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Citizen Explorer 1 (CX-1)

Filed under: Project-archive — mgrusin at 5:48 pm on Tuesday, September 8, 2009

Citizen Explorer was Colorado Space Grant Consortium’s do-it-yourself educational science satellite.  It carried two ozone-measuring instruments for low-resolution global measurements, and was designed to transmit that information directly to participating K-12 schools worldwide. The satellite was first conceived in 1996, received a launch vehicle slot in 1997, and came very close to launching in November 2000.

I served as both systems engineer and Command and Data Handling (CDH) lead on this mission. The systems engineering position was particularly challenging;  the extremely tight mass, volume, power, and especially budget restrictions, along with issues unique to a project run by undergraduate engineering students, required innovative technological and programmatic solutions.

Citizen Explorer’s Flight Computing system was designed for extremely low cost, ruggedness, and rapid development in an educational environment.  It consisted of an off-the-shelf 80386SX PC-compatible industrial control computer with minor but important modifications for spaceflight, networked via RS-485 to four 8051-based microcontrollers for low-level subsystem I/O.   The subsystem controllers were programmed in C and Assembly.  The main computer ran VxWorks, Spacecraft Command Language (SCL), and autonomy software developed in partnership with JPL.  The architecture required careful attention to reliability and recovery concerns, and required the identification and execution of many design tradeoffs.

With an original schedule of 14 months from paper to launch, CX-1 would have been an ambitious project for any team. Due to a series of launch vehicle slips, this schedule eventually stretched out to 3 years, but this was still not enough time to get everything working, and ultimately the Delta-II launched without CX-1 aboard. Several subsequent generations of students worked on CX-1 and eventually created a functioning spacecraft, but a second launch was not forthcoming.  CX-1 is now stored in COSGC’s cleanroom in the hope that it could still be manifested on a future flight.

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