James Webb Space Telescope is a boondoggle

James Webb Space Telescope (JWST) is going to
take mostly infrared pictures of the universe.
To reduce unwanted infrared light coming from
the Sun, JWST will be launched into the Sun-Earth
L2 point, which is 1.5 million kilometers away
from the Earth. This far out location was
justified by the shade made by the Earth. A quick
calculation proves that the L2 point is *not*
in the Earth's shade! The complete shade, called
umbra, extends only to a distance of 1.39 million
kilometers beyond the Earth, i.e., 110,000 km
short. The L2 point is in partial shade called
penumbra.

If JWST is launched into the L2 point, it will
sizzle in the sunlight almost as much as the
Hubble Space Telescope. If something goes wrong
with the JWST, the telescope will be difficult to
repair because the L2 point is far away from the
Earth. Worse yet, JWST has a monolithic design
not suitable for telerobotic repair or upgrade.
My conclusion: James Webb Space Telescope
should be redesigned to improve its thermal
insulation and compatibility with telerobots,
and then launched into low Earth orbit.

"Andrew Nowicki" wrote in message
...

My conclusion: James Webb Space Telescope
should be redesigned to improve its thermal
insulation and compatibility with telerobots,
and then launched into low Earth orbit.

Ain't gonna happen.

Andrew Nowicki wrote in news:4216D559.B6CA6011
@nospam.com:


If JWST is launched into the L2 point, it will
sizzle in the sunlight almost as much as the
Hubble Space Telescope.

Which is why it has its own sunshade. Also, it's
away from Earth's thermal radiation, which is the real
reason for that orbit. What's the problem with this?

If something goes wrong
with the JWST, the telescope will be difficult to
repair because the L2 point is far away from the
Earth. Worse yet, JWST has a monolithic design
not suitable for telerobotic repair or upgrade.
My conclusion: James Webb Space Telescope
should be redesigned to improve its thermal
insulation and compatibility with telerobots,
and then launched into low Earth orbit.

What telerobots?

You may have noticed they're not going to repair
Hubble, either. If JWST breaks, well, that's too
bad...and no upgrades.

We aren't going to have a Shuttle much longer and
it's not clear that CEV will be able to provide similar
support at even slightly lower mission cost.

--Damon

"Damon Hill" wrote in message
31...
Andrew Nowicki wrote in news:4216D559.B6CA6011
@nospam.com:


If JWST is launched into the L2 point, it will
sizzle in the sunlight almost as much as the
Hubble Space Telescope.

Which is why it has its own sunshade. Also, it's
away from Earth's thermal radiation, which is the real
reason for that orbit. What's the problem with this?


Absolutely right. It's thermal radiation from the Earth, not from the Sun,
that causes problems for infrared telescopes in low orbits, where the 300K
Earth fills nearly half the sky. The problem is general heating of the
spacecraft, which makes it use up helium coolant much faster. It is very
hard to reflect away this infrared radiation, which is mostly at wavelengths
of about 0.01mm. Most of the Sun's radiation is visible and near-IR light,
which is easily reflected by a sunshade.

If something goes wrong
with the JWST, the telescope will be difficult to
repair because the L2 point is far away from the
Earth. Worse yet, JWST has a monolithic design
not suitable for telerobotic repair or upgrade.
My conclusion: James Webb Space Telescope
should be redesigned to improve its thermal
insulation and compatibility with telerobots,
and then launched into low Earth orbit.

What telerobots?

You may have noticed they're not going to repair
Hubble, either. If JWST breaks, well, that's too
bad...and no upgrades.

We aren't going to have a Shuttle much longer and
it's not clear that CEV will be able to provide similar
support at even slightly lower mission cost.

--Damon

--
Mike Dworetsky

(Remove "pants" spamblock to send e-mail)

This is some of the most ignorant clap-trap I've read
lately from anyone other than Brad Guth or Thomas Lee
Elifritz.

Be aware that the designers of JWST are fully
knowledgeable of the environment the observatory will
be placed in and have designed it accordingly. JWST
is *not* designed to be in Earth's shade, nor will it
sit at the Earth-Sun L2 point (but rather in a halo
orbit around it). Notably, JWST will not be the first
infrared telescope deployed by NASA (Spitzer) nor the
first telescope placed around the Earth-Sun L2 point
(WMAP). Sometimes NASA does know what it's doing
enough not to make colossal, obvious mistakes.

