Why not build a space telescope directly at the moon?


If you want to get the most pristine, cleanest images of our Universe, it is best to leave the Earth. Here, on our planet, you can find a whole bunch of various effects, which prevent our visualization. Light pollution limit the range of our vision; the atmosphere is harmful to our resolution and our ability to see clearly; the clouds and the weather prevented us to collect light; the Sun and the Earth themselves will block a huge part of our field of view from any point on Earth.

And yet the Observatory like Hubble, Chandra, Fermi, Spitzer, and others have demonstrated the effectiveness of space-based telescopes. The types and the data they returned to Earth, taught us much more things than could teach similar observations made on the Ground. Why not then place the telescope on the moon? Believe it or not, but it’s a terrible idea. She has only one good point. And here’s why.

A telescope on the moon: is it bad?

The moon, at first glance, it may seem the perfect place to host the telescope. There is almost no atmosphere, eliminating any fears of light pollution. It is far from the Land, which should significantly reduce interference from any signals produced by humans. Very long nights also means that you can observe the same target continuously for 14 days without interruption. And since you have solid ground, you don’t need gyros or wheel for guidance. Everything seemed to be cool.

But when you start to think about how the Moon rotates around the Earth, the system Moon-Earth as a whole, which revolve around the Sun, you begin to understand some of the challenges that inevitably faces the whole idea.

First, if you put your telescope on the moon, which side will you choose: near or far? Each of them has its drawbacks.

If you place your telescope on the near (Earth facing) side of the moon, you will always see the Ground. This means you can send and receive signals to control your telescope and download the data without delays, and the only limitation is the speed of light. But it also suggests that interference from the Earth, such as radio signals, there will always be a problem that you will have to be considered.

On the other hand, if you are on the far side of the moon, you effectively protect yourself from everything that comes from the Earth, but you also have no direct data transfer path or the maintenance of the communication signal. Will have to install additional mechanism, the Orbiter or hold a connection on the near side to control the telescope.

In any case, you will have a lot of problems which will have to fight, and which commonly is not in the abyss of interplanetary space. The two largest:

Lentracte. I think that the Moon directs the tides on Earth? Tidal forces that the Earth exerts on the moon is 20 times stronger than the tidal forces that the Moon exerts on the Earth. Enough to provoke the satellite sickly lentracte.

The difference in temperature. Due to tidal locking of the moon to the Earth and its extremely slow rotation, it is bathed in sunlight almost constantly for 14 days and then plunges into complete darkness for 14 days. Daytime temperatures can reach over 100 degrees Celsius, and at night the Moon cools down to -173 degrees.

While the space telescope is able to control its temperature by passive or active cooling (or a combination of both), the telescope should cool down below the temperature of those wavelengths that it is trying to observe, or noise will be close to the expected signal. It would be a huge disadvantage for the ultraviolet, optical or infrared astronomy, if at least one of them tried to develop on the moon.

Design a telescope that can withstand these extreme temperatures while working, a very difficult task. Not surprisingly, the only telescope on the moon that we have is ultraviolet telescope on the near side of the traveller, which operates at wavelengths where Earth’s atmosphere absorbs almost all the light.

For most applications, sending into space would be a better option than the Moon. The surface of the moon, judging by the extreme temperatures and the difficulties of communication with the Earth, offers more disadvantages than the presence of the surface on which you can build or do something else.

But there is one very specific application that offers Moon: radio telescopes. The land is incredibly “radiogramme” the source for natural and human reasons. Even in space, the signals coming from the Earth, permeate the entire Solar system. But the Moon provides a stunning immunity to radio signals of the Earth: the far side of the satellite literally uses all of the lunar body as a shield.

At the beginning of this year, the cosmologist Joe silk wrote:

“The far side of the moon is the best place in the inner Solar system for monitoring low frequency radio waves — the only waves that are able to detect faint traces left by the Big Bang in space. GRT meet too much interference from electromagnetic pollution, caused by human activity, such as Maritime communications and shortwave broadcasting to get a clear signal, and the Earth’s ionosphere blocks the long wave”.

We could detect signals of inflation, the first stages of the Big Bang, and the formation of the first stars in the Universe with a lunar radio telescope. Although it is hoped to make it on Earth or in space, the lunar surface offers far more sensitivity, because protected from the Earth screen than any other option.

Currently, when any spacecraft goes behind the moon when viewed from Earth, he is in a radio blackout. The fact that radio waves can not pass through the moon, means that no signals you can’t send or receive during this time period. Orbiting satellites, any distant station or the Rovers and even the astronauts “Apollo” lose the ability to communicate with Earth.

But it also means that they are protected from all types of contaminating signals, which are born on the Earth. GPS connection, microwave, radar, cellular and Wi-Fi signals, and even digital camera are among the many land-based sources of pollutants to the radio Observatory. But on the far side of the moon all sources of interference 100% blocked. It is the purest environment for radio astronomy, which you can imagine.

Dr. Jillion Scudder also notes that this idea has its drawbacks. For data transfer you want something like a orbital device that can communicate both with the Ground and with a telescope. Telescope or array of telescopes to be built and deployed on the moon and linked together, if we talk about the mountains (preferably). Alternatively, you could hold the cables to the near side for transmission to the Ground.

And the biggest problem is the cost. Transportation of material to the moon, landing on the lunar surface, deploying and much more — a tremendous job. Even the most modest proposal, the Lunar array for radiookologie (LARC) consists of hundreds of antennas with simple design, distributed in a two-kilometer range. The project will cost $ 1 billion and will be the most expensive radiomuseum in the history of the Earth, if it is built.

Almost any sensible proposal in the field of astronomy implies that the space is much better the lunar surface for the placement of the telescope. Changes in temperature occur in all parts of the moon. Only radio astronomers could obtain an advantage by placing a telescope on the far side of the moon, but this would cost big money.

Until we find a way to knock off the costs or come up with something better, it is highly unlikely that we’ll ever see a lunar telescope, superior to other options. The universe is not going anywhere, she’s waiting for when we reveal her secrets.

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