Radio Telescopes on Moon to Study Cosmic Dark Ages

The Narrative Fallacy brings news that NASA has awarded a $500,000 grant to develop plans for an array of radio telescopes to be located on the moon. The telescopes would be used to gather data from the earliest stars and galaxies, observations of which are difficult from Earth due to the ionosphere and terrestrial broadcasts. The grant was part of NASA's sponsoring of 19 "Next Generation Astronomy Missions." Quoting: "The Lunar Array for Radio Cosmology (LARC) project ... is planned as a huge array of hundreds of telescope modules designed to pick up very-low-frequency radio emissions. The array will cover an area of up to two square kilometers; the modules would be moved into place on the lunar surface by automated vehicles. The new lunar telescopes would add greatly to the capabilities of a low-frequency radio telescope array now under construction in Western Australia, one of the most radio-quiet areas on Earth."

Comments

Hrm.

[KublaiKhan]

Just a bit far to go on a LARC, ain't it?

< /british >

Outstanding

[Protonk]

The moon makes for an excellent platform for automated telescopes. People are going to bring up the tired "appolo for diamonds" argument but it doesn't have any bearing on this. The moon has no atmosphere to speak of, little radio interference from the earth and ample room to set up a large array.

This requires less investment than manned missions (which dictate a return and have a HUGE space/safety cost). It will allow us to see other things than what is suggested in the grant--Changra, hubble and the like all have been used for things that were not conceived of during the design phase.

Re:Outstanding

[fred fleenblat]

(a) the cost of transit to/from the moon per pound is so high that only the lightest, skinniest people like paris hilton will be allowed in space. in fact they should be required to be sent into space.

(b) the moon has no oceans, therefore 100% of land area is available for condominiums, hotels, highrises, and shopping districts. Unlike the earth which of which only 20% or so is habitable land. Ideally we would launch the most habitable parts, like Washington DC, to the moon in their entirety to take full advantage of the economy of scale, then convert what was underneath Washington DC into higher value land, like a swamp.

(c) as you could see from last wednesdays lunar eclipse, the educational value of viewing the lunar eclipse from the moon would have been greater than viewing it from earth. No child left behind and all that.

What was the question?

Re:Outstanding

[CodeBuster]

We already have hear of that the extremly abrasive qualities of the lunar soil. That soil that will find its way into the telescope (especially bad for any moving parts.) I was going to mention the exact problem and it does has the potential to be a problem because, as you mention, lunar dust is extremely abbrasive and fine (imagine sub micron rock particulate with razor sharp and hooked edges because it has never been eroded by wind or water) so it tends to damage or compromise any softer materials that it comes into contact with. However, upon further reflection I believe that the problem, in this case, would be manageable for the following reasons:

(a) The telescopes and related equipment, or at least the parts directly in conctact with the lunar surface, will not be moving around after touchdown so the amount of dust that gets disturbed should be minimal and landing air bags (ala the mars missions) should help shield any sensitive parts during the landing cycle. the parts that do move will not disturb the dust because they will not be in direct contact with the lunar surface AND there are no air currents or other atmospheric effects on the moon to whip up dust from parts moving around (even if they are only millimeters above average surface elevation) which are not in direct contact with the lunar surface.

(b) radio telescopes can be made out of metals and durable plastics without the need for sensitive optics such as finely ground glass lenses so the danger from abbrasive lunar dust could be minimized in this regard by judicious use of durable and hardened parts.

The micrometeorites are a more serious issue. There have been subsequent pictures taken by probes of known Apollo landing sites which reveal new small craters (i.e. craters which occurred near the landing sites in between the time when the probes took the pictures and when the Apollo astronauts left the moon on the ascent stages of their landing vehicles). It is possible that many smaller meteorites have struck the Apollo lander descent stages that were left behind on the moon (although nobody can be sure because they are too small to resolve individually on the lunar surface by telescope and nobody has gone back since to check on their condition). However, even with this potential problem the radio telescope offers an interesting solution.

