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Amateur Radio Payloads Share Ride into Space with Soil Moisture Monitoring Satellite


Four NASA Educational Launch of Nanosatellites (ELaNA-X) CubeSats carrying Amateur Radio payloads launched successfully January 31 from California’s Vandenberg Air Force Base. The primary payload for the Delta II launcher was the Soil Moisture Active Passive (SMAP) satellite. SMAP's onboard radar will share Amateur Radio spectrum at 1.26 GHz. Amateur Radio is secondary on the 23 centimeter band, which covers 1240 to 1300 MHz.

“This is a good example of a compatible sharing partner,” ARRL CEO David Sumner, K1ZZ, observed. “Any interference to amateur communication in the band will be brief as the satellite passes overhead.”

SMAP and the four CubeSats all deployed successfully. The research CubeSats, launched on behalf of universities, will downlink their telemetry on the 70 centimeter band. The CubeSats and their downlink frequencies (modes) are:

Firebird II FU3

437.405 MHz (19k2 FSK)

Firebird I FU4

437.230 MHz (19k2 FSK)


437.485 MHz (9k6 FSK)

ExoCube (CP-10)

437.270 MHz (9k6 FSK)

The GRIFEX satellite is a University of Michigan project, in cooperation with JPL, while ExoCube (CP-10) is a space weather satellite developed by the California Polytechnic State University-San Luis Obispo and the University of Wisconsin in partnership with NASA, and sponsored by the National Science Foundation. The FIREBIRD program is a collaborative CubeSat space weather mission of two CubeSats designed and developed by Montana State University, the University of New Hampshire, The Aerospace Corporation, and Los Alamos National Laboratories — the FIREBIRD consortium. The FIREBIRD mission also is funded by the NSF.

SMAP carries a “synthetic aperture radar.” The L band (1.26 GHz) radar is designed to measure backscatter off the Earth’s surface. The amount of backscatter returned to the radar changes with the amount of moisture in the soil. RF pulses at this frequency are less affected by weather or by a moderate vegetation cover. The satellite is at approximately 425 miles up in a near-polar, sun-synchronous orbit. SMAP also includes a radiometer operating at 1.41 GHz to measure naturally occurring RF energy given off by Earth’s surface.




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