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Starlink satellites: There goes the neighborhood

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#26 17.5Dob

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Posted 27 May 2019 - 11:02 PM

i hope you're not serious... there are about 5000 satellites currently in orbit, and musk alone intends to put up 12,000 more. 5000->17000 leaves us with 3x the number of satellites in orbit after starlink is complete.

 

anyway, this is probably not really going to be a problem for hobby astrophotography... it's the synoptic survey people that are worried.

 

rob

You're leaving out the ~100,000 spent rocket boosters / heat shields/ etc.still floating around, that are larger and brighter than the "satellites" they launched....

 


Edited by 17.5Dob, 27 May 2019 - 11:18 PM.


#27 pfile

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Posted 27 May 2019 - 11:10 PM

there are not 100k spent rocket stages out there.

 

https://en.wikipedia...ki/Space_debris

 

stuff that's large enough to be tracked = ~17k-19k objects.

 

only when you get down to 1cm do you see some truly staggering numbers (900k)

 

rob



#28 GrandadCast

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Posted 27 May 2019 - 11:19 PM

"Tracking 8,764 airborne aircraft..." from the flight aware site @ 11:13 pm central time. 

I do not think the sky is falling. Heck let's see, how many imagers gripe about not having internet, especially for blind solve when plate solving. Problem solved. 

Jess



#29 pfile

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Posted 27 May 2019 - 11:34 PM

come on now, even at 30k feet an airplane can only be seen from a ~200 mile radius around the plane. a single starlink satellite can be seen from a ~1500 mile radius (@440km), and about a 1600 mile radius @ 550km.

 

rob


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#30 Jon Rista

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Posted 28 May 2019 - 02:08 AM

60 on top of the already, many times 10,000's of thousands ???? Pffft.....60 or a 1,000 more is not going to be an issue.

I have never tossed a single sub due to a satellite or even a stray jet. LEO sats need sunlight to even make them visible. During the Spring/Fall and especially Winter, the window of sunlight that can illuminate them only lasts 1 to 1- 1/2 hrs past astronomical twilight.

Lot's of angst about a non-problem

There are barely 4900 satellites in orbit right now. Fewer than that even in LEO. There are NOT tens of thousands of artificial satellites in orbit of earth right now. Adding twelve thousand on top of what we have right now would be adding nearly three times what we have now, and would bring the total to around 17,000 for the first time. And that is just StarLink. There are other companies planning to put anywhere from several thousand to tens of thousands of their own satellites up there as well...so we are looking at the ADDITION of tens of thousands of new satellites on top of the less than 5000 we have now. And in total, since Sputnik 1, there have been only about 9000 in total ever...so we have never even broken the 10k mark with the total number of satellites that have ever been in earth orbit...


Edited by Jon Rista, 28 May 2019 - 02:08 AM.


#31 Jon Rista

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Posted 28 May 2019 - 02:16 AM

You're leaving out the ~100,000 spent rocket boosters / heat shields/ etc.still floating around, that are larger and brighter than the "satellites" they launched....

 

Where are you getting this? We haven't launched that many rockets from the earth to space...a quick search indicates that there have been barely more than 5000 launches. Even if you assume there were two boosters per launch (there weren't) that would mean there could at most be 10k boosters in play. A lot of them burn up in the atmosphere or crash into the oceans. 

 

I think you must be thinking about DEBRIS in orbit. Current estimates have space debris at anywhere from 200,000 to 600,000 pieces. IIRC, the US Military estimates that there are ~200,000 bits of debris that they could eventually track, but they can only track objects within a certain range of size. The total estimates range from particulates anywhere from the size of a grain of sand to large fragments of destroyed satellites (both Russia and China have blown up a satellite of their own, one resulted in about 20k pieces or so, the other ~100k-150k.) These are mostly small pieces, though, ranging from a few millimeters in size to around softball size. It is this debris that is the real problem up there...and the reason the Kessler syndrome even exists...these are uncontrolled random-vector particles moving at speeds anywhere for 20,000 to 50,000 miles per hour, and even greater in terms of relative speed when orbits are opposed. A fleck of paint colliding with a satellite at ballistic speeds results in an explosion as all that kinetic energy is released within the satellite (we have done countless experiments of tiny objects like grains of sand or flecks of paint or small meteorites/rocks impacting objects like satellites or even test dummies made of ballistic gel to stand in for astronauts...so we have a lot of data about just what happens when a small particle moving at tens of thousand of miles per hour impacts another object). That then creates a huge amount of additional uncontrolled debris that can collide with other satellites, which then just propagate the disaster throughout the entire orbit. 


