Arecibo shutdown...

[Joe Gwinn]

On Wed, 2 Dec 2020 22:34:33 -0500, Phil Hobbs
<pcdhSpamMeSenseless@electrooptical.net> wrote:

On 12/2/20 10:46 AM, legg wrote:
On Wed, 02 Dec 2020 09:25:24 GMT, Jan Panteltje
pNaOnStPeAlMtje@yahoo.com> wrote:

On a sunny day (Tue, 01 Dec 2020 15:57:35 -0500) it happened legg
legg@nospam.magma.ca> wrote in <scbdsf9mspikb9q4eciiac8jvkun51im4n@4ax.com>:

On Thu, 19 Nov 2020 22:56:03 GMT, Steve Wilson <spam@me.com> wrote:

Arecibo has reached EOL.

https://arstechnica.com/science/2020/11/famed-arecibo-observatory-to-be-
decommissioned-in-wake-of-cable-breaks/

Arecibo workers seem rather lackadaisical about it all.

Why is nobody shouting \'incompetent gits\'?

Was there no maintenance budget?

Didn\'t an alarm go off after the first stress failure?

RL

Good point!
I did read they had 3 companies evaluate the structure,
2 said beyond repair.
Majority rule and science...
Politics and science do not always mix well.

I wonder how many other expensive toys the Univ of Central
Florida is currently abusing - and what others they may be
planning to acquire, with their twisted priorities?

RL

Arecibo was chronically underfunded for at least 20 years, long before
UCF got involved. The NSF said in 2007 that it might have to close for
budgetary reasons.

UCF got called in to rescue it in 2016, but ran out of time.

Yes. NSF has been trying to close Arecibo forever, and the first
thing to be cut is maintenance.

With cable-suspended structures (like many bridges), rusting in the
cores of the cables will always lead to failure of the entire
structure. I\'m sure that there was a cable-replacement schedule
somewhere now forgotten, because nobody was ready to buck up the
money.

Sort of like replacing HV transmission lines in California more often
than once per century, with line lifetimes being 20-30 years.

Anyway, I bet that the NSF is in fact quietly happy now.

I doubt that Arecibo will be repaired. It may perhaps be replaced
with a brand new modern telescope of similar purpose. The academic
and practical infrastructure is already there.

Hmm. Except that the hollow in which the current dish was built is
too small to compete with the new Chinese telescope of similar design.
But Chinese competition may be just the ticket to get replacement
funded.

Joe Gwinn

 

[bitrex]

On 12/4/2020 11:35 AM, Joe Gwinn wrote:

On Wed, 2 Dec 2020 22:34:33 -0500, Phil Hobbs
pcdhSpamMeSenseless@electrooptical.net> wrote:

On 12/2/20 10:46 AM, legg wrote:
On Wed, 02 Dec 2020 09:25:24 GMT, Jan Panteltje
pNaOnStPeAlMtje@yahoo.com> wrote:

On a sunny day (Tue, 01 Dec 2020 15:57:35 -0500) it happened legg
legg@nospam.magma.ca> wrote in <scbdsf9mspikb9q4eciiac8jvkun51im4n@4ax.com>:

On Thu, 19 Nov 2020 22:56:03 GMT, Steve Wilson <spam@me.com> wrote:

Arecibo has reached EOL.

https://arstechnica.com/science/2020/11/famed-arecibo-observatory-to-be-
decommissioned-in-wake-of-cable-breaks/

Arecibo workers seem rather lackadaisical about it all.

Why is nobody shouting \'incompetent gits\'?

Was there no maintenance budget?

Didn\'t an alarm go off after the first stress failure?

RL

Good point!
I did read they had 3 companies evaluate the structure,
2 said beyond repair.
Majority rule and science...
Politics and science do not always mix well.

I wonder how many other expensive toys the Univ of Central
Florida is currently abusing - and what others they may be
planning to acquire, with their twisted priorities?

