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How satellite ‘megaconstellations’ will photobomb astronomy images

nature.com

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Re: How satellite ‘megaconstellations’ will photobomb astronomy images

#141

Post by 0-_-0 »

vanderZwan wrote: post #124
0-_-0 wrote: post #117

Earlier quoted context omitted.

It seems to be around 1-2%, which I would say is trivial. This can be further reduced if you use multiple exposures because then only 1 contains the streak. Getting satellite data from SpaceX about satellite positions and turning off the receiver for a few seconds would also mitigate the issue. I don't understand how this is treated as a problem that's worth halting satellite launches over.

> which I would say is trivial I'm frankly amazed at the arrogance on display here. Do you honestly think you know better then the entire field of astronomy?

You point to saying that 2% is a small part of an image as a sign of arrogance? Isn't it a small part of an image?

Re: How satellite ‘megaconstellations’ will photobomb astronomy images

#142

Post by reitzensteinm »

vanderZwan wrote: post #126
reitzensteinm wrote: post #69

Earlier quoted context omitted.

I've been there, it's beautiful. Although under ten kilometers from a town of tens of thousands wasn't exactly what I had in mind; I was picturing some of the places I've been in Africa that don't have mobile reception and may well never get it if it means laying fiber. A solar powered base station that relayed mobile internet, even if slow, would make a meaningful difference. The point of my comment isn't to defend…

> I was picturing some of the places I've been in Africa that don't have mobile reception and may well never get it if it means laying fiber. When was the last time that you were in Africa? And in which country, because it's an entire continent. EDIT: So I guess HN doesn't like being called out on https://africasacountry.com/ issues? Well sorry not sorry, but as someone born in Ghana I'm more a little tired of the se…

This isn't about being able to afford infrastructure. It's about population density in rural areas.

North America and Australia (where I'm from) have the exact same issue. No country is going to spend a million bucks to lay fiber to ten person towns in the middle of nowhere.

Re: How satellite ‘megaconstellations’ will photobomb astronomy images

#143

Post by Chris2048 »

vanderZwan wrote: post #126
reitzensteinm wrote: post #69

Earlier quoted context omitted.

I've been there, it's beautiful. Although under ten kilometers from a town of tens of thousands wasn't exactly what I had in mind; I was picturing some of the places I've been in Africa that don't have mobile reception and may well never get it if it means laying fiber. A solar powered base station that relayed mobile internet, even if slow, would make a meaningful difference. The point of my comment isn't to defend…

> I was picturing some of the places I've been in Africa that don't have mobile reception and may well never get it if it means laying fiber. When was the last time that you were in Africa? And in which country, because it's an entire continent. EDIT: So I guess HN doesn't like being called out on https://africasacountry.com/ issues? Well sorry not sorry, but as someone born in Ghana I'm more a little tired of the se…

> So I guess HN doesn't like being called out on

Except they could have been referring to the continent. "some of the places" could refer to different places in different African countries, hence "some"; and doesn't imply all, everywhere, or "forever" in Africa.

Re: How satellite ‘megaconstellations’ will photobomb astronomy images

#144

Post by welterde »

pas wrote: post #138
jobigoud wrote: post #122

Earlier quoted context omitted.

> On its face it seems trivial To me it seems completely impossible. How exactly do you expect to replace the missing information? Statistically from the neighboring pixels or frames? That works if your goal is to make an image prettier, but if you want to make measurements on the data "inventing" the background is not good enough.

Take many short expo images, and integrate them. This way you will have smaller streaks. Yes, the sats will occlude things anyway, and their brightness is a big problem, but they are fast moving, they can be mitigated by moving to may short expo images combined. Yes, it's an undue burden, SpaceX should do more, but they can't solve it completely.

The readout time for astronomy CCDs is typically between 2 and 30s (going faster produces more noise), so there is a lower limit on how short you can make exposures.

