| |
CX2SA > SATDIG 05.09.09 05:15l 889 Lines 31733 Bytes #999 (0) @ WW
BID : 65322-CX2SA
Read: GUEST
Subj: AMSAT-BB-digest V4 448
Path: IZ3LSV<IK3GET<IW2OHX<OE6XPE<OE2XEL<DB0PM<DB0FHN<DB0MRW<DK0WUE<DB0RES<
IK2XDE<PY1AYH<PY1AYH<CX2SA
Sent: 090904/2359Z @:CX2SA.LAV.URY.SA #:65322 [Minas] FBB7.00e $:65322-CX2SA
From: CX2SA@CX2SA.LAV.URY.SA
To : SATDIG@WW
Today's Topics:
1. Re: Why PCSAT is hard to recover (Roger Kolakowski)
2. FO-29 schedule (Mineo Wakita)
3. Re: Why PCSAT is hard to recover (Armour, Randy (ITS))
4. Re: Trolls on the -bb (Bob McGwier)
5. Re: Trolls on the -bb (Robert Bruninga)
6. Re: Why PCSAT is hard to recover (Robert Bruninga)
7. CUTE-I silent (Mike Rupprecht)
----------------------------------------------------------------------
Message: 1
Date: Fri, 4 Sep 2009 10:21:40 -0400
From: "Roger Kolakowski" <rogerkola@xxx.xxx>
Subject: [amsat-bb] Re: Why PCSAT is hard to recover
To: <bruninga@xxxx.xxx>, "'Patrick Green'" <pagreen@xxxxx.xxx>
Cc: amsat-bb@xxxxx.xxx
Message-ID: <007501ca2d6b$055e57e0$0300a8c0@xxxxxxxx>
Content-Type: text/plain; charset="iso-8859-1"
Thank you Bob...
You always have a refreshing, clear, informative response for any inquiry
into your systems.
The fact that you recognize a design error publicly reassures us neophytes
that new designs are built considering past events.
It's always a pleasure hearing one of your explanations.
Roger
WA1KAT
----- Original Message -----
From: "Robert Bruninga" <bruninga@xxxx.xxx>
To: "'Patrick Green'" <pagreen@xxxxx.xxx>
Cc: <amsat-bb@xxxxx.xxx>
Sent: Friday, September 04, 2009 9:44 AM
Subject: [amsat-bb] Why PCSAT is hard to recover
> > Why is pcsat having so much trouble
> > carrying its 5 watts then? Even
> > when the satellite is in full sun?
> > Even on the Z panel? ...what went wrong.
>
> Error in design. Since it was our first satellite, and the
> first time that hamtronics TX and RX were flown in space, we put
> in multiple redundancy. Two identical RX=>TNC=>TX systems. We
> thought the most important thing was the command link.
>
> To make sure we could still access both TNC systems even with a
> TX or RX failure we added a second UHF RX to both systems. In
> additionl we had a relay to CROSS-CONNECT the transmitters.
>
> THen we made the mistake. We assumed that to recover from an
> anomoly, the most important thing was to regain the command
> link. Hence, from cold-boot, the spare UHF receivers would both
> come on AND the transmitters would be cross-connected. This
> assured we could access either TNC even if we had lost one RX or
> one TX.
>
> The mistake was assuming that in such a recovery effort, the
> first thing we would then do is TURN OFF the extra receivers and
> DISCONNNECT the cross conneced transmitters once we had command.
>
> Well... DUH.... If the reason the spacecraft crashed back to
> defaults was because it was low on power, then the last thing
> you want to do is QUADRUPLE the power budget by having the
> recovery-defaults turn on double the number of receivers and
> double the number of transmitters!
>
> So we need FOUR times the average power just to get command and
> that only happens during mid-day passes during maximum eclipse
> periods, and sometimes right at the beginning of full sun
> periods in the southern hemisphere.
