AMSAT-OSCAR 51 or AO-51 is the in-orbit name designation of a now defunct (following battery failure)

LEO Leo or Léo may refer to: Acronyms * Law enforcement officer * Law enforcement organisation * ''Louisville Eccentric Observer'', a free weekly newspaper in Louisville, Kentucky * Michigan Department of Labor and Economic Opportunity Arts an ...

amateur radio satellite of the OSCAR series; formerly known as ECHO, built by

AMSAT AMSAT is a name for amateur radio satellite organizations worldwide, but in particular the Radio Amateur Satellite Corporation (AMSAT) with headquarters at Washington, D.C. AMSAT organizations design, build, arrange launches for, and then opera ...

. It was launched on June 29, 2004 from

Baikonur Cosmodrome The Baikonur Cosmodrome ( kk, Байқоңыр ғарыш айлағы, translit=Baiqoñyr ğaryş ailağy, ; russian: Космодром Байконур, translit=Kosmodrom Baykonur, ) is a spaceport in an area of southern Kazakhstan leased to R ...

Kazakhstan Kazakhstan, officially the Republic of Kazakhstan, is a transcontinental country located mainly in Central Asia and partly in Eastern Europe. It borders Russia to the north and west, China to the east, Kyrgyzstan to the southeast, Uzbeki ...

on a

Dnepr Dnepr may refer to: *Dnieper, a river flowing through Russia, Belarus and Ukraine to the Black Sea * Dnepr (motorcycle), a Ukraininan motocycle brand * Dnepr (rocket), a 1999 space launch vehicle *Dnepr radar Dnepr may refer to: *Dnieper, a river ...

launch vehicle. It is in

sun synchronous A Sun-synchronous orbit (SSO), also called a heliosynchronous orbit, is a nearly polar orbit around a planet, in which the satellite passes over any given point of the planet's surface at the same local mean solar time. More technically, it is ...

low Earth orbit A low Earth orbit (LEO) is an orbit around Earth with a period of 128 minutes or less (making at least 11.25 orbits per day) and an eccentricity less than 0.25. Most of the artificial objects in outer space are in LEO, with an altitude never mor ...

. AO-51 contained an FM repeater with both 144 MHz (

VHF Very high frequency (VHF) is the ITU designation for the range of radio frequency electromagnetic waves (radio waves) from 30 to 300 megahertz (MHz), with corresponding wavelengths of ten meters to one meter. Frequencies immediately below VHF ...

) and 1.2 GHz ( L band) uplinks and 435 MHz (

UHF Ultra high frequency (UHF) is the ITU designation for radio frequencies in the range between 300 megahertz (MHz) and 3 gigahertz (GHz), also known as the decimetre band as the wavelengths range from one meter to one tenth of a meter (on ...

) and 2.4 GHz (

S band The S band is a designation by the Institute of Electrical and Electronics Engineers (IEEE) for a part of the microwave band of the electromagnetic spectrum covering frequencies from 2 to 4 gigahertz (GHz). Thus it crosses the convention ...

) downlinks. It also contained a digital subsystem that transmitted

telemetry Telemetry is the in situ data collection, collection of measurements or other data at remote points and their automatic data transmission, transmission to receiving equipment (telecommunication) for monitoring. The word is derived from the Gr ...

on 70 cm and provided a complete PACSAT

BBS BBS may refer to: Ammunition * BBs, BB gun metal bullets * BBs, airsoft gun plastic pellets Computing and gaming * Bulletin board system, a computer server users dial into via dial-up or telnet; precursor to the Internet * BIOS Boot Specificat ...

that could be configured on both V band and S band uplinks. As well, there was a 10-meter PSK uplink. AO-51 had four

receivers, two

transmitters, six

modems A modulator-demodulator or modem is a computer hardware device that converts data from a digital format into a format suitable for an analog transmission medium such as telephone or radio. A modem transmits data by Modulation#Digital modulati ...

, and 56 channels of telemetry. The two UHF transmitters were connected to four phased antennas, yielding right-hand circular polarization for the 435.300 downlink and left-hand circular polarization for the 435.150 downlink. The AO-51 FM satellite was easily workable with an amateur radio VHF dual band hand-held radio, as long as you knew when the satellite's footprint was within reach. Transatlantic contacts had been made without much effort, as long as the satellite was approximately mid-Atlantic so that the edge of the satellites footprint was within reach on either continent. As of May 2011 the satellite faced problems with the battery. By September, a work around for the battery issue was found, bringing the repeater back in use. On November 29, 2011, the AO-51 Command Team announced that AO-51 has ceased transmission and is not responding to commands.

External links

AO-51 Control Team NewsAMSAT news about AMSAT 2006 Space SymposiumHow to Work AO-51 with Your HT

References

{{DEFAULTSORT:Ao-51 Amateur radio satellites Communications satellites in low Earth orbit Spacecraft launched by Dnepr rockets Spacecraft launched in 2004