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RE: UO-36 over S.America?

If only life were so simple....

UO-36 has a lot of systems, and all these consume power.  It has advanced
attitude and orbit control, a number of flight computers, and other systems
that can't realistically be turned off.  These consime a certain amount of
power and we can't change that.  The orbit UO-36 is in provides variable
power (from between ~50w OAP to >150W OAP).  When we are in the low power
season, we don't have much power to go around.

Power isn't cheap in space.  Solar arrays are EXTREMELY expensive.  We
therefore have a couple of options - leave 1/2 the spacecraft on the ground,
or live with the fact that some payloads only operate for certain times.
The later is standard practice on many missions (not just amateur).  Payload
operating times are modulated by available to ensure that the power budget
is maintained.

In the case of UO-36, I have chosen to let the satellite decide when it has
enough power, rather than simply switching the downlink off for long
periods.  The groundstation will send a request to switch on the downlink,
and if there is power available, this will be actioned.  If during the
operation the power level drops below preset levels, the satellite will
reduce consumption by switching systems off.

I hope this helps explain things...

Chris G7UPN / ZL2TPO
UoSAT command station

-----Original Message-----
From: Jon Ogden [mailto:jono@enteract.com]
Sent: 03 April 2000 05:19
To: Chris Jackson; 'Joel Black'; amsat-bb@amsat.org; Fernando Mederos
Subject: Re: [amsat-bb] UO-36 over S.America?

on 3/31/00 4:09 AM, Chris Jackson at c.jackson@eim.surrey.ac.uk wrote:

> Due to the low power budget on UO-36 the satellite downlink is normally
> I will release a new version of MSPE that has the ability to switch the
> downlink on during the pass (hopefully later today).

This isn't meant to be an offense, but why the heck do we build satellites
with power budgets incapable of supporting normal amateur usage and

AO-10 is a great bird, but I don't think we are supposed to follow its power
budgeting scheme.

Why do we do this?  Let's see we have AO-27, KO-25, UO-36, SO-35 and who
knows what else.  All have power budget issues.  Where are we missing it
design wise?

OK, OK, so AO-27 and SO-35 have other payloads that take precedence, but it
still doesn't eliminate the problem of not enough power budget for normal

Again, it isn't meant as an insult.  It's a real problem that we put birds
up there that can't be used more regularly.



Jon Ogden



"A life lived in fear is a life half lived."
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