SpaceX working on fix for Starlink satellites so they don’t disrupt astronomy • Hacker News Board

Re: SpaceX working on fix for Starlink satellites so they don’t disrupt astronomy

#231

Post by joshvm » Mon, Dec 09, 2019, 1:48 AM UTC

notatoad wrote: post #183

Hoping i can get an answer here from somebody who actually knows, and not just a spacex fanboy or hater: what's the actual scope of the problem here? Shotwell's response and other comments i've seen seem to imply starlink satellites are primarily impacting amateur astronomy ("kids looking through telescopes") and that scientific research is performing post-processing to the recorded images which can mostly eliminate…

Shotwell's comment is extremely patronising under the circumstances. This doesn't affect kids looking through telescopes at all. If it's bright enough to see through an amateur telescope, it's bright enough to ruin a precision observation from a real instrument. A large part of the outcry is lack of tact from Spacex.

Satellites in images is not new and has caused astronomers problems for a while. It's not common, but most people in the field know someone it's happened to.So now the issue is there will be an order of magnitude objects in space.

Any kind of time series where you observe brightness over time would be affected by a satellite impinging the field. Spectroscopic measurements would also be affected. Astronomers use incredibly sensitive instruments looking for very faint objects - if a bright object is in the field of view, it can saturate the detector and ruin the image.

For context some measurements, like imaging exoplanets, are so precise that you have to block the light from the (already faint) target star to see what's around it.

In reality it's amateurs that can compensate with post processing. Professional astronomers are likely to just trash the data and try again.

Then there are upcoming survey instruments like the LSST which take very wide angle images (I expect they already have some mitigation strategy becuase of other spacecraft). That said, the smaller your field of view, the lower the chance of a satellite impinging.

One solution could be a mechanical shutter which could be activated when a satellite is about to impinge the field, or triggered by a database of satellite ephemirides.

Re: SpaceX working on fix for Starlink satellites so they don’t disrupt astronomy

#232

Post by s1k3b8 » Mon, Dec 09, 2019, 2:27 AM UTC

9192631770_Hz wrote: post #50

dylan604 wrote: post #6

“No one thought of this,” she said. “We didn’t think of it. The astronomy community didn’t think of it.” I really have trouble believing that nobody mentioned adding thousands of satellites would go unnoticed. It is damn near impossible to take any image of the night sky without having a satellite streak through the frame. I have plenty of images with multiple satellites visible at the same time. In wide angle timela…

Yes, I’m an astronomer and I can tell you this SpaceX statement is pure BS. The astronomy community absolutely thought of this before any of these satellites were launched. I’ve personally talked about it at public outreach events (and it was members of the public who brought it up) and topic has definitely come up at professional meetings...but there is just a general feeling of powerlessness, both from the point of…

> charlatan like Musk

If Musk was a charlatan, we wouldn't have this problem. Musk would have failed to put spacelink satellites in orbit and we wouldn't have this problem.

The reason why we have this problem is precisely because Musk isn't a charlatan.

> I also know a lot of people directly involved in SSA and all of them are very concerned with how much these new constellations are going to increase the risk of collisions

Just because they are concerned doesn't mean they are against SpaceX or Musk. Every venture is open to concern.

> SpaceX cultists

Is NASA and the US government SpaceX cultists? You act like Musk just sent this satellites up there without any warning or government approval. He didn't.

All you've done is toss ad hominems at Musk, SpaceX and those who support this venture.

Re: SpaceX working on fix for Starlink satellites so they don’t disrupt astronomy

#233

Post by portillo » Mon, Dec 09, 2019, 2:32 AM UTC

shaklee3 wrote: post #227

portillo wrote: post #210

Earlier quoted context omitted.

I am the author of the slides/paper. The analysis was done with the best data available at the time, but I am interested in knowing what parameters you think are off / have changed substantially since then. I can say that the mass and volume of the satellites has changed quite a lot, and therefore the number of rocket launches required is pretty off in the paper. But I have not seen much info to invalidate the rest o…

Correct me if I'm wrong, but I thought the mass estimates increased? either way, that should only affect how many that can launch at a given time. I didn't think that number had changed appreciably either.

In their original FCC filing, they were estimating 386 kg per satellite. The ones launched in May were 227 kg each, and those last month 260 kg (they added the Ka-band antennas).

I am not sure how much heavier will the satellites be when they integrate the ISLs (if they do), but I believe that in any case they will be under 330 kg.

Re: SpaceX working on fix for Starlink satellites so they don’t disrupt astronomy

#234

Post by CrazyStat » Mon, Dec 09, 2019, 2:59 AM UTC

DuskStar wrote: post #212

SamReidHughes wrote: post #100

Earlier quoted context omitted.

