[Ground-station] Satellite program

[Bruce Perens]

Here is SATNOGS rotator V3: https://wiki.satnogs.org/SatNOGS_Rotator_v3
The whole thing is built from extruder-printed parts and T-slot, and a few
easily-acquired parts, so someone without machining capacity can put it
together for a bit more than $220.
It would be nice to have an ME to make another design or to improve on this
one.

    Thanks

    Bruce

On Wed, May 16, 2018 at 7:18 PM, Phil Karn via Ground-Station <
ground-station at lists.openresearch.institute> wrote:

> I won't be at Dayton this year, but I do have some thoughts.
>
> Michelle is absolutely, positively 100% on the right track in developing
> digital microwave ground station equipment. That's the ONLY possible
> future for the amateur satellite service; unfortunately, it's been
> impossible to convince AMSAT of this fact. They'll probably keep flying
> analog 2m/70cm FM repeater satellites until the last member dies off.
>
> I do *not* assume most or even *any* of our satellites will be
> geostationary orbit; all or nearly all will be in low and relatively
> short-lived LEO orbits of the type most commonly used by cubesats. If
> our opportunity actually materializes to fly a payload on an upcoming
> GEO platform, great. But I ain't betting on it, nor do I think we'll get
> many more opportunities like that in the future. OTOH, we do know there
> will be many opportunities to reach LEO.
>
> So the usability of any digital microwave satellites we build implies
> developing two closely related items of technology: active spacecraft
> attitude determination and control (ADaC), and accurate real-time
> antenna pointing on the ground.
>
> You can buy complete off-the-shelf ADaC subsystems for cubesats, but
> they are very expensive. Much more expensive than I think they should
> cost, but maybe there are good reasons. Momentum wheels seem necessary,
> along with torquing coils and magnetometers. I am familiar with the
> latter two items but space qualified momentum wheels seem like a
> mechanical engineer's nightmare -- and I'm an EE, not a Mech E.
>
> AMSAT-type stations have long used az/el rotors to point VHF/UHF arrays
> to LEO satellites. In principle they could be used for microwave
> antennas but I don't think they're very well suited for the purpose. For
> one thing, they're oversized for the job of pointing small (< 1m)
> dishes. For another, they're very expensive. For a third, they aren't
> designed for precise pointing. We're going for a much larger user base
> than AMSAT has traditionally had; that means small, inexpensive and
> reliable. (Do we only get to pick two?)
>
> I am not sure what's already been discussed here about reproducible, low
> cost ground station antenna pointing systems. I do know a very little
> about the SATNOGS project but their design seems rather complex. This
> will be a key part of the project so easy reproduction is essential.
> Again, this seems more in line with a mechanical engineer's skills than
> my EE skills so I'm wide open to ideas.
>
> 73, Phil
>
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-- 
Bruce Perens K6BP - CEO, Legal Engineering
Standards committee chair, license review committee member, co-founder,
Open Source Initiative
President, Open Research Institute; Board Member, Fashion Freedom
Initiative.
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