Folks
Like Matt, I am not in favor of this. We need to design the system for services, not design the spacecraft as a bus for a collection of modules.
I recall two SDX payloads, but I'm old and my memory is failing. The Eagle block diagram from Oct 2005 shows a pair of SDX modules, and the SDX block diagram shows a U and an L uplink, an S1 and a V downlink. Of course, at that time the digital payload was to be C/C.
Did we decide to kill the L uplink for SDX/analog use in San Diego? I recall that we decided to not use an L uplink for the digital system.
I think Lyle's note sums it up - I am certainly not clear at all at the moment what's been dumped. Right now it looks to me as if at least 70% of the spacecraft was dumped at San Diego, and I am sure that is the view of many others.
From speaking to the folks on this side of the pond I don't even think most
people realise that since San Diego S1 was only ever considered for a wide band digital up/downlink, not a conventional narrow band up/downlink. Or maybe I've misunderstood.
I am sure that if Matt doesn't want S1 then I'm absolutely certain that as long as there's space for a five turn helix a la AO-40, connected to the SDX as we discussed in Oct 2005, a conventional analog downlink would satisfy the masses, whether or not they can hear it. Add to that the possibility of an L band uplink possibly sneaked off the digital SDX rx and everyone's happy. Except for the integration testers, that is.
I also believe that it is particularly important to understand and quantify further the real 'sewer' issue of S band that Jan King reported. I did my own spec an tests over the weekend, including a 360 degree scan at 20 degree az intervals at the horizon, and then again at 10 and 20 degree elevations using a 1.2m dish and CP patch that I used for AO-40, and since then AO-51. This opened up more questions than answers. For example, there is plenty of WiFi here in Central London, but _none_ of it is between 2400 and 2430MHz. I need to understand why elevation totally resolves some ISM interference but does not apparently have much effect on WiFi according to the spec an plots. Plus, what _real_ qualitative effect does it have on an SSB 3kHz signal, both out of band and in band?
I look forward to seeing you all tonight.
73, Howard G6LVB