RL

Arecibo was chronically underfunded for at least 20 years, long before
UCF got involved. The NSF said in 2007 that it might have to close for
budgetary reasons.

UCF got called in to rescue it in 2016, but ran out of time.

Yes. NSF has been trying to close Arecibo forever, and the first
thing to be cut is maintenance.

With cable-suspended structures (like many bridges), rusting in the
cores of the cables will always lead to failure of the entire
structure. I\'m sure that there was a cable-replacement schedule
somewhere now forgotten, because nobody was ready to buck up the
money.

Sort of like replacing HV transmission lines in California more often
than once per century, with line lifetimes being 20-30 years.

Anyway, I bet that the NSF is in fact quietly happy now.

I doubt that Arecibo will be repaired. It may perhaps be replaced
with a brand new modern telescope of similar purpose. The academic
and practical infrastructure is already there.

Hmm. Except that the hollow in which the current dish was built is
too small to compete with the new Chinese telescope of similar design.
But Chinese competition may be just the ticket to get replacement
funded.

Joe Gwinn

There was a bunch of swish gear up in the cryogenics/antenna-feed room,
once the first cable snapped I bet nobody went back up there so it\'s all
scrapified, now.

 

[Rick C]

On Wednesday, December 2, 2020 at 2:22:10 PM UTC-5, Martin Brown wrote:

On 02/12/2020 14:13, Rick C wrote:
On Wednesday, December 2, 2020 at 4:24:31 AM UTC-5, Jan Panteltje
wrote:
On a sunny day (Tue, 1 Dec 2020 13:06:09 -0800 (PST)) it happened
Rick C <gnuarm.del...@gmail.com> wrote in
b8fcfb74-c92a-4294...@googlegroups.com>:
\"the unique beam-steering mechanism suspended high above the
reflector dish allowed for a moveable focal point that could aim
at different parts of the sky.\"
That is EXACTLY what the drone gives you

You don\'t actually know anything about it. You have no idea if the
drone would be even remotely useful.

If it was a simple matter of moving the receiving portion of the
antenna, they would not have constructed such an elaborate
apparatus.
Conceptually it is just a simple matter of moving the feed horn so that
it stays at the focus of the object that they are tracking in the sky.

In practice that requires a 3 point suspension and some quite cunning
mathematics to make it happen smoothly and accurately. They are aiming
to maintain phase lock to a fraction of a wavelength.

As built originally it was designed for 430MHz. By the end of its life
and after a great deal of refiguring it was being operated up to 10GHz.

I refer you to the previously quoted text describing \"beam forming\". I don\'t think that equates to chasing a poorly formed focal point of an off axis parabolic reflector.

\"the unique beam-steering mechanism suspended high above the reflector dish allowed for a moveable focal point that could aim at different parts of the sky.\"

I don\'t know the details, but I\'m pretty sure it isn\'t just \"moving the feedhorn\".

The problem here is people who think those involved must not know what they are doing and they themselves must know more. Not uncommon in this group.

--

Rick C.

-- Get 1,000 miles of free Supercharging
-- Tesla referral code - https://ts.la/richard11209

 

[server]

On Wed, 2 Dec 2020 14:39:57 -0800 (PST), Rick C
<gnuarm.deletethisbit@gmail.com> wrote:

On Wednesday, December 2, 2020 at 2:22:10 PM UTC-5, Martin Brown wrote:
On 02/12/2020 14:13, Rick C wrote:
On Wednesday, December 2, 2020 at 4:24:31 AM UTC-5, Jan Panteltje
wrote:
On a sunny day (Tue, 1 Dec 2020 13:06:09 -0800 (PST)) it happened
Rick C <gnuarm.del...@gmail.com> wrote in
b8fcfb74-c92a-4294...@googlegroups.com>:
\"the unique beam-steering mechanism suspended high above the
reflector dish allowed for a moveable focal point that could aim
at different parts of the sky.\"
That is EXACTLY what the drone gives you

You don\'t actually know anything about it. You have no idea if the
drone would be even remotely useful.