> Our first commmand then IN SEQUENCE is
> 1) LOGON
> 2) Send command to separate the transmitters
> 3) Send command to turn off the two spare UHF reciverss
>
> If those are successful, AND PCSAT then has a full orbit in full
> sun, then we can recover. But the loggon password challenge
> from the satellite is the LONGEST packet in the command
> sequence, and if is not successful on the FIRST try, then the
> battery is exhausted and you loose the pass.
>
> Bob, Wb4APR
> >
> > On Sep 3, 2009, at 17:34, "Robert Bruninga"
> <bruninga@xxxx.xxx> wrote:
> >
> > >> To get good coverage you need as many
> > >> LEO satellites as possible so they should
> > >> each be as small as possible.
> > >> Intersatellite linking could be done
> > >> via automated ground stations. This
> > >> eliminates the need for high-power
> > >> transmtters and/or high-gain antennas
> > >> on the satellites for interlinkng.
> > >
> > > Yep, that is what we have been trying to do now for 8 years
> with
> > > the APRS satellites on 145.825. We just need several of
> them in
> > > orbit at the same time. We have demonstrated dual-hops
> several
> > > times whenever two or more of the APRS satellites (and
> ARISS)
> > > are operational at the same time. If we could get 6 to 10
> of
> > > the University cubesats to simply carry the 3.4" square APRS
> > > transponder (Byonics TinyTrck-4), then we would have a
> > > constellation providing nearly continuous connectivity via
> these
> > > satellites from any handheld or mobile APRS radio. With 6,
> you
> > > might have to wait 30 minutes or so to make yoru contacts.
> With
> > > 10 or so, you might have to wit no more than 5 to 10 minutes
> for
> > > connectivity.
> > >
> > > See www.aprs.org/cubesat-comms.html
> > >
> > >> It's better to put that gain and power
> > >> consumption on earth.
> > >
> > > The advantage of the APRS satellite concept and Packet, is
> that
> > > we can use a 5 Watt transmitter on the satellite to be able
> to
> > > hit any mobile or HT using its existing omni antenna because
> the
> > > packet has a low dutycycle. So running 5 watts on a cubesat
> is
> > > easy, because the transmitter dutycycle is only on less than
> say
> > > 5% of the whole-orbit time. (average power 1/4 Watt)
> > >
> > > Whereas ECHO which is on all the time, has to be set at 1/4
> watt
> > > TX power because it is on all the time.
> > >
> > > Also, EVERY APRS satellite would be on the same frequency
> > > 145.825 with no doppler to track, and since every one of
> them
> > > does the same generic relay, independent of callsign, then
> the
> > > user on the ground just operates... He does not have to do
> > > anything to go from one satellite to another...
> > >
> > > Bob, WB4APR
> > >
> > > _______________________________________________
> > > Sent via AMSAT-BB@xxxxx.xxx. Opinions expressed are those of
> the
> > > author.
> > > Not an AMSAT-NA member? Join now to support the amateur
> satellite
> > > program!
> > > Subscription settings:
> http://amsat.org/mailman/listinfo/amsat-bb
> >
>
> _______________________________________________
> Sent via AMSAT-BB@xxxxx.xxx. Opinions expressed are those of the author.
> Not an AMSAT-NA member? Join now to support the amateur satellite program!
> Subscription settings: http://amsat.org/mailman/listinfo/amsat-bb
>
------------------------------
Message: 2
Date: Fri, 04 Sep 2009 23:58:31 +0900
From: Mineo Wakita <ei7m-wkt@xxxxxxxxx.xx.xx>
Subject: [amsat-bb] FO-29 schedule
To: amsat-bb@xxxxx.xxx
Message-ID: <8CA2D702B4AA3ei7m-wkt@xxxxxxxxx.xx.xx>
Content-Type: text/plain; charset=us-ascii
4 Sep 22:45UTC
5 Sep 21:50UTC
JE9PEL, Mineo Wakita
------------------------------
Message: 3
Date: Fri, 4 Sep 2009 10:06:05 -0500
From: "Armour, Randy (ITS)" <Randy.Armour@xxxxxxxxx.xxx>
Subject: [amsat-bb] Re: Why PCSAT is hard to recover
To: <amsat-bb@xxxxx.xxx>
Message-ID:
<2E3F2E495FDB0D4B93F9DAA80AE3A4840C42D940@xxxxxxxxxxx.xxxxxxxxx.xxx>
Content-Type: text/plain; charset="us-ascii"
I would like to reiterate the sentiment Roger states. This list is
occasionally overtaken by emotionally charged "shoulda-woulda-coulda"
threads. Bob's clear and concise posts, that are understandable by those
of us that are not satellite experts, continue to make the Amsat-bb list
worthy of a daily read.
