Starlink

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geckzilla
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Starlink

Post by geckzilla » Sat May 25, 2019 9:24 pm

https://en.wikipedia.org/wiki/Starlink_ ... tellation)
SpaceX has plans to deploy nearly 12,000 satellites in three orbital shells by the mid-2020s
not sure why I never heard of this until just recently when people started posting pictures of dotted lines crossing the sky after this initial launch of 60 satellites. the astronomy community is pretty concerned. what do you all think of this? is it going to ruin observational astronomy? will Chris's allsky meteor cameras be inundated with satellite streaks?
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Chris Peterson
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Re: Starlink

Post by Chris Peterson » Sun May 26, 2019 2:06 am

geckzilla wrote:
Sat May 25, 2019 9:24 pm
https://en.wikipedia.org/wiki/Starlink_ ... tellation)
SpaceX has plans to deploy nearly 12,000 satellites in three orbital shells by the mid-2020s
not sure why I never heard of this until just recently when people started posting pictures of dotted lines crossing the sky after this initial launch of 60 satellites. the astronomy community is pretty concerned. what do you all think of this? is it going to ruin observational astronomy? will Chris's allsky meteor cameras be inundated with satellite streaks?
Well, these things are very small, and I expect not very bright. I'm sure they would show up in astroimages (primarily amateur, which tend to be wider field than professional images), but they should be easily edited out, so I don't thing they'll have much impact on astronomy.
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geckzilla
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Re: Starlink

Post by geckzilla » Sun May 26, 2019 6:31 am

Just reading over some of the things astronomers have said so far:
Their TLEs will not be very accurate for very long because these things are actively moving around to avoid collisions and maintain their net, so the margin of error is going to have to be quite large, blotting out large portions of the sky or even making it impossible in some cases to avoid them

Projects like LSST are going to at minimum end up with around 5 of them in each field

They are not THAT dim, depending on what your latitude is and which way Earth is currently tilting. At higher latitudes during summer, they will never pass through the Earth's umbra from your viewpoint, being visible all night long

Current imagery shows them being at around magnitude 3-4, which may increase slightly as their altitude raises

12000 LEO satellites is A LOT. Right now, if you count ALL space debris, including junk from launches and the faintest stuff that's far out, there are around 19400 bits out there. But these are all going to be low earth orbit! And in an operational net that ensures they're always overhead.

Further thoughts: How many more telecoms will want a piece of this pie? How many more shells of satellites will we eventually end up with?

h/t to Doug Ellison and others I have forgotten due to just reading so many sources
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Chris Peterson
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Re: Starlink

Post by Chris Peterson » Sun May 26, 2019 12:55 pm

geckzilla wrote:
Sun May 26, 2019 6:31 am
Just reading over some of the things astronomers have said so far:
Their TLEs will not be very accurate for very long because these things are actively moving around to avoid collisions and maintain their net, so the margin of error is going to have to be quite large, blotting out large portions of the sky or even making it impossible in some cases to avoid them

Projects like LSST are going to at minimum end up with around 5 of them in each field

They are not THAT dim, depending on what your latitude is and which way Earth is currently tilting. At higher latitudes during summer, they will never pass through the Earth's umbra from your viewpoint, being visible all night long

Current imagery shows them being at around magnitude 3-4, which may increase slightly as their altitude raises

12000 LEO satellites is A LOT. Right now, if you count ALL space debris, including junk from launches and the faintest stuff that's far out, there are around 19400 bits out there. But these are all going to be low earth orbit! And in an operational net that ensures they're always overhead.

Further thoughts: How many more telecoms will want a piece of this pie? How many more shells of satellites will we eventually end up with?

h/t to Doug Ellison and others I have forgotten due to just reading so many sources
It comes down to whether the harms are justified by the benefits. A worldwide communications net is potentially of high benefit (but perhaps we should see this as a regulated part of public infrastructure, not a wholly private venture). And I haven't yet seen anything that suggests much harm... why are some of these things in the field of astronomical instruments a problem?
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Re: Starlink

Post by geckzilla » Sun May 26, 2019 2:31 pm

It's a project that affects the whole globe, but it's hardly anyone was asked about it... it's just one billionaire using a global resource to fund his Mars fantasy while ostensibly "saving" humanity. The impact is on both optical and radio astronomy. They will emit in radio frequency on what was a quiet band... anyway, I'm sure you'll hear about it more and with greater accuracy on the actual impact in the coming weeks and months.