If it was a simple matter of moving the receiving portion of the
antenna, they would not have constructed such an elaborate
apparatus.
Conceptually it is just a simple matter of moving the feed horn so that
it stays at the focus of the object that they are tracking in the sky.

In practice that requires a 3 point suspension and some quite cunning
mathematics to make it happen smoothly and accurately. They are aiming
to maintain phase lock to a fraction of a wavelength.

As built originally it was designed for 430MHz. By the end of its life
and after a great deal of refiguring it was being operated up to 10GHz.

Looking at the pictures from the crashed reflector, the edges are
definitively not usable at 10 GHz. Perhaps the center part of the
reflector was coated with more or less solid surface, so at 10 GHz the
effective antenna diameter was perhaps 100 m or less.

I refer you to the previously quoted text describing \"beam forming\". I don\'t think that equates to chasing a poorly formed focal point of an off axis parabolic reflector.

Was the reflector parabolic or just spherical ?

Compare this with TV-satellite receiving systems capable of receiving
multiple TV-satellites in multiple orbital positions by installing a
separate feedhorn for each orbital position. Thus about +/-20 degree
orbital positions can be handled simultaneous. The reflector is
spherical so that the error for the extreme satellites is smaller on
average than with a truly parabolic reflector.

\"the unique beam-steering mechanism suspended high above the reflector dish allowed for a moveable focal point that could aim at different parts of the sky.\"

I don\'t know the details, but I\'m pretty sure it isn\'t just \"moving the feedhorn\".

The problem here is people who think those involved must not know what they are doing and they themselves must know more. Not uncommon in this group.

 

[Phil Hobbs]

On 12/2/20 10:46 AM, legg wrote:

On Wed, 02 Dec 2020 09:25:24 GMT, Jan Panteltje
pNaOnStPeAlMtje@yahoo.com> wrote:

On a sunny day (Tue, 01 Dec 2020 15:57:35 -0500) it happened legg
legg@nospam.magma.ca> wrote in <scbdsf9mspikb9q4eciiac8jvkun51im4n@4ax.com>:

On Thu, 19 Nov 2020 22:56:03 GMT, Steve Wilson <spam@me.com> wrote:

Arecibo has reached EOL.

https://arstechnica.com/science/2020/11/famed-arecibo-observatory-to-be-
decommissioned-in-wake-of-cable-breaks/

Arecibo workers seem rather lackadaisical about it all.

Why is nobody shouting \'incompetent gits\'?

Was there no maintenance budget?

Didn\'t an alarm go off after the first stress failure?

RL

Good point!
I did read they had 3 companies evaluate the structure,
2 said beyond repair.
Majority rule and science...
Politics and science do not always mix well.

I wonder how many other expensive toys the Univ of Central
Florida is currently abusing - and what others they may be
planning to acquire, with their twisted priorities?

RL

Arecibo was chronically underfunded for at least 20 years, long before
UCF got involved. The NSF said in 2007 that it might have to close for
budgetary reasons.

UCF got called in to rescue it in 2016, but ran out of time.

Cheers

Phil Hobbs

--
Dr Philip C D Hobbs
Principal Consultant
ElectroOptical Innovations LLC / Hobbs ElectroOptics
Optics, Electro-optics, Photonics, Analog Electronics
Briarcliff Manor NY 10510

http://electrooptical.net
http://hobbs-eo.com

 

[Jan Panteltje]

On a sunny day (Wed, 2 Dec 2020 09:52:42 +0000) it happened Martin Brown
<\'\'\'newspam\'\'\'@nonad.co.uk> wrote in <rq7o5a$107f$1@gioia.aioe.org>:

On 02/12/2020 09:35, Jan Panteltje wrote:
On a sunny day (Wed, 2 Dec 2020 09:19:04 +0000) it happened Martin Brown
\'\'\'newspam\'\'\'@nonad.co.uk> wrote in <rq7m68$gn$1@gioia.aioe.org>:

Accuracy with differential GPS is within some centimeters, but of course you could use lasers etc
and even cameras for position control.
Kids stuff.
It is a nice dish, old brains there?