Randy
KI4LMR
-----Original Message-----
From: amsat-bb-bounces@xxxxx.xxx [mailto:amsat-bb-bounces@xxxxx.xxxx On
Behalf Of Roger Kolakowski
Sent: Friday, September 04, 2009 9:22 AM
To: bruninga@xxxx.xxxx 'Patrick Green'
Cc: amsat-bb@xxxxx.xxx
Subject: [amsat-bb] Re: Why PCSAT is hard to recover
Thank you Bob...
You always have a refreshing, clear, informative response for any
inquiry
into your systems.
The fact that you recognize a design error publicly reassures us
neophytes
that new designs are built considering past events.
It's always a pleasure hearing one of your explanations.
Roger
WA1KAT
----- Original Message -----
From: "Robert Bruninga" <bruninga@xxxx.xxx>
To: "'Patrick Green'" <pagreen@xxxxx.xxx>
Cc: <amsat-bb@xxxxx.xxx>
Sent: Friday, September 04, 2009 9:44 AM
Subject: [amsat-bb] Why PCSAT is hard to recover
> > Why is pcsat having so much trouble
> > carrying its 5 watts then? Even
> > when the satellite is in full sun?
> > Even on the Z panel? ...what went wrong.
>
> Error in design. Since it was our first satellite, and the
> first time that hamtronics TX and RX were flown in space, we put
> in multiple redundancy. Two identical RX=>TNC=>TX systems. We
> thought the most important thing was the command link.
>
> To make sure we could still access both TNC systems even with a
> TX or RX failure we added a second UHF RX to both systems. In
> additionl we had a relay to CROSS-CONNECT the transmitters.
>
> THen we made the mistake. We assumed that to recover from an
> anomoly, the most important thing was to regain the command
> link. Hence, from cold-boot, the spare UHF receivers would both
> come on AND the transmitters would be cross-connected. This
> assured we could access either TNC even if we had lost one RX or
> one TX.
>
> The mistake was assuming that in such a recovery effort, the
> first thing we would then do is TURN OFF the extra receivers and
> DISCONNNECT the cross conneced transmitters once we had command.
>
> Well... DUH.... If the reason the spacecraft crashed back to
> defaults was because it was low on power, then the last thing
> you want to do is QUADRUPLE the power budget by having the
> recovery-defaults turn on double the number of receivers and
> double the number of transmitters!
>
> So we need FOUR times the average power just to get command and
> that only happens during mid-day passes during maximum eclipse
> periods, and sometimes right at the beginning of full sun
> periods in the southern hemisphere.
> Our first commmand then IN SEQUENCE is
> 1) LOGON
> 2) Send command to separate the transmitters
> 3) Send command to turn off the two spare UHF reciverss
>
> If those are successful, AND PCSAT then has a full orbit in full
> sun, then we can recover. But the loggon password challenge
> from the satellite is the LONGEST packet in the command
> sequence, and if is not successful on the FIRST try, then the
> battery is exhausted and you loose the pass.
>
> Bob, Wb4APR
> >
> > On Sep 3, 2009, at 17:34, "Robert Bruninga"
> <bruninga@xxxx.xxx> wrote:
> >
> > >> To get good coverage you need as many
> > >> LEO satellites as possible so they should
> > >> each be as small as possible.
> > >> Intersatellite linking could be done
> > >> via automated ground stations. This
> > >> eliminates the need for high-power
> > >> transmtters and/or high-gain antennas
> > >> on the satellites for interlinkng.
