Yep. Lots of very clearly uninformed opinions here. Can confirm there are many advantages and disadvantages of space-based vs ground-based telescopes. Saying "well astronomers should just use space telescopes those are better" is quite ridiculous and reveals a deep ignorance for how astronomy is actually done (as though an entire field of science has not maybe had that thought?).

Extreme expense and complexity of space based telescopes is one large downside (saying "well space x will make that cheaper" um, maybe? but that will not happen for quite some time, and you realize you are parroting a PR department known for being hyperbolic? While ignoring the actual, real impact these satellites are currently having on billions of dollars of astronomy research, which happens on 10-20 year timescales?).

There are numerous benefits conferred by ground based telescopes that cannot be accomplished in space. Ground based telescopes allow you to have much larger collecting area, allow you the option to maintain + upgrade instrumentation (not possible in space, and if someone mentions "hey they replaced the hubble mirror, didn't they?" yes, at the cost of 250 million dollars), not to mention the barrier to entry for building ground based instruments is much lower and allows smaller projects to have a large impact without requiring a ridiculous amount of funding. See, e.g. https://www.astro.princeton.edu/~gbakos/satellites/ <- one astronomer's page detailing the impact these satellites currently have on his work; this is just one example. Lots of links, e.g. https://www.forbes.com/sites/startswithabang/2019/11/27/this... that will confirm the bare basics of what I'm saying here.

People thinking "oh well ML should fix that" may also be completely unaware that: no it cannot, unless you just want a pretty picture, because astrophysics is done on pixel-level brightnesses and once you saturate a pixel, there is no more information there, not to mention that even non-saturated pixels will have an insane amount of noise now, which degrades the SNR of otherwise good observations. Astronomy is done with some of the most sensitive optical/IR/radio equipment that exists (a large motivation to fund astronomy is for the innovation here that is relevant to other applications).

People saying "oh but space x is going to add some anti-reflectivity coating so it'll all be alright, Elon will fix it." Ohhh boy. Yikes. Here's the incredible page addressing this on space-x: https://www.spacex.com/updates/starlink-update-04-28-2020/ <- it's incredible because it flat out admits to an astounding level of ignorance about the impact of this, and makes several promises that may seem nice to a non-astronomer but basically amount to "we'll do something but it will not really change anything at all for any astronomy research, but we totally understand now that someone has finally educated us on the bare basics of operating in space."

> For example, earlier this year we launched DarkSat, which is an experimental satellite where we darkened the phased array and parabolic antennas designed to tackle on-station brightness. This reduced the brightness of the satellite by about 55%,

To give you an idea of how completely meaningless this is to astronomy: these satellites currently have an average magnitude of 5.5, brighter than the brightest stars, and virtually all of astronomy tries to be sensitive to > 10th mag (i.e. 1.5% of the brightness of 5.5 mag, so we're looking for > 99% brightness reduction before this even begins to mean anything) + this coating will affect IR measurements because black coatings are black because they absorb light, and things that absorb light get hot and things that are hot emit IR radiation. LSST will have a 5-sigma single exposure sensitivity of at least 22 mag (0.000025% of the current satellite brightness, no that is not a typo, so we would need 99.99997% brightness reduction).

> The huge collecting area of a larger telescopes like Vera C. Rubin Observatory leads to a sensitivity that will render even the darkest satellites visible.They are so sensitive that it won't be possible to build a satellite that will not produce streaks, in a typical long integration. There is much that can be done to reduce the impact of satellite streaks, and that starts with an understanding of how astronomical sensors work.

So nice of them to think of that, um, now? The rest of that section is a goldmine, saying basically "here is why we really can't mitigate this for CCD detectors used by all of astronomy because, well, they are looking at dim things and bright things ruin a large portion of the observations" while also concluding with

> While it will not be possible to create satellites that are invisible to the most advanced optical equipment on Earth, by reducing the brightness of the satellites, we can make the existing strategies for dealing with similar issues, such as frame-stacking, dramatically more effective.

No, no, no, no, no and no. There is absolutely nothing you can do with 30,000 5-6th mag satellites in the sky at all times. They will be in your images. Frame stacking will help to a point, but not even close to what you would need (not even within a few orders of magnitude). We will lose a large amount of effective sensitivity and a large amount of science will be completely lost.

People still shrugging this off should remember: instruments like LSST cost the taxpayer half a billion dollars and took 20 years of development, countless and priceless time investment from a large fraction of astrophysicists and astronomers (many at the top of their field), and would allow us to do incredibly impactful science, both from a philosophical standpoint (being able to observe 20 billion galaxies + stars allows you to do cosmology and other astrophysics that is otherwise impossible, see the science book: https://arxiv.org/abs/0912.0201), and from a practical standpoint (like NEO's)

So: even if you don't think astronomy is important, you should still care about this. It's a colossal waste of money due to the complete arrogance and ignorance of one rich guy. Absolutely did not have to be this way.