On a similar topic, apparently the 5G band being auctioned off to telecoms will also be an incredible disruption to weather prediction since those bands are naturally extremely faint, so when a bunch of cell towers and phones start emitting in that range it's going to drown out weather observations.
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Chris Peterson
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Re: Starlink

Post by Chris Peterson » Sun May 26, 2019 2:42 pm

geckzilla wrote:
Sun May 26, 2019 2:31 pm
It's a project that affects the whole globe, but it's hardly anyone was asked about it... it's just one billionaire using a global resource to fund his Mars fantasy while ostensibly "saving" humanity. The impact is on both optical and radio astronomy. They will emit in radio frequency on what was a quiet band... anyway, I'm sure you'll hear about it more and with greater accuracy on the actual impact in the coming weeks and months.

On a similar topic, apparently the 5G band being auctioned off to telecoms will also be an incredible disruption to weather prediction since those bands are naturally extremely faint, so when a bunch of cell towers and phones start emitting in that range it's going to drown out weather observations.
I think there are a great many non-science factors that should be considered. But I'd also like to know more about the impact on ground-based astronomical research. I just haven't heard a lot yet.
Chris

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Re: Starlink

Post by geckzilla » Sun May 26, 2019 3:00 pm

Yeah, there hasn't been a lot at all to talk about until now! It's really surprising that there was virtually no discussion prior to this.
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Re: Starlink

Post by Chris Peterson » Mon May 27, 2019 1:49 pm

Imaged by my colleague Marco Langbroek a few days ago.
_
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Re: Starlink

Post by bystander » Mon May 27, 2019 1:51 pm

Know the quiet place within your heart and touch the rainbow of possibility; be
alive to the gentle breeze of communication, and please stop being such a jerk.
— Garrison Keillor

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Re: Starlink

Post by neufer » Mon May 27, 2019 8:19 pm

Click to play embedded YouTube video.
Click to play embedded YouTube video.
Click to play embedded YouTube video.
Art Neuendorffer

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Re: Starlink

Post by rstevenson » Tue May 28, 2019 1:12 pm

News item this morning (first I'd heard of this) suggests that the billionaire and team will be looking at the possibility of reducing the satellites' albedo, now that people have begun to express reservations. I can't imagine why this idea would come so late to the table. You'd think anyone putting up 12,000 satellites would have considered their visual effect before now -- but I suppose that would require a level of humility rarely exhibited by self-made billionaires.

Article also mentioned that the expected final albedo of the current bright ones will be about +6.

Space.com article here (from which the article I was reading seems to have been cadged)...

Rob

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Re: Starlink

Post by neufer » Tue May 28, 2019 2:00 pm

Click to play embedded YouTube video.
rstevenson wrote:
Tue May 28, 2019 1:12 pm

News item this morning (first I'd heard of this) suggests that the billionaire and team will be looking at the possibility of reducing the satellites' albedo, now that people have begun to express reservations. I can't imagine why this idea would come so late to the table. You'd think anyone putting up 12,000 satellites would have considered their visual effect before now -- but I suppose that would require a level of humility rarely exhibited by self-made billionaires.

Article also mentioned that the expected final albedo of the current bright ones will be about +6.

Space.com article here (from which the article I was reading seems to have been cadged)...
Art Neuendorffer

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Re: Starlink

Post by bystander » Mon Jun 10, 2019 2:48 pm

AAS Issues Position Statement on Satellite Constellations
American Astronomical Society | 2019 Jun 10

The American Astronomical Society notes with concern the impending deployment of very large constellations of satellites into Earth orbit. The number of such satellites is projected to grow into the tens of thousands over the next several years, creating the potential for substantial adverse impacts to ground- and space-based astronomy. These impacts could include significant disruption of optical and near-infrared observations by direct detection of satellites in reflected and emitted light; contamination of radio astronomical observations by electromagnetic radiation in satellite communication bands; and collision with space-based observatories.

The AAS recognizes that outer space is an increasingly available resource with many possible uses. However, the potential for multiple large satellite constellations to adversely affect both each other and the study of the cosmos is becoming increasingly apparent, both in low Earth orbit and beyond.

