Losing the (night) sky

Discuss the greatest threat to amateur astronomy today

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JohnM
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Losing the (night) sky

Post by JohnM »

I have just posted a link to a forthcoming discussion meeting on the impact of mega satellite constellations on both amateur and professional astronomy.

Please join the meeting live on You Tube as the number of people who watch is a good indication of how concerned astronomers are.

John Murrell
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Re: Losing the (night) sky

Post by UN_Owen_Was_Him »

Is there a recording, a transcript or something of that conference? It does sound interesting, as I was, too, worried about the effect of large scale satellite networks on the night sky.
JohnM
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Re: Losing the (night) sky

Post by JohnM »

The event was hosted by the Astronomical Society of Edinburgh and access to the recordings is from https://www.astronomyedinburgh.org/2021 ... sky-event/. In addition Andy Lawrence has written a book about the problem.

There was a workshop called SATCON which is linked from https://aas.org/posts/advocacy/2021/08/ ... ve-updates.

Part one came up with a number of recommendations, SATCON2 reviewed the progress though I have not looked at the meeting recordings yet.

I am not really sure how bright they are and what the impact will be on Amateur imaging - I have enough problem imaging the brighter satellites in my light polluted sky let alone those around mag 7 - You need a 100 times increase in sensitivity from your camera and telescope / lens compared to the mag 2 satellites.

Pete Lawrence apparently imaged the British Prospero satellite which would have been around mag 7 to 9 at it's brightest on The Sky at Night a couple of months ago but I have been unable to find out how he did this.

One thing to be aware if you are trying to image or avoid the LEO satellites is that the Two Line Elements (TLE) used by Heavens above and other sites are 'out of date' so the predictions of times will be in error. The problem is that the TLEs are measured by radar and are normally a couple of days old. This did not matter where satellites orbits did not change much over a few days but the LEO satellites use their Ion Thrusters to manoeuvrer for several weeks to move from their launch to operational orbits. Thus TLEs from a few days ago do not reflect the current positions. One of the recommendations of the SATCON1 workshop was that LEO satellite operators publish their current TLEs as computed by their operations centres. This has been done and the current elements are now available on the Celestrac website but you have to download these separately. Sites like Heavens Above don't seem to have implemented this change of data source yet.

I have my doubts about the magnitudes on the Heavens above site as well - I think they may be using the pre-visorsat magnitudes for Starlink Satellites and they are dimmer than shown, unless they flare.

Recently launched Starlink satellites are also dimmer than they were before as they now fly them in the so called 'sharks fin' altitude with the solar panel perpendicular to the Earth surface and shielded to some extent by the spacecraft body.

What has also become obvious recently is that the Starlink satellites get brighter when they are being de-orbited. I saw one recently that was about mag 1 as it approached the altitude where it would burn up.

John Murrell
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Re: Losing the (night) sky

Post by UN_Owen_Was_Him »

THank you for the recordings and for your in-depth answer! That's reassuring to know that this satellite network isn't necessary going to be the end of starry skies at night, I'll listen to the recordings tonight.
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Re: Losing the (night) sky

Post by JohnM »

The Starlink receivers are interesting technology - they are phased arrays that form beams on each satellite similar to what radio telescope interferometers such as LOFAR does.

There is a piece on the BBC Technology page at https://www.bbc.co.uk/news/technology-58061230 about possible problems with pigeons sitting on the dishes (In fact they seem to be flat rather than a dish).

The dishes and the associated electronic box are not very Green - they have quite a high power consumption that increases in the winter when the heater turns on to prevent snow / ice forming on the aerial. People in the colder parts of the US have found problems with the water running of the dish freezing and preventing the dish mechanical motion working.

Most of the information is available on the Starlink constellation and that is limited for instance they will not publish the 'shape models' that would allow reflectance and thus brightness to be calculated. There is very little information about the other constellations such as OneWeb though a large part of the company is owned by the UK Government.

Most of the data on the OneWeb satellite brightness is from a Russian space observation network at http://mmt9.ru/satellites/. Note their data does not include any Russian satellites but includes US military satellites that are not in the (Public) spacetrac element set ! The site also has extensive brightness records of Starlink satellites as well as otehrs such as Prospero I mentioned in my previous post.
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Re: Losing the (night) sky

Post by UN_Owen_Was_Him »

No Russian satellites, but the American ones, including the military ones? Sounds fun :twisted: apart from that, yes, I've worked with dish antennae for a while, and if you're in a place where winter is an actual thing, they're difficult to keep in good condition. My in-laws, in Russia, had sheltered their dish under a part of the apartment block's roof that they had lengthened with artisanal means, and got a-okay signal with a fixed dish like that. They were relieved when they started getting their TV channels through their Internet access, but it worked, more or less, for a couple years.
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Re: Losing the (night) sky

Post by Lariliss »

From an optimistic point of view Starlink is a fast roll-out for ambitious and for an important part vital aims.
Exactly, as it is mentioned above in the thread, there is not so much information on other satellites functioning on the orbit.
New technology constellations and maintenance should be a benefit, opposed to already orbiting facilities of smaller coverage networks already there.
Public criticism everywhere, including National level mitigation requests might settle down the uncomfort of light pollution.

The technology is not less green than 3G/4G, as it appears from technical descriptions.

https://en.wikipedia.org/wiki/Starlink#Technology
Criticism is open.
‘Similar competitive systems’ part is known.

New satellite launches (not only Starlink) should make the orbit greener, should bring us to debris elimination, should bring effectiveness and their higher purposes.
Number, Letter, Note: Know, Think, Dream.
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