AMSAT Archive

Technical

AMSAT OSCAR 7: the Ham Satellite That Refused to Die

When the AMSAT-OSCAR 7 (AO-7) amateur radio satellite was launched in 1974, its expected lifespan was about five years. The plucky little satellite made it to 1981 when a battery failure caused it to be written off as dead. Then, in 2002 it came back to life. The prevailing theory being that one of the cells in the satellites NiCd battery pack, in an extremely rare event, failed open — thus allowing the satellite to run (intermittently) off its solar panels.

A recent video by [Ben] on the AE4JC Amateur Radio YouTube channel goes over the construction of AO-7, its operation, death and subsequent revival are covered, as well as a recent QSO (direct contact).

The solar panels covering this satellite provided a grand total of 14 watts at maximum illumination, which later dropped to 10 watts, making for a pretty small power budget. The entire satellite was assembled in a ‘clean room’ consisting of a sectioned off part of a basement, with components produced by enthusiasts associated with AMSAT around the world. Onboard are two radio transponders: Mode A at 2 meters and Mode B at 10 meters, as well as four beacons, three of which are active due to an international treaty affecting the 13 cm beacon.

Positioned in a geocentric LEO (1,447 – 1,465 km) orbit, it’s quite amazing that after 50 years it’s still mostly operational. Most of this is due to how the satellite smartly uses the Earth’s magnetic field for alignment with magnets as well as the impact of photons to maintain its spin. This passive control combined with the relatively high altitude should allow AO-7 to function pretty much indefinitely while the PV panels keep producing enough power. All because a NiCd battery failed in a very unusual way

Outreach

Free Download: 50th Anniversary Edition of the AMSAT Journal

The 50th Anniversary special issue of the AMSAT Journal is freely available for download. Everyone interested in Amateur Radio satellite communications is encouraged to read this 50th Anniversary Journal and consider supporting AMSAT by becoming a member

About AMSAT

The Radio Amateur Satellite Corporation (as AMSAT is officially known) was first formed in the District of Columbia in 1969 as an educational organization. Its goal was to foster Amateur Radio’s participation in space research and communication. AMSAT was founded to continue the efforts, begun in 1961, by Project OSCAR, a west coast USA-based group which built and launched the very first Amateur Radio satellite, OSCAR, on December 12, 1961, barely four years after the launch of Russia’s first Sputnik.

Today, the “home-brew” flavor of these early Amateur Radio satellites lives on, as most of the hardware and software now flying on even the most advanced AMSAT satellites is still largely the product of volunteer effort and donated resources. Though we are fond of traditions our designs and technology continue to push the outside of the envelope.

For over 50 years AMSAT groups in North America and elsewhere have played a key role in significantly advancing the state of the art in space science, space education, and space technology. Undoubtedly, the work now being done by AMSAT volunteers throughout the world will continue to have far-reaching, positive effects on the very future of both Amateur Radio, as well as other governmental, scientific and commercial activities in the final frontier. Rarely have a group of “amateur” volunteers managed to do so much…for so many…with so little.1

AMSAT contact: info@amsat.org or 888-322-6728

  1. “About AMSAT”, The Radio Amateur Satellite Corporation, retrieved April 25 2019, https://www.amsat.org/about-amsat/. ↩︎

Technical

AO-91 Officially Commissioned

AO-91 was built as a partnership with Vanderbilt University ISDE and hosts four payloads for the study of radiation effects on commercial off the shelf components. The satellite was launched on November 18, 2017 as part of the ELaNa XIV mission, secondary payloads aboard the Delta II rocket that carried the Joint Polar Satellite System (JPSS-1) satellite to orbit. AO-91 also features the Fox-1 style FM U/v repeater with an uplink on 435.250 MHz (67.0 Hz CTCSS) and a downlink on 145.960 MHz. Satellite and experiment telemetry are downlinked via the “DUV” subaudible telemetry stream and can be decoded with the FoxTelem software. [ 1 ]

An AO-91 radio programming chart has been published in the AO-91 Commissioned, Declared Open for Amateur Use article on the AMSAT website.

Helpful links and comments from hams working this satellite have been posted in a “AO-91 is officially open” discussion on the Amateur Radio Subreddit.

References

[ 1 ] “AO-91 Commissioned, Declared Open for Amateur Use”, Radio Amateur Satellite Corp. (AMSAT), Retrieved November 23 2017, https://www.amsat.org/ao-91-commissioned-declared-open-for-amateur-use/.

Technical

Getting Started with Amateur Satellites

Technical

RadFxSat Heard Over Europe

RadFxSat (Fox-1B) was sucessfully launched on a Delta II rocket from Vandenberg Air Force Base at 1:47AM PST on November 18, 2017, and has been heard over Europe.

This satellite had been designated as AMSAT-OSCAR 91 (AO-91).

More information about the launch is available on the AMSAT website.

Technical

BY70-1 Cubesat Launched

“BY70-1 is a 2U CubeSat project for education and Amateur Radio. It features 3-axis stabilization and deployable solar panels. In addition to the FM transponder, BY70-1 has a camera, and plans call for downloading images and telemetry via a 9600 bps BPSK downlink. The IARU Amateur Satellite Frequency Coordination pages list an uplink of 145.920 MHz, and a downlink of 436.200 MHz.”[ 1 ]

Please visit the AMSAT-UK BY70-1 announcement for more information.

Footnotes

[ 1 ] “New Amateur Radio FM Transponder CubeSat Now in Space”, ARRL The national association for Amateur Radio, last modified December 29 2016, http://www.arrl.org/news/new-amateur-radio-fm-transponder-cubesat-now-in-space.