[Date Prev][Date Next][Thread Prev][Thread Next] - [Date Index][Thread Index][Author Index]

Re: was Arcjet, now solid boosters



>From: Tony Langdon <tlangdon@atctraining.com.au>
>I beg to differ, high inclination Molniya orbits don't do much for me.
>
>Why?
>
>Because we all know where apogee will be, right over the Northern Hemisphere
>(AKA wrong side of the world).  Some inclination is a good thing, but too
>much limits access for us in the extreme south.  And the constant argument
>of perigee that some people rave about only makes the problem more or less
>permanent.  AO-10 slowly gives everyone a bite at the cherry, so to speak.
>
>Even at 4000 km, there is not a lot of interesting stuff that can be worked
>from southern VK, unless a few SE Asian stations get serious about satellite
>operation.  At apogee (using AO-40's planned orbit as a reference), max
>elevation on higher (good for DX) passes is only around 20 degrees, and at
>my QTH, that precludes operation, unless I setup my own transponder out on
>the street to link back to the shack! (I have a "horizon" that varies
>between 10 deg in the NNW to 35 degrees in the NE, when seen from the back
>yard - AO-40 can climb as high as 48 degrees in its current orbit).
>
>Just another opinion from the other side of the world. :)
>

Tony,

Yes, I understand.  If AO-40 had not run into trouble, it would have been
placed into a 63 degree inclination orbit resulting with exactly that
circumstance for stations in the southern hemisphere.   The current orbit
with ~6 degree inclination provides a more equitable situation for you.  I
guess this may be one of the better outcomes from your perspective!

We in the far north would have had multiple passes every day, which would
have been great.  Well, the GTO gives us no view at perigee {its below our
horizon}, but we do have an apogee view.  The recent low squint angles near
apogee provided fair coverage for us up here, but I note that the good
passes would run for about three days followed by a couple days with
unsuitable viewing or completely missing a pass [perigee passes].  I
suspect a similar pattern with you down there.  I have not done an
exhaustive study, but with just casual observation it seems the current
orbit is limited to about a max elevation of ~30 degrees for me.  Since the
surrounding 15m high forrest can obscure AOS and LOS up to about 10
degrees, this does limit us some {I have chainsaw plans for some of those
trees} :>)  This is one reason the sat-antennas are up on the roof. 

Amsat-DL indicates that the initial arc-jet boost will only raise perigee
by about 200 km.  Perigee will only be ~500 km which will severely limit
range for everyone able to view it.  The S2 footprint will be further
limited, where the V or U low-gain antennas would have performed better for
perigee.  I wonder if there any intension or hope of raising perigee to
4000 km?  I might just have a small view at that altitude, and the
footprint would extend further.  I think that would beneefit everyone.  The
current precession seems to place apogee always late at local nightime.  I
wonder if it will slowly change {probably on an annual basis}.  This
precludes much operation for me during the week when I must get sleep in
order to go to work.  But I guess this is true for many.

Well, AO-40 and phase-jj are GTO birds, so I guess that will be a welcome
situation for you, and it will work out for us, too.  I certainly am happy
to have a new satellite up with a promise of "normal" operation soon
{hoping that the momentum wheels work and solar panels will extend OK}.  We
should be able to work each other occasionally.  I have almost everything
ready now; only waiting on the 2.4G preamp and have yet to test the 1.2G
convertor. 

73, Ed

----
Via the amsat-bb mailing list at AMSAT.ORG courtesy of AMSAT-NA.
To unsubscribe, send "unsubscribe amsat-bb" to Majordomo@amsat.org



AMSAT Top AMSAT Home