I was a bit wrong in my initial estimate. More satellites can't improve latency by much once they get dense enough, and it looks like Starlink has enough such that the altitude would be on the same scale as distance. Still doesn't matter for the typical home user. Like, I get 21 ms ping to servers in my local city.

> Still doesn't matter for the typical home user. 550km vs 1,150km might not matter, but it matters a ton vs 40,000km. Even without the bandwidth limits, I wouldn't be able to use geostationary internet for my normal usage.

Starlink has been LEO since it was first announced, so how bad geostationary internet may be is not relevant to the discussion about why SpaceX lowered the altitude.

Re: SpaceX working on fix for Starlink satellites so they don’t disrupt astronomy

#235

Post by Reason077 » Mon, Dec 09, 2019, 3:04 AM UTC

iudqnolq wrote: post #188

mstipetic wrote: post #177

Earlier quoted context omitted.

I live in a very large city in Europe. I think the number of stars you can see is less than 20. Ground based pollution is horrible, I don't know how you can compare those two.

Maybe because large telescopes aren't in very large cities.

Here’s an example of a large telescope in a very large city:

https://www.rmg.co.uk/discover/explore/great-equatorial-tele...

Re: SpaceX working on fix for Starlink satellites so they don’t disrupt astronomy

#236

Post by doubleunplussed » Mon, Dec 09, 2019, 3:27 AM UTC

jdashg wrote: post #202

doubleunplussed wrote: post #119

Earlier quoted context omitted.

It's not a dot, in a long exposure photograph, it's a line. You don't delete it spatially, you'll want to subtract off the extra photon counts along that line so you can retain whatever was in that part of the image. Now, I think that's possible - find lines one diffraction-spot wide, fit to its brightness and subtract it off. They should be damned near straight lines of constant brightness given how fast satellites…

You can't just subtract a bright signal and hope to see the weak signal underneath it, or we'd just subtract daylight during the day.

Depends how bright, I do it every day in a different context and it can work pretty well. The brighter, the more of that noise I was getting at. Sunlight is very, very bright , but satellites less so. I'd need to know how bright to know if the resulting noise would swamp the signal. Perhaps the fact that astronomers aren't doing this is evidence that it does.

Re: SpaceX working on fix for Starlink satellites so they don’t disrupt astronomy

#237

Post by [deleted] » Mon, Dec 09, 2019, 3:47 AM UTC

dylan604 wrote: post #6

“No one thought of this,” she said. “We didn’t think of it. The astronomy community didn’t think of it.” I really have trouble believing that nobody mentioned adding thousands of satellites would go unnoticed. It is damn near impossible to take any image of the night sky without having a satellite streak through the frame. I have plenty of images with multiple satellites visible at the same time. In wide angle timela…

[deleted]

Re: SpaceX working on fix for Starlink satellites so they don’t disrupt astronomy

#238

Post by laken » Mon, Dec 09, 2019, 3:59 AM UTC

mlyle wrote: post #200

rrss wrote: post #140

Earlier quoted context omitted.

60 satellites were launched on 24 may 2019. It looks like all the articles are after that, in response to people seeing the satellites in the sky.

Here's a 1999 article, well before the announcement of Starlink, talking about the increasing problems of trails spoiling deep sky observations--- https://www.sciencedirect.com/science/article/pii/S027311779... > From Table 1 it is clear that since 1985 the annual mean number of trails has risen from 2.5 to 2.9 in a 60 minute exposure, an increase of 16%; the number of spacecraft on orbit has increased by 39% in the…

The original assumption, as far as I'm aware, was that Starlink being in such a low orbit wouldn't have these issues that previous satellites had.

Re: SpaceX working on fix for Starlink satellites so they don’t disrupt astronomy

#239

Post by greglindahl » Mon, Dec 09, 2019, 4:00 AM UTC

iudqnolq wrote: post #224

greglindahl wrote: post #221

Earlier quoted context omitted.

That list of telescopes only goes back to 1932, and I studied astronomy at one of the institutions in question. As an example, why is this area named Observatory Hill? https://www.google.com/maps/place/Observatory+Hill,+Cambridg... > In general, I'm fine with scie!tists needing to accommodate people more than they had to 100 years ago. Indeed, that's the majority opinion.

You're right, not quite 100 years.

... it's named Observatory Hill, in the middle of Cambridge Massachusetts, quite near to downtown Boston, because it has an observatory that used to work great before light pollution.

Re: SpaceX working on fix for Starlink satellites so they don’t disrupt astronomy

#240

Post by tehjoker » Mon, Dec 09, 2019, 4:07 AM UTC

I don't understand why SpaceX is allowed to make this decision nearly unilaterally. This is so similar to how the modern tech companies treat data extraction: they find something unregulated and push until they get pushback.

This should have a been a worldwide consultation.