The AAS is actively working to assess the impacts on astronomy of large satellite constellations before their numbers rise further. Only with thorough and quantitative understanding can we properly assess the risks and identify appropriate mitigating actions. The AAS desires that this be a collaborative effort among its members, other scientific societies, and other space stakeholders including private companies. The AAS will support and facilitate the work by relevant parties to understand fully and minimize the impact of large satellite constellations on ground- and space-based astronomy.

On the increasing number of satellite constellations
ESO Announcement | 2019 Jun 07

IAU Statement on Satellite Constellations
International Astronomical Union | 2019 Jun 03

Statement on Starlink and ‘Constellations’ of Communication Satellites
National Radio Astronomy Observatory | 2019 May 31

Response to SpaceX Starlink Low Earth Orbit Satellite Constellation
International Dark-Sky Association | 2019 May 29
Last edited by bystander on Mon Jun 10, 2019 3:36 pm, edited 1 time in total.
Know the quiet place within your heart and touch the rainbow of possibility; be
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IAU: The Impact of Satellite Constellations

Post by bystander » Fri Feb 14, 2020 7:49 pm

Understanding the Impact of Satellite Constellations on Astronomy
International Astronomical Union | 2020 Feb 12
Know the quiet place within your heart and touch the rainbow of possibility; be
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ESO: Study Evaluates Impact of Satellite Constellations on Astronomy

Post by bystander » Thu Mar 05, 2020 5:29 pm

New ESO Study Evaluates Impact of Satellite Constellations on Astronomical Observations
ESO Organization Release | 2020 Mar 05
Astronomers have recently raised concerns about the impact of satellite mega-constellations on scientific research. To better understand the effect these constellations could have on astronomical observations, ESO commissioned a scientific study of their impact, focusing on observations with ESO telescopes in the visible and infrared but also considering other observatories. The study, which considers a total of 18 representative satellite constellations under development by SpaceX, Amazon, OneWeb and others, together amounting to over 26 thousand satellites [1], has now been accepted for publication in Astronomy & Astrophysics.

The study finds that large telescopes like ESO's Very Large Telescope (VLT) and ESO's upcoming Extremely Large Telescope (ELT) will be "moderately affected" by the constellations under development. The effect is more pronounced for long exposures (of about 1000 s), up to 3% of which could be ruined during twilight, the time between dawn and sunrise and between sunset and dusk. Shorter exposures would be less impacted, with fewer than 0.5% of observations of this type affected. Observations conducted at other times during the night would also be less affected, as the satellites would be in the shadow of the Earth and therefore not illuminated. Depending on the science case, the impacts could be lessened by making changes to the operating schedules of ESO telescopes, though these changes come at a cost [2]. On the industry side, an effective step to mitigate impacts would be to darken the satellites.

The study also finds that the greatest impact could be on wide-field surveys, in particular those done with large telescopes. For example, up to 30% to 50% of exposures with the US National Science Foundation's Vera C. Rubin Observatory (not an ESO facility) would be "severely affected”, depending on the time of year, the time of night, and the simplifying assumptions of the study. Mitigation techniques that could be applied on ESO telescopes would not work for this observatory although other strategies are being actively explored. Further studies are required to fully understand the scientific implications of this loss of observational data and complexities in their analysis. Wide-field survey telescopes like the Rubin Observatory can scan large parts of the sky quickly, making them crucial to spot short-lived phenomena like supernovae or potentially dangerous asteroids. Because of their unique capability to generate very large data sets and to find observation targets for many other observatories, astronomy communities and funding agencies in Europe and elsewhere have ranked wide-field survey telescopes as a top priority for future developments in astronomy.

On the Impact of Satellite Constellations on Astronomical Observations
with ESO Telescopes in the Visible and Infrared Domains
~ Olivier R. Hainaut, Adrew P. Williams
Know the quiet place within your heart and touch the rainbow of possibility; be
alive to the gentle breeze of communication, and please stop being such a jerk.
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Re: Starlink

Post by Orca » Thu May 21, 2020 10:43 pm

I am torn on this topic as well. As Chris pointed out we still don't know what the impact will be. What if the satellites could be designed to mitigate the potential negative effects on observation?

Providing broadband to a vast number of people who wouldn't otherwise have access is undoubtedly a good thing, and the benefits are certainly hard to ignore.

I do think it's a project that should have involved a lot more open discussion, considering that it will have a global effect...