Starship Asterisk*

by **NoelC** » Wed Apr 27, 2011 3:58 am

Thanks for the info. That would be a pretty good use for that position in space if it actually did fully shield the spacecraft from the sun...

http://en.wikipedia.org/wiki/Lagrangian_point wrote:The Sun-Earth L2 is a good spot for space-based observatories. Because an object around L2 will maintain the same orientation with respect to the Sun and Earth, shielding and calibration are much simpler. It is, however, slightly beyond the reach of Earth's umbra,[4] so solar radiation is not completely blocked.

How many spacecraft can be parked near enough to the L2 Lagrange Point? Isn't it likely to get crowded there? Will they start affecting one another?

-Noel

by **neufer** » Wed Apr 27, 2011 1:51 am

NoelC wrote:
alphachapmtl wrote:Any observatory would be better in space than on any planetary surface.
Why do you feel that is true? I tend to shy away from absolutes ("Any") because there are always exceptions.

Permanent shielding from the sun and thus a constant temperature is an advantage I was thinking of. Imagine the infrared observations that could be made in the cold of a permanently shaded crater with no atmosphere...

The James Webb Space infrared Telescope simply uses the Earth to shield it from the Sun while its own modest shield handles thermal infrared radiation from the Earth (and Moon). Most importantly the JWST can be pointed in almost any direction at any time.

1) An infrared (or radio) telescope in a Lunar South Pole crater must be both shielded and insulated from thermal radiation from the Moon itself.

2) Most importantly such a telescope could never observe the Northern Hemisphere Sky (nor most of the Zodiacal Sky).

3) Plus it takes a lot more energy to land a pound of material on the moon than to orbit a pound of material at the L2 Lagrange point(; and a large telescope on the moon will always require more material in the first place simply to support itself from gravitational stresses).

NoelC wrote:
And perhaps a design could be realized that happens to need servicing more often than would be practical for a completely autonomous space observatory. For example, something built with more and more capability over a long period of time.

I think the Moon is pretty stable, right?

http://apod.nasa.gov/apod/ap101010.html

by **NoelC** » Wed Apr 27, 2011 12:50 am

alphachapmtl wrote:Any observatory would be better in space than on any planetary surface.

Why do you feel that is true? I tend to shy away from absolutes ("Any") because there are always exceptions.

Permanent shielding from the sun and thus a constant temperature is an advantage I was thinking of. Imagine the infrared observations that could be made in the cold of a permanently shaded crater with no atmosphere...

And perhaps a design could be realized that happens to need servicing more often than would be practical for a completely autonomous space observatory. For example, something built with more and more capability over a long period of time.

I think the Moon is pretty stable, right?

-Noel

by **StarCuriousAero** » Mon Apr 25, 2011 6:13 pm

Many small radio telescopes using interferometry methods on the lunar far-side (rather than the poles) may be more useful for observations, and much more cost effective to get there than something like the VLT. Frequencies that we haven't been able to "silently" observe from the noisy earth-surface (or anywhere else within site of the earth for that matter), would then have clear viewing. This topic was actually heavily explored by myself and fellow classmates in the aerospace engineering graduating class from Cal Poly - San Luis Obispo, 2009, for our class's "Senior Project" of sorts.

by **alphachapmtl** » Sun Apr 24, 2011 8:15 pm

NoelC wrote:That's just slick.

I'm just dreaming of a couple VLT (Very Large Telescope) observatories permanently stationed on the moon. Wow, wouldn't we be able to see something with those!

-Noel

Any observatory would be better in space than on any planetary surface.
Of course, earth's surface has a tremendous cost advantage.

by **neufer** » Sun Apr 24, 2011 11:38 am

http://www.nims.go.jp/apfim/fim.html wrote:
Principle of field ion microscope (FIM).
<<Field ion microscope (FIM) was invented by Erwin E. Mueller in 1951 at the Pennsylvania State University. By FIM, man observed atoms for the first time. It was developed from its forefunner, the field emission microscpe. The instrument features a specimen in the form of a sharp needle mounted on a electrically insulated stage that is cooled to cryogenic temperatures (20 to 100K) in a ultrahigh vacuum chamber. The field ion image of the specimen is formed on a microchannel plate and phosphor screen assembly that is positioned approximately 50 mm in front of the specimen. To produce a field ion image, controlled amounts of image gas are admitted into the vacuum system. The type of image gas used depends on the material under investigation; common images gases are neon, helium, hydrogen and argon.

