Quote from: pochimax on 01/03/2020 09:51 amQuote from: envy887 on 01/02/2020 04:51 pmQuote from: pochimax on 01/02/2020 03:47 pmQuote from: envy887 on 01/02/2020 02:54 pmQuote from: Star One on 12/31/2019 08:26 amThe astronomer royal in the UK Martin Rees has now weighed in on the topic of satellite constellations like Starlink. He does attempt to be even handed in his comments.https://amp.theguardian.com/commentisfree/2019/dec/29/be-wary-of-elon-musk-despoiling-the-vault-of-heavenFrom the article:QuoteThis entails launching up to 40,000 spacecraft into orbit ... There would be roughly one in every square degree over the sky (the area on the sky covered by a small coin held at arm’s length).You would think that the Astronomer Royal would know that even though there are 41253 square degrees in the sky, and (potentially) 40000 satellites, that does NOT mean that there would be roughly 1 visible satellite per square degree of visible sky. While you can see about half the sky from any given location, you can only seen a much, much smaller fraction of all the satellites, because the vast majority are near or below the horizon. This is such a gross and basic error that it's hard to put any weight to the rest of his article.¿¿¿because the vast majority are near or below the horizon. How could this even be phisically possible???Do you know what are you talking about?? And you are questioning Mr. Rees??!!An observer on the surface of Earth can only see ~3.8% of the total area of a 550 km altitude shell. Any satellite at that altitude more than ~2700 km away is below the horizon. Unless the satellites are not evenly distributed but are congregating over one particular area for some reason, the remaining 96+% of the satellites won't be visible.Put another way, if 40,000 Starlinks cover 70% of the globe in a 550 km shell, focusing on low and mid latitudes, that's still 10,000 km of shell area per satellite. Satellites will be 100 km from each other, which for an observer 550 km away puts them 10 degrees apart in the sky. You will need a truly massive coin to cover two objects 10 degrees apart in the sky. They will be closer together near the horizon, of course, but counting all the ones above 30 degrees elevation they will still be 50 times more sparse than "one per square degree".Or to put it another way, at the areal densities Rees is suggesting, some 10,000 satellites would be visible above 30 degrees elevation for any observer!If you can see a 3.8% shell this is like 1.600 square degrees. So, obviously, you will see an all sky with 1.600 satellites or one satellite per square degree as Mr. Rees said.It is not necessary to confuse anybody here with wrong calculations that don't take into account that this are not fixed (geostationary) satellites but low orbital, moving ones, crossing the sky. Edit. It doesn' t matter satellites are moving. Simply, your calculations are nonsense. At any point on the surface you will always see 50% of the sky sphere, not only 3.8%. No matter how low or high satellites are.This is so wrong, it an be disproven with MS Paint. As I said earlier, unless you take into account orbit height, angle measurements from the center and a viewpoint on the surface are completely incomparable. Looking straight up, 1° spacing between satellites at 400km turns into 19° for an astronomer at 0km. This is highly nonlinear of course, but as a rule of thumb, the solid angle fov of a telescope is less than 1% of the corresponding solid angle measured from the center of the orbit. So a 1°x1° telescope would only be impeded on average by satellites spaced closer than 0.1°x0.1°, or 4 million randomly distributed.
Quote from: envy887 on 01/02/2020 04:51 pmQuote from: pochimax on 01/02/2020 03:47 pmQuote from: envy887 on 01/02/2020 02:54 pmQuote from: Star One on 12/31/2019 08:26 amThe astronomer royal in the UK Martin Rees has now weighed in on the topic of satellite constellations like Starlink. He does attempt to be even handed in his comments.https://amp.theguardian.com/commentisfree/2019/dec/29/be-wary-of-elon-musk-despoiling-the-vault-of-heavenFrom the article:QuoteThis entails launching up to 40,000 spacecraft into orbit ... There would be roughly one in every square degree over the sky (the area on the sky covered by a small coin held at arm’s length).You would think that the Astronomer Royal would know that even though there are 41253 square degrees in the sky, and (potentially) 40000 satellites, that does NOT mean that there would be roughly 1 visible satellite per square degree of visible sky. While you can see about half the sky from any given location, you can only seen a much, much smaller fraction of all the satellites, because the vast majority are near or below the horizon. This is such a gross and basic error that it's hard to put any weight to the rest of his article.¿¿¿because the vast majority are near or below the horizon. How could this even be phisically possible???Do you know what are you talking about?? And you are questioning Mr. Rees??!!An observer on the surface of Earth can only see ~3.8% of the total area of a 550 km altitude shell. Any satellite at that altitude more than ~2700 km away is below the horizon. Unless the satellites are not evenly distributed but are congregating over one particular area for some reason, the remaining 96+% of the satellites won't be visible.Put another way, if 40,000 Starlinks cover 70% of the globe in a 550 km shell, focusing on low and mid latitudes, that's still 10,000 km of shell area per satellite. Satellites will be 100 km from each other, which for an observer 550 km away puts them 10 degrees apart in the sky. You will need a truly massive coin to cover two objects 10 degrees apart in the sky. They will be closer together near the horizon, of course, but counting all the ones above 30 degrees elevation they will still be 50 times more sparse than "one per square degree".Or to put it another way, at the areal densities Rees is suggesting, some 10,000 satellites would be visible above 30 degrees elevation for any observer!If you can see a 3.8% shell this is like 1.600 square degrees. So, obviously, you will see an all sky with 1.600 satellites or one satellite per square degree as Mr. Rees said.It is not necessary to confuse anybody here with wrong calculations that don't take into account that this are not fixed (geostationary) satellites but low orbital, moving ones, crossing the sky. Edit. It doesn' t matter satellites are moving. Simply, your calculations are nonsense. At any point on the surface you will always see 50% of the sky sphere, not only 3.8%. No matter how low or high satellites are.
