[amsat-bb] Re: S band downlink on P3E

[Robert McGwier]

Dave Guimont wrote:
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>             73, Dave wb6llo at amsat.org
>                     Disagree: I learn....
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>                Pulling for P3E... 
>   

As are many of us.  That said,  The S transmitter is not the primary 
mode of P3E.   The S band transmitter on P3E will be hooked to a dish.   
This dish will have a half power beam width which will limit the 
usefulness of the S band transmitter to those times of nadir pointing.

The revelation of the results of our meeting, weeks before we could be 
ready to explain carefully that we are taking a system approach to the 
design of Eagle, is unfortunate.   Not because the conclusions are made 
public but because there is no context for the decision making process.

We cannot build an AO-40 class spacecraft.   We do not have the 
personnel,  the facilities,  and we likely do not have sufficient talent 
that we can devote to such an enterprise.  We have talent in this 
organization and around the world.  But all of that talent leads a life 
outside of AMSAT.   As an engineering manager for AMSAT  it is my 
responsibility to make cold hard decisions based on personnel,  
calculation, advice,   studies,   equipment availability,  the 
availability of launches that we can use and on and on.

The organization overreacted to AO-40.   It downsized Eagle 
considerably.   It set a goal of no motor.   It said "let's do digital" 
and "give them a whip antenna on two meters".  It did not say this in a 
crass manner but those were absolutely the conclusions of the 
organization policies when captured into engineering possibilities.    
It has literally taken me 11 months to ALMOST right the ship.    If the 
other people in the room will admit to it,  I single handedly saved the 
linear transponders in our current designs by

a) picking the receiver designer
b) picking the transmitter designer
c) choosing SDX as the overall concept for the linear transponder

EVERYONE is on board.  But do you think such things are done overnight?  
NO.  They are done with leadership and not by whining.  These decisions 
and their outcome led to a MUCH improved antenna system, power 
amplifier, and absolutely cutting edge efficiencies achievable for this 
transponder in our current plans.  It went from 25 kHz fed to a quarter 
wave monopole on the back side of the spacecraft  to serious antenna 
absolute eating valuable territory on the business side of the 
spacecraft and with bandwidth UP TO (but not necessarily) 100 kHz wide.  
The bandwidth will be determined by the TYPE of customers we wish to 
serve.  We do not want to serve only those who can transmit 10 kW 
EIRP.    We do want to support 1 KW EIRP SSB contacts.   We also want to 
support a text messaging service that will require a shortened dipole on 
70cm and 2m which will not be limited to APRS users.

The goals stated by the AMSAT board of directors for its next HEO 
spacecraft design as a follow on to P3E (besides supporting P3E in the 
interim) included aiding those people who live in CC&R (covenant 
restricted) communities.   It included aiding the first responders by 
giving them the ability to take a back pack full of equipment, set it 
up,  and operate quickly.   It stated that it wanted to produce a system 
of such satellites over a decade to be available 7/24. 

We have a concept, not a design, for a spacecraft.  This concept is an 
"upsizing" of the near cubical Eagle.  We are filling in the blanks on 
the concept in an attempt to present a design.  

The concepts we are building to include the ability to use the 
transponders on this spacecraft  365 days a year, in EVERY year the 
spacecraft is functional and to try and build  a spacecraft that will be 
there and still usable when the third in the constellation is launched.  
Do you think this is easy?  Of course not.  It is easy to pitch mud when 
you are not responsible for an outcome.

We are attempting to have NO bad seasons.   We are attempting to have NO 
funny orbital problems.     We are attempting to have the gain antennas 
solidly usable over 70% of the entire orbit.  For these reasons and 
because of the desire to serve the CC&R customers,  this meant we had to 
use microwaves to get sufficient gain on the antennas on the spacecraft 
and the ground.  We fully understand that Dick Jansson,  Drew,  Dave,  
Tony, and others can give us anecdotes of how they can throw enough gain 
on their antenna system and make S band work for them.  I believe they 
will not be happy with a 60 cm dish but will require a much larger dish 
to be happy and I am certain they would do it.  I do not care.  They are 
not who I am computing for.  These are not the customers I am trying to 
serve.  The customers I want to serve for the future of AMSAT cannot be 
served by a scratchy SSB signal and a (now) 4 foot dish.  I have a 
mission directive from the board of directors you elected and voted for 
to serve these NEW customers.  Those who will be here when the third 
satellite is launched.   They will not be where Dave will be by then.  I 
apologize for the crassness of this remark, but I am trying to make a 
point.  I know Dave and have for nearly 30 years..  We are building for 
a guessed audience, with a guessed legal and RF environment,  with a 
guessed ability to deliver 3 such payloads over the next 13 years.