> > >
> > > Yep, that is what we have been trying to do now for 8 years
> with
> > > the APRS satellites on 145.825. We just need several of
> them in
> > > orbit at the same time. We have demonstrated dual-hops
> several
> > > times whenever two or more of the APRS satellites (and
> ARISS)
> > > are operational at the same time. If we could get 6 to 10
> of
> > > the University cubesats to simply carry the 3.4" square APRS
> > > transponder (Byonics TinyTrck-4), then we would have a
> > > constellation providing nearly continuous connectivity via
> these
> > > satellites from any handheld or mobile APRS radio. With 6,
> you
> > > might have to wait 30 minutes or so to make yoru contacts.
> With
> > > 10 or so, you might have to wit no more than 5 to 10 minutes
> for
> > > connectivity.
> > >
> > > See www.aprs.org/cubesat-comms.html
> > >
> > >> It's better to put that gain and power
> > >> consumption on earth.
> > >
> > > The advantage of the APRS satellite concept and Packet, is
> that
> > > we can use a 5 Watt transmitter on the satellite to be able
> to
> > > hit any mobile or HT using its existing omni antenna because
> the
> > > packet has a low dutycycle. So running 5 watts on a cubesat
> is
> > > easy, because the transmitter dutycycle is only on less than
> say
> > > 5% of the whole-orbit time. (average power 1/4 Watt)
> > >
> > > Whereas ECHO which is on all the time, has to be set at 1/4
> watt
> > > TX power because it is on all the time.
> > >
> > > Also, EVERY APRS satellite would be on the same frequency
> > > 145.825 with no doppler to track, and since every one of
> them
> > > does the same generic relay, independent of callsign, then
> the
> > > user on the ground just operates... He does not have to do
> > > anything to go from one satellite to another...
> > >
> > > Bob, WB4APR
> > >
> > > _______________________________________________
> > > Sent via AMSAT-BB@xxxxx.xxx. Opinions expressed are those of
> the
> > > author.
> > > Not an AMSAT-NA member? Join now to support the amateur
> satellite
> > > program!
> > > Subscription settings:
> http://amsat.org/mailman/listinfo/amsat-bb
> >
>
> _______________________________________________
> Sent via AMSAT-BB@xxxxx.xxx. Opinions expressed are those of the
author.
> Not an AMSAT-NA member? Join now to support the amateur satellite
program!
> Subscription settings: http://amsat.org/mailman/listinfo/amsat-bb
>
_______________________________________________
Sent via AMSAT-BB@xxxxx.xxx. Opinions expressed are those of the author.
Not an AMSAT-NA member? Join now to support the amateur satellite
program!
Subscription settings: http://amsat.org/mailman/listinfo/amsat-bb
------------------------------
Message: 4
Date: Fri, 04 Sep 2009 11:34:38 -0400
From: Bob McGwier <rwmcgwier@xxxxx.xxx>
Subject: [amsat-bb] Re: Trolls on the -bb
To: "Timothy J. Salo" <salo@xxxxxxx.xxx>
Cc: amsat-bb@xxxxx.xxx
Message-ID: <4AA1338E.1090406@xxxxx.xxx>
Content-Type: text/plain; charset=ISO-8859-1; format=flowed
I have always enjoyed being told I was an idiot for not doing something
I actually did (in this case we). We have and I bet still are pursuing
these opportunities. I don't know, I am on the outside looking in (by
choice). Like all things it is always easy to say "why don't you?"
rather than to ask "did you?" and then ask "why has it not worked?" and
"may I be of some service?". (Don't bother now, you have surely pissed
a bunch of people off). But you were not really looking for
information here were you?. Having lived in a few glass houses, I
recommend not getting into stone throwing and to go positive. It is
always why don't "they" isn't it, why is that? If you have influence
with STP that would be good to offer. You should probably know ahead
of time that the immediate past president of AMSAT worked on and flew
a satellite in the STP program (Midstar) and even with that level of
connection we have gained no traction.
