[syhprum (OP)]

The Hubble telescope started life during the "cold war" as a modified version of a high technology reconnaissance satellite system.
I understud about six units were built but never put into service.
As the cost consists mostly of the research and develop time would it not have been expedient to have built at least one spare

[Bored chemist]

I understand that there was a second mirror (at least- there may also have been other spares) made by a different manufacturer- Kodak.
Both mirrors were "flight ready" in time for use.
They chose the mirror made by the company with the better reputation- Perkin Elmer.
In doing so, they picked the one which wasn't ground correctly.
When the problem with Hubble was discovered, they tested the other mirror. It was in spec.

https://airandspace.si.edu/collection-objects/hubble-space-telescope-backup-mirror/nasm_A20010288000

[Europa]

The Hubble telescope started life during the "cold war" as a modified version of a high technology reconnaissance satellite system.
I understud about six units were built but never put into service.
As the cost consists mostly of the research and develop time would it not have been expedient to have built at least one spare

Actually the reason that the Hubble's mirror was defective is because the Hubble was not meant to view the stars but meant to view the Earth as a spy satellite would, or read Gorbachev's mail in Gorbachev's hand, as it may be.  Not sure if there were more as the mirrors for these things are very hard to produce

[Bored chemist]

The Hubble telescope started life during the "cold war" as a modified version of a high technology reconnaissance satellite system.
I understud about six units were built but never put into service.
As the cost consists mostly of the research and develop time would it not have been expedient to have built at least one spare

Actually the reason that the Hubble's mirror was defective is because the Hubble was not meant to view the stars but meant to view the Earth as a spy satellite would, or read Gorbachev's mail in Gorbachev's hand, as it may be.  Not sure if there were more as the mirrors for these things are very hard to produce

That's nonsense from a number of points of view, not least that, a telescope is a telescope. You grind the primary mirror to a parabola whether you plan to point it up or down.

[Europa]

The Hubble telescope started life during the "cold war" as a modified version of a high technology reconnaissance satellite system.
I understud about six units were built but never put into service.
As the cost consists mostly of the research and develop time would it not have been expedient to have built at least one spare

Actually the reason that the Hubble's mirror was defective is because the Hubble was not meant to view the stars but meant to view the Earth as a spy satellite would, or read Gorbachev's mail in Gorbachev's hand, as it may be.  Not sure if there were more as the mirrors for these things are very hard to produce

That's nonsense from a number of points of view, not least that, a telescope is a telescope. You grind the primary mirror to a parabola whether you plan to point it up or down.

The fact is that a telescope is not a telescope, this is true because the mirror must be ground to exactly a certain specification depending on what it intends to focus on.  The Hubble was a complete failure after launch because it could not focus on the stars and new computer programming was installed to correct for the flaw.  You may or may not remember this, I do.  When launched the Hubble was only able to focus on the Earth and not the stars.  Look it up, it's all there.

[Bored chemist]

new computer programming was installed to correct for the flaw.  You may or may not remember this, I do. 

I remember what they actually did to fix the flaw.

https://esahubble.org/about/general/instruments/costar/

As you say,

  Look it up, it's all there.

The primary mirror of a telescope is ground and polished to a paraboloid.
It does not matter if you want to use it as a spy satellite (which is, indeed, where Perkin Elmer got their "expertise") or an astronomical telescope.


You have repeatedly shown that you do not know what you are talking about.
Why not stop wasting bandwidth?

[Europa]

new computer programming was installed to correct for the flaw.  You may or may not remember this, I do. 

I remember what they actually did to fix the flaw.

https://esahubble.org/about/general/instruments/costar/

As you say,

  Look it up, it's all there.

The primary mirror of a telescope is ground and polished to a paraboloid.
It does not matter if you want to use it as a spy satellite (which is, indeed, where Perkin Elmer got their "expertise") or an astronomical telescope.


You have repeatedly shown that you do not know what you are talking about.
Why not stop wasting bandwidth?

