[amsat-bb] Delfi-C3 status update 30 April 2008 08:00 UTC

[Wouter Jan Ubbels]

Hi all,

Delfi-C3 is in orbit and healthy, despite some minor issues, please find a
status update below:

1. Telemetry indicates that all solar panels and antennas have deployed
properly

2. Telemetry indicates nominal values for all housekeeping values

3. We have already obtained payload data, and have been able to generate IV
curves of the Thin Film Solar Cell experiment, note that those uring
RASCAL can view the IV curves by clicking Options-->show IV curves in
RASCAL.

4. The spacecraft is operating in science mode, we have had one orbit in
emergency mode, which was most probably due to a databus issue

5. Up till now we have received 7000+ (!) frames from amateurs using RASCAL
around the globe, amazing, thank you all so much!!

6. We have verified command uplink functionality yesterday, and were able to
command the spacecraft today on the low elevation (4.9max) pass over our GS
at 0737UTC

7. The spacecraft has decided to consistently use the backup radio on
145.930MHz for its telemetry downlink, we were able to request a full
on-board database dump while in range of our groundstation yesterday and
analysis of the database confirms this. We currently have a good
understanding why this is the case. We will try to switch downlinks to the
primary radio on 145.870MHz during the next good pass over our GS, so
amateurs in Western Europe might want to check that frequency also and might
experience intermittent telemetry while we are commanding. Note that we
suspect that the TX frequency could be 1 to 2 kHz lower on this radio, so
tuning around slowly is the best strategy.

8. The spacecraft seems to have an issue with the downlink TX switching off
into the orbit, which is the reason while Delfi-C3 has not been heard on
most descending passes over VK/ZL, we think we have a good understanding of
why it is. The TX itself is fine, but it switches off automatically when it
does not get data from the OBC for a certain amount of time. We are working
on resolving this issue. This also happened during the pass over our GS at
0737 UTC but we were able to command it back on. For those in Western Europe
we would like to ask to keep tracking Delfi-C3 even if you can not hear it
at first, as we will try to turn the TX back on as soon as we notice that it
has been turned off.

9. Thank you all for your observations on the spin rate, these are really
helpful! We currently think that the spacecraft is tumbling with approx
10deg/second, which corresponds to a 36 second period. Since the s/c
downlink antenna is almost truely circular, polarization sense can change
from RHCP to LHCP completely depending on s/c orientation, we use circular
antennas on our GS as well, and when we switch to the opposite polarizaiton
sense the signal is wiped out completely, switching back gives solid copy
with strong sigs.

10. NORAD object E #32787 seems to match best


thanks for all your observations and efforts so far!

73 on behalf of the Delfi-C3 team,

Wouter Jan Ubbels