On 1/18/21 10:45 AM, Bob kb8tq wrote:
Hi
That’s pretty neat !!!
At least as I read the posters ( and I could have easily missed something …):
Their pulse technique (using the giant telescopes) gives them an instant reading
on the distance / delay to the cubesat. Even if there are propagation issues,
they are
measured (and eliminated) in that pulse process. With GPS, we don’t get that
sort
of live data.
In terms of setting up something to use it in my back yard ….yikes … that’s one
mighty big “antenna” on their ground station. Since you have to deliver enough
power
to the sat *and* back via reflection to “trigger photo diodes” the “minimum”
required
optics could be pretty big …. They don’t go into that so who knows ….
In the current implementation, this looks like a “one user at a time” sort of
system.
I suspect that’s fine if the minimum optics are anywhere near as big as what’s
in that picture.
If this all *can* be done with a backyard sized telescope, scheduling could be
interesting ….
Bob
I'll bet they used those facilities because they were available, not
because they needed that much aperture.
As an example, the TBIRD mission sent Gbps+ data rates from LEO to Earth
with a few cm aperture on the spacecraft and <1 meter on Earth.
You can visually see a laser pointer on the Earth's surface from ISS
with no additional optics (you can also see a 800+W metal halide
spotlight) - there was an experiment where they did this from some
fairly dark place in the Southwest desert.
The lack of easy multi-user access with two way systems is why GPS is a
one way system.
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