Hacker News Board Hacker News, browsed like a classic message board
Live data from Hacker News

How bad are satellite megaconstellations for astronomy?

leonarddavid.com

Post reply on HN
Print view View original

151–160 of 197 posts

Re: How bad are satellite megaconstellations for astronomy?

#151

Post by bythreads »

martinky24 wrote: post #115
bythreads wrote: post #113

I always thought spacex should stick a 5 dollar webcam to each sattelite pointing upwards and create the worlds largest telescope to just shut everybody up

Can you expand on how sticking a $5 webcam on each starlink satellite would quell concerns? I’m in the astronomy community and I can’t quite figure it out. If you could expand on what you’re thinking and some of the science behind it, that’d be great.

Half baked for sure, but : I thought given the ultra precise location and clocks, combined with the laser coms you could build a large array, or a inferometer with a baseline the size of the leo orbit.

Could be used for whole sky surveys, transient detections, wide angle monitoring, and high res imaging (granted this last one might require more operational finesse than a 5 dollar webcam c ould give you since you'd need fractional wavelength accuracy (right?). A radio antenna pointing outwards would in all honesty probably be better.

But 42.000 x X mega pixels in orbit pointing outwards at least will give you some nice big piles of data to play woth - and the downlink is baned in

Re: How bad are satellite megaconstellations for astronomy?

#152

Post by DiogenesKynikos »

labcomputer wrote: post #144
rickydroll wrote: post #43

Earlier quoted context omitted.

https://en.wikipedia.org/wiki/Extremely_Large_Telescope The 39-meter primary mirror has 798 1.4-meter segments, each individually adjustable. The scaffolding required to hold all the segments is "significant" and must be assembled in orbit. We would stick this out next to the James Webb at L2, which means we would need the ability to travel to L2 to construct this mythical orbital extremely large telescope. With our…

> With our current technology, we can build ELT on Earth for a fraction of the cost of putting it in orbit. That's going to change soon. The reason the ELT needs individually adjustable panels is to provide corrections for refraction in the atmosphere as it swirls around. A space-ELT doesn't need that (well, maybe some cheap slow actuators to set the focus on a large non-rigid mirror). As the cost of launches drop, w…

Every 30-meter-class telescope uses segmented mirrors, because nobody knows how to make a single, monolithic 30-meter-diameter mirror.

It's only barely technically feasible to construct these 30-m telescopes on the ground. The idea that they can be constructed in space is just fanciful.

Re: How bad are satellite megaconstellations for astronomy?

#153

Post by nullc »

rblatz wrote: post #116
nullc wrote: post #102

Earlier quoted context omitted.

You're not imaging with cryogenic CCDs --- satellite trail can blow out whole rows.

Just do it in space and avoid the whole atmosphere and ground based light pollution. Space is cheaper than ever now, this is a problem for amateur astronomers, and hobbyists shouldn’t hold back progress.

Space imposes extraordinary costs and limitations which heavily precludes exploratory research. Instruments are built for space to achieve specific tasks which we know will be successful.

Instrument development has to first occur on earth-- including the research that lets us know which things will yield results deployed in space.

Astronomy aside, fleets of satellites once they turn to junk may eventually make further launching problematic.

Re: How bad are satellite megaconstellations for astronomy?

#154

Post by WithinReason »

StellarScience wrote: post #42

There certainly is a real concern for astronomers, but the photo illustrations used in the article are selected to make things seem worse than they really are. They're wide field of view, long-duration exposures. That used to be the way astronomers imaged space, with film systems a century ago. But these days astronomical telescopes tend to have much narrower fields of view (like tiny soda straws peering into one par…

Not to mention this only happens at dusk and dawn when the satellites are in sunlight.

Re: How bad are satellite megaconstellations for astronomy?

#155

Post by WithinReason »

labcomputer wrote: post #140
whoopdedo wrote: post #134

Earlier quoted context omitted.

> these days some of the best astronomy is performed by telescopes in space, so astronomy overall benefits by having easier access to space. Public access satellites. The FCC requires broadcast licensees to demonstrate that they're acting "in the public interest". Should private rocket launches have to give a minimum amount of their payload to research and non-profit purposes?

Sure, why not? A Hubble-sized telescope is only about 12 tons, which is only about 70% the mass of what a Falcon 9 can deliver to low earth orbit, and SpaceX does that 100x per year (it's only May and they've launched 47 so far this year). For reference, Spitzer is 1 ton and Chandra is 6 tons. The elephant in the room is that launching one Hubble per year to a Hubble-like orbit only uses about 1% of SpaceX's current…

Fun fact: in 2012 the Department of Defense donated 2 Hubble-class telescopes to NASA it had lying around and didn't need:

https://en.wikipedia.org/wiki/2012_National_Reconnaissance_O...

