Lunar Radio Telescope to Unlock Cosmic Mysteries

https://spectrum.ieee.org/lunar-radio-telescope

by rbanffy • 6 months ago

57 19 6 months ago

spectrum.ieee.org

8bitsrule2• 6 months ago

Very readable explanation of why and how useful a dark-side lunar radio telescope would be.

TLDR: As a result of expansion of the universe, over 13B years the wavelength of neutral hydrogen signals has been stretched from 21cm to 'tens of meters'. On Earth, this part of the spectrum is cluttered with noise from Earth and Sun. For 14 days at a time...not a problem on the dark-side.

KineticLensman3• 6 months ago

It’s far side, not dark side. The moon doesn’t have a dark side anymore than the earth does

wumms3• 6 months ago

NASA uses "dark side" (meaning far side, not night side) when facing the public [0]:

A series of test images shows the fully illuminated “dark side” of the Moon that is not visible from Earth.
The far side of the Moon was first observed in 1959

[0] https://science.nasa.gov/earth/earth-observatory/the-dark-si...

perilunar2• 6 months ago

Well the point is it needs to be both. The telescope needs to be on the far side to shield it from Earth, and the dark side to shield it from the Sun. But yes, it's only on the dark side 50% of the time.

8bitsrule2• 6 months ago

For 14 days a month, it's the dark side. That's the whole idea. Astronomy 101.

Panzerschrek• 6 months ago

Is it really necessary to have a lander to perform radio-astronomic observations in moon's shadow? Isn't it easier to have an orbiting spacecraft instead and perform observation while it's orbiting behind the moon?

AngryData• 6 months ago

There is perhaps some extra opportunity in a 10-14 day solid observation window, but I don't see why a satellite version couldn't still work in smaller windows.

Another reason could be testing for building a much large radio antenna on the moon's surface in the future which is mentioned to farther down in the article. The moon itself and it's dust has electromagnetic effects that might effect measurements and learning about them now could help future planning.

aragilar• 6 months ago

You'd build an array (see e.g. VLA mentioned in the article or SKA), and it is much easier to combine the data from an array if everything isn't flying around and so there are varying distances between the antennae.

xattt• 6 months ago

Isn’t the benefit here that you don’t have to deal with things such as significant Doppler shift, or having to maintain a supply of propellant for orbit-keeping?

pavel_lishin• 6 months ago

How significant would doppler shift be for a lunar orbit?

jupitr• 6 months ago

It's not necessary, but is significantly more radio-quiet than a lunar orbit. And secondly, though unfortunately not something we could really exploit this time, the stable temperatures of the lunar night greatly help with calibration for sensitive measurements like the 21cm Dark Ages signal

DoctorOetker• 6 months ago

on the other hand and orbiter could have a much larger effective telescope diameter by SAR.

perilunar2• 6 months ago

My immediate thought was why not put it in the Earth-Moon L2 Lagrange point, like the James Webb Space Telescope, where it would be permanently shaded from RF from both the Earth and the Sun. But...

1. James Webb is in the Earth-Sun L2 point, where it is largely (though not completely) shaded from the Sun. A radio telescope at Earth-Sun L2 wouldn't be shaded from Earth RF. [edit: JWST is in a halo orbit which keeps it out of the shadow]

2. The Earth-Moon L2 point is shaded from the Earth, but not the Sun. So no benefit compared to the far-side lunar surface.

3. According to TFA, being on the lunar surface gets the telescope out of the solar wind, which is noisy at the low radio frequencies being observed.

Lunar Radio Telescope to Unlock Cosmic Mysteries

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