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How bad are satellite megaconstellations for astronomy?

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Re: How bad are satellite megaconstellations for astronomy?

#171

Post by djao »

nullc wrote: post #153
rblatz wrote: post #116

Earlier quoted context omitted.

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 furthe…

SpaceX deliberately launches satellites into orbits which are too low to sustain on their own. Once the satellites run out of propellant, which happens after a few years of normal operation, they cannot remain in orbit indefinitely and eventually burn up in the atmosphere.

On very rare occasions, a launch malfunctions in such a way that the satellites end up in unintended orbits that do turn into long-term junk, but this is not the norm.

Re: How bad are satellite megaconstellations for astronomy?

#172

Post by nimish »

schiffern wrote: post #164
labcomputer wrote: post #141

Earlier quoted context omitted.

So just write all grant proposals with an extra 5% slop.

Budgets are fixed, so again this also boils down to "just do 5% less science." Believe it or not, actually using 100% capacity on the big expensive telescope you paid for isn't some brilliant unheard-of suggestion like people seem to think. This Dunning-Kruger idea always seems to crop up whenever this particular topic is in the news. There simply isn't any "slop in the system" that lets you get that 5% (and climbing…

Doing 5% less science is an acceptable cost for full commercial space exploitation. I'd rather have internet service in 100% of the US than an extra few graduate theses.

And who knows, necessity is the mother of invention so one of those grad students could invent a way around it.

Re: How bad are satellite megaconstellations for astronomy?

#173

Post by thayne »

lifeisstillgood wrote: post #143
thayne wrote: post #130

Earlier quoted context omitted.

If you are looking for short period events, losing a single frame can mean losing critical data. > Or they can just use that information for better scheduling: wait a minute or two to image a particular spot, so there won't be satellites in the field of view. Which means more time and effort, and ultimately money needs to be spent on scheduling observations to avoid the thousands of these satellites. And sometimes it…

GRB - Gamma Ray Burst (I am guessing)

Yes

Re: How bad are satellite megaconstellations for astronomy?

#174

Post by joshuakogut »

jonplackett wrote: post #9

Is this a bit of a temporary problem, in the the very technology causing the issue - substantially cheaper access to space - will presumable ultimately put a frikkin massive telescope, or many massive telescopes into orbit where they’ll also not have to deal with the many other issues ground telescopes have to deal with. I get that this still sucks for any individual with a Telescope though.

> put a frikkin massive telescope, or many massive telescopes into orbit

See: Hubble, JWST, and more to come

edit: JWST is in a different point from LEO but still counts

Re: How bad are satellite megaconstellations for astronomy?

#175

Post by joshuakogut »

ooterness wrote: post #126
martinky24 wrote: post #123

Earlier quoted context omitted.

Doesn’t the moon rotate

No. The moon is tidally locked to the Earth, so its rotation exactly matches its orbital period. If you put a telescope on the far side, it'll always be pointing away from Earth.

This is the principle behind the lagrange point chosen for the James Webb Space Telescope. It's occluded from the brightness of the sun by the earth.

Re: How bad are satellite megaconstellations for astronomy?

#176

Post by mrguyorama »

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.

This is equivalent to saying "Just do one percent the space science we do now"

Where is SpaceX offering to put up a billion dollars worth of space observatories to offset their pollution of a public good?

Re: How bad are satellite megaconstellations for astronomy?

#177

Post by ggreer »

bmitc wrote: post #109
ggreer wrote: post #65

Earlier quoted context omitted.

Useful for anything? Starlink useful to its 2.7 million subscribers. And it's already profitable. As of last year, SpaceX makes more in subscription fees than it costs to build and launch the satellites. The economics will only become more favorable when SpaceX improves their launch capabilities with Starship.

I'm not sure how the existence of subscribers and profit negates the point. Their are plenty of things that have those that aren't useful beyond a capitalistic sense.

SpaceX provides internet access. Millions of customers pay for it. The revenue from the customers is more than enough to cover the business costs. The negative externalities are much smaller than say... aircraft or cargo shipping. If a sustainable business like that isn't enough to justify usefulness, then what is?

Re: How bad are satellite megaconstellations for astronomy?

#178

Post by labcomputer »

DiogenesKynikos wrote: post #152
labcomputer wrote: post #144

Earlier quoted context omitted.

> 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.

Yes, but in space the segments don't need real-time corrections for atmospheric effects (and the whole structure doesn't need to be built to withstand the strong winds at the top of a mountain). The idea that you can't build that in space is just naive.

Re: How bad are satellite megaconstellations for astronomy?

#179

Post by ggreer »

bmitc wrote: post #107
ggreer wrote: post #100

Earlier quoted context omitted.

What environmental impact? So far there have been 162 Starlink launches. Each launch uses around 200 tons of RP-1, which is equivalent to the fuel capacity of a Boeing 747. In other words: A single 747 burns more fuel in a year than all the Starlink launches in the past five years.

Rocket launches are far more environmentally non-friendly than planes. You can't just look at fuel capacity. It's the composition and where the waste product gets dumped. Rockets dump their waste much higher up in parts of the atmosphere much more sensitive to it. Comparing a rocket and plane isn't an effective comparison in terms of environment impact. So this: > A single 747 burns more fuel in a year than all the S…

Falcon 9's exhaust is almost entirely carbon dioxide and water vapor. If anything the exhaust is less polluting than aircraft or combustion vehicles, as air-breathing engines create nitrogen oxides.

Re: How bad are satellite megaconstellations for astronomy?

#180

Post by labcomputer »

schiffern wrote: post #164
labcomputer wrote: post #141

Earlier quoted context omitted.

So just write all grant proposals with an extra 5% slop.

Budgets are fixed, so again this also boils down to "just do 5% less science." Believe it or not, actually using 100% capacity on the big expensive telescope you paid for isn't some brilliant unheard-of suggestion like people seem to think. This Dunning-Kruger idea always seems to crop up whenever this particular topic is in the news. There simply isn't any "slop in the system" that lets you get that 5% (and climbing…

Yes, but that's a system problem, not a user problem. The comment I replied to posited that a specific user would collect 5% less data. If you add ~5% to your grant proposal, you get the same amount of data.

As for the system problem, that is solved by building 5% more observing capacity. Or, more realistically, starting new telescope projects slightly earlier. This really isn't as complicated as you're trying make it out to be. Pot, meet kettle.

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