NASA, Astronomers Mull Putting Telescope on Moon

[Boris_Badenov]

NASA, Astronomers Mull Putting Telescope on Moon<br /><br />Thursday , November 30, 2006<br /><br /> <br /><br /> <br />BALTIMORE — The moon has very little atmosphere, and lots of dust.<br /><br />Those are some of the things being considered this week at the home of the Hubble Space Telescope, where astronomers are discussing the opportunities offered by NASA's plan to return to the moon, including the possibility of a telescope on the lunar surface.<br /><br />The moon is a large, stable platform with very little atmosphere to interfere with viewing the stars. However, the size of any lunar telescope; whether it would be built on Earth and unfold on arrival, or be assembled on the moon; and how it would be funded all remain to be decided.<br /><br />Scott Horowitz, a NASA associate administrator, told the group the space agency is still early in the design stage for the next moon rockets and vehicles but wants significant capability to transport scientific instruments, living quarters and other cargo to the moon.<br /><br />"We're building a pickup truck and we're going to fill the bed with whatever we can,"<br /><br />Of the about-125-metric-ton launch vehicle being designed, about one quarter will be payload, Horowitz said.<br /><br />"We're still trading off how much is available on the exploration lander for scientific payload, we still don't know the exact number," Horowitz said.<br /><br />The meeting at the Space Telescope Science Institute on the campus of Johns Hopkins University, which coordinates the use of the orbiting Hubble, comes a week before NASA is to unveil its moon exploration strategy at a conference in Houston.<br /><br />NASA is planning on using a new crew vehicle, the Orion, and new Ares rockets to return to the moon. NASA hopes to begin flying Orion with astronauts by 2014 and return to the moon no later than 2020.<br /><br />Unlike the Apollo missions of the late 1960s and early 1970s, the new technology will enable NASA to reach any part of the moon, includin <div class="Discussion_UserSignature"> <font color="#993300"><span class="body"><font size="2" color="#3366ff"><div align="center">. </div><div align="center">Never roll in the mud with a pig. You'll both get dirty & the pig likes it.</div></font></span></font> </div>

 

[vogon13]

Would a rotating mercury mirror retain it's shape if allowed to solidify in the frigid lunar night?<br /><br />(without excessive volitalization?)<br /><br />Perhaps the mirror could be melted and filtered (to clean off the lunar dust) and reformed periodically.<br /><br /> <div class="Discussion_UserSignature"> <p><font color="#ff0000"><strong>TPTB went to Dallas and all I got was Plucked !!</strong></font></p><p><font color="#339966"><strong>So many people, so few recipes !!</strong></font></p><p><font color="#0000ff"><strong>Let's clean up this stinkhole !!</strong></font> </p> </div>

 

[Boris_Badenov]

<font color="yellow"> Would a rotating mercury mirror retain it's shape if allowed to solidify in the frigid lunar night? </font><br /><br /> I seem to recall reading about a plan for this already.<br /> The mercury would be literally molecules thick, & they would use a crater as the dish. I can't remember where I read it. <div class="Discussion_UserSignature"> <font color="#993300"><span class="body"><font size="2" color="#3366ff"><div align="center">. </div><div align="center">Never roll in the mud with a pig. You'll both get dirty & the pig likes it.</div></font></span></font> </div>

 

[docm]

Mercury mirrors, AKA liquid mirrors, rely on the mercury remaining a liquid and being spun into the proper curvature. Mercury melts at -38.83 °C/-37.89 °F, so they're not really an option for the dark side where the temperatures reach -233 °C/-387 °F.<br /><br />Another limitation of liquid mirror telescopes is that they depend on gravity and can only point straight up. With the moon's low gravity that might be a problem as well.<br /><br /> <div class="Discussion_UserSignature"> </div>

 

[halman]