In article ,
Andrew Nowicki wrote:
If JWST is launched into the L2 point, it will
sizzle in the sunlight almost as much as the
Hubble Space Telescope.

That's why they are building a "sun shade" for it.

Mike Dworetsky wrote:

It's thermal radiation from the Earth, not from the Sun,
that causes problems for infrared telescopes in low orbits, where the 300K
Earth fills nearly half the sky. The problem is general heating of the
spacecraft, which makes it use up helium coolant much faster. It is very
hard to reflect away this infrared radiation, which is mostly at wavelengths
of about 0.01mm. Most of the Sun's radiation is visible and near-IR light,
which is easily reflected by a sunshade.

Clean, polished gold and silver have *infrared*
emissivity in the range of 0.01 to 0.03. They
are good enough to reach the microkelvin
temperature range in cryogenic equipment.
A passive tube-shaped insulation surrounding
the telescope in low Earth orbit could reduce
its temperature to 70 K or so. It seems that
NASA is going to send JWST to L2 because they
cannot design decent thermal insulation.

On 2005-02-19, Andrew Nowicki wrote:

If JWST is launched into the L2 point, it will
sizzle in the sunlight almost as much as the
Hubble Space Telescope. If something goes wrong

Goodness, it's amazing you thought of that, because Lord knows the
engineers designing billion-dollar flagship projects never think to do
the maths...

My conclusion: James Webb Space Telescope
should be redesigned to improve its thermal
insulation and compatibility with telerobots,
and then launched into low Earth orbit.

....compatibility with telerobots. Why am I not surprised?

This happens every damn couple of months. Something new is announced -
CEV, or SS1, or hypothetical telerobot servicers, or Kliper, or the ESA
Soyuz pads... and it becomes Flavour Of The Month to solve every
possible problem (especially if it doesn't actually exist yet). An dit
hangs around for a while, and in time it'll be forgotten and replaced
with something else new! shiny!

(What was the 'Dilbert' comment? "We need a nano-technology stem cell to
fight terrorism..."

--
-Andrew Gray

Dear Andrew,
Be very careful. You seem to be going down the same
road as Brad Guth and Thomas Lee
Elifritz. When they first posted they were just in love with thier own
ideas/inventions, asking questions to try and improve them. However once
people started showing a number of faults in thier ideas rather than admit
they had made some mistakes they just try defending thier same old ideas more
and more. As they did this over time they drifted into weirder and weirder
ideas until they became the kooks you see today.

Brad this there are buildings on Venus based on single pixels of picture
taken on that planet. Thomas claims all sort of fossils as visible in the
pictures from Mars but can't tell anyone where to look. He also think NASA
is out to get him when they take a Sunday off to stay at home.

Look at youself now. You made a claim about the Earth's shadow without
posting your math or a reference URL. That is a kook sign.

You made a wild claim about the heating effect of partial shadowing with any
math about what real level of heating would be. Kook sign.

You made a claim about direct sunlight hitting the telescope but somehow
forgot to check wether there was a sunshade to counter that well known
problem. Not checking out a design before make predictions on it operation
is also a kook sign.

Then you stated what you think NASA is going to do instead, predicting a
totally diffirent orbit that what all the planning out there says. Read
carefully, making wild claims about NASA's future actions based only on your
thinking (not published reports from the government or NASA) is a MAJOR kook
sign.

Really Andrew. It is time to look carefully at what it is your really want
from life. And if it is to really going your own way then you better work a
bit harder than Brad or Thomas on your design. If all you do is talk about
them instead of doing real work at developing your ideas then you will just
become another Brad or Thomas - posting words on the usenet but no-one else
will care about what you have to say.

Earl Colby Pottinger

--
I make public email sent to me! Hydrogen Peroxide Rockets, OpenBeos,
SerialTransfer 3.0, RAMDISK, BoatBuilding, DIY TabletPC. What happened to
the time? http://webhome.idirect.com/~earlcp

Andrew Nowicki wrote:

A passive tube-shaped insulation surrounding
the telescope in low Earth orbit could reduce
its temperature to 70 K or so. It seems that
NASA is going to send JWST to L2 because they
cannot design decent thermal insulation.

You're projecting your own cluelessness onto
the engineers who designed JWST, who actually know
what they are doing.

Paul