SuitSat-2 goes to college

Eleven electrical engineering students at The College of New Jersey had a hand in designing some of the software defined radio (SDR) hardware that will fly aboard SuitSat-2.

The college seniors signed up last fall for "Software Defined Radio," taught by adjunct professors Bob McGwier, N4HY, and Frank Brickle, AB2KT - both members of the Amateur Radio on the International Space Station (ARISS) SuitSat-2 team.

The second-generation SuitSat will have a software designed Amateur Radio transponder (SDX) on board. SuitSat-2 is being viewed as a test bed for the hardware AMSAT hopes to launch on its Phase 3E Eagle satellite.

McGwier and Brickle designed practical, goal-based experiments for the students' projects with an eye toward turning out something that would be a useful SuitSat-2 component. Team members Steve Bible, N7HPR, and Joe Julicher, N9WXU, provided circuit boards employing "bleeding-edge" technology -- dsPIC33F 16-bit direct memory access digital signal controllers. Brickle says the circuits will serve as SuitSat-2's heart and brain.

Early on, the students studied signal processing and communication theory as well as what Brickle calls "esoteric corners of computer science." Then, using Matlab -- a high-level technical computing language -- the students implemented modulators and demodulators for SSB, FM, BPSK and AFSK.

"Students get a little bit of verbal swimming instruction, and then we toss them straight into the ocean," is how Brickle described the process.

By mid-semester, the students were designing their experiments and getting them up and running. Boards were powered up without diagnostic hardware or software, since that's how the circuitry will be on orbit -- "walking a tightrope without a net," as Brickle sees it.

"Given the complexity of what the SDR/SDX in SuitSat-2 will be required to provide, the applications will need to run in an unprecedented software environment: pre-emptive multitasking under freeRTOS," he explained. FreeRTOS is an open-source, round-robin operating system for embedded devices.

Instead of being scared off, the students ran with the challenge and demonstrated obvious enthusiasm, Brickle reports. "We will be doing a very good thing if we continue to involve these kids, and more like them, in our future AMSAT projects," he said. What surprised him most, he added, was that the students focused on taking new approaches to "very fundamental engineering issues that aren't flashy or trendy." McGwier, who's AMSAT-NA's vice president of engineering and a member of the AMSAT Board of Directors, remarked that both students and teachers shared in the excitement.

The SuitSat-2 team, under the leadership of Lou McFadin, W5DID, has been working on the design of a power converter for the solar panels, the internal housekeeping unit, the antenna mount, the transmitting and receiving hardware and how it will mount atop the suit's helmet.

An ISS crew could launch SuitSat-2 during a spacewalk as early as next fall. SuitSat-2 could have an operational lifetime of six months or more.

Rosalie White, K1STO/ARISS

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