[eagle] Re: A new opportunity (Phase 4 lite?)

Bill Ress bill at hsmicrowave.com
Thu Jul 19 18:29:26 PDT 2007


I would second that! That would make it compatible with all the regions.

John B. Stephensen wrote:
> If this works out, it will be a big boost for amateur radio. Given the 
> amount of power available, compatibility with their C-band uplink, 
> regulatory issues outside region 2 and the ease of antenna pointing, a C/X 
> transponder may have an advantage over C/S2.
> 73,
> John
> ----- Original Message ----- 
> From: "Robert McGwier" <rwmcgwier at gmail.com>
> To: "AMSAT Advisors" <advisors at amsat.org>
> Cc: "'EAGLE'" <eagle at amsat.org>
> Sent: Tuesday, July 17, 2007 21:52 UTC
> Subject: [eagle] A new opportunity (Phase 4 lite?)
>> In the last few weeks we have been presented with a new opportunity to
>> launch RF platforms into space.   This note will necessarily be cautious
>> because we do not wish to do or say anything that will throw a monkey
>> wrench into the works.  More specific details than are given here will
>> come from one voice, and that is from Rick.
>> This is a major development.  One which will refocus some of the energy
>> of the organization should it come to pass.  That said, no one in
>> management has proposed we stop Eagle and Jim Sanford will remain its
>> project manager irrespective of what goes forward on the new project
>> because we are still looking for rides for it.
>> The following is adapted from Rick's note to the board of directors,
>> with comments from me (and edits).  We are being asked to propose that
>> we ride on someone else's satellite with our RF gear and antennas.  The
>> primary is not a small satellite.  It will go to geosynchronous orbit.
>> There are MULTIPLE rides being discussed but we have to get our act
>> together for round one.  The planned lifetime of the large satellite is
>> over a decade and they have a track record of exceeding it.  At the
>> beginning of life it produces 1 kw of excess power and we are trying to
>> ask for at least 1/3 of that because at the end of life, after years of
>> solar degradation, that is what the primary  expects it to produce as
>> excess power.  They do station keeping to maintain their subsatellite 
>> point.
>> They provide the ride.  Thus, we do not need a motor, fuel tanks,
>> hydrogen bottles, propellant flow assemblies, or liquid ignition units.
>> They provide the electricity, thus we do not need solar cells or a 
>> battery.
>> We will not need an attitude control system at all or even attitude
>> sensors except for "gee whiz" like cameras or experiments.
>> They could easily provide us about as much space and mass as the Eagle
>> would have consumed, BUT WE DO NOT NEED IT.  Rick suggested to them that
>> we would probably need as much antenna space as we have proposed for
>> Eagle, and they did not blink.  Mechanical constraints (moment of
>> inertia ratios) allowing for a motor are completely out of the picture.
>>   We will be rigidly mounted to their frame and they do the work.
>> They will be asked to provide some thermal control for our RF modules,
>> which will sit on the Nadir pointing side of their spacecraft, which is
>> 3 axis stabilized, and will of course be subjected to hours in the sun
>> and hours in the dark. A careful thermal design is required.
>> We will never need to point another antenna on the ground after the very
>> first time should their payload behave. We will not need to despin a
>> phased array at 3 rpm.  WE WILL need a phased array but it will be
>> adjusted in tiny increments on a daily basis at most.  No more spin
>> modulation unless there is some failure on their bird.
>> We need our very high efficiency power amplifiers, both the proposed
>> linear and hard limiting design to be, as much as possible, producers of
>> RF and not heat.  They are offering this opportunity because they have
>> discovered that if a goodly portion of the heat that is dumped from
>> their solar arrays at the beginning of life is consumed in RF, light,
>> etc.,  it saves them a considerable number of resources.  This was one
>> clever study by an in house engineer.
>> They have been given some basic technical information on our proposed
>> payload. We, AMSAT, must get together now and provided them with real
>> answers on our proposed payload in a formal written proposal, but they
>> were given these rough estimates.  We need to provide the follwing which
>> includes but is not limited to:
>> 1) Size & Mass [less than 50kg, probably closer to 20kg, no batteries, ]
>> Antenna Configuration (space required) [they were told the same as
>> Eagle, a 60cm per side hexagon or some equivalent]  Frankly, it needs no
