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

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

#251

Post by chungus_khan »

tigershark wrote: post #186
h5arehe5ra4h wrote: post #167

Earlier quoted context omitted.

For most usages yes. For gaming though it's right on the edge: theoretical minimum at 350km orbit is 40ms roundtrip, which would work for most games. But many complications, including position of the satellite, latencies within the networking components, packet loss etc, can easily slow this to 100ms+, which is unsuitable for many online games.

No, the round trip for electromagnetic waves at 350km it’s about 2 ms not 40. The lowest orbit of the satellites though would be 550km and not 350km, but it would still be less than 4ms. From where did you get the 40ms figure that it’s wrong by an order of magnitude?

I don't know where they got that figure from, but it is unrealistic to not also expect a decent amount of latency to be introduced by the transmission hardware, particularly under load. I have no idea how much, but this has generally been the case with most systems of this sort.

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

#252

Post by justin66 »

woliveirajr wrote: post #250
justin66 wrote: post #214

Earlier quoted context omitted.

This definitely wasn't ruined (it's amateur video) but if anyone wants to see Starlink photobombing an astronomer, this amateur video of a recent meteor shower is an example: https://www.youtube.com/watch?v=uHI8Z5qpd6I (an astronomer friend thought I'd be able to identify the satellite amongst all the meteors, which was sweet... I think it's a bit after the 2 minute mark)

Aside note: I didn't imagine one could see / film that much meteors during the night in some city. If I remember correctly, I saw 2 or 3 my whole life, and was driving at some road.

I know you can see the Leonids in San Francisco, at least if you're not standing directly under a streetlight. Some years are brighter than others. A lot of it is making note of when to go outside and look.

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

#253

Post by justin66 »

ricardobeat wrote: post #229
justin66 wrote: post #214

Earlier quoted context omitted.

This definitely wasn't ruined (it's amateur video) but if anyone wants to see Starlink photobombing an astronomer, this amateur video of a recent meteor shower is an example: https://www.youtube.com/watch?v=uHI8Z5qpd6I (an astronomer friend thought I'd be able to identify the satellite amongst all the meteors, which was sweet... I think it's a bit after the 2 minute mark)

Is it the one making a line starting from the bottom left corner, or the thing that makes a very short bright streak at 2:08?

I assume it's the brightest one, yeah.

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

#254

Post by jsjohnst »

Since there are folks here in the field, does anyone know what the feasibility of building something similar to the VLA, but with thousands of smaller satellites? If doable, seems potentially possible to cover a lot more sky at once with less terrestrial interference. No idea if this is practical or not.

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

#255

Post by jsjohnst »

chungus_khan wrote: post #251
tigershark wrote: post #186

Earlier quoted context omitted.

No, the round trip for electromagnetic waves at 350km it’s about 2 ms not 40. The lowest orbit of the satellites though would be 550km and not 350km, but it would still be less than 4ms. From where did you get the 40ms figure that it’s wrong by an order of magnitude?

I don't know where they got that figure from, but it is unrealistic to not also expect a decent amount of latency to be introduced by the transmission hardware, particularly under load. I have no idea how much, but this has generally been the case with most systems of this sort.

Electromagnetic waves travel at essentially the speed of light. The speed of light is roughly 300km per millisecond. So if they are 550km up, that’s roughly 4ms round trip. Even with horrible inefficiency, it won’t likely increase that by 10x.

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

#256

Post by sectiondetail »

strainer wrote: post #241
cbanek wrote: post #204

Earlier quoted context omitted.

So while it sounds good that we've fixed the launch industry and can launch everything cheaper, that we should only have space based telescopes, space telescopes are a very different game from ground based telescopes. First, as others have pointed out, is size. Ground based mirrors are very large, in the 10s of meters, and those mirrors are extremely heavy, like tons. You can't lift one of those mirrors up on one roc…

> Ground based mirrors are very large, in the 10s of meters, and those mirrors are extremely heavy, like tons. Seemingly fantastically - SpaceX is currently constructing a system designed to launch 100 tons to LEO, for as low as $35/kg [1]. Musk says this capability is what the Starlink business is to pay for. It appears lately, more realistic than it has sounded. [1] https://caseyhandmer.wordpress.com/2019/10/29/the…

One of the things I'm most excited about related to Starship is its landed mass capability for science purposes. Imagine being able to build radio and optical telescopes in the Daedalus crater on the central lunar far side. They'd be shielded from the optical and radio noise of the sun for 2 weeks out of 4, and permanently shielded from Earth. Or imagine infrared telescopes at the bottom of permanently shadowed polar craters, where ambient temperatures are even colder than in interplanetary space. No need to design and deploy a complex sunshield and worry about maintaining spacecraft orientation. The science potential of reusable heavy-lift rockets can't be understated.

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

#257

Post by hgoel »

mstipetic wrote: post #187
ryan93 wrote: post #178

Earlier quoted context omitted.

You can’t manufacture complicated objects in space

We shouldn't have been able to land on the moon using whiteboard engineering and calculator level computers, but we did

That won't magically make it feasible to manufacture such precise objects in space anytime soon.

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

#258

Post by unfunco »

Filligree wrote: post #146
mstipetic wrote: post #134

Earlier quoted context omitted.

This sounds to me like a new technology and a way of operating has come and we're trying to make it accommodate the old way of doing things. If we really have a way to launch thousands of satellites easily, can't we replace the terrestrial functionality with that? Let's launch hundreds of satellites observing near earth asteroids. If a private company can do it, governments definitely can

Terrestrial telescopes are huge . Hubble is comparatively tiny, and launching a telescope the same size as the ones we use down here would be completely out of the question with any near-term launch capability.

Is the ISS not comparable in size?

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

#259

Post by skuthus »

mlyle wrote: post #242
laken wrote: post #238

Earlier quoted context omitted.

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.

That's a bit of a strange assumption. Height doesn't have too great of an impact, other than reaching eclipse from solar illumination a little earlier. Given that Iridium has been a nuisance and they're at 780km, versus Starlink at 550km and 1150km...

A quote from a user above who worked for both SpaceX and the astronomy community:

"Now, that being said, even I was confused why this would cause a problem. The satellites are in low earth orbit, so low that they won't be able to reflect the sunlight, since they are in earth's shadow. Only during twilight and dawn will satellites be in the right position to reflect the sunlight back to the ground off of some panel.

Now, these are not prime observing hours for many people, since it is still not as dark as it could be. So most people point into the darkest parts of the sky (up) rather than at parts where there is still twilight (like nearer the horizon).

But for some types of observations, like near earth asteroids, you want to point into the evening sky to look for them, since that is one of the places you want to look, and the sky conditions should be good enough. In these pictures you'll get streaks of light as the satellites pass through."

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

#260

Post by Rebelgecko »

mstipetic wrote: post #187
ryan93 wrote: post #178

Earlier quoted context omitted.

You can’t manufacture complicated objects in space

We shouldn't have been able to land on the moon using whiteboard engineering and calculator level computers, but we did

Why shouldn't we have been able to land on the moon?
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