They could operate at up to 8GHz you do the sums (3GHz was more common).
The dish surface figure after its second face lift was good to 2mm.

I\'m not sure how they compensated for wind loading and thermal cable
stretch on the support gantry position but since it obviously worked
they must have been able to do it. Lateral motion doesn\'t hurt so much.

OK
thank you, good info.
But does not seem unsolveable to me with a drone.
Sure in high windloads drone is likely out.
But from an other POV if they just leave the thing as scrap metal now you have nothing.
Drone is also safer for those poor techncians, 2 drones, one for backup.

Sadly I think after this collapse you basically have nothing. It
probably isn\'t worth rebuilding again after this massive setback.

It will leave us a bit blind to near Earth asteroids but there is a very
low probability of a catastrophic Deep Impact event. There are plenty of
optical survey instruments looking as well - unfortunately they are also
about to be blinded by Musk\'s satellite internet constellations.

https://www.space.com/satellite-megaconstellation-impact-astronomy-report.html

Yes, thousands of sats, not only from Musk.
OTOH I am very impressed what he has achieved and for \"modern dishes\"
look at this teardown:
https://arstechnica.com/information-technology/2020/12/teardown-of-dishy-mcflatface-the-spacex-starlink-user-terminal/

Now that is for you RF PCB designers!
So basically an active? array replacing the focusing dish with LNB... flat!
Also Musk will test his new starship second stage to 15 km this week I think.
That dish is REALLY state of the art, you also see those flat dishes for sale now
for normal geostatic satellite receivers, was considering buying one, about 1000$ for
one that automatically steers to satellites, like this:
https://www.cardwriter.nl/selfsat-snipe-4-met-bluetooth-afstandsbediening.html
How big can you make one of those flat receivers - ?

 

[Jan Panteltje]

On a sunny day (Wed, 2 Dec 2020 06:13:19 -0800 (PST)) it happened Rick C
<gnuarm.deletethisbit@gmail.com> wrote in
<57732775-abd9-4257-97dd-4642253bbd34n@googlegroups.com>:

On Wednesday, December 2, 2020 at 4:24:31 AM UTC-5, Jan Panteltje wrote:
On a sunny day (Tue, 1 Dec 2020 13:06:09 -0800 (PST)) it happened Rick C
gnuarm.del...@gmail.com> wrote in
b8fcfb74-c92a-4294...@googlegroups.com>:
\"the unique beam-steering mechanism suspended high above the reflector dish allowed for a moveable focal point that could aim
at
different parts of the sky.\"
That is EXACTLY what the drone gives you

You don\'t actually know anything about it.

Well since I modified the hardware and wrote the soft to control the drone I do about that.
and I have quite some experience using satellites and dishes.
So what\'s your experience with any of those?


>You have no idea if the drone would be even remotely useful.

You are just trolling,

 

[Jan Panteltje]

On a sunny day (Wed, 02 Dec 2020 09:43:48 -0500) it happened legg
<legg@nospam.magma.ca> wrote in <hq9fsfd3po48hu5ne383dm9197oim6793b@4ax.com>:

On Wed, 02 Dec 2020 09:25:24 GMT, Jan Panteltje
pNaOnStPeAlMtje@yahoo.com> wrote:

On a sunny day (Tue, 01 Dec 2020 15:57:35 -0500) it happened legg
legg@nospam.magma.ca> wrote in <scbdsf9mspikb9q4eciiac8jvkun51im4n@4ax.com>:

On Thu, 19 Nov 2020 22:56:03 GMT, Steve Wilson <spam@me.com> wrote:

Arecibo has reached EOL.

https://arstechnica.com/science/2020/11/famed-arecibo-observatory-to-be-
decommissioned-in-wake-of-cable-breaks/

Arecibo workers seem rather lackadaisical about it all.

