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

John B. Stephensen kd6ozh at comcast.net
Thu Jul 19 18:09:18 PDT 2007

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.



----- 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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