Hubble to be retired early....

[Dr Mordrid]

http://www.cbsnews.com/stories/2004/01/30/tech/main596838.shtml

A new space telescope with enhanced IR imaging is to be launched about 2010/2011. This one will be placed in a very high orbit at an Lagrangian point (L2; 930,000 miles from Earth) beyond the moon for better seeing. This location would put the Earth between the telescope and the sun.

Dr. Mordrid

[Brian Ellis]

Sorry, Doc, better brush up on your astronomy. The two stable Lagrangian points are situated to form an equilateral triangle with one side from the centre of the earth to the centre of the moon. As the moon orbits the earth, so the LP moves round.

As it is an equilateral triangle, the distance from the satellite to the earth (or to the moon) is the same as from the moon to the earth, i.e., 356, 517 to 406,711 km.

The other three LPs are unstable and could not be used to keep a satellite positioned.

There is no way that the LP can be perpetually in the earth's shadow and, if it were, the telescope would not work for very long, as its batteries would not be recharged

[Dr Mordrid]

Who needs to study? You do....as in read up on the JWST (James Webb Space Telescope) before commenting on its reported positioning and operations.

The L1 and L2 points are situated with L1 between the sun and earth and L2 behind the moon. Both are slightly unstable on a time scale of approximately 23 days, requiring satellites parked in these orbits to perform small but regular course corrections. Still; those involved feel that the L2 position offers better "seeing" and is therefore worth the mild inconvenience.

It's my understanding that these adjustments will be done using ion drive thrusters similar in operation to the engine used on Deep Space One, which means the onboard fuel will last a long, LONG time. It'll have to since the JWST isn't built for servicing. A good thing since we don't have manned spacecraft capable of reaching the L2 point....yet.

The L2 point will not be entirely shielded from the sun, requiring the JWST to have a sun-shield....but smaller than would be required at other L points. I'd presume the solar arrays would be on the opposite side of this shield from the telescope proper.

The shield is also required to allow the JWST to cool to its operating temperature: 45K (-370 F). Can't have an IR telescope warmer than its target objects

Dr. Mordrid

[Brian R.]

Anyway, looks like they're going to reconsider keeping Hubble alive.

http://www.cbsnews.com/stories/2004/01/16/tech/main593826.shtml

[cjolley]

God I hope so.
chuck

[cjolley]

http://abcnews.go.com/sections/SciTech/US/hubble_astronomy_040202-1.html

chuck

[GuchiGuh]

is this te one that has folding mirrors?

[VJ]

You are thinking about higher ranged BMWs...


Jörg

[GuchiGuh]

Nonono!!! Every kid knows that a BMW is more advanced then a Hubble!

[gt40]

Originally posted by GuchiGuh
Nonono!!! Every kid knows that a BMW is more advanced then a Hubble!

[GuchiGuh]

yes?

[VJ]

Oh, I see... Just like every kid knows Santa Claus exists ...


Jörg

[GuchiGuh]

HAHAH!
okok comon guys, that was a serious question about the folding mirrors! I saw on Discovery Channel once a Hubble whose Mirrors are folded up like an Umbrella or something? Can somebody confirm?

[Ajax]

Hubble's latest:

(M64) Evil Eye galaxy.

[VJ]

Originally posted by GuchiGuh
okok comon guys, that was a serious question about the folding mirrors! I saw on Discovery Channel once a Hubble whose Mirrors are folded up like an Umbrella or something? Can somebody confirm?

I don't think Hubble has folding mirrors. The construction is more or less a cilinder in which the telescope is situated. It does have two folding solar panels...

http://hubble.esa.int/science-e/www/object/index.cfm?fobjectid=31384

(esp. click model, and then the two arrows that move up/down to show more/less of the interior)

Jörg