Why is nobody shouting \'incompetent gits\'?

Was there no maintenance budget?

Didn\'t an alarm go off after the first stress failure?

RL

Good point!
I did read they had 3 companies evaluate the structure,
2 said beyond repair.
Majority rule and science...
Politics and science do not always mix well.

It was administrated by the University of Central Florida.
After the first incident their evaluators said it could
continue functioning - but no repair notice was given.

After the second incident the advice became \'too dangerous
to attempt repair.

You don\'t get a third notice. It collapsed on Tuesday.

RL

Ok
maybe it will end up like the pyramids as a tourist attraction?

 

[Rick C]

On Thursday, December 3, 2020 at 12:48:08 AM UTC-5, Jan Panteltje wrote:

On a sunny day (Wed, 2 Dec 2020 06:13:19 -0800 (PST)) it happened Rick C
gnuarm.del...@gmail.com> wrote in
57732775-abd9-4257...@googlegroups.com>:
On Wednesday, December 2, 2020 at 4:24:31 AM UTC-5, Jan Panteltje wrote:
On a sunny day (Tue, 1 Dec 2020 13:06:09 -0800 (PST)) it happened Rick C
gnuarm.del...@gmail.com> wrote in
b8fcfb74-c92a-4294...@googlegroups.com>:
\"the unique beam-steering mechanism suspended high above the reflector dish allowed for a moveable focal point that could aim
at
different parts of the sky.\"
That is EXACTLY what the drone gives you

You don\'t actually know anything about it.
Well since I modified the hardware and wrote the soft to control the drone I do about that.
and I have quite some experience using satellites and dishes.
So what\'s your experience with any of those?
You have no idea if the drone would be even remotely useful.
You are just trolling,

Not trolling, just calling BS. I know that beam forming involves a lot more than just moving your receiver.

You may know lots about drones, but you seem to not know much about beam forming.

--

Rick C.

-+ Get 1,000 miles of free Supercharging
-+ Tesla referral code - https://ts.la/richard11209

 

[Martin Brown]

On 02/12/2020 22:39, Rick C wrote:

On Wednesday, December 2, 2020 at 2:22:10 PM UTC-5, Martin Brown
wrote:
On 02/12/2020 14:13, Rick C wrote:
On Wednesday, December 2, 2020 at 4:24:31 AM UTC-5, Jan
Panteltje wrote:
On a sunny day (Tue, 1 Dec 2020 13:06:09 -0800 (PST)) it
happened Rick C <gnuarm.del...@gmail.com> wrote in
b8fcfb74-c92a-4294...@googlegroups.com>:
\"the unique beam-steering mechanism suspended high above the
reflector dish allowed for a moveable focal point that could
aim at different parts of the sky.\"
That is EXACTLY what the drone gives you

You don\'t actually know anything about it. You have no idea if
the drone would be even remotely useful.

If it was a simple matter of moving the receiving portion of the
antenna, they would not have constructed such an elaborate
apparatus.
Conceptually it is just a simple matter of moving the feed horn so
that it stays at the focus of the object that they are tracking in
the sky.

In practice that requires a 3 point suspension and some quite
cunning mathematics to make it happen smoothly and accurately. They
are aiming to maintain phase lock to a fraction of a wavelength.

As built originally it was designed for 430MHz. By the end of its
life and after a great deal of refiguring it was being operated up
to 10GHz.

I refer you to the previously quoted text describing \"beam forming\".
I don\'t think that equates to chasing a poorly formed focal point of
an off axis parabolic reflector.

I refer you to the various references that I have already posted. The
main dish is spherical and there are aspherical off axis Gregorian
reflectors inside the radome that bring the raw beam to a precise focus.

http://egg.astro.cornell.edu/alfalfa/ugrad/backgrnd/intro2arecibo.pdf

You don\'t have to take my word for it:

https://www.naic.edu/ao/telescope-description

The sky moves so to observe an object they have to track their target.
Likewise when they are a node in VLBI - where their big dish provided
excellent signal to noise on faint sources but they have a limited time
on track. This is the guide for observers wanting to apply for time to
do VLBI - its tracking range is rather restrictive with declination.

https://www.naic.edu/~astro/aovlbi/#4

https://fermi.gsfc.nasa.gov/science/mtgs/vlbi/Salter-Poster.pdf

I am not sure if they ever did drift scans since the early days.

