NASA's Ames Research Center in Moffett Field, Calif., is preparing to send its fifth in a series of smartphone-controlled small spacecraft into orbit. The PhoneSat 2.5 mission will demonstrate the power of smartphone components to support space-based communications systems and survive the radiation environment of low Earth orbit, as high as 220 miles (350 kilometers) above Earth. It will also pave the way for a constellation of cooperative satellites scheduled to launch later this year.
PhoneSat 2.5, selected for launch by NASA’s Cubesat Launch Initiative, will deploy into orbit from NASA's next flight of the Space Exploration Technologies (SpaceX) Falcon 9 rocket. The company's third commercial cargo resupply mission to the International Space Station will deliver several tons of supplies, including new science experiments and technology research, and is scheduled to lift off from Cape Canaveral Air Force Station in Florida mid-late April.
"If I showed PhoneSat to you, you'd ask, 'where's the phone?'," said Bruce Yost, program manager for NASA's Small Spacecraft Technology Program at NASA's Ames Research Center in Moffett Field, Calif. "That's because while we buy a smartphone off the shelf, much like the one in your pocket or purse, we take it apart and repackage it to fit in the cubesat form and work in space. This differs from the first PhoneSat that packed in the entire smartphone."
PhoneSat 2.5 builds upon the successful flights of previous NASA smartphone satellites launched into orbit last year. Each smartphone is housed in a standard cubesat structure, measuring roughly four inches square. NASA is using these pioneering missions to gauge the use of consumer-grade smartphone technology as the main control electronics of a capable, yet very low-cost, satellite, reports Andrew Petro, program executive for the Small Spacecraft Technology Program in the Space Technology Mission Directorate at NASA Headquarters in Washington, which funds the PhoneSat series.
In addition to the large memory, fast processors, GPS receivers, gyroscope and magnetometer sensors and high-resolution cameras commonly found in smartphones, the PhoneSat 2.5 also houses a low-cost commercial attitude determination and control system (ADCS) that contains reaction wheels that by slowing down or speeding up, can rotate the satellite. Engineers hope to determine if this ADCS can orient PhoneSat in space, a critical capability for satellites that may need to point towards a specific object of scientific interest like an asteroid, star or features on Earth. The mission also gather further information about the orbital lifespan of the smartphone components.
“By advancing the price performance of nanosatellites using consumer electronics, we can make some of the more crazy ideas become economically viable,” said Jasper Wolfe, PhoneSat ADCS lead of SGT Inc., at Ames.
PhoneSat 2.4, which launched last November, achieved its primary mission objectives and demonstrated a smartphone can serve as an avionics controller, and demonstrating use of its magnetometer and an Ames-designed magnetorquer could actively align the satellite’s orientation with Earth's magnetic fields. This is a first for Ames satellites, which to date have used passive, permanent magnetic torque rods. PhoneSat 2.4 continues to transmit data, which means its solar arrays, battery charging circuit, Arduino watchdog and data router are still operating correctly. However, in early January, the Phonesat 2.4 smartphone began to experience recurring resets coinciding with a period of numerous solar flares and as a result, the satellite no longer executes flight application software.
“We expect PhoneSat 2.5's orbital lifetime to be as long as six weeks" said Cedric Priscal, PhoneSat software lead of SGT Inc., at Ames. "This operation time will help us demonstrate that the system can survive being exposed to the doses of space radiation all satellites must endure in low Earth orbit, and help us gather data on the effects radiation has on the satellite."
What kind of smartphone has a battery life of six weeks? NASA equipped the four sides of the PhoneSats with solar panels to help replenish the batteries and keep the spacecraft alive.
PhoneSat 2.5 also includes a higher-gain two-way radio communications capability, known as an S-Band antenna. Engineers will test the antenna's capability to send commands to the spacecraft and telemetry back to ground station on Earth, in preparation for NASA's Edison Demonstration of Smallsat Networks (EDSN) mission, scheduled for launch late this year.
The EDSN mission plans to launch eight identical cubesats, based on the PhoneSat architecture, to demonstrate the concept of using many small spacecraft working together in a cooperative manner. EDSN will fly the cubesats in a loose formation. Each satellite will be able to cross-link communicate with the other so that engineers can study space-to-space communications and how small, low-cost, powerful satellites can perform space weather monitoring duties.
While orbiting Earth, ground station controllers at Santa Clara University in California, also will attempt to command PhoneSat 2.5 to transmit photographs of what it sees using the smartphone camera to gather information for future low cost onboard camera systems and star trackers.
"We're answering the question, how useful are consumer grade electronics for atmospheric or Earth science, communications, or other space-born applications?," said Ken Oyadomari, PhoneSat communications lead of SGT Inc., at Ames.
"The next step is to add a propulsion system to pave the way for CubeSats to explore further into the solar system," said Oriol Tintore, PhoneSat mechanical lead of SGT Inc., at Ames.
Though it's unlikely you'll find one of those on your smartphone anytime soon.