AMSAT-OSCAR 51 (Echo)
AMSAT-OSCAR 51 was successfully launched on 28.06.2004 on a Dnepr-1 rocket from the Baikonour Cosmodrome in Kazakhstan. The first contact took place at 1452UTC and the first important telemetry data was send. The batteries were fully charged and the solar panels provided enough power. In the next few days, the software was loaded and the telemetry showed good values.
The 25-inch cubes is weighing about 10kg. AO-51 has four VHF receivers and two UHF transmitters, one multi-mode receiver and a 2.4 GHz transmitter. It orbits the Earth in a high 850KM, sun synchronic orbit. The inclination is 98.2 °.
With four VHF receivers, two UHF transmitters, six modems, fifty-six channels of telemetry, and various other subsystems AO-51 is quite a complex spacecraft. The two UHF transmitters are connected to two antenna arrays, one in the right-hand circular polarization (RHCP) and one in the left-hand circular polarization (LHCP). Transmitter A (435.150) is connected to the LHCP antennas and is often used for digital modes. Transmitter B (435.300) is often used for analog and is connected to the RHCP antenna.
Orbital parameters
Name AO-51 NORAD 28375 COSPAR designation 2004-025-K Inclination (degree) 98.214 RAAN 257.170 Eccentricity 0.0084104 ARGP 147.287 Orbit per day 14.40467899 Period 1h 39m 58s (99.97 Min) Semi-major axis 7135 km Perigee x apogee 697 x 817 km Drag factor 0.000032586 1/ER Mean anomaly 213.357
Downlink
435,225 MHz FM analog Voice
435.150 MHz FSK 9600 bps, AX.25 (TX A)
435.300 MHz FSK 9600 bps, AX.25 (TX B)
Uplink
145.920 MHz FM + 67 Hz PL
145.860 MHz FSK 9600 bps, AX.25
Mode and Antenna Polarization:
T: Linear
V: Linear
U: TX A (usually digital) LHCP
U: TX B (usually analog) RHCP
L: Linear
S: Linear
Call
Broadcast callsign PECHO-11
BBS callsign PECHO-12
Status
After much trial and error, we have found a “sweet spot” where AO-51 will stay operational through eclipse for the time being. Cell 3 is a dead short, and cell 2 now goes to zero in eclipse also. It’s amazing the satellite will operate on 2/3rds the designed voltage input! How long AO-51 can be kept operational is anyone’s guess. By the end of this year, eclipses will be headed for 30 minutes long. It is unlikely it will continue to operate as-is at that point. Enjoy while you can.
Uplink is 145.880, no PL
Downlink is 435.150 at about 1 watt
Nov 29, 2011 The satellite no longer respond to commands and it seems that the last battery cell that kept it operational has failed also. So the end of AO-51
Homepage and other references:
Latest news: http://www.amsat.org/amsat-new/echo/CTNews.php