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OneWeb successfully launches 34 more satellites into orbit

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Re: OneWeb successfully launches 34 more satellites into orbit

#41

Post by greglindahl »

Mountain_Skies wrote: post #6
stareatgoats wrote: post #5

Earlier quoted context omitted.

I believe GP was talking about the ever growing space debris. https://www.esa.int/Safety_Security/Space_Debris/Space_debri...

These satellites should be in low enough orbits that any junk from them burns up in the atmosphere as their orbits decay. Maybe there could be an issue from collisions in low orbit pushing objects into higher orbits but those likely would be erratic orbits with low points that still subject it to decay.

OneWeb's constellation is high enough that it'll take a lot more than 25 years for any satellite that fails to deorbit itself to decay. On the way down, these debris will cross the ISS orbit and the most popular sun-synchronous orbits.

Starlink is lower, but still above the ISS and the SSO at 282km.

Re: OneWeb successfully launches 34 more satellites into orbit

#42

Post by zaroth »

greglindahl wrote: post #40
zaroth wrote: post #29

Earlier quoted context omitted.

The satellite would not be passing through the shot for the entire exposure. If you had software to detect and delete frames with a satellite moving through them, how many frames from a multi-hour exposure would have to be deleted? I assume it can even be done digitally in post-production, but even if you had to actually close the aperture ahead of the satellite crossing through your frame, we know exactly where the…

We studied this technique in the graduate-level observation class I took 30 years ago. It is not trivial for a lot of reasons, especially for modern wide-field telescopes with multiple satellites in the field of view at all times.

I appreciate the expert feedback. A lot of very complex things often seem trivial from an outside perspective.

I think everyone can agree this will be at least somewhat a burden on astronomy and will at least marginally increase the cost in obtaining certain imagery.

I guess it’s possible that there are certain types of images which may even become prohibitive or impossible to obtain, but I personally haven’t read a scientific analysis making this claim.

I also think most everyone is agreeing that we attack this problem from both sides. Limit the reflectivity of the satellites and work on enhancing software to mitigate the effects.

In the end there is a tremendous benefit to society both from astronomy as well as having affordable worldwide broadband internet.

I’m not going to go so far to say that we need to sacrifice one for the other, but I think the capabilities and opportunities provided by Starlink to billions of people are too great to pass up. Even if there is a significantly increased cost to perform certain observations. Even if it means some observations can only be made from orbit in the future. Even if some observations become entirely impossible? Hopefully that can be avoided.

Re: OneWeb successfully launches 34 more satellites into orbit

#43

Post by jws »

dmitrygr wrote: post #2

between this and Elon's stuff, how long till it is impossible to do astronomy or safely launch anything into space?

I propose: LEO satellites are not a problem for astronomy.

• Atmosphere distorts observations.

• Astronomers do not like distortion.

• Astronomers like dark backgrounds.

• For a satellite to be illuminated, it must be visible to the sun.

         a 
  - - - - - 
       b/  \
        | E|           SUN
        \  /
  - - - - -
Here is the Earth (E), the Sun, and two satellites in low earth orbit, a and b. The dashed lines are the earth’s shadow.

LEO satellites are really low, like 1/20th of a diameter of the earth. That means that in order to be illuminated in a night sky, they have to be on the dark side of the Earth (left of center here), but not so far that they have dipped into the shadow. “a” is in position for that, but “b” is not. Illuminated, dark side satellites are all in a band around the Earth at the twilight line.

Astronomers don’t like lit skies, so they wait until local dark. Once you get to local dark, the twilight lit satellites are off toward the horizon where you don’t want to observe because there is a huge pile of atmosphere.

If you are making a cool picture of Orion rising out of a desert lake, well, yeah, you may need to edit out some satellites depending on the time of year, but astronomers can do their job just fine.

Re: OneWeb successfully launches 34 more satellites into orbit

#44

Post by chkaloon »

I just spent a week at a remote Alaska village 120 miles from Nome to help with the Iditarod. The villages there rely on rural broadband, which is essentially a single satellite-fed community receiver which pushes signal out to access points at each house. Very expensive, slow, high latency, and nasty data caps. It will be interesting to see how these efforts change that monopoly and as a result those communities.