Boris1961,<br /><br />The Moon is a natural location for space observatories, both light and radio. The slow rotation would allow long exposure times during each period, whereas the Hubble is limited to 10 or 15 minutes on each orbit, which puts the gyroscopes in constant use, if I understand the system correctly. Micrometeorites are a hazard anywhere there is no atmosphere, including orbit, but, so far, the Hubble has not been significantly degraded by strikes, as far as I know. And the Moon is not limited to visible light astronomy, either, as both infrared and ultraviolet can be detected on the surface.<br /><br />Just as Aericbo was a natural bowl shaped feature, which was adapted to radio astronomy, so many Lunar craters are prime locations for radio telescopes. Due to the low gravity, the size of the dish could be much larger than anything possible on Earth, perhaps kilometers in diameter. Even on the near side of the Moon, craters that are deep enough could offer substantial shielding from Earth's racket, and noise cancelation programs similar to the adaptive optics being used in the newest terrestrial telescopes might eliminate a large portion of the radio energy emanating from Earth.<br /><br />And adaptive optics are the best solution available at this time to the problem of atmospheric turbulence, but getting out of the atmosphere is still the ideal solution. By casting mirrors in sections, and assembling the sections on the Moon, very large mirrors could be possible, as the support cradle and pointing equipment would not be any where near as massive as required on Earth. And there would be no need for the astronomers to live on the Moon, as the data could be transmitted to Earth for analysis. Some personnel would be needed for maintenance, but such a staff would be small, I would think.<br /><br />Properly cared for, a lunar telescope could last for generations, with little in the way of operating costs, while providing data that would be very expensive <div class="Discussion_UserSignature"> The secret to peace of mind is a short attention span. </div>

 

[cuddlyrocket]

We need to consider what kind of telescope is likely to be built on the Moon given the limitations of planned spaceraft etc - restricted mass, construction capability and maintenance and operation staff.<br /><br />A large optical telescope can be ruled out on those grounds, and a small one may as well be put in LEO.<br /><br />Radio telescopes are possible - you can make a simple one simply be stringing wires up. And radio benefits more than optical by being shielded from Earth.<br /><br />Actually, I suspect the first radio telescope will be built <i>facing</i> Earth, as it won't be an independent instrument, but rather part - with Earth-based telescopes - of a <i>very</i> long base line (300,000 km!) interforometer mimicing a telescope of that diameter (easier to construct these at radio wavelengths).

 

[mithridates]

I brought this up on the other thread but nobody seemed to know - what about a telescope on a near-Earth asteroid instead? One that rotates slowly enough should do the trick, and with the lower gravity it would be easier to set up, and not as much of a magnet for rocks and whatnot that get brought in by the higher gravity of the Moon. <div class="Discussion_UserSignature"> <p>----- </p><p>http://mithridates.blogspot.com</p> </div>

 

[Boris_Badenov]

<font color="yellow"> A large optical telescope can be ruled out on those grounds, and a small one may as well be put in LEO. </font><br /><br /> Just how large or small are you considering? My 4.5" telescope on the Moon would perform Magnitudes better than it does here in Snowflake AZ. Also, you can build a structure out of aluminum foil in .16g that would be as sturdy as steel in 1g.<br /> The main mirror on the Hubble is only 95", that is smaller than some telescopes that are more than 100 years old. <br /> I believe that it would be possible to assemble an optical Interferometer on Luna Firma with a diameter of as much or more than 100 miles. Imagine the Deep Space objects you could observe with that kind of resolution, as well as the studies that could be made of outer Solar System objects. <div class="Discussion_UserSignature"> <font color="#993300"><span class="body"><font size="2" color="#3366ff"><div align="center">. </div><div align="center">Never roll in the mud with a pig. You'll both get dirty & the pig likes it.</div></font></span></font> </div>

 

[mrmorris]

<font color="yellow">"I believe that it would be possible to assemble an optical Interferometer on Luna Firma with a diameter of as much or more than 100 miles."</font><br /><br />I'd like to see NASA try a similar concept of Lunar telescopes on an even smaller scale. I envision two scopes with relatively small mirrors -- say 1/2 meter and separated within viewing distance -- possibly only a hundred meters or so. Optical interferometers must know *exactly* how far apart they are to function, so it would be useful for the two to be close enough that a laser rangefinder from one could hit the other.<br /><br />The technology is available, the mass is minimal, and the scopes could perform useful science while being a relatively low-cost testbed

 

[halman]

CuddlyRocket,<br /><br />Perhaps I am wrong, but any speculations regarding building telescopes of the light variety on the Moon are based on the assumption that such a project would not begin immediately, and probably not for another 25 years or so. However, even the proposed lunar lander would be able to ferry portions of a light telescope to the Moon, as the mirror would not be a solid piece of glass, pyrex, or other material. A honeycomb structure supporting a thin surface layer would be more likely, and mirrors cast in segments are commonly made now. As freight capacity to the Moon improves, sending the mount in a single trip would become possible, especially if it is partially disassembled. Assembly by a 3 or 4 person crew could be accomplished in a matter of weeks, once a stable site had been graded and packed.<br /><br />Advances in terrestrial astronomy techniques makes construction of another orbital light telescope unlikely in the near future, as the Keck instrument is rivaling the Hubble in resolution. Low Earth Orbit is also a less than ideal location for a telescope, as the orbital velocity limits viewing time of any given point to just a few minutes. The Hubble Deep Field view was made up of numerous 10 minute exposures, which requires precise aiming on a repeated basis. A lunar telescope would be able to duplicate the same exposure in a single, unbroken viewing, lasting several days.<br /><br />Rather than throwing more money into a space telescope right now, we should concentrate on developing the ability to build a large instrument on the Moon in a generation, because that ability would enable many other activities, such as prospecting for ice at the lunar poles, drilling cores several kilometers below the lunar surface, and establishing permanent habitats. Analysis of the existing Hubble data will take years, as images are generated in hours which take months in some cases to fully interpret. The quest for knowledge should lead expansion of our <div class="Discussion_UserSignature"> The secret to peace of mind is a short attention span. </div>