\"the unique beam-steering mechanism suspended high above the
reflector dish allowed for a moveable focal point that could aim at
different parts of the sky.\"

I don\'t know the details, but I\'m pretty sure it isn\'t just \"moving
the feedhorn\".

Most of it is about precise tracking in terms of a single observation.
The tracking movement is typically precomputed and run from tapes on
these older instruments. Though they may now do it from solid state.

Between observations they can change which front end receiver antenna is
actually at the focus. They have ~5\" arc pointing accuracy.

The problem here is people who think those involved must not know
what they are doing and they themselves must know more. Not
uncommon in this group.

You are talking to a former radio astronomer. Although I did very little
observational work with big single dishes I do know people who did.

--
Regards,
Martin Brown

 

[Jan Panteltje]

On a sunny day (Wed, 2 Dec 2020 22:31:04 -0800 (PST)) it happened Rick C
<gnuarm.deletethisbit@gmail.com> wrote in
<96e90652-7120-4ee0-bc66-c6ea4c5303f5n@googlegroups.com>:

On Thursday, December 3, 2020 at 12:48:08 AM UTC-5, Jan Panteltje wrote:
On a sunny day (Wed, 2 Dec 2020 06:13:19 -0800 (PST)) it happened Rick C
gnuarm.del...@gmail.com> wrote in
57732775-abd9-4257...@googlegroups.com>:
On Wednesday, December 2, 2020 at 4:24:31 AM UTC-5, Jan Panteltje wrote:
On a sunny day (Tue, 1 Dec 2020 13:06:09 -0800 (PST)) it happened Rick C
gnuarm.del...@gmail.com> wrote in
b8fcfb74-c92a-4294...@googlegroups.com>:
\"the unique beam-steering mechanism suspended high above the reflector dish allowed for a moveable focal point that could
aim
at
different parts of the sky.\"
That is EXACTLY what the drone gives you

You don\'t actually know anything about it.
Well since I modified the hardware and wrote the soft to control the drone I do about that.
and I have quite some experience using satellites and dishes.
So what\'s your experience with any of those?
You have no idea if the drone would be even remotely useful.
You are just trolling,

Not trolling, just calling BS. I know that beam forming involves a lot more than just moving your receiver.

You may know lots about drones, but you seem to not know much about beam forming.

Since I designed my first video camera in 1967-1968 and that involves optics
and making a beam is no different for light or lower frequency EM radiation
I call your expertise on that bluff.
In 1968 when I started working for the national TV network
we got 6 month in the school benches training,
one of the subjects was satellites, expert came over specially for those lessons.
Later .... (as the miller told his tale) I worked for a very large company
that made communication equipment where I had to write the service docs for the traveling wave amplifiers for their dishes
from the lab reports.
When I was captured by the flying cup and saucer the aliens ..
better not talk about it, so beware, do not mess with those!

 

[Phil Hobbs]

On 12/3/20 4:55 AM, Martin Brown wrote:

On 02/12/2020 22:39, Rick C wrote:
On Wednesday, December 2, 2020 at 2:22:10 PM UTC-5, Martin Brown
wrote:
On 02/12/2020 14:13, Rick C wrote:
On Wednesday, December 2, 2020 at 4:24:31 AM UTC-5, Jan
Panteltje wrote:
On a sunny day (Tue, 1 Dec 2020 13:06:09 -0800 (PST)) it
happened Rick C <gnuarm.del...@gmail.com> wrote in
b8fcfb74-c92a-4294...@googlegroups.com>:
\"the unique beam-steering mechanism suspended high above the
reflector dish allowed for a moveable focal point that could
aim at different parts of the sky.\"
That is EXACTLY what the drone gives you

You don\'t actually know anything about it. You have no idea if
the drone would be even remotely useful.

