Satellites and Space in Amateur Radio

Many radio amateurs have traditionally had a deep interest in aviation, astronautics and space sciences. In the immediate pre-WWII era, Dr. Grote Reber W9GFZ invented the science of radio astronomy, which to this day serves as an important source of information about the universe in which we live. And by 1953, Ross Bateman W4AO and William Smith W3GKP were successfully bouncing amateur radio signals off the surface of the Moon.

A decade later, the first amateur radio spacecraft, OSCARs I and II (Orbiting Satellite Carrying Amateur Radio) thrilled thousands of amateurs with weak CW signals from space that they could detect on 2m. Even though these satellites had transmit power of only around 100mW, and a battery lifetime of only about 20 days, these were important milestones in the development of amateur radio in space.

In 1963, OSCAR III became the first amateur radio spacecraft to realize Dr. Arthur Clarke's dream of a radio relay station in space. OSCAR III's transponder provided 50kHz bandwidth of 2m relay capability, and served over 1,000 users during the 22 days it was in operation, many of them simultaneously.

By the 1970's, OSCAR 5 had demonstrated the feasibility of transmitting from space on HF frequencies with a 10m beacon, and responded to remote commands transmitted from the ground. And in 1972, OSCAR 6 ushered in the era of "Phase 2" amateur spacecraft, characterized by circular, low orbits and long satellite lifetimes, measured in years rather than days. Since the launch of OSCAR 6, there has always been an operational amateur radio spacecraft on-orbit.

OSCAR 6 demonstrated new levels of complexity. A Mode A transponder (see sidebar about Transponder Modes) was widely used, and a 70cm beacon demonstrated the feasibility of UHF downlink signals. A "codestore" facility allowed CW messages to be uplinked to the satellite, stored in a digital memory, and then either broadcast or delivered on-demand, later in the orbit, over a different part of the Earth. Sophisticated command capabilities from the ground, and solar power (rather than just batteries) helped keep the satellite operational for over four years.

With the launch of OSCAR 7 in 1974, the amateur satellite community now had two satellites in operation simultaneously. IN fact, many amateurs outside the US reported that the OSCAR-6 codestore bulletins provided them with their most timely and reliable information about the launch of OSCAR 7. OSCAR 7 sported a microwave beacon, and a Mode B transponder based on a new design, with 8 W of downlink power.

OSCAR 7 operated for six and a half years, until a battery cell that had failed to an open circuit shorted internally during a period when the satellite was in eclipse (in the Earth's shadow for 20 minutes each orbit) . Fully two decades later on June 21 of this year, the shorted cell reopened, and today the satellite (a near-antique by high-tech standards) is once again in limited operation in Mode B on a daily basis.

While the Phase 2 "birds" were doing yeoman service (and OSCAR 8 was added to the constellation), the amateur satellite community (by then known as AMSAT) began to focus its attention on the design of a new kind of amateur satellite.

Phase 3 satellites would have new, highly elliptical "Molniya" orbits that would make them available for much longer stretches of time than the 10 to 15 minute span typical of a Phase 2 satellite, whose low orbital altitude has it passing quickly though the sky at any one location.

The first Phase 3 satellite, Phase 3A was lost at launch in 1980, but Phase 3B was designated AMSAT OSCAR-10 after it achieved orbit in 1983. It was slightly damaged by a series of glancing collisions with the launch vehicle after separation, but has provided good service since, even after the on-board computer failed in 1986 due to prolonged exposure to radiation. AO-10's Mode B transponder is still in operation.

The next Phase 3 bird, AO-13, was launched in 1988. It was largely modeled on the successful AO-10, with some evolutionary improvements and corrections for known problems. Unfortunately, an obscure problem in its orbital mechanics caused the orbit to decay prematurely, and AO-13 was destroyed by reentering the atmosphere in 1996, after nearly a decade of service. The long-awaited and highly publicized AO-40 (known before launch as Phase 3-D) encountered severe damage not long after launch, probably due to a propulsion systems incident, but is still very much in operation with VHF, UHF and L-band microwave uplinks and an S-band (2.4 GHz) downlink, which can be received with a 2-meter all-mode receiver combined with an inexpensive downconverter at the antenna. Your editor recently jokingly referred to AO-40 in an AMSAT discussion group as "the most successful satellite that ever blew up". Successful contacts using SSTV and PSK-31, as well as the more traditional CW and SSB modes, are made every day though AO-40.

There has been significant amateur radio activity involving manned spacecraft as well. The Russians maintained an active amateur 2m station and packet radio BBS on board their Mir space station, and many 2m voice contacts were made using handitalkies from orbiting Space Shuttles during the SAREX program. Today, both projects are combined into the ARISS project on board the International Space Station, through which both voice contacts with the space station crew and unattended packet radio operation have been maintained.

In June, ISS Expedition 2 crew memeber Jim Voss testified before the US Senate Committee on Commerce, Science and Transportation that ARISS "offers the opportunity for students to experience the excitement of space flight by talking directly with crewmembers of the ISS via Amateur Radio." He also reported the comments of Allen White, WB4MIO, who helped to coordinate Voss' ARISS contact with students at a middle school in Alabama "There is no way I can adequately describe the excitement this created in our school and community...I think this was the most exciting educational event of the year for these students."

And amateur radio in space is not just voice contacts. Space-based digipeating of packet radio signals via the ARISS station, as well as through the Naval Academy's PCSat spacecraft (which achieved widespread press coverage for being built on a $50,000 budget from off the shelf parts) are received by a network of ground stations and recorded at the ariss.net web site. PSK-31 is used for contacts through AO-40. Successful SSTV contacts have also been made through AO-40 demonstrating a capability that will be used later from the ARISS station to broadcast images from the space station to Earth-bound amateurs.

Want to get in on the fun?

There are many different kinds of spacecraft and operating modes available in space and satellite amateur radio today, and this article can only be the briefest overview of the history and current state of this end of our hobby. Just deciding which particular aspect you might be interested in exploring requires some investigation and study.

One good place to start that learning is the ARRL Operating Manual (you do have a copy, don't you?) chapter on satellites and space.

More technical detail and historical information is available in the Radio Amateurs Satellite Handbook. However, this technology changes so rapidly that some of the best sources of information are on-line on the Internet. The best place to start on-line is the AMSAT-NA web site, http://www.amsat.org

AMSAT maintains several email lists, and publishes a quarterly journal, as well as a weekly new bulletin which includes the Weekly Satellite Report, giving the status and operating parameters of all spacecraft involved in amateur radio. This is a very valuable reference since spacecraft status and schedules are constantly changing.

AMSAT Area Coordinators are local volunteer elmers who are willing to introduce you to the fundamentals of satellite work and help you get started. I happen to be one, and can also help you hook up with other active satellite folk locally like our own PMRC vice-president Al W3STW.


Hope to see some of you on the birds someday soon...

AMSAT nets

AMSAT International HF net:

Sundays 1900 UTC 14.282 MHz

AMSAT-NA East Coast

Tuesdays 2100 local 3.840 MHz

Houston AMSAT VHF Net

Tuesday Evenings 2000 Central Time locally on AA3RG 146.64-

Also on IRLP and online

see: http://amsatnet.com

de Maggie K3XS


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