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US Naval Academy PSK31 CubeSat Transponders Active


PSK31 transponders on two US Naval Academy CubeSats are operational, according to Bob Bruninga, WB4APR. The CubeSats launched on May 20 from Cape Canaveral on an Atlas 5 launcher. The launch included a pair of 1.5U CubeSats — the PSAT APRS/PSK31 satellite and BRICsat, a propulsion/PSK31 satellite — as well as a 3U CubeSat, USS Langley (Unix Space Server Langley). The launch also included The Planetary Society’s LightSail-1.

Bruninga said PSAT is a student satellite project named in honor of USNA alum Bradford Parkinson, of GPS fame. It contains an APRS transponder for relaying remote telemetry, sensor, and user data from remote users and Amateur Radio environmental experiments or other data sources back to Amateur Radio experimenters via a global network of Internet-linked ground stations. A Brno University transponder on PSAT supports multi-user PSK31 text messaging (28.120 MHz uplink/435.350 MHz FM downlink). Bruninga said the PSAT telemetry on 145.825 MHz (1200 baud AX.25) is working okay, but the digipeater is off at present, since the PSK31 transponder is the primary mission. The APRS downlink page is now capturing PSAT telemetry.

The PSK31 multi-user FDMA transponder experiment on PSAT and BRICsat is similar to the one on RAFT and PCSAT2. It allows text messaging among up to 30 modest ground stations simultaneously, Bruninga said. The BRICsat and PSAT PSK31 transponders are on separate spacecraft but on the same frequency, although one has PSK telemetry on 315 Hz, the other on 365 Hz.

Bruninga said BRICsat’s telemetry has been heard, but has been cycling off, due to low power. He said the BRICsat PSK31 downlink has been heard, but only barely when it’s on. The USS Langley spacecraft has not been heard yet, he said.

BRICsat transmits 9600 baud telemetry on 437.975 MHz. The USS Langley satellite transmits 9600 baud telemetry on 437.475 MHz.

The LightSail-1 packet 9600 baud (FSK) AX.25 downlink is on 437.435 MHz. The Planetary Society’s Jason Davis is asking radio amateurs to e-mail him any data they collect from LightSail, including any screenshots.

Bruninga has invited APRS radio amateurs worldwide to tune into the packet downlinks and IGate packets into the global APRS-IS system, so they will appear on the APRS downlink page, and also to try out the “exciting, new full-duplex PSK31 way of multi-user communication.”

PSAT is one of five APRS-networked Amateur Radio satellites that will be in orbit during 2015, and all will appear on the live APRS downlink page. The others include PCsat-1, in orbit since 2001, QIKcom-1, set to launch in September, QIKcom-2, set to launch in December, and the ARISS packet radio system on board the International Space Station since 2007.





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