 

[willpittenger]

How much can a crater dish steer to track an object? <div class="Discussion_UserSignature"> <hr style="margin-top:0.5em;margin-bottom:0.5em" />Will Pittenger<hr style="margin-top:0.5em;margin-bottom:0.5em" />Add this user box to your Wikipedia User Page to show your support for the SDC forums: <div style="margin-left:1em">{{User:Will Pittenger/User Boxes/Space.com Account}}</div> </div>

 

[rogers_buck]

Aericibo does a pretty good job of sky coverage. Of course off-axise abberations for optical observations are less attractive.<br /><br />Seems like building a telescope might be a good prospect for an industrialized moon. Glass production for habitats could be a priority industry that could be adapted.<br /><br /> For example, a massive solar furance for glass making. Glass could be created in a furnace and floated to a spinning form on a river of molten tin. Lasers could be used in the open vaccuum to vaporize the final figuring in a method reminiscent of 3D printing. Aluminization would be relatively simple since the whole thing would be in a vaccuum. The big mirrors made in this way could be linked as interferometers. The stiffness of the material and the 1/3 gravity would make the requirements for active flex mountings less critical than on the earth. There would be no need for ambient light shields other than those required to keep out earthshine and direct sunlight. Placement in high-lattitude craters should solve those problems.<br />

 

[rogers_buck]

The medium of outter space itself has some interesting prospects for creating unique optical telescopes. Imagine a spinning disk of cohesive polymer excreted from a space probe in orbit around the earth or moon. The disk is spun out in the shadow of the planet to its desired size and then brought face on into the sunlight. As ultraviolet light hardens the polymer it will tend to form optical waveguides creating a dense honeycombe of these light pipes as it hardens. The membrane could then be brought to the moon and inflated to form a giant lens with a pressure adjusted focus. Could be real interesting.<br />

 

[Boris_Badenov]

<font color="yellow"> I envision two scopes with relatively small mirrors -- say 1/2 meter and separated within viewing distance -- possibly only a hundred meters or so. </font><br /><br /> You are, as usual, absolutely correct. <br />We have a tendency to think in pretty grandiose terms when we don't have to foot the bill, or do the legwork.<br /> The scope that you are proposing would be quite within the abilities of the first missions to fly. It will be many years before we can place super massive telescopes on the Moon. And by that time we may not want to anymore. <div class="Discussion_UserSignature"> <font color="#993300"><span class="body"><font size="2" color="#3366ff"><div align="center">. </div><div align="center">Never roll in the mud with a pig. You'll both get dirty & the pig likes it.</div></font></span></font> </div>

 

[willpittenger]

<blockquote><font class="small">In reply to:</font><hr /><p>Mercury melts at -38.83 °C/-37.89 °F, so they're not really an option for the dark side where the temperatures reach -233 °C/-387 °F.<p><hr /></p></p></blockquote><br />I think what was brought up was to <font color="yellow">let</font>the mercury freeze. As long as its shape remains what was spun, you could then tilt the mirror off to whereever without spinning it anymore. <div class="Discussion_UserSignature"> <hr style="margin-top:0.5em;margin-bottom:0.5em" />Will Pittenger<hr style="margin-top:0.5em;margin-bottom:0.5em" />Add this user box to your Wikipedia User Page to show your support for the SDC forums: <div style="margin-left:1em">{{User:Will Pittenger/User Boxes/Space.com Account}}</div> </div>

 

[earth_bound_misfit]

Personally, I'll like to see a manned presence on the Moon before such an endeavor. <div class="Discussion_UserSignature"> <p> </p><p> </p><p>----------------------------------------------------------------- </p><p>Wanna see this site looking like the old SDC uplink?</p><p>Go here to see how: <strong>SDC Eye saver </strong>  </p> </div>

 

[gunsandrockets]

"Would a rotating mercury mirror retain it's shape if allowed to solidify in the frigid lunar night? "<br /><br />I had the same idea myself some months ago. When I brought it up it was claimed that mercury didn't freeze properly for use as a mirror. I don't know whether that is really true, but I never followed up on it.

