OperatorUniversity of Surrey[1]
COSPAR ID1984-021B[2]
SATCAT no.14781
Spacecraft properties
Launch mass60 kilograms (130 lb)
Start of mission
Launch date1 March 1984, 17:59 (1984-03-01UTC17:59Z) UTC
RocketDelta 3920
Launch siteVandenberg SLC-2W
Orbital parameters
Reference systemGeocentric
Inclination98.25 degrees
OSCAR 12 →

UoSAT-2, which is also known as UO-11 and OSCAR-11, is a British satellite orbiting in Low Earth Orbit. The satellite functions as an amateur radio transmitter (known as an OSCAR) and was built at the University of Surrey. It launched into orbit in March 1984 and remains orbital and active, though unstable with irregular periods of transmission. All of the Analog telemetry channels have failed, making telemetry from OSCAR 11 useless. The satellite was still heard transmitting telemetry in 2015, thirty years after launch.[3][4]

It was operated by Surrey Satellite Technology Ltd. (SSTL).


The satellite was the second in the UoSAT series of satellites built by University of Surrey; preceded by UoSAT-1 and followed by UoSAT-3.

The satellite carries a Digitalker speech synthesiser,[5][6] magnetometers, a CCD camera, a Geiger-Müller tube, and a microphone to detect the vibrations of micrometeoroid impacts.[6] Like UoSAT-1 it transmits telemetry data on the VHF beacon at 1200 baud, using asynchronous AFSK,[7] though now all analogue telemetry channels have failed;[8] on an FM receiver the audio signal resembles the cassette data format of the contemporary BBC Micro computer.[6] Actually it is a BASICODE signal, but no citation. Slight modulation had also been observed on the S band beacon.[9]

UoSAT-2's solar arrays were bought at a premium compared to those of UoSAT-1, the design having been space tested by its predecessor.[6]


The British affiliate of AMSAT distributed a library of software for the BBC Micro to track UoSAT-2 and other satellites and analyse telemetry broadcasts.[10] A commercial fixed-frequency receiver, Astrid, was also produced by British firm MM Microwave[11] for the education market, with accompanying BBC Micro software to display raw telemetry frames. For versatility the Astrid set included a demodulator to load signals through the serial port of any computer.[6]

South Atlantic anomaly

data upsets
data upsets

As it went around the earth it encountered data upsets, geo-located around the South Atlantic anomaly.


According to a February 2008 status report the satellite had no viable battery backup, operating only from its solar panels, and a watchdog timer on board was suspending activity for up to three weeks following any power anomaly. At the time of the report it was experiencing continuous sunlight for the last time, with the prediction that "permanent eclipses" in its orbit would begin in the middle of March 2008, limiting transmissions to "a short time, possibly less [than] a single orbit, every 21 days."[8] By April 2008 the updated prediction was that eclipses would continue until 2019.[12]

After a 21-month gap in observations, UoSAT-2 resumed sending telemetry sometime before 10 December 2009, and is apparently continuing the watchdog-controlled transmission regime, though now on a ten-days-on, ten-days-off schedule. Its condition has not otherwise improved apart from some recovery of battery power, allowing broadcasts to continue into each eclipse.[10]

Current observation reports for UoSAT-2 can be viewed and logged at the Oscar Satellite Status Page.[4]

1988 Ski-Trek arctic expedition

The satellite was instrumental in providing a communications link, known as Nordski Comm, from the Ski-Trek support teams to the expedition party. The position of the skiers' emergency beacon was calculated daily by Cospas-Sarsat ground stations and relayed to them, and thousands of amateur radio listeners, as a spoken message from the Digitalker on board UoSAT-2. The message could also serve as an emergency channel to the skiers in the event that all other radio links failed.[5][13]


  1. ^ "UoSAT-2 transmitting for 26 years". SSTL. Archived from the original on 8 March 2010. Retrieved 25 June 2012.
  2. ^ "Satellite Catalogue". Celestrak. Retrieved 25 June 2012.
  3. ^ Wallis, Clive (8 March 2014). "OSCAR-11 Report 2014". Archived from the original on 1 April 2014. Retrieved 11 July 2014.
  4. ^ a b Carr, David; Bruninga, Bob (11 July 2014). "OSCAR Satellite Status page by KD5QGR". Retrieved 11 July 2014.
  5. ^ a b "Last-Minute Satellite Turns 20". Wired. Condé Nast Publications. 2 March 2004. Retrieved 26 April 2009.
  6. ^ a b c d e Cook, Mike (June 1986). "Way into the world of satellite telemetry: Mike Cook reviews the Astrid telemetry package". The Micro User. Stockport, UK: Database Publications. 4 (4): 152. ISSN 0265-4040.
  7. ^ "Amateur Satellite Summary - UoSAT-OSCAR-11". AMSAT. AMSAT. Retrieved 17 January 2014.
  8. ^ a b Wallis, Clive (17 February 2008). "OSCAR-11 Report: 2008-02" (Zip). AMSAT-UK. Retrieved 2 August 2020.
  9. ^ Wallis, Clive (26 January 2008). "OSCAR-11 Satellite". Retrieved 23 February 2008.
  10. ^ a b Wallis, Clive (30 September 2010). "Current OSCAR-11 report". Archived from the original on 1 April 2014. Retrieved 13 October 2010.
  11. ^ Webb, Stephen R. (16 January 2008). "Even More FAQs". Archived from the original on 2 August 2009. Retrieved 13 October 2010.
  12. ^ Wallis, Clive (21 April 2008). "Final Monthly OSCAR-11 Report". Retrieved 24 April 2009.
  13. ^ Meerman, Michael (May 1988). "Trip to the North Pole: Ski-Trek and NordSki-Comm". Archived from the original on 14 July 2003.