>> symmetry at all.  It can be completely determined by the needs of the
>> antennas and the envelope restricting us.
>> 2) Given that, there is no need for a very thick spacecraft since it has
>> NOTHING in it but RF modules and computer(s).
>> 3) Power requirements [they were told about 300 Watts]
>> 4) Efficiency (how much power becomes heat) [we agreed to choose 0% to
>> start thermal design]  (sic, from Rick.  I don't understand what needs
>> to be calculated if we agree that we produce 300w of heat, then our body
>> will quickly rise to a very high temperature and melt.  I think they
>> want to upper bound the thermal control needed for us.   ;-) . )
>> 5) Need for some of their on board resources to be specified and more
>> details follow after our study.
>> 6) They must be told a REALISTIC schedule that we can meet. That will
>> determine what launches will be available to us and where the multiple
>> payloads will be placed.
>> We do know their power bus is many times our planned voltage, and we
>> need to decide if we or they build the power converter.  This is pretty
>> obvious because they don't want to power TWT's, etc. from 5 or 14V!!!
>> If we do multiple payloads with them, as is currently proposed, they
>> would consider providing a "LAN" for us to communicate between
>> satellites to our payloads (think direct, bird to bird interlinking).
>> If the design study says we will not impact them greatly, they can
>> provide us this link.
>> For Eagle, we have planned to use 3400-3410 MHz for Earth->Space and
>> 5830-5850 MHz for Space->Earth. It may be necessary to switch these to
>> be compatible with their transponders which are on nearly identical
>> frequencies BUT IN THE OPPOSITE DIRECTION. We don't want to transmit
>> near their receive frequencies.  This raises a serious problem as Region
>> 1 does not permit us to radiate signals from the satellite in the
>> 3400-3410 MHz band if they can see it.
>> So it is clear, I will need to call engineering meetings, and more than
>> one, in the next couple of months.  We are prepared to spend the money
>> on these meetings and bet this will be pulled off.  If it looks like we
>> really will close this deal (as in signing an MOU) then we will
>> definitely bet the farm on it.
>> Right now,  we probably should think we are basing the payloads
>> initially on what has been thought of for Eagle and we need to rethink
>> this because one thing should be crystal clear. THESE ARE NOT ADEQUATE.
>>   Think about what it will mean to have a very loud transmitter, either
>> analog or digital, available 7/24/365.25 at the same spot in the sky.
>> We do not have sufficient capacity in our current design, period.  We
>> would not want to do the SMS text messaging in the linear transponder,
>> but would likely move it back to Microwave for example.  This relieves
>> the phase noise demands on the system for SMS (maybe not other
>> considerations TBD).  Also, the user antennas on the ground are fixed.
>> We need some redesign starting from our basic payloads and then building
>> them out to meet what capacity we think we can support but this will be
>> the first time we have ever spent all of our power on the RF and very
>> little on anything else!
>> I hope you can see that we must be both bold and professional with a
>> dash of caution. A dash only because the probable time schedule will not
>> allow us to pontificate for half a decade.  If we pull this off,  there
>> is very little doubt in my mind that this will change not only AMSAT,
>> but amateur radio in general, and if we do our job well, in a big way.
>> We must thank Lee McLamb profusely for finding out this opportunity was
>> becoming available.  Special circumstances allowed us, following his
>> notice to us, to move VERY quickly to "go in at the top of the
>> organization".  That was done (MAN do I love low friends in high places
>> and in this case, at the very top).
>> More details will follow as the okay comes from Rick. Please refrain
>> from speculation or much gossip.  I know I would be heart broken if the
>> wrong leak or wrong public statement caused us to lose this major
>> opportunity.  I will not be entertaining a thousand questions but I do
>> want everyone to think about the redesign of the payloads carefully to
>> support a geosynchronous bird.
>> 73's
>> Bob
>> N4HY
>> -- 
>> AMSAT Director and VP Engineering. Member: ARRL, AMSAT-DL,
>> "If you're going to be crazy, you have to get paid for it or
>> else you're going to be locked up." Hunter S. Thompson
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> _______________________________________________
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> Eagle at amsat.org
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