COLD HARD CALCULATION went into this analysis based on our best guesses 
and analyses.   Given what we believe the environment will be  We can 
only do this on microwaves and we can only do it digitally.   PERIOD.  
End of story.  God (as demonstrated through the mathematics of Claude 
Shannon)  has dictated this outcome.  We did not sit in a back room and 
decide what new toys we would throw your way to delight ourselves and to 
screw you (no more smoke and no more drink in there,  we have grown old 
and boring) .  To do it,  I have to build a very complex antenna system 
that will take up most of the available area on the spacecraft for 
antennas.  I cannot build a three axis stabilized spacecraft (I do not 
have the team or the money to do it),  so I must do it with phased 
arrays.    Matt Ettus has given us a great head start on this design and 
Tom Clark and John Stephensen have done great work on the antennas so 
far.  We will test these antenna designs in the next twelve months 
thanks to a very generous antenna test range offer and design help by 
one of our members.

The direction Jim and I gave our engineering team was that we cannot 
rely on this to work perfectly and meet every operational goal 
perfectly.  STUFF HAPPENS.   We are attempting to be ambitious but we 
absolutely must have a credible back up in case this system does not 
meet our expectations.   We now have the upgraded Mode B transponder 
design which I believe will be the sweetest one flown since Oscar 7's 
Mode B. Fully equipped with the channelized AGC (Leila or Stella),  
generating HELAPS with modern technology and new fantastic amplifier 
components. 

I gave the argument to our engineering team  that I have witnessed one 
experimental, new widget after another get built, flown, and then have 
its designers disheartened and dejected because it got "RUDAK'ed".  It 
never really gets used or fully developed.  It drifts into an inert lump 
that people mumble about when they are asked of their involvement.  I 
insisted on enough spacecraft power generation to run BOTH the linear 
transponder and the digital transponder simultaneously and 365 days a 
year,  EVERY year.  This is the single most expensive decision we have 
made.  We might spend 1/2 to 3/4 MILLION dollars on solar panels to 
accomplish this.  I have insisted we have enough antenna space to make 
all of the antennas credible and based on calculation of the required 
antenna gains to close the links.  Again,  Claude Shannon has 
interpreted the natural laws and dictated the outcome.   Cold hard 
calculation has gone into the needed solar generators,   and the size of 
spacecraft required to support this.

It will be about 4 feet across and look initially like a scaled DOWN 
AO-40 at launch if the concept becomes our design.

We cannot deliver the quality of services we are demanding of ourselves 
if we fly all of the bands to be flown on P3E.  We do not have the power 
or the antenna territory to meet our goals for these services.

I have taken my direction from the board of directors of this 
organization.  They made the vision statement.  They can change it.  You 
elected them.

Several things will happen in October.   We will install four 
directors.  I may, or may not,  be one of them.  The board will vote 
whether or not to retain me as the VP Engineering.  I have made almost 
NO ONE happy by slowing down those who drive me crazy with wanting to 
rush head long in a ready fire aim approach by demanding that we 
calculate our way to the vision statement to show the directors the 
consequences of the decision making processes.  I have to tell you,  I 
am damn proud of how much has been done in eleven months.   Stuff got 
put on hold that aggravated many.  We all make decisions about the way 
things have to go but I have done my best to aim us in a technically 
feasible direction.  I do not have time to do all the everyone wants me 
to do.  I will continue to do my best if I stay in the job.

I offer the following.  If the board votes to change their vision 
statement and not to build the spacecraft we are proposing,  I will 
tender my resignation as VP Engineering since I will have failed to do 
the job they elected me to do which was to produce a usable concept to 
meet their vision.    I am not interested in flying a carbon copy of P3E 
when I know it makes no sense whatsoever.   I am 52 years old and one of 
the most active technical contributors in all of amateur radio.  I will 
not waste my time doing what I know in my heart and my head is not in 
the best interests of amateur radio even if it is currently perceived to 
be for the good of  the shrinking aging membership of AMSAT.  It would 
be irresponsible of me not to attempt to aid the organization in 
addressing a new group of members while attempting to thread the needle 
of serving our current members.  If elected to the board, and it changes 
direction,  I will offer my seat to the first alternate.  Vote for 
someone else if you do not want P3E built and you do not want the AMSAT 
vision statement attempted if you have not cast your vote.

The story you have just been told should not have come out in this 
form.   It was NEVER meant to be displayed in this form.  The 
calculations were made at the first of July.  They have undergone 
several iterations and were not really put in there latest form until 
August.   In an attempt to get further interest from the microwave 
community, we made a decision to give a sneak peek to get some technical 
aid from RF specialists.  This has backfired badly because we,  the 
volunteers who have sacrificed countless hours on your behalf,  have not 
had the time to put together a hundred pages of supporting documentation 
to tell the story in a coherent fashion so not only do we look like 
idiots,  we have had to do things like waste 3.5 hours writing this 
silly note when I should have been asleep.

Lastly.  I have been accused here of being a con artist.   I resent 
it.   I don't need to con anyone.  Frankly,  I don't have to be here at 
all.  I choose to be.

Bob
N4HY

-- 
AMSAT VP Engineering. Member: ARRL, AMSAT-DL, TAPR, Packrats,
NJQRP/AMQRP, QRP ARCI, QCWA, FRC. ARRL SDR Wrk Grp Chairman
"You see, wire telegraph is a kind of a very, very long cat.
You pull his tail in New York and his head is meowing in Los
Angeles. Do you understand this? And radio operates exactly
the same way: you send signals here, they receive them there.
The only difference is that there is no cat." - Einstein