The fact remains that when the Hubble was launched that a supposed serious flaw in the mirror made it IMPOSSIBLE to focus to the stars.  So the satellite was a complete waste of money, except that the Soviets knew that it was focusing on them which was the point.  So focusing on Earth was the purpose of the Hubble, the designers hoped that it would also function on the stars however they had to install new parts to achieve the secondary goal of astronomy.  You do know that the space shuttle primarily launched military satellites right and that science was just a back seat afterthought right?

[Bored chemist]

When launched the Hubble was only able to focus on the Earth

Nope. That's just wrong.

[Europa]

When launched the Hubble was only able to focus on the Earth

Nope. That's just wrong.

Again when the Hubble was launched it was not able to focus correctly until new optics parts were manually installed in orbit.  It's there, you can search it on your own I presume

[Bored chemist]

The fact remains that when the Hubble was launched that a supposed serious flaw in the mirror made it IMPOSSIBLE to focus to the stars.

It also made it impossible to focus on Earth (or the Moon for that matter).

It was a screw up, not a conspiracy.
The Soviets knew that the West had spy satellites and we knew that they had them.
Your story makes no sense.

So focusing on Earth was the purpose of the Hubble

It could not do that.


If you think it could, then prove it.

the designers hoped that it would also function on the stars

Why do you claim that some of the best optical designers in the world- the ones who made spy satellite telescopes- were too stupid to realise that a bad telescope does not work?
If it won't give you a clear image of a star, it certainly won't give a clear image of a Russian Newspaper.

The mirror is 2.4 metres across.
The wavelength of light it uses (i.e. visible light) is about 1/2 million of a metre.
So the angular resolution is diffraction limited at about 1/4.8 million radians.
The height is about 550 Km
So the resolution on the ground can't possibly be better than about 0.1 metre.

Are you suggesting that Mr Gorbachev's mail was only ever in the form of advertising hoardings with letters a couple of feet high?

(And that he was in the habit of only reading it outside on sunny days)

[Bored chemist]

Again when the Hubble was launched it was not able to focus correctly until new optics parts were manually installed in orbit.  It's there, you can search it on your own I presume

And, since it could not focus on the Earth , it was not a spy satellite, was it?

[Europa]

The fact remains that when the Hubble was launched that a supposed serious flaw in the mirror made it IMPOSSIBLE to focus to the stars.

It also made it impossible to focus on Earth (or the Moon for that matter).

It was a screw up, not a conspiracy.
The Soviets knew that the West had spy satellites and we knew that they had them.
Your story makes no sense.

So focusing on Earth was the purpose of the Hubble

It could not do that.


If you think it could, then prove it.

the designers hoped that it would also function on the stars

Why do you claim that some of the best optical designers in the world- the ones who made spy satellite telescopes- were too stupid to realise that a bad telescope does not work?
If it won't give you a clear image of a star, it certainly won't give a clear image of a Russian Newspaper.

The mirror is 2.4 metres across.
The wavelength of light it uses (i.e. visible light) is about 1/2 million of a metre.
So the angular resolution is diffraction limited at about 1/4.8 million radians.
The height is about 550 Km
So the resolution on the ground can't possibly be better than about 0.1 metre.

Are you suggesting that Mr Gorbachev's mail was only ever in the form of advertising hoardings with letters a couple of feet high?

The Hubble mirror was the highest optic ever put in a spy satellite, perhaps someday it's Earth photos will be declassified.  It was also probably a failure as no others were ever launched as digital image capture was revolutionizing photography at this time

[Bored chemist]

It's there, you can search it on your own I presume

I pointed it out to you.

I remember what they actually did to fix the flaw.

https://esahubble.org/about/general/instruments/costar/

You had come up with some silly idea about software fixing it.
You can do image deconvolution, but it' never as good as getting the damned thing in focus in the first place.

[Bored chemist]

The Hubble mirror was the highest optic ever put in a spy satellite, perhaps someday it's Earth photos will be declassified. 

Well, if they are they won't be much good.
It's moving too fast; the pictures will be blurred.
You really don't know much about optics, do you?

https://earthsky.org/space/can-the-hubble-space-telescope-be-used-to-observe-earth/

[Bored chemist]

digital image capture was revolutionizing photography at this time

You do know that Hubble is a digital camera, don't you?
They don't pop up there and put a new roll of film in it from time to time.

