Category: Ham Satellite news

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Parkes 64m Radio Telescope Listens for AO-40
With our attempts to restore AO-40 we have received today significant support from Parkes Observatory in Australia. http://www.parkes.atnf.csiro.au/
The Parkes Observatory is operated by the Australia Telescope National Facility (ATNF) which is part of Commonwealth Scientific and Industrial Research Organisation (CSIRO).

From here were received the live pictures of Apollo 11 Moon landing, 1969. See above homepage of Parkes.

The radiotelescope has a diameter of 64 metres and the system noise figure is approx. 25 K.

From about 6:00 UTC, a 4 MHz wide spectrum with center frequency of 1097 MHz was scanned with high level technique in order to find the LO frequency of the AO-40 L1 receiver. A band of approx. +/- 20 kHz around the actual LO frequency was examined intensively. Three hours were needed to prepare the setup for AO-40 and to search.

Unfortunately nothing was heard which could be a signal of AO-40!!

The fact that nothing was heard of the L1 receiver s LO does not lead to the conclusion that AO-40 is completely dead. The receivers of Parkes are not really fitted for frequencies below 1.25 GHz, and naturally one does not know how good the L1 receiver s LO is shielded or how much of the signal would go through the antenna to the outside world. During the next days more research follows.

The L1 command receiver is continuously switched on, and it would have been good news if we had such a confirmation that the 10 V power source for the L1 receivers is still functioning. All receivers and also the IHU are supplied with the 10 V source.

All command stations are continuing to send commands to the satellite in order to switch the batteries.

I would like to say a great thank you on behalf of AMSAT-DL to Brett Dawson, VK2CBD and the team of Parkes observatory, especially to Dr. John Reynolds (Officer in Charge) and John Sarkissian (Operations Scientist).

Peter Guelzow, DB2OS
President AMSAT-DL

AMSAT-DL Oscar 40-sida

Klla: AMSAT-DL

Hej! Hr r en rtt fin frklaring p Oscar 40 lget,Vi hller tummarna!! 73 Hkan

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The problem is, that the Main Battery clamps the bus voltage down toabout 14V or even less, from its nominal 24V.

As Stacey described, this is obviously due to several battery cells in the main battery, which failed shortened in some sort of domino effect.

It happened so fast, that we were not able to completely isolate the main battery and use only the aux battery. At the moment both batteries are in parallel.. this will not damage the AUX battery, but it prevents it from charging.

The extremely low battery (and bus) voltage is a problem, because the transmitters and other electronics were not designed or may not work at these low voltages..

The IHU and receivers should still work, but without telemetry it is hard to predict what the current situation really is..

Since the solar panels pump all their energy into the remaining cells of the main battery, they will indeed get very hot.. Our hope now is (and that s what is to be expected) that these cells will ventall their electrolyte and dry out. When that happens, the cells should fail high resistance and our bus voltage should come up..

Thus, the improving sun angle should help in speeding up this process.But again, we yet do not know how long this will take.. but chances not bad for this to happen..

73s Peter, DB2OS
Pres. AMSAT-DL

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