Dutch antennas unfolded behind the moon | Hacker News Reader

Dutch antennas unfolded behind the moon

ru.nl

105 pointssohkamyung21 comments

Why would you put antennas behind the moon?

I read the article: these antennas are radio telescopes (or perhaps just do the same job). So they're using the moon to block interfering radio signals from Earth.

They're listening to a doppler shifted version of the hydrogen alpha spectral line (~450 THz doppler shifted down to ~30 MHz) down to about the VHF television band (hence the almost "rabbit ears" style antennas). Being on the other side of the Moon shields them from powerful terrestrial transmitters. The massive doppler shift means they're listening (observing) to bubbling atoms of hydrogen closer in time to the Big Bang than what was observed by COBE or WMAP.

https://lambda.gsfc.nasa.gov/product/cobe https://map.gsfc.nasa.gov

> We have the opportunity to perform our observations during the fourteen-day-long night behind the moon, which is much longer than was originally the idea.

And from the sun.

> The moon night is ours, now.

That probably sounds less creepy in Dutch.

"De maan is nu van ons" ;-)

This reminds me of another instance of Dutch hubris:

https://beeldbank.rws.nl/MediaObject/Details/Monument__Hier_...

The satellite is in L2. More details in https://www.nature.com/articles/d41586-018-05231-9

Self nitpicking: It's the Earth-Moon L2, not the Sun-Earth L2. Even more info https://en.wikipedia.org/wiki/Lagrangian_point

I wonder how the antennas "unfold".

Are they perhaps nested rolled cones of thin metal?

I found a video of the Dutch team testing the 'unfolding' mechanism used in the NCLE. It looks like a spool that unwinds.

NCLE antenna deployment test - 25x: https://www.youtube.com/watch?v=hca3MeX-8rw

Web page with video: https://www.isispace.nl/projects/ncle-the-netherlands-china-...

OK, I get it.

It's like an extreme version of metal tape measures. Which are ~flat when rolled up, and then curve enough when unrolled to become ~rigid. But in this case, they seem to become almost cylindrical when unrolled.

I know that it's likely an old design. It's just that I know nothing about satellite design.

Some early Amateur Radio satellites (Project OSCAR) literally did use silver-plated steel tape measures.

http://www.rfcafe.com/references/popular-electronics/oscar-3...

Many university-grade cubesats use tape measure antennas today. They can be easily stored during launch by wrapping them around the satellite body, secured with nylon fishing wire and then released by burning through the nylon with a NiChrome heating element.

Aside- I was talking to a friend who works at a satellite company. He mentioned that one of the forthcoming missions, they are sending up a space-based 3D printer that prints trusses since it's more compact to send up the printer and feedstock than long structural elements. I wonder if you could print your antenna in space to get a larger one (but folding is probably more parsimonious).

This just reminds me too much of this movie: https://m.imdb.com/title/tt1034314/

Anyone know how and why this Dutch/Chinese collaboration came about?

I know that ESA headquarters are in the Netherlands. Do they just have so much space funding they have to look outside of Europe?

The ESA collaborates with everyone all of the time. It’s a great way to get the best instruments onto each launch opportunity.

Dutch universities have funding outside of ESA or Europe. A lot of it is determined at the national level. there have been more academic collaborations recently between the two countries. The article doesn't mention ESA so i think it's just a chinese mission accepting a contribution from radbout and others.

I appreciate the photos of the antennae. It’s not a critical mission element, but photos do speak louder than words.

https://www.sciencealert.com/there-s-now-a-radio-telescope-i...

At the bottom, it says:

> This article was originally published by Universe Today. Read the original article.

But it doesn't provide a link to the original article: only to the main Universe Today website.

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