UO-11

UO-11
UoSAT-OSCAR 11
Launch date 1 March 1984
Launch vehicle Thor Delta 3920
Launch site Vandenberg AFB, Lompoc, CA USA
Mass 60 kg (130 lb)
Orbital elements
Regime Sun-synchronous orbit
Inclination 98.25°
Altitude 697 km (433 mi)

UO-11 (aka UoSAT-OSCAR 11, UoSAT-2 or UoSAT-B) is an amateur satellite built at the University of Surrey and launched into orbit on 1 March 1984. It remains orbital and active, though unstable with irregular periods of transmission. The satellite was still heard transmitting telemetry in December 2010, more than twenty-six years after launch.[1] It transmits a beacon at 145.826 MHz, with inactive beacons at 435.025 MHz and 2401.5 MHz.

It is operated by Surrey Satellite Technology Ltd (SSTL), who also build UoSATs.

Contents

Characteristics

The satellite carries a Digitalker speech synthesiser,[2][3] magnetometers, a CCD camera, a Geiger-Müller tube, and a microphone to detect the vibrations of micrometeoroid impacts.[3] Like UoSAT-1 it transmits telemetry data on the VHF beacon at 1200 baud, using asynchronous AFSK,[4] though now all analogue telemetry channels have failed;[5] on an FM receiver the audio signal resembles the cassette data format of the contemporary BBC Micro computer.[3] Slight modulation had also been observed on the S band beacon.[6]

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.[3]

Support

The British affiliate of AMSAT distributed a library of software for the BBC Micro to track UO-11 and other satellites and analyse telemetry broadcasts.[7] A commercial fixed-frequency receiver, Astrid, was also produced by British firm MM Microwave[8] 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.[3]

Status

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: since the middle of March 2008 there have been eclipses in its orbit which will continue "permanently", limiting transmissions to "a short time, possibly less [than] a single orbit, every 21 days."[5] The eclipses are now expected to continue until 2019.[9]

After a 21-month gap in observations, UO-11 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.[7]

Current observation reports for UO-11 can be viewed and logged at the Oscar Satellite Status Page.[10]

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 UO-11. The message could also serve as an emergency channel to the skiers in the event that all other radio links failed.[2][11]

References

  1. ^ UoSAT-2 transmitting for 26 years, SSTL press release, 1 March 2010.
  2. ^ a b "Last-Minute Satellite Turns 20". Wired. Condé Nast Publications. 2 March 2004. http://www.wired.com/science/discoveries/news/2004/03/62471. Retrieved 26 April 2009. 
  3. ^ 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. 
  4. ^ "Amateur Satellite Summary - UoSAT-OSCAR-11". AMSAT. 31 May 2003. http://www.amsat.org/amsat/sats/n7hpr/uo11.html. Retrieved 24 February 2008. [dead link]
  5. ^ a b Wallis, Clive (17 February 2008). "OSCAR-11 Report: 2008-02". AMSAT-UK. http://www.uk.amsat.org/content/view/628/. Retrieved 24 April 2009. 
  6. ^ Wallis, Clive (26 January 2008). "OSCAR-11 Satellite". http://www.users.zetnet.co.uk/clivew/oscar11.htm. Retrieved 23 February 2008. 
  7. ^ a b Wallis, Clive (30 September 2010). "Current OSCAR-11 report". http://www.g3cwv.co.uk/u2rpt.htm. Retrieved 13 October 2010. 
  8. ^ Webb, Stephen R. (16 January 2008). "Even More FAQs". http://www.g3tpw.co.uk/Page8EvenMoreFAQs.html. Retrieved 13 October 2010. 
  9. ^ Wallis, Clive (21 April 2008). "Final Monthly OSCAR-11 Report". http://www.users.zetnet.co.uk/clivew/u2rpt.htm. Retrieved 24 April 2009. 
  10. ^ Carr, David; Bruninga, Bob (16 January 2010). "OSCAR Satellite Status page by KD5QGR". http://oscar.dcarr.org/. Retrieved 16 January 2010. 
  11. ^ Meerman, Michael (May 1988). "Trip to the North Pole: Ski-Trek and NordSki-Comm". http://www.meerman.fsnet.co.uk/NorthPole. Retrieved 26 April 2009. 

External links


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