[amsat-bb] S band and Eagle: an appeal for a higher level discussion

Bruce Robertson broberts at mta.ca
Thu Sep 7 15:06:17 PDT 2006

There has been a recent restatement of disappointment regarding the Eagle
design committee's recent choice to use S band as an uplink not a downlink.
Note that the next two HEO's scheduled to launch *will* have S band
downlinks, so there's no worry that people like I, who live in radio quiet
areas, will be unable to use our developing S band equipment in the future.

As I understand it, the Eagle design team have used standard predictions of
801.11 usage to determine mathematically that by the time of launch the
radio environment will simply not support reliable communications. I cannot
imagine that they like these conclusions. Implementing new bands entails
new risks, after all. But numbers don't lie (or shouldn't), and it would be
a horrible disservice to all of us if they designed and launched a bird
that was effectively mute at launch.

The design team have said again and again on this list that they would
welcome contradicting evidence that is cogent, and I, for one, believe
them. They're our volunteers, and they deserve our support. I can't provide
that contradicting evidence: I'm not skilled or qualified. But I can assess
an argument, and the responses so far have not been nearly as rigorous. 
They have amounted to "works for me", which I think misses the point. 

Please, please, those of you who are qualified and competent and hold the
opposing opinion, take the design committee at their word and assess their
work, check their assumptions, present cogent opposing arguments. There is
some thought that a dish antenna properly implemented will overcome the
obstacles described by the design team. Let's model this. Or those who live
in heavy 802.11b environments, do some experiements with terrestrial links
(which I suppose could be assumed worse than earth/sky). Who knows? Maybe
it's all like my last tax return, where a missed decimal point made me
think I'd have to take out a second mortgage to pay our taxes :-) This list
and the wiki exist so that we can undertake that sort of dialogue, and for
my part, it is my favorite part of participation in AMSAT.

Some have suggested that Eagle fly with an S-band downlink on the off
chance that it *does* work despite the theory; others, that we survey the
members to see what they'd like. I fully support the design teams rejection
of the former approach. Launch weight is very expensive and the kitchen
sink approach is not to my mind sensible. As to the latter, a survey
presumably pertains only to *working* bands, not ones that are polluted out
of existance.

It's human nature for us more readily to see our misfortunes as caused by
the malace of others, but I think we should strongly avoid terms like "bait
and switch". We'll get much further if we all assume the goodwill of
everyone involved. 

73, Bruce

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