View source for UoSAT-2

{{Short description|British satellite}}
{{Use dmy dates|date=September 2020}}
{{Infobox spaceflight
| name                  = UoSAT-2
| image                 = 
| image_caption         =

| mission_type          = 
| operator              = [[University of Surrey]]<ref>{{cite web|title=UoSAT-2 transmitting for 26 years|url=http://blog.sstl.co.uk/archives/288-UoSAT-2-transmitting-for-26-years.html|archive-url=https://web.archive.org/web/20100308022758/http://blog.sstl.co.uk/archives/288-UoSAT-2-transmitting-for-26-years.html|url-status=dead|archive-date=8 March 2010|publisher=SSTL|access-date=25 June 2012}}</ref>
| website               =
| COSPAR_ID             = 1984-021B<ref>{{cite web|title=Satellite Catalogue|url=http://celestrak.com/satcat/|publisher=Celestrak|access-date=25 June 2012}}</ref>
| SATCAT                = 14781 
| mission_duration      =

| spacecraft_bus        = 
| manufacturer          = [[Surrey Satellite Technology Ltd|SSTL]]
| dry_mass              = 
| launch_mass           = {{convert|60|kg|lb}}
| dimensions            = 
| power                 =

| launch_date           = {{start-date|1 March 1984, 17:59|timezone=yes}}&nbsp;UTC 
| launch_rocket         = [[Delta 3000|Delta 3920]] 
| launch_site           = [[Vandenberg Air Force Base|Vandenberg]] [[Vandenberg AFB Space Launch Complex 2|SLC-2W]]
| launch_contractor     =

| disposal_type         = 
| deactivated           = 
| last_contact          = 
| decay_date            =

| orbit_epoch           = 
| orbit_reference       = [[geocentric orbit|Geocentric]]
| orbit_regime          = [[Sun-synchronous orbit|Sun-synchronous]]
| orbit_periapsis       = 
| orbit_apoapsis        = 
| orbit_inclination     = 98.25&nbsp;degrees
| orbit_period          = 
| apsis                 = gee

| programme             = [[OSCAR]]
| previous_mission      = [[OSCAR 10]]
| next_mission          = [[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 analogue telemetry channels failed in 2005, but as of 2014 the status channels were still operational.<ref name="report-2014-03">{{cite web|url=http://www.g3cwv.co.uk/u2rpt.htm|title=OSCAR-11 Report 2014|last=Wallis|first=Clive|date=8 March 2014|access-date=11 July 2014|url-status=dead|archive-url=https://web.archive.org/web/20140401131737/http://www.g3cwv.co.uk/u2rpt.htm|archive-date=1 April 2014}}</ref> The satellite was still heard transmitting telemetry in 2025, forty-one years after launch.<ref>{{cite web |title=AMSAT OSCAR Satellite Status |url=https://www.amsat.org/status/ |website=www.amsat.org |archive-url=https://web.archive.org/web/20250415204950/https://www.amsat.org/status/ |archive-date=15 April 2025 |url-status=live}}</ref>

It was operated by [[Surrey Satellite Technology Ltd]].

== Characteristics ==
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 synthesis]]er,<ref name="wired-news">{{cite magazine|title=Last-Minute Satellite Turns 20|url=https://www.wired.com/science/discoveries/news/2004/03/62471|url-status=dead|archive-url=https://web.archive.org/web/20080626074323/https://www.wired.com/science/discoveries/news/2004/03/62471/|archive-date=26 June 2008|magazine=[[Wired (magazine)|Wired]]|publisher=Condé Nast Publications|date=2 March 2004|access-date=26 April 2009}}</ref><ref name="cook-1986"/> magnetometers, a CCD camera, a [[Geiger-Müller tube]], and a microphone to detect the vibrations of [[micrometeoroid]] impacts.<ref name="cook-1986"/> Like [[UoSat-OSCAR 9|UoSAT-1]] it transmits telemetry data on the [[VHF]] beacon at 1200 baud, using asynchronous [[AFSK]],<ref name="amsat-summary">{{cite web |url=http://www.amsat.org/amsat-new/satellites/sat_summary/uo11.php |url-status=dead|archive-url=https://web.archive.org/web/20041013132019/http://www.amsat.org/amsat-new/satellites/sat_summary/uo11.php|archive-date=13 October 2004|title=Amateur Satellite Summary - UoSAT-OSCAR-11 |author=<!--Staff writer(s); no by-line.--> |website=AMSAT}}</ref> though now all analogue telemetry channels have failed;<ref name="report-2008-02"/> on an FM receiver the audio signal resembles the [[Compact Cassette#Data recording|cassette data]] format of the contemporary [[BBC Micro]] computer.<ref name="cook-1986">{{cite journal |last=Cook |first=Mike |date=June 1986 |title=Way into the world of satellite telemetry: Mike Cook reviews the Astrid telemetry package |journal=[[The Micro User]] |volume=4 |issue=4 |pages=152 |publisher=Database Publications |location=Stockport, UK |issn=0265-4040}}</ref> Actually it is a BASICODE signal, but no citation. Slight modulation had also been observed on the [[S band]] beacon.<ref name="wallis-site-2006">{{cite web|url=http://www.users.zetnet.co.uk/clivew/oscar11.htm|title=OSCAR-11 Satellite|access-date=23 February 2008|last=Wallis|first=Clive|date=26 January 2008}}</ref>