Edited by Jon Rista, 28 May 2019 - 02:21 AM.


#32 terry59

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Posted 28 May 2019 - 06:36 AM

You seem to have missed the point. With tens of thousands of satellites flying around in all the various LEO altitudes, the possible number of safe launch windows shrinks dramatically.

Well, the point is these services are and will continue to be there to ensure safe launch and injection. Personally I'm more concerned with the potential for deliberate attacks resulting in a plethora of debris fields than stuff just running into each other. Must be that military mindset

 

wink.gif 


Edited by terry59, 28 May 2019 - 07:34 AM.


#33 claudioarchi

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Posted 28 May 2019 - 07:05 AM

In case that you haven't seen it. A video by Dylan O'Donnell

https://youtu.be/28ktlzCn2lU

What a great piece of spacejunk we'll have to deal against. For the sake of wall Street?

#34 GrandadCast

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Posted 28 May 2019 - 08:21 AM

It appears most of the information is a rehash of the same information on BillBobAstro sites and YouTube, without any real knowledge of what truly will happen. Trying to find non bias or accurate information is hard. Just read an article on https://www.universe...ght-sky-menace/ and thinking it would be a bit more reputable than BillBob. However, there again knowledge about the Starlink shows catching up on information is needed regarding end of life for the unit. Not only will Starlink de-orbit itself, SpaceX refilled with the FCC (made headlines months ago) to change orbit height with one of the a benefit that the unit would also de-orbit within five years and not 50 years or so if the unit cannot de-orbit itself. Now is Elon making that up, don’t think so but will let your guys know in 10 years.

 

So I have had to remove streaks with planes before, I normally don’t image right after dark anyway so satellite trails are not a problem that I can remember, software will get better for that task and I will still build my observatory this summer. 

 

Jess



#35 Francois

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Posted 28 May 2019 - 09:03 AM

I will state it again: Kessler syndrome is not possible at 550km. Reentry lifetime there is 5 years, with the sun quiet. Even in the absolute worst case scenario where someone starts launching tungsten pellets at that altitude, you'd just need to halt launches for a couple years, less if the sun is active at the time. The real problem is in sun-sync and polar orbits, above 700km, for low orbits (geostationary is also at risk). Starlink is not a debris risk in its post-late-2018 iteration.

 

OneWeb is actually concerning, and since they're a UK company launching on French soil, the FCC/FAA get no say in their debris mitigation plan.

 

Before spreading fear, uncertainty and doubt, please break out the nearest used envelope and do some math.



#36 Phillip Creed

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Posted 28 May 2019 - 09:21 AM

Here's my Idiot-Boy-From-Flyover-Country take on this:

It's not a good thing, for sure.  But I don't think it'll be apocalyptic for imaging.

First, there's going to be large portions of the sky they can't affect near the anti-solar point.  They CAN be seen after the end of astronomical twilight, but if you look at the Heavens Above site for ~40°N, most of these are brightest when low in the north.  And regardless of time of night, anything low to the north is worth waiting several months for, anyway.

 

I will note this is a MUCH bigger issue if you're trying to image further north, but you can only go so far north around the summer solstice before twilight becomes the bigger impediment.

Second, as LEO satellites, they will appear to move quickly, in and out of your imaging frame in a matter of seconds when using a telescope.  I will grant that a 5-minute sub could gather quite a few of them once all 12,000 are deployed.  But stacking frames is a good way to reduce/eliminate the impact.

 

And it would seem one adjustment would be to stack shorter subs as a mitigation technique.  Of course, to get a good SNR worth writing home about with short subs will require fast--FAST--optics.

But the trend's already in that direction, anyway.  You already have an 8" and 11" RASA and TS makes a number of Power Newts that can operate at either f/4 or f/2.8.  I see larger Power Newts and RASAs in the future if short subs becomes the only way to go.

