini satellite.
With such advanced technology available off-the-shelf for a few hundred dollars, NASA didn’t see the value of reinventing the wheel. “Manufacturers have invested gazillions of dollars into research and development of smartphones,” Cockrell said, “Countless research dollars make them fast, with a large memory and a lot of sensors.” And if NASA invested in similar technology it would likely require millions and millions of dollars, Cockrell said.
Cheap satellites have a number of advantages—if they can survive space’s rigors, Cockrell said. If the program proves successful, they would allow NASA to take a different approach while exploring the universe. “With multiple copies of your satellite, even if one fails, you can afford to have another one at the system level still functioning,” the engineer said.
The materials in each PhoneSat 2.4—as this iteration is called—cost approximately $7,500, off the shelf. The PhoneSat’s design and fabrication took about a year by a team of fewer than 10 engineers—who are all entry level, Cockrell said. Usually only senior NASA engineers work on satellite projects, but since the cost is lower, it’s feasible to give junior engineers a shot.
The next version, 2.5, is set to launch in February aboard a commercial SpaceX rocket and will continue to test the two-way radio and orientation systems, according to NASA officials. Further launches are expected in 2014 as the space agency aims to demonstrate how networking eight small satellites can be used—eventually—to monitor things like the Earth’s climate, space weather, and other global-scale phenomena.