[eagle] Re: A new opportunity (Phase 4 lite?)

Ken Ernandes n2wwd at mindspring.com
Fri Jul 20 06:49:08 PDT 2007


Bob -

Is the back and forth rocking a reaction of the body due to [primarily]
dithering the solar panel and/or yaw angle?  If so, the off-pointing
amplitude will likely be relatively small, considering what will likely be a
large inertia ratio of the body to solar panels.  The body rocking should be
dampened by the reaction wheels to keep an Earth sensor reasonably centered.


It might be interesting if an actual off-nadir amplitude is available.

73, Ken Ernandes N2WWD



-----Original Message-----
From: eagle-bounces at amsat.org [mailto:eagle-bounces at amsat.org] On Behalf Of
Robert McGwier
Sent: Friday, July 20, 2007 9:19 AM
To: Bill Ress
Cc: 'EAGLE'
Subject: [eagle] Re: A new opportunity (Phase 4 lite?)

That would be under consideration and when you have all of the relevant 
information,  we can go do the link budgets and decide if we can build 
it and the political and regulatory issues will factor in then.

We would still need to build a phased array because we are informed that 
  for thermal control reasons, the satellite rocks back and forth around 
one or more axes at a very slow rate to try to keep the power and heat 
generation down on the solar panels.  Both the reality and the amplitude 
of this rocking needs to be understood.  No one more than I would like 
for us to found out that this is wrong and that we can expect it to be 
stable.  BUT, I wonder if we can even afford to make that decision.  It 
would be horrible indeed, if there were a large disaster,  and our comms 
gear, promised to FEMA/NTIS etc. was found to be unusable because our 
primary had rocked the satellite for operational reasons and we had 
decided to put a fixed beam antenna on the platform.

On 10 Ghz: So we would try to get just enough gain to illuminate the 
earth but Ooooops,  that won't quite get it because the path loss at X 
band is much higher and would not allow for the ground user terminal we 
would like to support.  If you overcome the path loss with gain, you do 
not illuminate the visible earth.  Any phased array we are capable of 
building I don't think would allow for continent shaping of the beam and 
if it could, would we really want to be unable to work the DX in the 
middle of the Pacific Ocean?

There are both technical and political reasons why the decisions made 
are what they are.  I don't believe the reasons have changed that much 
but I do know we have the opportunity to revisit this and we should.

Our primary satellite owner will respond to our request for 300w and 
should they say yes, there is little doubt we will find a way to spend 
it and our job is to optimize that.

Another consideration, is that they are looking for efficiency.  I do 
not believe you can give me the same efficiency at 10 GHz you can give 
me at 3.4 GHz.  I believe the power flux density on 3.4 GHz will be low 
enough we can claim noninterference but that will have to be tested 
(with regulatory authorities).

Much to do!

Bob



Bill Ress wrote:
> John,
> 
> I would second that! That would make it compatible with all the regions.
> 
> John B. Stephensen wrote:
>> If this works out, it will be a big boost for amateur radio. Given the 
>> amount of power available, compatibility with their C-band uplink, 
>> regulatory issues outside region 2 and the ease of antenna pointing, a
C/X 
>> transponder may have an advantage over C/S2.
>>
>> 73,
>>
>> John
>> KD6OZH
>>


-- 
AMSAT Director and VP Engineering. Member: ARRL, AMSAT-DL,
TAPR, Packrats, NJQRP, QRP ARCI, QCWA, FRC. ARRL SDR WG Chair
"If you're going to be crazy, you have to get paid for it or
else you're going to be locked up." Hunter S. Thompson
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