Quote from: pochimax on 01/02/2020 03:47 pmQuote from: envy887 on 01/02/2020 02:54 pmQuote from: Star One on 12/31/2019 08:26 amThe astronomer royal in the UK Martin Rees has now weighed in on the topic of satellite constellations like Starlink. He does attempt to be even handed in his comments.https://amp.theguardian.com/commentisfree/2019/dec/29/be-wary-of-elon-musk-despoiling-the-vault-of-heavenFrom the article:QuoteThis entails launching up to 40,000 spacecraft into orbit ... There would be roughly one in every square degree over the sky (the area on the sky covered by a small coin held at arm’s length).You would think that the Astronomer Royal would know that even though there are 41253 square degrees in the sky, and (potentially) 40000 satellites, that does NOT mean that there would be roughly 1 visible satellite per square degree of visible sky. While you can see about half the sky from any given location, you can only seen a much, much smaller fraction of all the satellites, because the vast majority are near or below the horizon. This is such a gross and basic error that it's hard to put any weight to the rest of his article.¿¿¿because the vast majority are near or below the horizon. How could this even be phisically possible???Do you know what are you talking about?? And you are questioning Mr. Rees??!!An observer on the surface of Earth can only see ~3.8% of the total area of a 550 km altitude shell. Any satellite at that altitude more than ~2700 km away is below the horizon. Unless the satellites are not evenly distributed but are congregating over one particular area for some reason, the remaining 96+% of the satellites won't be visible.Put another way, if 40,000 Starlinks cover 70% of the globe in a 550 km shell, focusing on low and mid latitudes, that's still 10,000 km of shell area per satellite. Satellites will be 100 km from each other, which for an observer 550 km away puts them 10 degrees apart in the sky. You will need a truly massive coin to cover two objects 10 degrees apart in the sky. They will be closer together near the horizon, of course, but counting all the ones above 30 degrees elevation they will still be 50 times more sparse than "one per square degree".Or to put it another way, at the areal densities Rees is suggesting, some 10,000 satellites would be visible above 30 degrees elevation for any observer!
Quote from: envy887 on 01/02/2020 02:54 pmQuote from: Star One on 12/31/2019 08:26 amThe astronomer royal in the UK Martin Rees has now weighed in on the topic of satellite constellations like Starlink. He does attempt to be even handed in his comments.https://amp.theguardian.com/commentisfree/2019/dec/29/be-wary-of-elon-musk-despoiling-the-vault-of-heavenFrom the article:QuoteThis entails launching up to 40,000 spacecraft into orbit ... There would be roughly one in every square degree over the sky (the area on the sky covered by a small coin held at arm’s length).You would think that the Astronomer Royal would know that even though there are 41253 square degrees in the sky, and (potentially) 40000 satellites, that does NOT mean that there would be roughly 1 visible satellite per square degree of visible sky. While you can see about half the sky from any given location, you can only seen a much, much smaller fraction of all the satellites, because the vast majority are near or below the horizon. This is such a gross and basic error that it's hard to put any weight to the rest of his article.¿¿¿because the vast majority are near or below the horizon. How could this even be phisically possible???Do you know what are you talking about?? And you are questioning Mr. Rees??!!
