Amateur Radio in Space By Steve Ford, WB8IMY
Overview • Amateurs have been building satellites since the earliest days of space travel. • These satellites are known as “OSCARs”—Orbiting Satellite Carrying Amateur Radio. • The first Amateur Radio satellite was OSCAR 1 and it reached orbit in 1961.
Satellites: Relays in the Sky • Like commercial satellites, Amateur Radio satellites are primarily used to relay signals from one location to another. • From their vantage points in orbit, satellites can “see” large portions of the Earth. This is known as a satellite’s “footprint.” • Every station within the footprint can communicate through the satellite
The Footprint of OSCAR 50 • In this illustration, everyone within the circular footprint of OSCAR 50, an FM repeater satelllite, can communicate with each other.
Satellite Orbits • Most Amateur Radio satellites travel in low Earth orbits at altitudes of 800 to 1500 km. • At this altitude, a satellite completes one orbit every 90 to 100 minutes. • At the same time, the Earth is turning beneath the satellite. • The result is that all stations on the ground will enjoy several 15-minute communication sessions with each satellite each day. • You can predict pass times with web tools such as www.n2yo.com or software.
OSCARs 29 and 52 • OSCARs 29 and 52 relay Single Sideband (SSB) voice and CW transmissions.
Amateur Radio on the International Space Station • There is also a fully equipped amateur facility aboard the International Space Station.
APRS on the ISS • The International Space Station often functions as a digital relay for APRS packet data.
Station Equipment: FM • For OSCAR 50, all you need is a dual-band FM rig and a directional antenna.
Station Equipment: SSB/CW • For OSCARs 29 and 52, you will need a dual band SSB/CW rig. A full duplex model such as the Kenwood TS-2000 or Icom IC-9100 is best, but any will do for short contacts.
Active Satellite Frequencies • Saudi-OSCAR 50 (FM Repeater, 67 Hz CTCSS) • Time Transmit Receive (MHz) • AOS (start) 145.840 436.805 • AOS+3 Minutes 145.845 436.800 • Zenith (maximum) 145.850 436.795 • Zenith+1 Minute 145.855 436.790 • LOS (end) 145.860 436.785 • Linear Transponders (SSB/CW) • Uplink Passband Downlink Passband • VUSat-OSCAR 52 435.225 – 435.275 MHz 145.875 – 145.925 MHz • Fuji-OSCAR 29 145.900 – 146.000 MHz 435.800 -- 435.900 MHz • AMSAT-OSCAR 7 432.125 – 432.175 MHz 145.925 – 145.975
The Future • More satellites on the way. Many are FM repeaters, but there are a few SSB/CW birds on the schedule as well.