The "up front" buy in is very hard to get. STP may seem like it is open
"to all" but the reality feels a whole lot like some completely
different than "open to all" and that some pretty sure ideas of who
would get these rides was done ahead of time and includes but is not
necessarily limited to the owners of Midstar and related institutions as
being examples of the "good guys". AMSAT not being a good guy, we
can't even get an invite to a meeting on how to get invited.
The general tone of the amsat-bb these days seems to be condemnation of
failure to achieve the near impossible rather than asking for an
accounting of why it is so difficult over and over. I see that even
then, people will (in their understandable frustration) lash out and
call you a bum and a liar. Even when explanations of the difficulty are
provided, they appear to fall on deaf ears and blind eyes. Karl
Meinzer, he of the "never failed to get one before" launch history, has
utterly failed to get a ride for P3e. We in amsat-na tried in all
sorts of ways to help get this going. We built equipment for it and
helped in other ways and even paid for ongoing support of housing P3e
(done in open board meetings and I believe that every single one of the
motions for $$ support in these board meetings was made by me). We then
ran head long into the HORROR of ITAR. Please read the president's
message here
http://www.amsat.org/amsat-new/index.php
of how it has taken years and tens of thousand of dollars in legal fees
to just get a "you have been bad, don't be bad again or you will be
fined and maybe clobbered". And only after all of that can we now ask
officially can we PLEASE go play with our friends in the amateur radio
sandbox?
If at 56 I have learned anything at all from my failures and successes
it is that it is always better to walk a mile in someone else's shoes
before throwing a stone and if you cannot get anyone to listen to you,
give up before you sound like a shrill moron and live to fight another
day. I am certain this is a lesson it is better to learn late than not
at all.
Bob
N4HY
Timothy J. Salo wrote:
> John B. Stephensen wrote:
>
>> P3E is a HEO with the same engine as P3D and no benefactor funding a
launch.
>> It seems more reasonable to focus on projects that we can pay to launch or
>> where someone has already donated the launch.
>>
>
> I believe that AMSAT should at least consider using the DoD
> Space Test Program (STP), which provides launches for satellites
> of interest to the federal government. In fact, the STP has
> already launched a number of amateur satellites. Of course, HEO
> launches will still be hard to come by. But, I think it is
> pretty clear that amateurs can't afford an HEO launch, so we
> ought to at least try to find someone else to pay for it.
>
> But, in order to get the government to pay, we need to tell
> a story that the government is interested in. In my view,
> the federal government is most likely to fund at least two
> types of projects:
>
> o Projects that develop the next generation of space
> scientists and engineers. (This is a large part of the
> reason NASA funds ARISS and SAREX activities. I think
> this is also why the Naval Academy stuff gets launched.)
>
> o Research projects. Note that AO-40 actually flew a NASA
> GPS experiment that resulted in at least one journal
> article. Unfortunately, no one seems to want to talk
> about research experiments that have flown on, and often
> subsidized, amateur satellites (much less display this
> information prominently on the AMSAT Web pages).
>
> Perhaps more importantly, I don't believe that the federal
> government is likely to fund us primarily to provide
> emergency communications. There are simply too many other
> alternatives available today: satellite phones,
> cellular-base-stations-on-a-truck, and lots of fixed and
> portable satellite ground stations.
>
> If you have an interest in this topic, you might want to read
> my DoD Space Test Program paper. (Unlike most AMSAT Symposium
> presentations, it is available on the Internet. But, that is
> another difficult topic for AMSAT...)
>
> But, to be able to successfully tell these stories, AMSAT
> needs to attract new classes of members, particularly
> today's and tomorrow's engineers, scientists, and technically
> curious. And, to attract these new classes of members, I
> believe that AMSAT will need to update some of its views.
> The Web is vitally important: it is probably the dominant
> portion of AMSAT's public face seen by prospective members
> and prospective funding agencies. For example, all the
> excellent material published in the Journal would benefit
> AMSAT much more if it was available on the Web.
>
> By the way, the AFRL University Nanosatellite Program (UNP)
> Web site [!] says that 3,500 students have participated in
> the program over the last decade. Every one of these
> young people has a demonstrated interest in building satellites.
> AMSAT ought to consider every one of them a prospective member
> and volunteer.
