AO-85 Commissioned and Turned Over to AMSAT-NA Operations
Fox-1A (AO-85) has been formally commissioned and turned over to AMSAT Operations, which now is responsible for the scheduling and modes. Fox-1A is AMSAT-NA’s first CubeSat.
“Many new techniques are incorporated, and lessons will be learned, as with any new ‘product,’” said AMSAT Vice President-Engineering Jerry Buxton, N0JY. “We will incorporate changes from what we learn in each launch, to the extent possible, in subsequent Fox-1 CubeSats. To our members, we want to say that the Fox Team is very proud and pleased that our first CubeSat is very successful and hopefully will be for some time.”
The Fox-1 Project is a series of CubeSats. A total of five will be built and flown. Launches already have been scheduled for three more, and a new NASA CubeSat Launch Initiative proposal will be submitted for the fifth launch.
Of the four NASA-sponsored CubeSats on the October 8 Educational Launch of Nanosatellites (ELaNa) on October 8 that put AO-85 and 12 other spacecraft into orbit, one (ARC1) never functioned, and a second, BisonSat, was lost after a few weeks of operation.
The Fox Team notes that an apparent lack of receiver sensitivity and difficulty in turning or holding on the repeater with the 67 Hz CTCSS tone are probably the most notable observations about AO-85.
“We have determined a probable cause for the sensitivity issue, and while that can’t be fixed on AO-85 we are taking steps to prevent similar issues on the rest of the Fox-1 CubeSats,” Buxton assured. “The tone-detection threshold, along with the receive sensitivity issue, makes it hard to bring up the repeater. This is being addressed by adjusting the values for a valid tone detection in the other Fox-1 CubeSats, now that we have on-orbit information about temperatures and power budget.” The November/December edition of AMSAT Journal will include full details on these technical issues.
AMSAT has provided guidelines for using AO-85.
Uplink power should be on the order of a minimum 200 W EIRP for full quieting at lower antenna elevations. Your mileage may vary. Successful contacts have been made using an Arrow-style antenna.
- Polarity is important. The satellite antennas are linear. If you are using linearly polarized antennas, you will need to adjust throughout the pass. Full-duplex operation facilitates these adjustments while transmitting and is highly recommended.
- The downlink is very strong and should be heard well with almost any antenna and is 5 kHz deviation. AMSAT said that users may perceive that the audio is low. “This is an effect of the filtering below 300 Hz, which provides for the data-under-voice (DUV) telemetry, coupled with any noise on the uplink signal resulting from lack of full quieting or being off frequency,” Buxton explained. “That makes for less fidelity than a typical receiver in terms of audio frequencies passed.”
- The satellite’s downlink frequency varies with temperature. Due to the wide range of temperatures the satellite is exposed to during eclipse, the transmitter can be anywhere from around 500 Hz low at 10° C to near 2 kHz low at 40 °C. The uplink frequency has been generally agreed to be about 435.170 MHz, although the automatic frequency control (AFC) makes that hard to pin down while also helping with off-frequency uplink signals.
“It is important to remember that science is the reason behind the Fox-1 satellites,” AMSAT said. “Not only does science help with the launch cost, it provides a great amount of educational value both from the science payload and in amateur radio itself. The DUV telemetry is an excellent way to provide the science without sacrificing the use of the satellite for communication, which would be the case if higher speed downlinks were needed. DUV provides constant science as long as the repeater is in use, which in turn provides more downlink data for the science - a mutually beneficial combination.” — Thanks to AMSAT News Service via Jerry Buxton, N0JY