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Re: P3D information



At 02:05 PM 10/6/2000 -0500, Jon Ogden wrote:

>The problem is though that from what I have seen of ground tracks of the
>projected orbits that most if not all of the perigee passes will be in the
>southern hemisphere.  So the bird might not even be visible to those of us
>up north during that time.  I seem to recall something about the desire for
>the orbit is to have it at approximately the same point overhead every 36
>hours or so.

Jon,

The every other day stuff that you refer to is much later, after it reaches 
the 63 degree inclination. Right now I am only thinking about what I can 
expect during the initial orbits, that is the first few days or months.

Right after launch it is in a GTO type orbit with inclination of 6.5 
degrees. In other words it spends most of its time over the equator. Indeed 
at  perigee it is not above my horizon. For much of the rest of the orbit, 
however, including apogee, I will see several hours of access with 
elevation up to around 43 degrees for my latitude (40). Range is out 40,000 
km or so.

But I will also have some time at 10 degrees elevation where the range is 
only 9500 km.

There has been information here in the last few weeks about an experiment 
which downloads picture and sound files taken right after launch.
http://www.uk.amsat.org/p3d_9k6.htm
The frequency is 435.950. Presumably the omni antennas on P3D will be used. 
I have not seen what the transmitter power will be. But it is clear that 
the experimenters expect that an AO-13 class station should suffice.

Also in these first weeks or months there will be 400 psk telemetry that we 
can copy. I think the omni antennas will still be the used for these 
transmissions. I don't think the downlink frequency or power has been 
specified. Maybe there will be several different frequencies used at 
different times. But my guess is that 435 will be one of them, and again I 
am expecting that my AO-13 70 cm yagi and preamp will be fine.

As to the possibility of receiving the telemetry with say an Arrow antenna, 
which has been a big part of this thread, I don't know. Without doing any 
calculations, I might guess that the times when it is at 10 degree 
elevation and 9500 km range might be ok.

73, ron w8gus. 
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