>
> (I also believe that many of these types of prospective
> members that AMSAT needs in order to be successful expect
> a voluntary organization like AMSAT to operate transparently,
> and for its directors and officers to be able to discuss the
> organization in public in a professional manner. Does
> anyone else think that it is ironic that discussions about
> the future of AMSAT are categorized under "troll"?)
>
> -tjs
>
> _______________________________________________
> Sent via AMSAT-BB@xxxxx.xxx. Opinions expressed are those of the author.
> Not an AMSAT-NA member? Join now to support the amateur satellite program!
> Subscription settings: http://amsat.org/mailman/listinfo/amsat-bb
>
>
--
(Co)Author: DttSP, Quiktrak, PowerSDR, GnuRadio
Member: ARRL, AMSAT, AMSAT-DL, TAPR, Packrats,
NJQRP, QRP ARCI, QCWA, FRC.
"You don't need to see the whole staircase, just
take the first step.", MLK.
Twitter:rwmcgwier
Active: Facebook,Myspace,LinkedIn
------------------------------
Message: 5
Date: Fri, 4 Sep 2009 13:07:31 -0400
From: "Robert Bruninga" <bruninga@xxxx.xxx>
Subject: [amsat-bb] Re: Trolls on the -bb
To: <amsat-bb@xxxxx.xxx>
Message-ID: <A04427309B23459FAAB7706CA18D0867@xxxxx.xxxx.xxx>
Content-Type: text/plain; charset="US-ASCII"
I can clarify this:
>> I believe that AMSAT should at least
>> consider using the DoD Space Test
>> Program (STP), which provides launches
>> for satellites of interest to the US
>> federal government.
Its not the Feds, its only DOD exclusively. Not even NASA can
participate in STP. We have been briefing the STP for a decade
now, and are very familiar with the process. And it is not even
close to "open to all".
It is a Department of Defense program that priortizes DOD
payloads. Nothing else. And the number one selection criteria
is "DOD Relevance".
>> In fact, the STP has already launched a
>> number of amateur satellites.
Sort-of. The Naval Academy and NRL have gotten a few rides to
space, but not because they met STP criteria. Our only DOD
relevance is "space education" and even that is evaluated dead
last (65 out of 65)... Our rides were mostly out of back door
luck. It only works if someone is on the inside, and a lucky
opportunity is found(see below).
>> But, in order to get the government to
>> pay, we need to tell a story that the
>> government is interested in.
>>
>> o Projects that develop the next
>> generation of space scientists/engineers.
Our briefs are exactly on that basis and we are always evaluated
dead last.
>> o Research projects. ...
>>
>> o [emergency comms] ... I don't believe
>> that the fed... is likely to fund us
>> primarily to provide emergency comms.
>> There are simply too many other
>> alternatives available today...
True, except, they all need infrastructure and investment, and
they all want hundreds of megabits per second all the time! From
anywhere anytime... They kill any modest idea with chrushing
requirements creep.
Once, when explaining this crushing demand which dooms almost
every simple solution, I did get a great comment in support of
the KISS principle from the skipper of a Nuclear Sub. While
describing my attempts to get the 145.825 MHz Packet digipeater
satellites operating at 1200 baud to support HT and Mobile
amateur radio emergency text messaging (APRS), his comment was
something like this:..
"1200 baud? Great! When my sub has NO COMMS AT ALL, a 1200
baud CHAT channel sounds FANTASTIC!"...
And look at the popularity of text messaging, IM, Twitter, etc.
A lot can be said in a few dozen bytes. We should concentrate
on the KISS principle...
>> By the way, the AFRL University
>> Nanosatellite Program (UNP) Web
>> site [!] says that 3,500 students
>> have participated in the program
>> over the last decade.
Yes! And most of the time when I meet these students at
conferences, etc, they are not hams and have no idea what the
amateur radio hobby is about, and so they are not like us,
focused on the comms, but instead are focused on something else.