Re: How bad are satellite megaconstellations for astronomy?

#156

Post by fecal_henge »

sitkack wrote: post #137
StellarScience wrote: post #42

There certainly is a real concern for astronomers, but the photo illustrations used in the article are selected to make things seem worse than they really are. They're wide field of view, long-duration exposures. That used to be the way astronomers imaged space, with film systems a century ago. But these days astronomical telescopes tend to have much narrower fields of view (like tiny soda straws peering into one par…

You ignore the entirety of the LSST which will take more image data in its first year than all of humanity. It is wide field, and these constellations cannot just be stacked out. You think you are more informed than you are.

Why is stacking not possible in this case?

Re: How bad are satellite megaconstellations for astronomy?

#157

Post by DiogenesKynikos »

StellarScience wrote: post #121
schiffern wrote: post #112

Earlier quoted context omitted.

It's not really that it saturates the entire image, it's that bright objects creates non-linear and ghosting artifacts which degrade the sensitivity of the entire exposure, even after post-processing in software. https://www.space.com/bluewalker-3-prototype-satellite-brigh... https://www.nature.com/articles/s41586-023-06672-7 https://iopscience.iop.org/article/10.3847/1538-3881/abba3e/...

Thanks for providing all those links. Indeed, the key there is peak magnitude. BlueWalker 3 has a giant array that reflects light like a mirror. So when you happen to get the angle of incidence exactly equal to the angle of reflection, it shines quite brightly. Of course since it's reflecting all sunlight in one direction, that means from all other spots on earth it will be extremely dim. Also note that BlueWalker 3,…

> So one solution is to schedule astronomy for the middle of the night, when none of these low earth satellites will lit by the sun at all.

Let me translate that a bit: "So one solution is to just eliminate 20% of all available observing time."

Re: How bad are satellite megaconstellations for astronomy?

#158

Post by hagbard_c »

bmitc wrote: post #105
hagbard_c wrote: post #63

Earlier quoted context omitted.

If the promises made for new launch systems like SpaceX' Starship (and maybe even, one day, in some unknown future, Bezos' Blue Origin manages to launch something larger than a phallic pond hopper?) it should become radically less expensive to launch larger telescopes into orbit and/or to e.g. the moon.

That "should" needs a lot of backing up, and I don't understand why we need to singlehandedly rely on the same company creating the issues to apparently solve them with wishful thinking.

> I don't understand why we need to singlehandedly rely on the same company creating the issues to apparently solve them with wishful thinking.

It is because you did not start your own re-usable space vehicle company. Bezos did but thus far he seems to treat it as a billionaire's toy, throwing a few fellow class members just over the Kármán line. There's a few others making attempts to actually get to space - Rocket Labs etc. - but mostly it comes down to Musk's creation which opened the door to radically lower costs, i.e. without them the usual suspects would have had no reason to keep on pushing 70's technology at whatever price they manage to extract from the governments and the market.

Re: How bad are satellite megaconstellations for astronomy?

#159

Post by Havoc »

throw_pm23 wrote: post #34
Havoc wrote: post #13

As much as I sympathize this feels like a necessary evil to me in a sense vaguely accerlationism like. I do think starlink can do more to help the situation though. Sure they tweaked some of the satellites to minimise it, but they could do more. Presumably the know the precise location and orientation of each sat. Surely that can be packaged into a data stream that helps unfk the images? Maybe with a sprinkling of th…

When you are driving towards a wall or a cliff you don't necessarily want to accelerate.

You do if you think the gap between this cliff and the next can be jumped

Re: How bad are satellite megaconstellations for astronomy?

#160

Post by TeMPOraL »

sapiogram wrote: post #95
TeMPOraL wrote: post #88

Earlier quoted context omitted.

> There’s a much longer list of large radio based telescopes which have minimal advantages in space to the point where we haven’t launched any What if they could be put behind the Moon, completely shielding them from Earth RF emissions? It's been a cost-prohibitive idea now, but might not be for much longer.

The largest filled-aperture radio telescope in the world has a 500-meter diameter, and reportedly only cost $180 million. For comparison, the International Space Station costs $3 billion per year just to operate. Doing stuff in space is expensive .

Right, but the whole reason people are so excited about SpaceX is because they're making the costs of doing stuff in space drop like a stone.
Post reply on HN