Longest Operating Satellite Celebrates 50th Anniversary

Launched on November 15, 1974, a microsat named OSCAR-7 continues to operate fifty years later, serving radio amateurs around the world. It is recognized as the oldest operating satellite, even preceding the launch of NASA’s famed Voyager 1 and Voyager 2 satellites launched in 1977.


OSCAR satellites (meaning Orbital Satellites Carrying Amateur Radio) are built by members of the Radio Amateur Satellite Corporation (AMSAT). Many members have been employees at Goddard Space Flight Center and similar companies or organizations that are central to U.S. space programs. They pioneered the concept of using secondary payloads in place of ballast to manage the center-of-gravity requirements for a launch. Although OSCAR-7 was largely built on the basement workbenches of AMSAT volunteer engineers. It still had to pass the rigorous tests required of any space bound vehicles – perhaps even more so. The owner of the primary payload, NOAA-4/ITOS-G, had to be assured that the adjacent payload, built by a bunch of “hobbyists,” would not jeopardize the mission.



Largely designed and built with relatively new CMOS technology, NASA engineers predicted that OSCAR-7 would last perhaps one to three years. Given the fact that the components were not radiation hardened, even that was felt to be generously optimistic.

Yet, OSCAR-7 lived long enough to make several important contributions. It is believed to host the first ground-to-satellite-to-satellite-to-ground communications. Following the nearly identical orbit of its predecessor, OSCAR-6, the two satellites occasionally lapped each other and provided ground stations the opportunity to pass messages between the two satellites before returning to earth.

More significantly, OSCAR-7 was used to investigate the possibility of locating downed aircraft and disabled sea vessels by using Doppler analysis of signals from emergency location transmitters (ELT’s). Scientists from the Russian COSPAR/U.S. SARSAT teams simulated ELT’s on amateur radio stations and demonstrated how receiving and relaying ELT transmissions and analyzing Doppler shift as OSCAR-7 passed overhead could accurately locate the emergency beacons. As a result of this test using an amateur radio satellite, the COSPAR/SARSAT program is credited with saving over 57,000 lives in over 17,000 mishaps.

Eventually, OSCAR-7 came to lead a double life. After its batteries shorted and failed, its first life ended in 1981 after 6.5 years of faithful operation. Due to the design of the power system, the shorted batteries cut off the available power from the solar cells.

Remarkably, 21 years later in June, 2002, an amateur radio operator heard OSCAR-7’s telemetry beacon. This reception was confirmed by radio operators around the world. It can only be guessed that a battery reverted to an open state and power from the solar cells was restored.

OSCAR-7 is now affectionately referred to as the “Sleeping Beauty” of satellites and continues to provide ground-breaking scientific contributions. Using years of analysis of orbital data, OSCAR-7 engineers were able to confirm the existence of orbital perturbances, or disturbances that were previously predicted by NASA scientists.

How much longer will OSCAR-7 function? Its telemetry beacon has become somewhat erratic in the past few months and its radio transponders now change modes unpredictably. Regardless of its remaining life, OSCAR-7 has found its place in the record books for the foreseeable future.

Persons interested in a detailed account of OSCAR-7’s development and history can visit https://www.amsat.org/amsat-ao-7-a-fifty-year-anniversary/.

 

OSCAR-7. Proof that sometimes the best way to solve a problem is to simply have a bit of a lie down.

 

I have worked many stations through this old bird using CW and SSB. It is quite a special satellite.

 

IMHO -

It would be nice if the ARRL and other worldwide standards bodies send send a HF repeater into low orbit.
Anyway, how can I hear OSCAR?

 

Absolutely amazing. Manufacturers could learn a thing or two about hardening, just for durability. Makes me even more proud of my hobby.

 

Oscar 7: Frequencies and lots of other information are here:
https://www.amsat.org/two-way-satellites/ao-7/

 

'Amateur' ain't 'amateurish' ;-)

 

Exactly! Simply because we're not getting paid for what we do isn't a reason not to do it like a professional should the desire strike you.

Absolutely amazing that there is an antique in space still operating.

 

Worked Oscar with HT in a Taxi ....Mobile Taxi Satellite

 

Maybe NASA should have AMSAT make their satellites instead of Boeing?

 

Oscar 7 helped launch my career.

 

Very cool, thanks for that!

...but the pedant in me says that Voyager 1 and Voyager 2 are not satellites.

 

IIRC, one of AO-7's modes has a 10-meter downlink.

 

I was on it just yesterday on SSB; did notice some FM'ing of signals, but still had 3 short QSO's on it. My current favorite is RS-44 (with it's 6000 - mile footprint); I also operate JO-97 & the ISS repeater.

The one I really miss was AO-13 ; with it's "Molniya" elliptical orbit, DX could be worldwide when it was at the highest point of its orbit. I remember working a Japanese station once on it; AO-13's footprint was wide enough that it was just barely over the horizon for both of us.

AO-7 is the satellite equivalent of the "Energizer Bunny" - "It keeps going- & going - & going.....!"

Tm WA1LBK

 

My daughters saying is .... a cup of tea and a lye down .