My comments about getting a launch through STP may sound
negative, but they are not. They are simply saying that the way
through STP has to be at the backdoor, through the STUDENTS and
the UNIVERSITIES. That is where we are failing to make the
contacts and mentoring them through the joy of communictions as
an end in itself.
If they WANT to communicate and let others communicate, then
they WILL find a way to wriggle it on board as part of their
"research" and their "education"... And I can think of no
better proponents for modest data-rate TEXT MESSAGING, then the
teens and 20-somethings that live and breath it.
See my article on Universal HAM Radio Text Messaging in the Sept
QST. And or this web page: www.aprs.org/aprs-messaging.html
Anyway, we need to mentor the students (or anyone else that has
backdoor access to potential projects that might fly). A modern
amateur radio transponder can be the size of a pack of cigaretts
and can fit on just about anyone else's ride...
Bob, Wb4APR
------------------------------
Message: 6
Date: Fri, 4 Sep 2009 13:16:34 -0400
From: "Robert Bruninga" <bruninga@xxxx.xxx>
Subject: [amsat-bb] Re: Why PCSAT is hard to recover
To: <amsat-bb@xxxxx.xxx>
Message-ID: <73DB15041DFA49FDAA60C55BE4C4E6BD@xxxxx.xxxx.xxx>
Content-Type: text/plain; charset="US-ASCII"
> Is this cross-connect sequence hard coded
> in the firmware? No way to replace that
> small bit of code directly from earth?
We used the KISS principle and since we had no programmers on
the team, we put no cotroller or CPU on board. PCSAT is nothing
but a pair of TNC's, and pairs of TX and RX's. And a simple 555
timer chip that reboots them if they have not beaconed in over a
minute.
The STOCK TNC's have all the command, control, telemetry, I/O we
needed. All of our satellites to date flew with nothing but a
TNC as the "system" with the 555 backup timer as a fail safe
reset.
Bob
> On 9/4/09 9:44 AM, "Robert Bruninga" <bruninga@xxxx.xxx>
wrote:
>
> >> Why is pcsat having so much trouble
> >> carrying its 5 watts then? Even
> >> when the satellite is in full sun?
> >> Even on the Z panel? ...what went wrong.
> >
> > Error in design. Since it was our first satellite, and the
> > first time that hamtronics TX and RX were flown in space, we
put
> > in multiple redundancy. Two identical RX=>TNC=>TX systems.
We
> > thought the most important thing was the command link.
> >
> > To make sure we could still access both TNC systems even
with a
> > TX or RX failure we added a second UHF RX to both systems.
In
> > additionl we had a relay to CROSS-CONNECT the transmitters.
> >
> > THen we made the mistake. We assumed that to recover from
an
> > anomoly, the most important thing was to regain the command
> > link. Hence, from cold-boot, the spare UHF receivers would
both
> > come on AND the transmitters would be cross-connected. This
> > assured we could access either TNC even if we had lost one
RX or
> > one TX.
> >
> > The mistake was assuming that in such a recovery effort, the
> > first thing we would then do is TURN OFF the extra receivers
and
> > DISCONNNECT the cross conneced transmitters once we had
command.
> >
> > Well... DUH.... If the reason the spacecraft crashed back to
> > defaults was because it was low on power, then the last
thing
> > you want to do is QUADRUPLE the power budget by having the
> > recovery-defaults turn on double the number of receivers and
> > double the number of transmitters!
> >
> > So we need FOUR times the average power just to get command
and
> > that only happens during mid-day passes during maximum
eclipse
> > periods, and sometimes right at the beginning of full sun
> > periods in the southern hemisphere.
> > Our first commmand then IN SEQUENCE is
> > 1) LOGON
> > 2) Send command to separate the transmitters
> > 3) Send command to turn off the two spare UHF reciverss
> >
> > If those are successful, AND PCSAT then has a full orbit in
full
> > sun, then we can recover. But the loggon password challenge
> > from the satellite is the LONGEST packet in the command
> > sequence, and if is not successful on the FIRST try, then
the
> > battery is exhausted and you loose the pass.