 

[halman]

willpittenger,<br /><br />A fixed dish is aimed by moving the feedhorn, which changes the aiming point of the dish. With a large enough dish, and the low gravity on the Moon, very large changes in aim would be possible. <div class="Discussion_UserSignature"> The secret to peace of mind is a short attention span. </div>

 

[cuddlyrocket]

halman<br /><br />Any telescope you can build on the Moon can be built more cheaply in Earth orbit (not necessarily in LEO). This will be true unless and until we have built up the infrastructure on the Moon to utilise lunar resources in construction. And that's a long time off.<br /><br />To justify a lunar telescope, you need some advantage that using the Moon gives you. The only two I can think of are the shielding effect and the fact that it's a good place to site one leg of an interferometer (and that only until they solve the station-keeping problem for a multi-satellite interferometer).<br /><br />In planning what to do on the Moon, it's not enough to discover whether it's possible. You also need to see what are the advantages over alternatives that outweigh the additional cost.

 

[mrmorris]

<font color="yellow">"To justify a lunar telescope, you need some advantage that using the Moon gives you. The only two I can think of are the shielding effect and the fact that it's a good place to site one leg of an interferometer (and that only until they solve the station-keeping problem for a multi-satellite interferometer). "</font><br /><br />You just answered your own conundrum... put *both* legs of an optical interferometer on the moon... as I suggested above. Stationkeeping concerns go away, yet you still have atmosphere-free viewing and the advantages of interferometric resolution.<br /><br />If the trial with the initial two scopes proves satisfactory, the project can be easily extended. Keep adding two or three more scopes on each visit. Put each new scope in rangefinder view of at least the two closest scopes (perhaps 100-300 yards separation). As the array increases in size, the resolution will rapidly eclipse anything available today. If the scopes were built as collabsable dobsonians like this concept then they would not only be low-mass, but low volume as well. Such collapsible scopes would be much simpler and lighter with a man-in-the-loop as opposed to requiring the scopes to be able to extend themselves.<br /><br />It would certainly demonstrate that putting people on the moon can do something tangible to advance scientific capability. Also -- a diostributed array of scopes like this adds redundancy. If one of the scopes gets taken out by a meteorite -- all is not lost. We're going to the moon already -- this is a given (or at least a firm assumption). A Lunar scope of this style with even six half-meter elements spread over a few hundred meters would produce a poor-man's TPF. If the array were to get up to 30-50 elements spread over a few kilometers -- it'd be one *heck* of a TPF. I think the advantages are obvious... but then I *would

 

[rocketman5000]

'cuse my ignorance, but what is a TPF?

 

[mithridates]

Nobody knows? Has nobody ever looked at the idea of setting up a telescope on a near-Earth asteroid? <div class="Discussion_UserSignature"> <p>----- </p><p>http://mithridates.blogspot.com</p> </div>

 

[mrmorris]

<font color="yellow">'cuse my ignorance, but what is a TPF? "</font><br /><br />Terrestrial Planet Finder. The current 'Holy Grail' of telescopes.

 

[mrmorris]

<font color="yellow">"Has nobody ever looked at the idea of setting up a telescope on a near-Earth asteroid? "</font><br /><br />I didn't see anything promising with a Google. <br /><br />My own guess would be that rotation would be an issue. Most NEAs will be rotating -- some quite rapidly. Also -- the low gravity is a problem. The 1/6 G of the moon is sufficient to anchor a telescope. The negligible pull of an asteroid would provide poor anchoring. Essentially -- an NEA provides little advantage beyond a free-flying space-based telescope and does provide additional complications. I can't see it happening.

 

[willpittenger]

<blockquote><font class="small">In reply to:</font><hr /><p>A fixed dish is aimed by moving the feedhorn, which changes the aiming point of the dish.<p><hr /></p></p></blockquote><br />The dish is not a perfect sphere. So how do you always ensure the beams bounce to the right point? <div class="Discussion_UserSignature"> <hr style="margin-top:0.5em;margin-bottom:0.5em" />Will Pittenger<hr style="margin-top:0.5em;margin-bottom:0.5em" />Add this user box to your Wikipedia User Page to show your support for the SDC forums: <div style="margin-left:1em">{{User:Will Pittenger/User Boxes/Space.com Account}}</div> </div>