In LEO the apparent movement of satellites is around 3.6 arcmin per second, which means for an average sized detector that covers maybe 20 arcmin it takes about 6s to produce a streak that covers the full length of the detector (bit longer depending on the angle). If you want it to cover less than 50% of the length of the detector you have to limit your exposure time to under 3s, which means your duty cycle will be between 60% (if you have a fast camera) and 10%(!).

And that's without even considering the loss of sensitivity you incur, because each image will have lower signal to noise since even with those long readout time the readout noise is still significant.

Re: How satellite ‘megaconstellations’ will photobomb astronomy images

#145

Post by 0-_-0 »

vanderZwan wrote: post #120
0-_-0 wrote: post #115

Earlier quoted context omitted.

Is it a difficult problem to solve though in software? On its face it seems trivial, and something that should be part of an astronomer's job description. The cost of not having internet satellites seems to be many orders of magnitude higher than writing software to get around the problem.

First of all, as GP pointed out: whose cost? Second of all: I highly doubt that this is "trivial", given that observatories are built in the most remote areas of the planet because light pollution was already an enormous problem before these satellites appeared, despite the extra costs that adds to any such project.

Light pollution is global, while a satellite streak is localised to a part of an image. These are not the same problem.

Re: How satellite ‘megaconstellations’ will photobomb astronomy images

#146

Post by Swenrekcah »

0-_-0 wrote: post #141
vanderZwan wrote: post #124

Earlier quoted context omitted.

> which I would say is trivial I'm frankly amazed at the arrogance on display here. Do you honestly think you know better then the entire field of astronomy?

You point to saying that 2% is a small part of an image as a sign of arrogance? Isn't it a small part of an image?

It is a small part of an image, but that does not mean it's not a significant disturbance.

Think for instance about CO2 levels. Is it such a big deal if they reach 1% of the atmosphere? It's only a small part after all.

Re: How satellite ‘megaconstellations’ will photobomb astronomy images

#147

Post by dx87 »

0-_-0 wrote: post #141
vanderZwan wrote: post #124

Earlier quoted context omitted.

> which I would say is trivial I'm frankly amazed at the arrogance on display here. Do you honestly think you know better then the entire field of astronomy?

You point to saying that 2% is a small part of an image as a sign of arrogance? Isn't it a small part of an image?

You didn't say it's small, you said it's "trivial". This isn't about people taking pretty pictures, this is about people trying to do actual work. It doesn't matter if it's 1% or 100% if it still ruins what they're working on. So yes, you're being arrogant by saying that just because it's a "trivial" amount that's ruined, when you don't understand what they're doing.

Re: How satellite ‘megaconstellations’ will photobomb astronomy images

#148

Post by gus_massa »

There was a big discussion a month ago https://news.ycombinator.com/item?id=23926699

In a comment by vilhelm_s in the previous thread has a link to a site that explain that the usual software can select correct the parts of the images and create a nice image https://skyandtelescope.org/astronomy-blogs/imaging-foundati...

Re: How satellite ‘megaconstellations’ will photobomb astronomy images

#149

Post by welterde »

0-_-0 wrote: post #140
welterde wrote: post #125

Earlier quoted context omitted.

CCDs are not really receivers that can be turned off for a couple seconds. A physical shutter moves in front of the detector and covers it (for most instruments as they exist right now).

Can you move the shutter in front of the receiver when you know a satellite will transit?

Sure. And for small field of view things that might be the future. But if you are looking at large chunks of the sky at some point with enough satellites the shutter will have to stay shut for the whole duration of the exposure.. so not really a good solution for that.

Re: How satellite ‘megaconstellations’ will photobomb astronomy images

#150

Post by ashtonbaker »

sumedh wrote: post #128
RedShift1 wrote: post #7

This is bad. This is really really bad. The EU has invested billions in telescopes and that's now going to go to waste. Instead advancing human knowledge it's just going to fill rich guy pockets even more.

> Instead advancing human knowledge it's just going to fill rich guy pockets even more. Isnt Elon helping to advance human knowledge as well?

Not really?
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