[amsat-bb] AO-73 / FUNcube Full time Transponder Mode (Amateur Mode) Proposed Test Sat 22 Mar

[Jim Heck]

Hi Folks,

On 22 Mar, we will be commanding the satellite into transponder mode for one
or two orbits so we can assess the effect of lower power being radiated by
the sat on the battery temperature. We expect the sat to be put into full
time transponder mode (aka amateur mode) during the first morning pass on
Sat 22 Mar over the UK, ie at approximately 0930 UTC.

We are aware that the on/off timings for the transponder are not now ideal,
due to seasonal changes. In the coming months the situation will get worse
such that in June the transponder will only be available for very short
periods in the Northern Hemisphere.

We are therefore planning to alter the schedule such that the transponder is
on continuously at weekends, ie after approx 1900 UTC on Fridays, to Sunday
evening. This will give radio amateurs a greater opportunity to use the
transponder. Unfortunately there is no way of automating this schedule, so
its maintenance will rely on the availability of command stations.

Before implementing this schedule, it is necessary that we characterise the
effect of maintaining transponder mode for long periods of time. We expect
that the space craft will be slightly colder than when transmitting at full
power, as the heat generated inside the spacecraft by the PA will be less.

We are concerned that this lowering of the temperature may bring the battery
temp lower than is advisable. Its specification is that it should not be
charged if its temperature is below -5 degs, or some damage might be done to
the battery. Currently the minimum temperature we see that the battery
reaches is approximately -2 degs.

If you notice that the transponder is open on 22 Mar, please feel free to
use it.

Please note that we have learnt from experience that commanding the sat is
not an exact science, and that not all commands sent are received by the
satellite, probably due to interference. We will announce on AMSAT-BB and on
the FUNcube web site (www.funcube.org.uk) the progress of our tests. We
would be very grateful if as many listening stations as possible receive the
TLM and forward it to the warehouse on Sat 22 Mar. Thank you.

73s Jim, G3WGM