The field ion image is produced by the projection of image gas atoms that are ionized by the high positive voltage on the specimen onto the fluorescent screen. The image gas atoms in the vicinity of the specimen are polarized because of the high field and then attracted to the apex region of the specimen. After a series of collisions with the specimen during which the image gas atoms lose part of their kinetic energy, these image gas atoms become thermally accommodated to the cryogenic temperature of the specimen. If the field is sufficiently high, these image gas atoms are field ionized by a quantum-mechanical tunneling process. The ions produced are then radially repelled from the surface of the specimen towards the microchannel plate and screen assembly. A microchannel plate image intensifier positioned immediately in front of the phosphor screen produces between 10³ and 10⁴ electrons for each input ion. These electrons are accelerated towards the phosphor screen where they produce a visible image.>>

by **islader2** » Sun Apr 24, 2011 4:17 am

The name of my home city is Arecibo. No offense taken--there is always a spell checker handy.

by **Chris Peterson** » Sat Apr 23, 2011 7:57 pm

BMAONE23 wrote:in a 1/6th gravity environment, we could make primary mirrors that were easily 10 times current limitations but wouldn't need any adaptive optics hardware. It would be interesting to make an optical telescope with a primary mirror the size of a lunar crater similar to the Radio Telescope at Aricebo. Though it would always only point in one direction

Actually, it would scan a 360° swath of sky along a fixed lunar declination as the Moon rotated. That's worse then always pointing in one direction since it would make the telescope largely unusable.

by **PODoyle** » Sat Apr 23, 2011 6:39 pm

Isn't Shackleton crater cold enough to allow ambient temperature superconductors? If so, what a great place to build a superconducting radio telescope, or to store electricity in superconducting coils.

by **BMAONE23** » Sat Apr 23, 2011 6:18 pm

in a 1/6th gravity environment, we could make primary mirrors that were easily 10 times current limitations but wouldn't need any adaptive optics hardware. It would be interesting to make an optical telescope with a primary mirror the size of a lunar crater similar to the Radio Telescope at Aricebo. Though it would always only point in one direction

by **NoelC** » Sat Apr 23, 2011 4:56 pm

That's just slick.

I imagine this is incredibly useful information as well for planning things like heating/cooling of an outpost, illumination (or lack of) for observatories, where to put solar panels for power, etc.

It occurs to me an outpost down there would only ever be able to see half the sky... Are there similar features at the north pole?

I'm just dreaming of a couple VLT (Very Large Telescope) observatories permanently stationed on the moon. Wow, wouldn't we be able to see something with those!

-Noel

by **biddie67** » Sat Apr 23, 2011 4:00 pm

I am in awe about the many different methods that the astro-scientists have devised to measure/quantify/analyze/etc. objects and phenomenon out there in the solar system and beyond ...

by **nstahl** » Sat Apr 23, 2011 12:26 pm

This is great. Something new and interesting and a striking image.

by **orin stepanek** » Sat Apr 23, 2011 11:30 am

Click to play embedded YouTube video.

by **owlice** » Sat Apr 23, 2011 10:24 am

What an interesting APOD! I learned a lot from this one, and found this page, which some might enjoy, in my related travels. I enjoyed the musical interlude, too.

by **APOD Robot** » Sat Apr 23, 2011 4:14 am

Shadows at the Lunar South Pole

Explanation: What is it? It's a multi-temporal illumination map, of course. To make it, the wide angle camera on the Lunar Reconnaissance Orbiter spacecraft collected 1,700 images over a period of 6 lunar days (6 Earth months), repeatedly covering an area centered on the Moon's south pole. Converted to binary values (shadowed pixels set to 0, illuminated pixels set to 1) the images were stacked to produce a map representing the percentage of time each spot on the surface was illuminated by the Sun. Remaining convincingly in shadow, the floor of the 19 kilometer diameter Shackleton crater is seen near the center of the map. The lunar south pole itself is at about 9 o'clock on the crater's rim. Since the Moon's axis of rotation stays almost perpendicular to the ecliptic plane, crater floors near the lunar south and north poles can remain in permanent shadow and mountain tops in nearly continuous sunlight. Useful to future outposts, the shadowed crater floors could offer reservoirs of water ice, and the sunlit mountain tops ideal locations for solar power arrays.

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