Quote from: Star One on 12/31/2019 08:26 amThe astronomer royal in the UK Martin Rees has now weighed in on the topic of satellite constellations like Starlink. He does attempt to be even handed in his comments.https://amp.theguardian.com/commentisfree/2019/dec/29/be-wary-of-elon-musk-despoiling-the-vault-of-heavenFrom the article:QuoteThis entails launching up to 40,000 spacecraft into orbit ... There would be roughly one in every square degree over the sky (the area on the sky covered by a small coin held at arm’s length).You would think that the Astronomer Royal would know that even though there are 41253 square degrees in the sky, and (potentially) 40000 satellites, that does NOT mean that there would be roughly 1 visible satellite per square degree of visible sky. While you can see about half the sky from any given location, you can only seen a much, much smaller fraction of all the satellites, because the vast majority are near or below the horizon. This is such a gross and basic error that it's hard to put any weight to the rest of his article.
The astronomer royal in the UK Martin Rees has now weighed in on the topic of satellite constellations like Starlink. He does attempt to be even handed in his comments.https://amp.theguardian.com/commentisfree/2019/dec/29/be-wary-of-elon-musk-despoiling-the-vault-of-heaven
This entails launching up to 40,000 spacecraft into orbit ... There would be roughly one in every square degree over the sky (the area on the sky covered by a small coin held at arm’s length).
DESCRIPTIONOver past years, considerable efforts have gone into designing, building, and deploying large networks of satellites in mainly low-Earth orbits. Until now, the number of satellite constellations has been below 100, but is rapidly increasing to hundreds, with independent plans of potentially deploying tens of thousands, outnumbering all previously launched satellites. While the communications enabled by them are beneficial in many respects, satellite constellations pose a significant or debilitating threat to important existing and upcoming astronomical infrastructures. Scientific concerns are three-fold. First, surfaces of these satellites are often made of highly reflective metal, and reflections from the Sun can be detrimental to the sensitive capabilities of large astronomical telescopes, including wide-angle survey telescopes under construction. Second, astronomical observations at radio wavelengths are threatened through radio leaks. Third, the increasing number of satellites creates a potentially critical problem whose impact must be better understood before large constellations are launched. As members of the astronomical community, we need to understand the impact to our field, some possible solutions and how to work collaboratively with designers, deployers, policy-makers and other stakeholders in this new and largely unregulated frontier of space. As such, we propose a special session, which includes a panel of pundits and discussions in these areas, as well as updates to the state of affairs in other areas of light pollution, radio interference and space debris. This proposed special session is a concerted effort of the AAS Committee on Light Pollution, Radio Interference and Space Debris.
This is so wrong, it an be disproven with MS Paint. As I said earlier, unless you take into account orbit height, angle measurements from the center and a viewpoint on the surface are completely incomparable. Looking straight up, 1° spacing between satellites at 400km turns into 19° for an astronomer at 0km. This is highly nonlinear of course, but as a rule of thumb, the solid angle fov of a telescope is less than 1% of the corresponding solid angle measured from the center of the orbit. So a 1°x1° telescope would only be impeded on average by satellites spaced closer than 0.1°x0.1°, or 4 million randomly distributed.
When there are 50,000 satellites in the sky, “you’ll see the sky crawling,” says Tony Tyson, a University of California Davis astronomer and physicist. “Every square degree will have something crawling in it.”
It turns out, we think, that surfaces that scatter light, or reflect light diffusely, are also significant contributors,[from tweets]Seitzer: if all we have to contend with was a 1,584-satellite Starlink constellation, astronomers could probably handle it. But it’s not.Pat Seitzer, U. Mich.: concern about the megaconstellations is not just their numbers but their brightness: potential to be brighter than 99% of existing objects in orbit
SA piece 2020-01-16The Scientific American runs a piece that might be considered not completely even handed. (this is not the first piece by this author, or the first piece on this topic in SA that I personally would not consider completely even handed)Posted for reference, try to keep things on an even keel.
In ignoring a key piece of federal environmental legislation, the FCC could be sued in a court of law—and lose—potentially halting further launches of mega constellations until a proper review is carried out.
“Astronomers are having these issues [and think] there’s nothing they can do legally,” says the paper’s author Ramon Ryan, a second-year law student at Vanderbilt University.
maybe this is not uncommon, but a paper by a student doesn't seem to be a fully credible source for legal advice.
I haven't read Sci Am in a long while.What is scientific about this legal speculation?
Quote from: freddo411 on 01/16/2020 06:11 pmI haven't read Sci Am in a long while.What is scientific about this legal speculation?>>Scientific American articles used to be sort of, kind of, review papers covering some topic but in a more readable format than actual review papers.Unfortunately those days are long past. Today Scientific American articles are written by journalists.
Just received this statement from the FCC regarding whether their process for licensing satellites, such as SpaceX's Starlink mega constellation, is in violation of the National Environmental Policy Act (NEPA) and thus unlawful.(note, the emphasis on "any" is their's)
