AMRAD OSCAR (AO-27)
AO-27 is an amateur satellite constructed by the Amateur Radio Research and Development Corporation (AMRAD) at the facilities of Interferometrics in McLean, Virginia.
It was originally designed as a commercial satellite known as EYESAT-1 but its completion was halted part way through the project. An agreement was made for AMRAD to finish the construction of the satellite and add an amateur satellite transponder. AO-27 is an “FM Repeater” in space. It essentially consists of a crystal controlled FM receiver operation at 145.850 MHz and a crystal controlled FM transmitter operating at approximately 436.795 MHz. Output power of the transmitter can be set to over 1 watt (rarely used), 0.5 watts (normal operation), or under 0.1 watts (exciter only). The uplink antenna is the linear polarized whip on the top face of the spacecraft and is shared with the commercial payload’s receivers. The downlink antenna is a 1/4 wave whip mounted on the bottom face of the spacecraft. Polarization is nominally linear, the rotation and revolution of the spacecraft and propagation effects will cause the actual signal polarization at a ground station to vary widely during a pass.
Orbital parameters
Name AO-27 NORAD 22825 COSPAR designation 1993-061-C Inclination (degree) 98.251 RAAN 190.750 Eccentricity 0.0008681 ARGP 171.364 Orbit per day 14.29136207 Period 1h 40m 45s (100.75 Min) Semi-major axis 7173 km Perigee x apogee 788 x 801 km Drag factor -0.000009537 1/ER Mean Anomaly 188.766
Downlink
436.795 MHz (FM)
Uplink
145.850 MHz (FM)
Mode and Antenna Polarization:
V: Linear
U: Linear
Telemetry
Decoding is possible with a 1200 bps AFSK (packet) modem in kiss mode. The kiss output can be used as input to for example the AMRAD AO-27 decoder from DK3WN.
The channels 1 thru 15 are from the receiver. The AART board in the receiver has a problem that it will latch the lines on the bus so the RX telemetry was disabled right before launch. Parameter = A*n² + B*n + C Ch name C B A unit ------------------------------------------------------------------- 16 Battery 0 : +1.900 -0.0041666 0 Volts 17 Battery 4 : +1.900 -0.0041666 0 Volts 18 Battery 2 : +1.900 -0.0041666 0 Volts 19 Battery 6 : +1.900 -0.0041666 0 Volts 1A Battery 1 : +1.900 -0.0041666 0 Volts 1B Battery 5 : +1.900 -0.0041666 0 Volts 1C Battery 3 : +1.900 -0.0041666 0 Volts 1D Battery 7 : +1.900 -0.0041666 0 Volts 1E Solar Array : +7.9650682 +0.0686763 0 Volts 1F 8 V Bus : +7.0473333 +0.0113333 0 Volts 20 5 V Bus : +3.7500000 +0.0125000 0 Volts 21 10 V Bus : +8.1699655 +0.0204189 0 Volts 22 Battery #5 : +145.08000 -0.9200000 0 deg C 23 10 V Bus Cur : -8.5766634 +4.6595804 +0.0090934 mAmps 24 8 V BUS Cur : -0.2637419 +1.9861031 -0.0002043 mAmps 25 5 V BUS Cur : -1.6011952 +5.3687733 -0.0001976 mAmps 26 -X Array Cur : +2.5393978 +1.2945522 0.0029869 mAmps 27 +X Array Cur : +3.8778891 +1.2337216 0.0034585 mAmps 28 -Y Array Cur : +1.9453662 +1.2869215 0.0036150 mAmps 29 +Y Array Cur : +0.8377529 +1.3201728 0.0030064 mAmps 2A -Z Array Cur : -5.1705101 +1.3962301 0.0002714 mAmps 2B +Z Array Cur : +3.7194087 +1.1232609 0.0041865 mAmps 2C External Cur : -1.3147137 +1.5779074 0.0013702 mAmps 2D BCR Input Cur : +9.8611991 +1.0931975 0.0099122 mAmps 2E BCR Output Cur: 0 +1.000 0 Count 2F BCR Plate Temp: +145.08000 -0.9200000 0 deg C 30 BCR PC-Board : +145.08000 -0.9200000 0 deg C 31 Battery #0 : +145.08000 -0.9200000 0 deg C 32 TX-A RF OUT : -21.995773 -8.1787836 +0.2143451 mWatts 33 TX-B RF OUT : -111.61003 -5.2876206 +0.2271923 mWatts 34 TX THER A : +140.69230 -0.8846154 0.000 deg C 35 TX THER B : +140.69230 -0.8846154 0.000 deg C 36 TX THER C : +140.69230 -0.8846154 0.000 deg C 37 TX THER D : +140.69230 -0.8846154 0.000 deg C 50 EDAC Counter : 0 1 0 Count 51 Eclipse : 0 1 0 Count 52 Set Point : 0 1 0 Count 53 Tepr State : 0 1 0 Count FF VERSION : 4.0 0 0 Version
Status
Inactive, FM repeater – Telemetry transfer over Italy. Don’t transmit unless you hear the FM repeater functioning.
Update information: October 18th, 2012 We tried to do a restart of the high level code today which did not work out. We left the transmitter on to drain the batteries in hopes of clearing any latch ups. On the next pass, we could turn the bird back on so it survived the battery draining. The modem problem was back and we got that cleared. Its back up on the secondary bootloader. Michael, N3UC
Homepage and other references:
Main website: AO27.org (or http://www2.umbrasi.com/)