NASA uses off-the-shelf electronics to plot a cheaper future in space
By G.F. | SEATTLE
THE PhoneSat's name is literal: it contains the functional innards of a phone reformulated to fit into a satellite. The fourth iteration, and fifth physical version, of NASA's PhoneSat was put into low-earth orbit (LEO) on April 18th as part of the SpaceX resupply mission to the International Space Station (ISS).
PhoneSat 2.5 is the fifth of its kind to circle the globe, and should remain in orbit for at least six weeks. A year ago, NASA boosted two 1.0 models and a 2.0 version, which de-orbited after a week; PhoneSat 2.4 went up last November and remains circling despite expectations to the contrary (though its comms systems went erratic in January). A more sophisticated multi-satellite constellation that uses the same approach is nearing debut too.
Bruce Yost, the manager for the small spacecraft programme at NASA Ames Research Centre, which oversees the PhoneSat, says that the billions of dollars invested in smartphones by the telecoms industry has led many, including NASA, to ask: "Could we leverage this technology to do the sorts of things we want with small spacecraft?" So far, the answer has been a resounding yes.
PhoneSats are based on Google's Android phones: the Nexus One provided the foundation of the 1.0 series and the Nexus S for the 2.0 models. NASA estimates hard costs of between $3,500 and $7,000 for each unit, which were packed into CubeSats, a basic 10 by 10 cm nanosatellite format, which may extend from 5 cm to 30 cm in depth. As with most advanced smartphones, the Nexus S includes a camera, a GPS receiver, and an array of sensors, such as a gyroscope and accelerometer. A larger battery and more powerful radio were wired in to make it satellite-ready, but the agency performed no special radiation-resistant hardening or other modifications.
NASA added additional, low-cost technology in the 2.0 series to provide better communication and control. The 2.4 version tested whether a smartphone's built-in magnetometer (which measures the strength and direction of a magnetic field), used for compass readings, could direct a NASA-designed magnetorquer to orient a satellite in alignment with Earth's magnetic fields. It worked.
The 2.5 upgrade adds a higher-gain antenna to receive signals in the microwave S band (2 to 4 GHz) as well as an inexpensive system for measuring and maintaining attitude control. The inclusion of reaction wheels will allow the tiny satellite both to rotate itself and to maintain a fixed position relative to the Earth and the heavens—useful for communications and astronomical observations. The smartphone camera will be used to snap pictures as part of this test.
PhoneSat 2.5 will provide guidance for future missions. Mr Yost says fabrication has just completed for a swarm of eight CubeSats (a bit larger at just over 15 cm deep) all built on the PhoneSat platform. The Edison Demonstration of Smallsat Networks (EDSN) will test intrasatellite communication, allowing the creation of a mesh cloud in space for relaying data. Such clouds could allow satellites to better coordinate information gathering among themselves and reduce the reliance on ground stations. The EDSN satellites will carry a custom-built radiation sensor from Montana State University that can measure space weather to create multipoint measurements in the cluster.
Mr Yost is optimistic about the future of these programmes, but also about applying their lessons to related disciplines. Finding success in applying mobile technology to space, he would like to examine other industries, like the automotive world—anywhere, as he says, satellites can leverage money spent by other people to solve problems specific to those industries. This includes designing and building launch vehicles. "Where is the PhoneSat equivalent of the launch vehicle?" he asks.