[Europa]

It's there, you can search it on your own I presume

I pointed it out to you.

I remember what they actually did to fix the flaw.

https://esahubble.org/about/general/instruments/costar/

You had come up with some silly idea about software fixing it.
You can do image deconvolution, but it' never as good as getting the damned thing in focus in the first place.

I came up with nothing, as new optics and software were installed manually on the Hubble

https://www.nasa.gov/content/hubbles-mirror-flaw

If you read you will see that nearsighted is mentioned, so the new optics allowed for far sighting to the universe

[Europa]

digital image capture was revolutionizing photography at this time

You do know that Hubble is a digital camera, don't you?
They don't pop up there and put a new roll of film in it from time to time.

The refinements to CCD Spectroscopy during this time frame made the instruments launched obsolete before being installed.  New optics do not require such large lenses as computer enhancements actually now do much of the focusing when in past generations the lens was 100 percent responsible for this. 

 

[Bored chemist]

I came up with nothing,

You do realise this is a discussion forum, don't you?
Other people can see what you wrote.
They can see that you came up with this

new computer programming was installed to correct for the flaw. 

People are laughing at you.

If you read you will see that nearsighted is mentioned

Yes.
They say this
" replacement instruments that fixed the flaw much the same way a pair of glasses correct the vision of a near-sighted person"
Do you see that they say "in much the same way as"?
They do not say that the telescope was shortsighted.
They do actually say what the problem is here
https://www.nasa.gov/content/goddard/hubble-space-telescope-optics-system
"To remedy the spherical aberration".

And that's not a focussing defect. You can't change the position of the mirror and fix it like you can with shortsightedness.

Just because you don't understand the difference doesn't mean that there isn't one.

  New optics do not require such large lenses

They don't use lenses much.
They use mirrors.

computer enhancements actually now do much of the focusing

Only one of us has ever studied optics.
It is impossible to make a silk purse out of a sow's ear.
Yes, you can get the computer to fiddle with the image.
But fundamentally, you do much better if you have a better mirror in the first place.
And astronomers- even amateur ones- have been grinding "diffraction limited" mirrors for a long time.

It's easy to get an essentially perfect mirror.
It's very hard to put stuff in space.
Why wouldn't you use the best available mirror?

[Europa]

I came up with nothing,

You do realise this is a discussion forum, don't you?
Other people can see what you wrote.
They can see that you came up with this

new computer programming was installed to correct for the flaw.

People are laughing at you.

If you read you will see that nearsighted is mentioned

Yes.
They say this
" replacement instruments that fixed the flaw much the same way a pair of glasses correct the vision of a near-sighted person"
Do you see that they say "in much the same way as"?
They do not say that the telescope was shortsighted.
They do actually say what the problem is here
https://www.nasa.gov/content/goddard/hubble-space-telescope-optics-system
"To remedy the spherical aberration".

And that's not a focussing defect. You can't change the position of the mirror and fix it like you can with shortsightedness.

Just because you don't understand the difference doesn't mean that there isn't one.

  New optics do not require such large lenses

They don't use lenses much.
They use mirrors.

computer enhancements actually now do much of the focusing

Only one of us has ever studied optics.
It is impossible to make a silk purse out of a sow's ear.
Yes, you can get the computer to fiddle with the image.
But fundamentally, you do much better if you have a better mirror in the first place.
And astronomers- even amateur ones- have been grinding "diffraction limited" mirrors for a long time.

It's easy to get an essentially perfect mirror.
It's very hard to put stuff in space.
Why wouldn't you use the best available mirror?

Actually cameras use both lenses and mirrors and the Hubble was both a telescope and a camera.  Nothing you might have studied says any different.

[Bored chemist]

Actually cameras use both lenses and mirrors and the Hubble was both a telescope and a camera.

I didn't say otherwise, did I?

It's perfectly possible to build a camera with only mirrors rather than lenses.
https://en.wikipedia.org/wiki/Catoptrics

What I said was

They don't use lenses much.
They use mirrors.

Hubble's mirror has a mass of about 800 Kg, what do you think the lenses weigh?
What's your definition of "much"?