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How bad are satellite megaconstellations for astronomy?

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Re: How bad are satellite megaconstellations for astronomy?

#141

Post by labcomputer »

schiffern wrote: post #117
hedora wrote: post #114

Earlier quoted context omitted.

Even if they don’t know where the satellites will be, a simple motion detection algorithm in the stacker would delete the streak caused by the satellite. A given pixel will only be impacted for a few exposures, so just grab 5% more images. I’d guess terrestrial light pollution is a much bigger problem.

>so just grab 5% more images. You say it like major observatory telescopes are sitting idle, but they're not. In practice what actually happens is you lose 5% of your scientific data return. >terrestrial light pollution Problem is that it's global vs local, so our normal solution for terrestrial light pollution (build telescopes in a remotely populated area) doesn't work.

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

Re: How bad are satellite megaconstellations for astronomy?

#142

Post by KiwiJohnno »

stevage wrote: post #71
pfdietz wrote: post #55

Earlier quoted context omitted.

Propellant is very cheap.

Yeah but it is still mass and volume that might reduce available payload?

Not really. Starship is aiming for 150 MT to LEO. The launch mass of JSWT was 6.5 MT.

Yes, JSWT was launched into a L2 transfer orbit and not LEO, but from the above margins there is probably enough spare capacity for this.

Re: How bad are satellite megaconstellations for astronomy?

#143

Post by lifeisstillgood »

thayne wrote: post #130
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…

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)

Re: How bad are satellite megaconstellations for astronomy?

#144

Post by labcomputer »

rickydroll wrote: post #43
_dain_ wrote: post #28

Earlier quoted context omitted.

> That needs some citations. The James Webb Telescope's mirror is 6.5m in diameter. It took decades and billions of dollars of overruns and a prayer to launch and work correctly. There is no hope of most hardware repairs. Because it had to get launched folded up, because the launch vehicles were so space- and mass-constrained. The unfolding mechanism was enormously complicated and added to much of the cost. Now we ca…

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, we will hit a point where it is cheaper to put the telescope in space where you don't need those expensive atmosphere correctors.

Re: How bad are satellite megaconstellations for astronomy?

#145

Post by dexwiz »

labcomputer wrote: post #141
schiffern wrote: post #117

Earlier quoted context omitted.

>so just grab 5% more images. You say it like major observatory telescopes are sitting idle, but they're not. In practice what actually happens is you lose 5% of your scientific data return. >terrestrial light pollution Problem is that it's global vs local, so our normal solution for terrestrial light pollution (build telescopes in a remotely populated area) doesn't work.

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

Why would they not already be trying to maximize grant size?

Re: How bad are satellite megaconstellations for astronomy?

#146

Post by labcomputer »

rickydroll wrote: post #89
_dain_ wrote: post #61

Earlier quoted context omitted.

For one thing, before this decade is out we will have the lift capacity to get an ELT-worth of mass to L2. And the lack of need to correct for atmospheric distortion would simplify the design considerably. But it's beside the point. Such a singular mega-telescope would no longer be the only way to do astronomy in space. A world of radically lower launch costs gives more possibilities. We could have a fleet of thousan…

It doesn't simplify the design; it increases its complexity. All the problems of telescopes on Earth become significantly more problematic in space: temperature, flexure, warping, backlash, pointing models, optical alignment, and collimation are some of the issues. Electronics, sensors, and consumables fail or run out, which means you need to be able to get there to fix things. Then, as research projects change, you…

> Electronics, sensors, and consumables fail or run out, which means you need to be able to get there to fix things. Then, as research projects change, you need to change instruments.

So launch another. Launch capacity is getting cheap... let's use it.

Consider that 1% of SpaceX's annual launch capacity is enough to put one Hubble in orbit every year. Instead of sending astronauts to fix the fucked-up mirror, you just launch one with a not-broken mirror.

We as a planet don't even build that many ground-based telescopes with a 2.5m+ mirror each year. Think about how astronomy would change if you could just take every telescope we build today and put it in space.

Re: How bad are satellite megaconstellations for astronomy?

#147

Post by [deleted] »

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…

[deleted]

Re: How bad are satellite megaconstellations for astronomy?

#148

Post by labcomputer »

p_j_w wrote: post #96
delichon wrote: post #32

Earlier quoted context omitted.

Don't Chandra, Webb and Hubble, et. al. sufficiently prove the usefulness?

The cost of getting those into space is a relatively small part of the overall cost. The amount of cost benefit one of these telescopes would see just to the cost reductions gained specifically because of Starlink are insignificant.

> The cost of getting those into space is a relatively small part of the overall cost.

Well, technically, I suppose you could argue that the direct launch costs are small. However, most of the cost of the telescope itself are driven by the high launch costs.

That's the classic problem for satellites: Launch is expensive, so you can't afford to fail. So you have to use mil-spec everything. Every screw has to come with a piece of paper attesting to the provenance of the chromium used to make the stainless steel. Every system has to be built and tested and have triple redundancy. You have to use teflon-insulated wires, because god forbid anything outgases while on orbit. You have to over-build everything, and test all the vibration modes on those giant vibration tables NASA owns. So now "the satellite is expensive". Oh, and since the satellite is expensive, the launcher can't afford to fail and costs just spiral out of control.

But look what happens when you have cheap launches: You don't care if the satellite has a 1% chance of failing. If it does, learn from your mistake, make that one thing better and launch again. Now that you only need two nines instead of five, all of your costs go down. You can use regular-grade chips, and hardware store screws. Instantly the price of everything drops by several orders of magnitude.

Re: How bad are satellite megaconstellations for astronomy?

#149

Post by ghaff »

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…

The upset is also because urban people or people in many denser areas generally don’t really benefit from Starlink etc. You can bet if those types of satellites were the only readable way for them to get internet, astronomy would suddenly fall way down on their list of priorities.

Re: How bad are satellite megaconstellations for astronomy?

#150

Post by bmitc »

jryle70 wrote: post #124
bmitc wrote: post #107

Earlier quoted context omitted.

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…

> is not an accurate summary of the environmental impact of rocket launches. So what is the accurate summary of the environmental impact of rocket launches? 10 times more than B747? 100 times? How would it look compared to aviation? > rocket launches are incredibly disruptive to the local ecosystems of the launch sites. Not according to FAA when they issued license for SpaceX's launches at KSC - [0] [0] - https://www…

You can just search for it. The general answer is that it is not good, and it's getting worse. The comparison to aviation, once again, is not really needed. Aviation is extremely polluting and damaging to the environment (not just poluttants but also disease and invasive seed spreading). There's nonquestion about that. But it isn't related to rocket launches anymore than other pollution.

Here's a couple of articles.

https://research.noaa.gov/2022/06/21/projected-increase-in-s...

https://www.nytimes.com/2024/01/09/science/rocket-pollution-...

What's more, and this is touched some in the articles, deorbiting satellites so routinely is dumping toxic metals and plastics into the upper atmosphere at increasing rates. We're literally turning the atmosphere into a burn skyfill.

> Not according to FAA when they issued license for SpaceX's launches at KSC

The FAA is not an environmental or even scientific agency. Additionally, the FAA has revealed itself to be a captured regulator in several instances. There's no question that it is susceptible to political and monetary pressures.

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