It would be interesting to see if refractors could adapt to a short-sub future.  Perhaps, if 0.5X - 0.6X reducers replace the ubiquitous 0.8X reducers.

In short, I'm concerned, but am reasonable hopeful astrophotography will continue to thrive.

Just my 1 cent's worth.

 

It'd be worth two cents, but it turns out both pennies were sentient entities, and then Thanos snapped his fingers.

 

Clear Skies,

Phil



#37 fetoma

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Posted 28 May 2019 - 11:33 AM

I saw a trail of 4 or 5 last night here in South Jersey. It was odd looking but it caught my eye.



#38 Eddie_42

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Posted 28 May 2019 - 02:15 PM

Just wait until China gets their system in place.  Also which country is going to have giant billboards first? https://astronomy.co...boards-in-space

 

I guess there are always model railroad building we can get into instead.

Ugg....this dumb thing.  see rant over here

 

As for the "glinting"  its a limited time frame of the evening to get glints like that. Its a neat phenomenon to witness since they are all co-planar, but they are also still in initial stages that will 1.) Spread out across the entire orbit ring and 2.) raise their orbit another ~100km.   Imagining in the hours after twilight MIGHT catch a couple of satellites glinting....and those satellite MIGHT be Starlink.   If you are 2hrs past twilight, the glints are gone. 

 

Too much chicken little here.  How many times have people complained about a GEO satellite up there.....those are STATIONARY (relatively). <start shouting> OMG this satellite is ALWAYS in my field....what will we ever do"  AHHHHHH

 

Back to reality - there are ~~19,000 objects being tracked on orbit today (https://www.space-track.org/#/catalog  create an account, its free) This is also the Unclassified catalog, give some wiggle room.   Running a basic query for CURRENT orbits with a 128min period (roughyl 1500km circular) the breakdown is this (debris included in counts):

 

14294 objects under

4579  objects above

18873 TOTAL

 

How many active forum threads are there around that have people experiancing ANY issues wtih the 14,000 objects in LEO today?  How many major astro telescopes cant operate because of satellites in LEO?  Between the narrow FOV of a scope, and the fact we image and view the stars from the SHADOWY side of Earth, its all a non-starter

 

 

Sorry not Sorry if im a little rant like on this......Satellites are my job, near and dear to me. 


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#39 Jon Rista

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Posted 29 May 2019 - 11:27 AM

Well, the point is these services are and will continue to be there to ensure safe launch and injection. Personally I'm more concerned with the potential for deliberate attacks resulting in a plethora of debris fields than stuff just running into each other. Must be that military mindset

 

wink.gif

Yeah...I'm concerned about deliberate attacks as well... Sheesh. What a cluster...



#40 Jon Rista

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Posted 29 May 2019 - 11:44 AM

I will state it again: Kessler syndrome is not possible at 550km. Reentry lifetime there is 5 years, with the sun quiet. Even in the absolute worst case scenario where someone starts launching tungsten pellets at that altitude, you'd just need to halt launches for a couple years, less if the sun is active at the time. The real problem is in sun-sync and polar orbits, above 700km, for low orbits (geostationary is also at risk). Starlink is not a debris risk in its post-late-2018 iteration.

 

OneWeb is actually concerning, and since they're a UK company launching on French soil, the FCC/FAA get no say in their debris mitigation plan.

 

Before spreading fear, uncertainty and doubt, please break out the nearest used envelope and do some math.

What exactly are you calling Kessler syndrome? Just the number of satellites up there? Kessler syndrome refers to the collisional cascade, not the number of satellites. 

 

Why is Kessler syndrome not possible at 550km? From what I understand about it, any orbit is at risk. The original 1978 paper mostly focused mostly on the ~800-1000km range, but was also pretty clear that a catastrophe in that band could easily spread well beyond it and obliterate other orbits. The point is that with so many manmade objects in LEO in particular, the RISK of Kessler syndrome (of a collisional cascade) increases. Kessler was concerned with just "thousands" of objects...now we are talking about tens of thousands, and most of them in LEO and not higher orbits.

