Comment by SachaMichel | Hacker News Reader

Comment by SachaMichel | Hacker News Reader

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I was going to disagree about the impacts of the starlink constellations because the trails can mostly only be seen during twilight (dusk/dawn) observations. However in this case you're 100% right. The Caltech article below states

"The streaks are most apparent in so-called twilight observations, those taken at dawn or dusk, which are important for finding near-Earth asteroids that appear close to the sun in the sky. ZTF has discovered several asteroids of this nature, including 2020 AV2, the first asteroid spotted with an orbit that fits entirely within the orbit of Venus.

"In 2019, 0.5 percent of twilight images were affected, and now almost 20 percent are affected," says Przemek Mróz, study lead author and a former Caltech postdoctoral scholar who is now at the University of Warsaw in Poland."

We may potentially have a serious problem on our hands unless we really ramp up exterrestrial observation, or maybe we won't have a problem, we might just all be dead on impact.

Link to article https://www.caltech.edu/about/news/palomar-survey-instrument...

Seems kinda disingenuous to quote that part without the “however”…

“Yet despite the increase in image streaks, the new report notes that ZTF science operations have not been strongly affected. Study co-author Tom Prince, the Ira S. Bowen Professor of Physics, Emeritus, at Caltech, says the paper shows a single streak affects less than one-tenth of a percent of the pixels in a ZTF image.

"There is a small chance that we would miss an asteroid or another event hidden behind a satellite streak, but compared to the impact of weather, such as a cloudy sky, these are rather small effects for ZTF."

If the effects are small compared to cloudy weather, is it really that serious of a problem?

The main problem is that we’re ONLY talking about Starlink right now.

What happens when every developed nation wants to launch their own constellations?

It’s kinda the same situation as environmental pollution. Is the world justified in restricting a developing nation from undergoing their industrial revolution like others have before simply because they were too late to the party?

What kind of wars is this going to cause?

Why can the not just ignore the very small parts of images with satellites in them? The orbits of starlink are published publicly so it becomes easy to rule out bright spots in images.

> we might just all be dead on impact

The asteroids in question are tiny. One of the links in the article under discussion is to a previous article about an asteroid that hit the Earth near Iceland 5 hours after being detected. It was about 3 meters wide. That's way too small to justify worries about global damage on impact.

What we've found at the last minute so far has been small, but that doesn't mean that the only last-minute discoveries will be small asteroids always and forever.

As others have said, so what are you going to do about this last minute discovery absent some sort of space-based planetary defense system, in which case this discussion is moot?

If it's big enough to flatten a city but not big enough to kill the ecosphere you might be able to evacuate some of the people affected if you spot it sufficiently early to calculate it's trajectory with good precision.

No, but the bigger they are, the more light they reflect, which means the further away we should be able to see them... if we look in the right direction.

> that doesn't mean that the only last-minute discoveries will be small asteroids always and forever.

Larger asteroids are much easier to see, and the issues being discussed with difficulties in seeing in this thread don't apply to larger asteroids.

Well if a big problematic astroid needs to be 3 times brighter to be detected due to StarLink (made up number) it can come 9 times closer without being detected. O(n^2) is baked in sadly.

Suppose it was a 1km asteroid? How is knowing about it a few extra hours in advance going to help? To give everyone on the planet time to freak out and still not actually do anything about it since there’s nothing we can do?

Do we still have 1km NEOs left to discover?

> Suppose it was a 1km asteroid?

Then it's a lot easier to see, and we would see it a lot further away. The seeing difficulty issues people are talking about in this thread don't apply to asteroids that large.

Then who cares?

Of course you're right. People who might have been warned in time to evacuate, but weren't because there was a Starlink constellation in the way, won't care at all! The dead, after all, are beyond such earthly matters.

> People who might have been warned in time to evacuate, but weren't because there was a Starlink constellation in the way

This won't happen for an asteroid large enough to be a threat. Those asteroids are easy enough to see that the Starlink constellation does not impede their detection. That was the point of my previous post (the GP of yours).

Are we sure there's no overlap between the range of impactors susceptible to occlusion and the range of impactors capable of producing a disaster if they strike a populated area?

(Granted it's multiplying small probabilities, but so is this whole discussion, so I don't feel too bad about it.)

> Are we sure there's no overlap between the range of impactors susceptible to occlusion and the range of impactors capable of producing a disaster if they strike a populated area?

Yes. The key point is that the larger the object, the further away we can see it. And the further away we can see it, the more time we have between the initial sighting and any possible collision with Earth.

The lower bound for a "potentially hazardous object", i.e., one that could cause disastrous damage in a collision, is 140 meters wide, and we can see those far enough away that they are years to decades from getting close to Earth (i.e, time enough to plan a space mission to deflect them enough to miss Earth). Newer surveys are getting to the point where they can detect 10 meter wide objects, which can still cause substantial damage (similar to, say, a hurricane or a tornado), far enough away that they are days to weeks from getting close to Earth (i.e., more than enough time to evacuate possible impact areas if needed).

Even if such an object were temporarily occluded by a low Earth orbit satellite, the occlusion would only last for minutes at most (because the satellite and the distant object are moving across the sky at very different rates). So for objects of the above sizes, occlusion doesn't prevent us from seeing them well in advance.

See here for more info:

https://en.wikipedia.org/wiki/Spaceguard

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