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| Mission type | Amateur radio |
|---|---|
| Operator | AMSAT-NA |
| COSPAR ID | 2004-025K  |
| SATCAT no. | 28375 |
| Website | The Echo Project Page |
| Spacecraft properties | |
| Launch mass | 11.14 kilograms (24.6 lb) |
| Start of mission | |
| Launch date | 29 June 2004, 06:30:06 (2004-06-29UTC06:30:06Z) UTC[1] |
| Rocket | Dnepr |
| Launch site | Baikonur 109/95 |
| Contractor | ISC Kosmotras |
| Orbital parameters | |
| Reference system | Geocentric |
| Regime | Low Earth |
| Semi-major axis | 7,132.45 kilometres (4,431.90 mi) |
| Eccentricity | 0.0082657 |
| Perigee altitude | 702 kilometres (436 mi) |
| Apogee altitude | 820 kilometres (510 mi) |
| Inclination | 98.22 degrees |
| Period | 99.91 minutes |
| Epoch | 4 December 2013, 10:20:06 UTC[2] |
AMSAT-OSCAR 51orAO-51 is the in-orbit name designation of a now defunct (following battery failure) LEO amateur radio satellite of the OSCAR series; formerly known as ECHO, built by AMSAT. It was launched on June 29, 2004 from Baikonur Cosmodrome, Kazakhstan on a Dnepr launch vehicle. It is in Sun synchronous low Earth orbit.
AO-51 contained an FM repeater with both 144 MHz (VHF) and 1.2 GHz (L band) uplinks and 435 MHz (UHF) and 2.4 GHz (S band) downlinks. It also contained a digital subsystem that transmitted telemetry on 70 cm and provided a complete PACSAT BBS 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 VHF receivers, two UHF transmitters, six modems, 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.[3] 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.[4]
{{cite web}}: CS1 maint: numeric names: authors list (link)
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