 

We have already had a collision of two satellites in fact...In Feb 2009 an Iridium and Cosmos satellite collided at ~41,000kph. That was in 2009...we did not even have 2000 satellites in total in orbit then. Now we are talking about cranking up the count to over 20,000 (and again, this is not just about Starlink, it is about the whole entire idea of plastering our skies with countless satellites for the purpose of bringing internet to the middle of uninhabited deserts or the uninhabited poles. OneWeb is in fact worse than StarLink at an altitude of 1200km...they will be visible and illuminated by the sun most of the night!!) 



#41 bigeastro

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Posted 29 May 2019 - 11:55 AM

We are going to look back at this sometime in the future, when I am not probably around and say what the heck were we thinking?  We were so primitive back then.

 

More stuff in space with little or no regulation is not a good idea.  


Edited by bigeastro, 29 May 2019 - 11:55 AM.


#42 Stelios

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Posted 29 May 2019 - 12:58 PM

Guys, unless we limit this to specifically effects on imaging, I'll move it to Off-Topic-Observatory. First and only warning. 

 

No military, politics, etc. Not here. 



#43 bigeastro

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Posted 29 May 2019 - 01:00 PM

The effects on imaging of a few thousand more items glittering in space are gong to be pretty bad.   Not much else to say on that point.


Edited by bigeastro, 29 May 2019 - 01:00 PM.


#44 Jon Rista

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Posted 29 May 2019 - 01:41 PM

The effects on imaging of a few thousand more items glittering in space are gong to be pretty bad.   Not much else to say on that point.

Especially since many of us image wider fields, not just narrow fields. I'm moving to f/3.6 soon, which with the ASI183 would be ~2x1.5 degrees FoV. With the ASI1600 it would be even larger. The FSQ106 still has a 44mm image circle in this configuration, meaning I could use a full frame sensor, which would be nearly 6x4 degrees! I get enough sat trails each night with a field of just 77x46 arcminutes...



#45 Eddie_42

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Posted 29 May 2019 - 02:06 PM

OneWeb is in fact worse than StarLink at an altitude of 1200km...they will be visible and illuminated by the sun most of the night!!) 

No.  Objects at 1200km will not be illuminated "most of the night", satellites near the terminator will glint, and the opportunity for glinting is longer at the higher alititude yes, but we are talking an order of magnitude in minutes (about 3 to 3.5) when traveling 90deg to the terminator.  Even if they are highly inclined (80-100degrees) and follwing close to the terminator, they might glint often relative to the ground targets under them, however the ground is moving...for your local area, the glint is a limited time window.  Once you are past sunset a few hours, the opportunity for glints is gone. 

 

Also light intensity drop off on a 1/r^2 magnitude.  So the same glint off two satellites at each of the aforementitoned altitudes... 1200/550 = 2.2 time farther =  21% of the brightness

 

Practicle question:   There are currently 670 objects with an Apogee and Perigee between 1000km and 1400km, nightly....how many of them are problematic to telescope use?

 

Locations closer to the poles will get some added effects, and the seasons complicate the matter more. 3D geometry on orbits is a complex topic for certain. 


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#46 astro_1

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Posted 29 May 2019 - 05:14 PM

It is a concern for the obvious reasons mentioned, future launch windows, telescope surveys etc. Look at the current and future telescope building projects underway to help find exoplanets, costing $millions. It's bad enough they have to find dark sky locations to try and compensate for atmosphere turbulence, now 1,000's more junk in space.

And for what? Is there really a need for internet access in un-populated areas on the planet ? 

 

And yes, I am biased towards astronomy

 

I think all the space faring countries should have a method/process in place to clean up the junk in orbit now before any launches of this magnitude.



#47 bobzeq25

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Posted 29 May 2019 - 05:34 PM

It is a concern for the obvious reasons mentioned, future launch windows, telescope surveys etc. Look at the current and future telescope building projects underway to help find exoplanets, costing $millions. It's bad enough they have to find dark sky locations to try and compensate for atmosphere turbulence, now 1,000's more junk in space.

And for what? Is there really a need for internet access in un-populated areas on the planet ? 

 

And yes, I am biased towards astronomy

 

I think all the space faring countries should have a method/process in place to clean up the junk in orbit now before any launches of this magnitude.

And who are you going to get to enforce that?  Few people care at all, much less care more than they do about Internet access.

 

Your best bet might be Elon Musk, who routinely does what other people think can't be done.

