AMSAT-OSCAR 51
AMSAT-OSCAR 51 or AO-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. 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.
Q663611
LEO
Concept
Q455647
amateur radio satellite
Concept
Q455647
OSCAR
Concept
Q295309
AMSAT
ORG
Q177477
Baikonur Cosmodrome
LOC
Q232
Kazakhstan
LOC
Q49674
Dnepr
MISC
Q174241
sun synchronous
Concept
Q663611
low Earth orbit
Concept
Q181417
FM
Concept
Q273693
repeater
Concept
Q152466
VHF
Concept
Q2362353
L band
UNK
None
uplinks
UNK
Q628096
UHF
Concept
Q2018880
S band
Concept
None
downlinks
UNK
Q209867
telemetry
Concept
Q4652715
PACSAT
MISC
Q210499
BBS
Concept
Q4874866
PSK
Concept
Q152466
VHF
Concept
Q628096
UHF
Concept
Q5607
modems
Concept
Q5121676
circular polarization
UNK
Q779460
footprint
UNK
Q4653126
AMSAT-OSCAR 51
MISC
2004-06-29T00:00:00Z^^http://www.w3.org/2001/XMLSchema#dateTime
June 29, 2004
DATE
2011-05-01T00:00:00Z^^http://www.w3.org/2001/XMLSchema#dateTime
May 2011
DATE
2011-11-29T00:00:00Z^^http://www.w3.org/2001/XMLSchema#dateTime
November 29, 2011
DATE
+51^^http://www.w3.org/2001/XMLSchema#decimal
51
NUMBER
-51^^http://www.w3.org/2001/XMLSchema#decimal
-51
NUMBER
-51^^http://www.w3.org/2001/XMLSchema#decimal
-51
NUMBER
+1.2^^http://www.w3.org/2001/XMLSchema#decimal
1.2
NUMBER
+2.4^^http://www.w3.org/2001/XMLSchema#decimal
2.4
NUMBER
+70^^http://www.w3.org/2001/XMLSchema#decimal
70
NUMBER
+10^^http://www.w3.org/2001/XMLSchema#decimal
10
NUMBER
-51^^http://www.w3.org/2001/XMLSchema#decimal
-51
NUMBER
+56^^http://www.w3.org/2001/XMLSchema#decimal
56
NUMBER
+435.300^^http://www.w3.org/2001/XMLSchema#decimal
435.300
NUMBER
+435.150^^http://www.w3.org/2001/XMLSchema#decimal
435.150
NUMBER
-51^^http://www.w3.org/2001/XMLSchema#decimal
-51
NUMBER
-51^^http://www.w3.org/2001/XMLSchema#decimal
-51
NUMBER
-51^^http://www.w3.org/2001/XMLSchema#decimal
-51
NUMBER
item operated
space launch vehicle
country