The individual telescope elements of the radio telescope are less important than the network of them which makes up the whole. This why radio telescopes on earth, such as the very long baseline array, with stations on different continents aggregated together into a single "picture", are distributed rather then building one VERY large singular dish (i.e. one half the size of earth). The individual telescope elements on the moon could be replaced with new ones as needed if individual units, for whatever reason, become non-operable.

Re:As I understand it

[rijrunner]

Well, not quite.

This type of observatory requires a lot of smaller units that add up to a total resolution of the receiving surface. The best resolution is directly overhead of the site. As you try to observe items that are low on the horizon, you lose a great deal of the quality of the observation as the effective size of the array is diminished.

For example:

                        **** (what you are observing)

                        ^^^^ (The array).

The array is effectively as wide as its deployment diameter.

Now, suppose you are observing from a couple other angles:

                                  ****

                        ^^^^

From that angle, the array is apparently smaller. You can angle them to make sure you have the same strength, but you have to increase the size of the array as a direct function of the observation angle to give equivalent baselines for the observation.

So, yes, you can see in any direction around the Moon, but placement on the Moon is not a simple matter.

Consider that you don't want it pointing towards the sun either. Or, maybe you do. That's an interesting argument right there. You'll get data from the sun, but you'll also have periods where you have nothing *but* data from the sun. Similarly, Jupiter kicks out a lot of radio signals. A lot of design decisions end up still needing a fairly complex shield to make sure that you're getting only the radio waves you are searching for.

Arguably, you would want to place it near the lunar poles. Not for any of the BS arguments about the potential for water there, but because they have the least interference from Earth and the Sun. It also means you can survey the same stretch of sky for longer periods as out-of-plane bodies there are a lot easier to track and remain in the same cone of observation irrespective of the current lunar position. (ie, something that is at zenith over the lunar pole is not going to vary more than about 6 degrees from being overhead over the course of a year. Even something 25 degrees, or so, would still be visible pretty much all the time). If you go to lower latitudes, then it gets closer to a 14-day non-observation lineup followed by a 14 day period of variable observation from minimal to optimal and back as the object traverses the sky. The closer you get to the lunar equator, the more of the sky you will see, but the less the observation time and the more variable the quality of the observation.

Ideally, they design a small inexpensive setup which can be done a few times on various areas of the Moon. Just choosing one set of criteria is going to be interesting. This is not like Hubble which can be pointed in any direction. There are a lot of rocks in the way.

Re:The Standard Objection Applies..

[F�an�ro]

There are no geostationary orbits that stay behind the moon. But we could maybe put a satellite in a Lissajous orbit around the lagrange point L2 behind the moon.

To send signals back you would need a relay satelite thougth

Re:Yeah right

[Deadstick]

The moon's orbit is not perfectly circular, and its axis of rotation is not quite perpendicular to the plane of the orbit. Those effects combine to produce an apparent rocking motion, on a time scale of weeks, called libration. Thanks to that, we can see almost 60 percent of the moon's surface at one time or another.

rj

If you really want to know...

[TrekkieGod]

The universe is a huge place, what makes NASA think that our telescopes are able to see the "earliest stars and galaxies"?

The cosmic microwave background left over from the big bang as measured by WMAP tells us the approximate age of the universe. Red-shift measurements tells us the distances of the stars we observe. The speed of light tells us how long it takes for the light of those stars to get here. Ta-da.

Or is this one of those "We are in the center of the universe" ideologies again?

We ARE at the center of the universe. So is everywhere else. The Big Bang wasn't an explosion that filled out existing space from which there's a center. Space itself expands from that point on, so the same infinitesimal point where the big bang started is the place where you're standing in now. The standard analogy is the surface area of a balloon as you fill the balloon up. There's just no preferred center.

Re:The Standard Objection Applies..

[Steneub]

Logged in to post exactly this. Putting a telescope in a lagrange point solves the problem of not being able to directly communicate with it due to it being on the other side of the moon. Another advantage of direct communication is getting visual confirmation of any movements or adjustments made. Sensors are great, but I don't care how good the tech is - something will always go wrong that you didn't think of.