If it was a simple matter of moving the receiving portion of the
antenna, they would not have constructed such an elaborate apparatus.
Conceptually it is just a simple matter of moving the feed horn so
that it stays at the focus of the object that they are tracking in
the sky.

In practice that requires a 3 point suspension and some quite
cunning mathematics to make it happen smoothly and accurately. They
are aiming to maintain phase lock to a fraction of a wavelength.

As built originally it was designed for 430MHz. By the end of its
life and after a great deal of refiguring it was being operated up
to 10GHz.

I refer you to the previously quoted text describing \"beam forming\".
I don\'t think that equates to chasing a poorly formed focal point of
an off axis parabolic reflector.

I refer you to the various references that I have already posted. The
main dish is spherical and there are aspherical off axis Gregorian
reflectors inside the radome that bring the raw beam to a precise focus.

http://egg.astro.cornell.edu/alfalfa/ugrad/backgrnd/intro2arecibo.pdf

You don\'t have to take my word for it:

https://www.naic.edu/ao/telescope-description

The sky moves so to observe an object they have to track their target.
Likewise when they are a node in VLBI - where their big dish provided
excellent signal to noise on faint sources but they have a limited time
on track. This is the guide for observers wanting to apply for time to
do VLBI - its tracking range is rather restrictive with declination.

https://www.naic.edu/~astro/aovlbi/#4

https://fermi.gsfc.nasa.gov/science/mtgs/vlbi/Salter-Poster.pdf

I am not sure if they ever did drift scans since the early days.

\"the unique beam-steering mechanism suspended high above the
reflector dish allowed for a moveable focal point that could aim at
different parts of the sky.\"

I don\'t know the details, but I\'m pretty sure it isn\'t just \"moving
the feedhorn\".

Most of it is about precise tracking in terms of a single observation.
The tracking movement is typically precomputed and run from tapes on
these older instruments. Though they may now do it from solid state.

Between observations they can change which front end receiver antenna is
actually at the focus. They have ~5\" arc pointing accuracy.

The problem here is people who think those involved must not know
what they are doing and they themselves must know more.   Not
uncommon in this group.

You are talking to a former radio astronomer. Although I did very little
observational work with big single dishes I do know people who did.

Poor Collins. As some indie song I recall says, \"...they become what
they deplore.\"

Cheers

Phil Hobbs

--
Dr Philip C D Hobbs
Principal Consultant
ElectroOptical Innovations LLC / Hobbs ElectroOptics
Optics, Electro-optics, Photonics, Analog Electronics
Briarcliff Manor NY 10510

http://electrooptical.net
http://hobbs-eo.com

 

[Rick C]

On Thursday, December 3, 2020 at 4:55:30 AM UTC-5, Martin Brown wrote:

On 02/12/2020 22:39, Rick C wrote:
On Wednesday, December 2, 2020 at 2:22:10 PM UTC-5, Martin Brown
wrote:
On 02/12/2020 14:13, Rick C wrote:
On Wednesday, December 2, 2020 at 4:24:31 AM UTC-5, Jan
Panteltje wrote:
On a sunny day (Tue, 1 Dec 2020 13:06:09 -0800 (PST)) it
happened Rick C <gnuarm.del...@gmail.com> wrote in
b8fcfb74-c92a-4294...@googlegroups.com>:
\"the unique beam-steering mechanism suspended high above the
reflector dish allowed for a moveable focal point that could
aim at different parts of the sky.\"
That is EXACTLY what the drone gives you

You don\'t actually know anything about it. You have no idea if
the drone would be even remotely useful.

If it was a simple matter of moving the receiving portion of the
antenna, they would not have constructed such an elaborate
apparatus.
Conceptually it is just a simple matter of moving the feed horn so
that it stays at the focus of the object that they are tracking in
the sky.

