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

Re: Geostationary Satellites?



>When I was working on geosync satellites at Hughes in the mid-1960's
>there were rumors going around of some talks between Hughes and the
>ARRL, but nothing ever came of it.  We did have repeaters just outside
>the 2 meter band on the NASA ATS-1 and ATS-3 (a ~12 MHz split
>permitted L-C filters for the duplexers.)

>Orbital slots weren't a problem then, but launch costs certainly were.

>Bob, n7xy
-----------------------------------------------------------------------------

As Bob stated, there may have been talks going on in the past, and if we are
ever going to fly a ham payload on somebody else's satellite, it would happen
because somebody (possibly some ham) who works high enough up in one of these
companies decides that a ham transponder would be a good thing. There are many
issues that weigh against such a project. The mass of the ham payload, its
power consumption, and placement of antennas outside the spacecraft are three
issues that come to mind. A ham payload would have to be integrated into the
satellite design at an early stage, you couldn't just bolt it on at the last
minute. Since the commercial guys are in business to make a buck, any
diversion of resources to a ham project would have to be explained to the
stockholders.
All of these factors make it seem unlikely, but Amsat never fails to amaze me
on the support that they can dig up, so I am reluctant to say that it will
never happen. Oscar 1 was launched way back in the 60's because some general
in the Air Force thought it would be a good idea to let the hams have a ride.
Amsat needs to develop and nurture contacts with people in the industry, this
is one of the things that your elected Amsat leadership tries to do behind the
scenes.

Orbital slots are not a limiting factor, since a ham satellite would operate
on different frequencies than the commercial birds. The limiting factor on
commercial orbital slots is the antenna beam width for dishes on the ground,
you don't want two satellites on the same frequency in the same antenna beam.

The commercial satellites are highly optimized for the job that they do, so I
doubt that one could be "retuned" to a ham band at the end of its commercial
life as one person suggested. Another person asked about the cost of
commercial geosynchronous satellites, I seem to recall they are in the $200 to
$400 million range for a small cheap satellite. 

A problem with geostationary satellites (assuming that we built our own) is
that you need to expend fuel to keep it in a fixed location. If we were
willing to forgo the convenience of having fixed antennas on the ground, one
could envision a constellation of smaller satellites in high but not
stationary orbits. They would necessarily need to be smaller and cheaper than
Phase 3D, with smaller solar arrays and less power budget. We could try to
launch more spinners like AO-13, which would require an AO-13 type station for
users on the ground, or try for a smaller 3 axis design that could keep its
high gain microwave antennas pointed at the Earth. If we gave up on VHF
operation, a microwave satellite could allow ground stations to get by with
smaller antennas that might be acceptable even in restricted neighborhoods.
With several AO-13 size satellites in Molyna orbits we could get close to 100%
availability and perhaps become attractive to the public service and emergency
preparedness hams.

It also seems to me that the type of orbits we put our high altitude
satellites in are similar to the orbits that the scientific world likes for
their magnetospheric research missions. Many of these missions would benefit
from having multiple satellites making the same measurements from different
locations in the magnetosphere and the Van Allen belts. If we had the right
scientific contacts perhaps we could sell rides for instruments or collaborate
on construction of a dual purpose satellite constellation.

I am hoping that a successful Phase 3D mission will pull in new members for
Amsat and new recruits to ham radio, perhaps then we will have the funding to
pursue these future missions.

Dan Schultz N8FGV
----
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