From the ARRL: 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 degrees C to near 2 kHz low at 40 degrees 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