 

https://forum.nasasp...p?topic=48222.0

 

Of course, someone will have to pay him to do it.  There are also legal issues.  Right now, it's illegal to touch someone else's satellite, even if it's nonfunctional.


Edited by bobzeq25, 29 May 2019 - 05:47 PM.


#48 Eddie_42

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Posted 29 May 2019 - 06:00 PM

I think all the space faring countries should have a method/process in place to clean up the junk in orbit now ......

100% agree....now would be nice.   The issue is that there isnt money in it. 

 

Of course, someone will have to pay him to do it.  There are also legal issues.  Right now, it's illegal to touch someone else's satellite, even if it's nonfunctional.

It is indeed. The current law/code also assignes all launch bodies and any debris with the original satellites owner. I.E. if a fuel tank goes boom...all the debris is yours too.

 

There are many a theory on collecting space junk (spent bodies, old buses, debris, etc)...In my opinion, the biggest issue precluding any progress in collecting the junk is the fuel cost. Until we figure out something more effecient then lighting methane on fire, heavy maneuvers are just out of reach.  Its relativley easy to jump up there, grab something and come back. Phasing around in your orbital plane or changing your altitude is doable too, so maybe you get a couple peices. The hard part is twisting your plane around (change in Inclination or Right Ascension), the fuel cost is temendous due to your kinetic energy. 


Edited by Eddie_42, 29 May 2019 - 06:05 PM.


#49 Phillip Creed

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Posted 30 May 2019 - 12:51 PM

No.  Objects at 1200km will not be illuminated "most of the night", satellites near the terminator will glint, and the opportunity for glinting is longer at the higher alititude yes, but we are talking an order of magnitude in minutes (about 3 to 3.5) when traveling 90deg to the terminator.  Even if they are highly inclined (80-100degrees) and follwing close to the terminator, they might glint often relative to the ground targets under them, however the ground is moving...for your local area, the glint is a limited time window.  Once you are past sunset a few hours, the opportunity for glints is gone. 

 

Also light intensity drop off on a 1/r^2 magnitude.  So the same glint off two satellites at each of the aforementitoned altitudes... 1200/550 = 2.2 time farther =  21% of the brightness

 

Practicle question:   There are currently 670 objects with an Apogee and Perigee between 1000km and 1400km, nightly....how many of them are problematic to telescope use?

 

Locations closer to the poles will get some added effects, and the seasons complicate the matter more. 3D geometry on orbits is a complex topic for certain. 

I just noticed this part of the proposed Starlink system.  Some 2,800 of these are supposed to 1,150-km in height.

For sake of comparison, what are the brightest objects in that 1000 - 1400 km range?

Clear Skies,

Phil



#50 Eddie_42

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Posted 30 May 2019 - 04:23 PM

No.  Objects at 1200km will not be illuminated "most of the night", 

I will offer an addendum to this, after some furthe consideration.  I've been approaching this in the midset of a polar (or near polar) orbit, akin to the Iridium Satellites. However, the initial batch is at 53Deg inclination. I cant find anything about the full constellation layout, where the 1200km satellite shell will be. The first 2 prototypes went to 97 deg, but thats likely due to the ride share they went up on, more then operational use case.

 

Satellites in this area, particlary in the norther sky during summer months, will have a longer visibility window, even lasting through the night for various rings.  I still challenge how bright they will be, especially the ones at 1200km. The current craft up there are slated to be around magnitude 5-7, the light falls off quick (inverse square of distance) and gives the 1200km shell a much lower magnitude.  Couple that with improved albedo in the design shop, their physical size, and the narrow FOV of a telescope.....its all going to be ok.

 

Tool here to get ALL sunlit passes over the course of 24hrs (includes pre-dawn, and post-dusk, rather than being noon centered).  But I tossed in Washington State (where it defaulted), and got 6000 passes from assorted satellites (did not deconflict unique sats, just total pass count). The magnitudes go way down there, some in the 12-15 range, but the point being....sunlit satellites over the evening is nothing new, and no-one complained last week.

 

Phillip, I cant find a terribly consise source to answer your question. I have looked, and will continue too as time allows


Edited by Eddie_42, 30 May 2019 - 04:40 PM.



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