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Re: Repeater on the Moon



As I said previously, nothing is ever absolutely impossible, there are
exceptions to every rule, but when someone in Amsat proposes to do a
"piggy-back" mission on someone else's satellite, these are some of the issues
that come up:

Launches to geosynchronous orbit are almost always weight limited. The
lifetime of a geosynchronous satellite in commercial service nearly always
depends on its fuel supply which is used for station keeping in the
geosynchronous orbit. When the satellite runs out of fuel it is retired to a
higher orbit. The owner of the commercial satellite, who is in business to
make money, normally fills the fuel tanks with as much fuel as the launch
vehicle can lift in order to insure a long life in revenue service. Any
additional payload that piggy-backs along will reduce the fuel load and the
lifetime of the satellite. For this reason, a piggy-back ride to
geosynchronous orbit seems to be unlikely.

It is not impossible that there could someday be an exception to this rule,
but I'm not holding my breath. Possibly a government sponsored mission, but
again, whoever is sponsoring the mission wants a long satellite mission
lifetime. It is reported that the US military once launched a ton of ballast
weight on one of their geosynchronous missions because part of the
communications payload was not ready to fly. However this was a last minute
decision and it would have been difficult to qualify and test any design for a
piggy back payload in the short time remaining before launch. 

Any modification to the existing satellite design introduces new complications
to the mission. An RF payload will need to be tested and certified that it
will be compatible with the other communications gear on the satellite.
Antennas must be mounted on the outside of the spacecraft, this will change
the center of gravity, the thermal design, and countless other things.
Everything must be tested and certified and the time required to review this
data adds labor costs to the primary mission. 

Ballast weight does not need to be tested for RF compatibility, it does not
require antennas, it does not change the thermal or mass properties of the
spacecraft. Indeed it was added on precisely because they did not want to make
a last minute modification of the thermal or mass properties of the satellite
that would have been caused by the missing payload.

There have been piggyback missions in other types of orbits. AO-21 was a
piggyback amateur payload on a much larger Russian satellite in low Earth
orbit. For the SAREX and ARISS missions, NASA has picked up the enormous costs
of certification and paper work for the amateur hardware to fly on the shuttle
because of the perceived benefit to their program from educational school
contacts and crew morale issues.
 
A profit making company like Hughes has much different business practices than
a non-profit volunteer organization like Amsat. We don't keep track of labor
hours, but a company lives and dies by labor costs, for example. There are
intangible cultural issues to consider, many people in the for-profit world
have no concept of what Amsat is or how we work, and therefore don't know what
to think about us. We don't fit their paradigm. We could go to them as a
paying customer and ask them to build us a satellite, or fit us into an
existing satellite, but the labor costs would insure that the final cost to
Amsat would almost certainly be much more than what it would cost us to build
the entire satellite by ourselves.

------------------------------------------------------------------------
Karl Bullock wrote:

>I'll have to admit I'm new to AMSAT, and this is certainly to have been
>brought up before, but as to issues of paying for satellites,
>particularly the _really_ expensive stuff (such as geostationary,
>moon-based, etc.), what has been the consideration in the past of a
>"partnership" between commercial interests and AMSAT on a _single_
>package? For example, Hughes is probably the best known satellite 
>maker in the U.S. Has Hughes ever been approached with the concept of
>integrating a small amateur package _into_ one of their satellites? Since
>they're going up anyway, I'm sure the funds could more easily be raised
>to "modify" an existing satellite design, rather than building and
>launching one from scratch. Adding another foot or so to the size
>shouldn't be that much more expensive (maybe I'm wrong).



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