Re: OneWeb successfully launches 34 more satellites into orbit

#45

Post by greglindahl »

dreamlayers wrote: post #37

On Saturday March 21st I was at the tip of Canada's Point Pelee National Park, approximately 41.909055, -82.509154. At 9:12 EDT (1:12 AM UTC on the next day), I saw a an approximate disordered line of satellites passing above Orion. They were all going at the same speed and in a very similar direction, west to east close to parallel with the belt of Orion. But they were all on slightly different almost parallel track…

There are a couple of websites out there that give you future and past locations of "Starlink trains", which is what you probably saw.

This site https://findstarlink.com/ does arbitrary locations but not times in the past. As does this one https://james.darpinian.com/satellites/?special=starlink ... presumably if you looked around a bit more than I just did you could find one that does historical viewings.

Re: OneWeb successfully launches 34 more satellites into orbit

#46

Post by greglindahl »

chkaloon wrote: post #44

I just spent a week at a remote Alaska village 120 miles from Nome to help with the Iditarod. The villages there rely on rural broadband, which is essentially a single satellite-fed community receiver which pushes signal out to access points at each house. Very expensive, slow, high latency, and nasty data caps. It will be interesting to see how these efforts change that monopoly and as a result those communities.

Good news, there are several satellite constellations on the way to break that monopoly, including some small ones that just address Alaska.

Re: OneWeb successfully launches 34 more satellites into orbit

#47

Post by aivisol »

mrfusion wrote: post #12
dmitrygr wrote: post #2

between this and Elon's stuff, how long till it is impossible to do astronomy or safely launch anything into space?

Spreading FUD. Spacex has the most advanced satellite management and deorbiting systems ever made. Fully approved by the fcc.

Do you have any details about this? As an amateur astronomer I am concerned about increased number of objects in orbit and their eventual fate. How the quality of deorbiting system measured? Have they deorbited any yet and their success rate is higher than others? Also I had no idea FCC approves satellite guidance systems, I thought they mostly supervise radio spectrum.

Re: OneWeb successfully launches 34 more satellites into orbit

#48

Post by _Microft »

34679 wrote: post #23
_Microft wrote: post #16

Earlier quoted context omitted.

This is a poor comparison. The contrast of a cars to the background of Earth is low, ofcourse we can not see any. Remove Earth and let these cars fly on orbits 500km below ISS and, oh boy, would you suddenly see car roofs and windows glinting in the dark everywhere. Amazing for satellite watchers and annoying for astronomers were e.g. Iridium flares. See [0][1]. Worst case for Iridium flares was them being about 50x…

What percentage of the sky do you envision will be occupied by man made objects?

To put this question into perspective:

The Iridium flare which you saw in video [0] so nicely next to what looked like a full-moon was produced by a flat, reflective surface of less than 2m² area at a distance of over 600km. Percentage does not matter here.

Re: OneWeb successfully launches 34 more satellites into orbit

#49

Post by new_realist »

cagenut wrote: post #33
new_realist wrote: post #28

Earlier quoted context omitted.

There’s no way Starlink will be better than fiber. You have to pay a 25 ms penalty just to play, and then you have the cost of each hop, of which there are many.

highly recommend you watch these two latency modelings: https://www.youtube.com/watch?v=QEIUdMiColU https://www.youtube.com/watch?v=m05abdGSOxY

I should also note that many of the simulated Starlink paths between NYC and London are actually higher latency than the best fiber path, which is less than 60 ms (https://arstechnica.com/tech-policy/2010/09/first-nyclondon-...). The author ignores routing and RF delays in the space network, but compares RTT to the public Internet. A joke.

Re: OneWeb successfully launches 34 more satellites into orbit

#50

Post by greglindahl »

aivisol wrote: post #47
mrfusion wrote: post #12

Earlier quoted context omitted.

Spreading FUD. Spacex has the most advanced satellite management and deorbiting systems ever made. Fully approved by the fcc.

Do you have any details about this? As an amateur astronomer I am concerned about increased number of objects in orbit and their eventual fate. How the quality of deorbiting system measured? Have they deorbited any yet and their success rate is higher than others? Also I had no idea FCC approves satellite guidance systems, I thought they mostly supervise radio spectrum.

Every country is supposed to regulate space debris, and in the US, that happens to have been assigned to the FCC. BTW, many people in the industry thinks that the international standard of 25 years needs to be strengthened.
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