In practice that requires a 3 point suspension and some quite
cunning mathematics to make it happen smoothly and accurately. They
are aiming to maintain phase lock to a fraction of a wavelength.

As built originally it was designed for 430MHz. By the end of its
life and after a great deal of refiguring it was being operated up
to 10GHz.

I refer you to the previously quoted text describing \"beam forming\".
I don\'t think that equates to chasing a poorly formed focal point of
an off axis parabolic reflector.
I refer you to the various references that I have already posted. The
main dish is spherical and there are aspherical off axis Gregorian
reflectors inside the radome that bring the raw beam to a precise focus.

So it is not just a matter of moving the receiving element to obtain a proper focus. Focusing requires elements that are far too cumbersome to hang off a drone?

\"the unique beam-steering mechanism suspended high above the
reflector dish allowed for a moveable focal point that could aim at
different parts of the sky.\"

I don\'t know the details, but I\'m pretty sure it isn\'t just \"moving
the feedhorn\".
Most of it is about precise tracking in terms of a single observation.
The tracking movement is typically precomputed and run from tapes on
these older instruments. Though they may now do it from solid state.

You seem to be focusing on the tracking rather than the focusing that I was addressing.

Between observations they can change which front end receiver antenna is
actually at the focus. They have ~5\" arc pointing accuracy.
The problem here is people who think those involved must not know
what they are doing and they themselves must know more. Not
uncommon in this group.
You are talking to a former radio astronomer. Although I did very little
observational work with big single dishes I do know people who did.

I\'m surprised you contradicted yourself then. You said it is just a matter of moving the feedhorn and then talk about \"Gregorian reflectors inside the radome\". The context of my statements were about the idea of suspending all this from a drone. Clearly not practical. I guess technically you did say \"Conceptually\" it was about moving the feedhorn, so \"technically\" not in contradiction of using a drone.

--

Rick C.

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[Rick C]

On Thursday, December 3, 2020 at 5:49:13 AM UTC-5, Jan Panteltje wrote:

On a sunny day (Wed, 2 Dec 2020 22:31:04 -0800 (PST)) it happened Rick C
gnuarm.del...@gmail.com> wrote in
96e90652-7120-4ee0...@googlegroups.com>:
On Thursday, December 3, 2020 at 12:48:08 AM UTC-5, Jan Panteltje wrote:
On a sunny day (Wed, 2 Dec 2020 06:13:19 -0800 (PST)) it happened Rick C
gnuarm.del...@gmail.com> wrote in
57732775-abd9-4257...@googlegroups.com>:
On Wednesday, December 2, 2020 at 4:24:31 AM UTC-5, Jan Panteltje wrote:
On a sunny day (Tue, 1 Dec 2020 13:06:09 -0800 (PST)) it happened Rick C
gnuarm.del...@gmail.com> wrote in
b8fcfb74-c92a-4294...@googlegroups.com>:
\"the unique beam-steering mechanism suspended high above the reflector dish allowed for a moveable focal point that could
aim
at
different parts of the sky.\"
That is EXACTLY what the drone gives you

You don\'t actually know anything about it.
Well since I modified the hardware and wrote the soft to control the drone I do about that.
and I have quite some experience using satellites and dishes.
So what\'s your experience with any of those?
You have no idea if the drone would be even remotely useful.
You are just trolling,

Not trolling, just calling BS. I know that beam forming involves a lot more than just moving your receiver.

You may know lots about drones, but you seem to not know much about beam forming.
Since I designed my first video camera in 1967-1968 and that involves optics
and making a beam is no different for light or lower frequency EM radiation
I call your expertise on that bluff.

\"No different\" conceptually, but the practical differences make using a drone at Arecibo an absurd idea. Did your experience teach you anything about practicality?

I don\'t get why you are continuing to support your clearly absurd suggestion.

--

Rick C.

++ Get 1,000 miles of free Supercharging
++ Tesla referral code - https://ts.la/richard11209