> >
> > Bob, Wb4APR
> >>
> >> On Sep 3, 2009, at 17:34, "Robert Bruninga"
> > <bruninga@xxxx.xxx> wrote:
> >>
> >>>> To get good coverage you need as many
> >>>> LEO satellites as possible so they should
> >>>> each be as small as possible.
> >>>> Intersatellite linking could be done
> >>>> via automated ground stations. This
> >>>> eliminates the need for high-power
> >>>> transmtters and/or high-gain antennas
> >>>> on the satellites for interlinkng.
> >>>
> >>> Yep, that is what we have been trying to do now for 8
years
> > with
> >>> the APRS satellites on 145.825. We just need several of
> > them in
> >>> orbit at the same time. We have demonstrated dual-hops
> > several
> >>> times whenever two or more of the APRS satellites (and
> > ARISS)
> >>> are operational at the same time. If we could get 6 to 10
> > of
> >>> the University cubesats to simply carry the 3.4" square
APRS
> >>> transponder (Byonics TinyTrck-4), then we would have a
> >>> constellation providing nearly continuous connectivity via
> > these
> >>> satellites from any handheld or mobile APRS radio. With
6,
> > you
> >>> might have to wait 30 minutes or so to make yoru contacts.
> > With
> >>> 10 or so, you might have to wit no more than 5 to 10
minutes
> > for
> >>> connectivity.
> >>>
> >>> See www.aprs.org/cubesat-comms.html
> >>>
> >>>> It's better to put that gain and power
> >>>> consumption on earth.
> >>>
> >>> The advantage of the APRS satellite concept and Packet, is
> > that
> >>> we can use a 5 Watt transmitter on the satellite to be
able
> > to
> >>> hit any mobile or HT using its existing omni antenna
because
> > the
> >>> packet has a low dutycycle. So running 5 watts on a
cubesat
> > is
> >>> easy, because the transmitter dutycycle is only on less
than
> > say
> >>> 5% of the whole-orbit time. (average power 1/4 Watt)
> >>>
> >>> Whereas ECHO which is on all the time, has to be set at
1/4
> > watt
> >>> TX power because it is on all the time.
> >>>
> >>> Also, EVERY APRS satellite would be on the same frequency
> >>> 145.825 with no doppler to track, and since every one of
> > them
> >>> does the same generic relay, independent of callsign, then
> > the
> >>> user on the ground just operates... He does not have to do
> >>> anything to go from one satellite to another...
> >>>
> >>> Bob, WB4APR
> >>>
> >>> _______________________________________________
> >>> Sent via AMSAT-BB@xxxxx.xxx. Opinions expressed are those
of
> > the
> >>> author.
> >>> Not an AMSAT-NA member? Join now to support the amateur
> > satellite
> >>> program!
> >>> Subscription settings:
> > http://amsat.org/mailman/listinfo/amsat-bb
> >>
> >
> > _______________________________________________
> > Sent via AMSAT-BB@xxxxx.xxx. Opinions expressed are those
> of the author.
> > Not an AMSAT-NA member? Join now to support the amateur
> satellite program!
> > Subscription settings:
http://amsat.org/mailman/listinfo/amsat-bb
> >
>
>
>
------------------------------
Message: 7
Date: Fri, 4 Sep 2009 19:36:49 +0200
From: "Mike Rupprecht" <mail@xxxxxxxxxxxxxx.xx>
Subject: [amsat-bb] CUTE-I silent
To: <amsat-bb@xxxxx.xxx>
Message-ID: <003a01ca2d86$4865d020$d9317060$@xx>
Content-Type: text/plain; charset="us-ascii"
17:30 UTC - 45 deg pass - nothing heard from CUTE-I over Europe.
Can anyone confirm this, please ?
73, Mike
DK3WN
------------------------------
_______________________________________________
Sent via amsat-bb@xxxxx.xxx. Opinions expressed are those of the author.
Not an AMSAT member? Join now to support the amateur satellite program!
http://amsat.org/mailman/listinfo/amsat-bb
End of AMSAT-BB Digest, Vol 4, Issue 448
****************************************
Read previous mail | Read next mail
| |