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.<ref name="cook-1986"/>

== Support ==
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.<ref name="report-2010-09" /> A commercial fixed-frequency receiver, ''Astrid'', was also produced by British firm MM Microwave<ref name="webb-mmmicrowave">{{cite web|title=Even More FAQs|last=Webb|first=Stephen R.|url=http://www.g3tpw.co.uk/Page8EvenMoreFAQs.html|date=16 January 2008 <!-- HTTP Date field -->|access-date=13 October 2010|archive-url=https://web.archive.org/web/20090802162736/http://www.g3tpw.co.uk/Page8EvenMoreFAQs.html|archive-date=2 August 2009|url-status=dead}}<!-- NB: Self-published source.  Referenced for company name only as misprinted in TMU --></ref> 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.<ref name="cook-1986" />

==South Atlantic anomaly==
[[File:UoSAT upsets.jpg|thumb|left|Data upsets]] 
As it went around the Earth it encountered data upsets, geo-located around the South Atlantic anomaly.

== Status ==
According to a February 2008 status report the satellite had no viable battery backup, operating only from its [[Photovoltaic module|solar panel]]s, 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 [[eclipse]]s" 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."<ref name="report-2008-02">{{cite web|url=http://www.users.zetnet.co.uk/clivew/2008news.zip|format=Zip|title=OSCAR-11 Report: 2008-02|access-date=2 August 2020|last=Wallis|first=Clive|date=17 February 2008|publisher=AMSAT-UK}}</ref> By April 2008 the updated prediction was that eclipses would continue until 2019.<ref name="report-2008-04">{{cite web|first=Clive|last=Wallis|title=Final Monthly OSCAR-11 Report|url=http://www.users.zetnet.co.uk/clivew/u2rpt.htm|date=21 April 2008|access-date=24 April 2009}}</ref>

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.<ref name="report-2010-09">{{cite web|url=http://www.g3cwv.co.uk/u2rpt.htm|title=Current OSCAR-11 report|last=Wallis|first=Clive|date=30 September 2010|access-date=13 October 2010|url-status=dead|archive-url=https://web.archive.org/web/20140401131737/http://www.g3cwv.co.uk/u2rpt.htm|archive-date=1 April 2014}}</ref>

Current observation reports for UoSAT-2 can be viewed and logged at the Oscar Satellite Status Page.<ref>{{cite web |title=AMSAT OSCAR Satellite Status |url=https://www.amsat.org/status/ |website=www.amsat.org |access-date=14 December 2023}}</ref>

== 1988 Ski-Trek arctic expedition ==
The satellite was instrumental in providing a communications link, known as ''Nordski Comm'', from the [[Soviet-Canadian 1988 Polar Bridge Expedition|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.<ref name="wired-news" /><ref name="meerman-ski-trek">{{cite web |last=Meerman |first=Michael |title=Trip to the North Pole: Ski-Trek and NordSki-Comm |date=May 1988 |url=http://www.meerman.fsnet.co.uk/NorthPole/index.html |archive-url=https://web.archive.org/web/20030714130634/http://www.meerman.fsnet.co.uk/NorthPole/index.html |archive-date=14 July 2003}}</ref>

== References ==
{{Reflist}}

== External links ==
{{Portal|Spaceflight}}
*[http://www.uk.amsat.org/ AMSAT-UK]
*[http://www.ee.surrey.ac.uk/Personal/L.Wood/UoSAT-2/ Twenty years in space...] the UoSAT-2 launch video
*[http://www.dd1us.de/spacesounds%202.html Homepage DD1US / Sounds from Space] – Recordings of UO-11 speech and telemetry

{{UoSAT}}
{{OSCAR satellites}}
{{Orbital launches in 1984}}

[[Category:University of Surrey]]
[[Category:Satellites orbiting Earth]]
[[Category:Amateur radio satellites]]
[[Category:Satellites of the United Kingdom]]
[[Category:Spacecraft launched in 1984]]