Submitted by ChieftainMcLeland t3_11eqjsg in space
FlingingGoronGonads t1_jahp0sh wrote
Reply to comment by Adeldor in Satellite Constellations Are an Existential Threat for Astronomy by ChieftainMcLeland
This is borderline Misinformation. You are attempting to create an impression that there is no problem, and that everything has been or will be mitigated. Some choice quotes, with sources:
From that totally disreputable, clickbait publication, Science.org:
> The Rubin Observatory, with an 8.4-meter mirror that will take pictures of the sky the size of 40 full Moons in 30-second exposures, "is the perfect machine for running into these satellites," Tyson says.
> He and his team conducted simulations that suggested the track of a satellite image across their camera would saturate each camera pixel as it passes, and cause leakage into neighboring ones. The resulting artifacts "cannot be removed in software. We have failed in doing that," Tyson says. The team looked at altering schedules to avoid satellite trails, but with such a wide field of view, avoiding thousands of satellites would end up as "a wild goose chase," he says.
Speaking of the Rubin Observatory:
> Simulations of the LSST observing cadence and the full 42,000 SpaceX satellite constellation show that as many as 30% of all LSST images would contain at least one satellite streak. With constellations of 400,000 LEOsats, most images will have very bright streaks.
> Due to its rapid cadence, LSST cannot usefully avoid tens of thousands of LEOsats.
> Darkening satellites to 7th magnitude would simplify removal of some artifacts in LSST images, but there is no guarantee most of the satellites will be limited in brightness to fainter than 7th magnitude.
> The bright main satellite trail would still be present, potentially creating bogus alerts and systematics at low surface brightness. This is a challenge for science data analysis, adding significant effort and potentially limiting discovery of the unexpected.
> However there is a larger challenge: because of the unprecedented large samples, LSST science will be limited by systematics rather than sample variance (area incompleteness). Of concern are various systematic effects that do not simply scale with the number of lost pixels—in other words, the residuals from these mitigation strategies on the science cases for which LSST was designed. For example, the LSST ability to detect asteroids approaching from directions interior to the Earth's orbit may be severely impacted because those directions are visible only during twilight when LEO satellites are brightest—nearly every LSST image taken at this time would be affected by at least one satellite trail. [My emphasis added]
TLDR: I could provide further quotes, especially about the harm to radio astronomy, but the point here is that software can't remove the streak when the CCD has been saturated - that would be like dumping thousands of identical lemons into a bin that initially contains only one or two, shaking the bin vigorously, and then trying to identify the original occupants. This isn't about amateur astrophotography - this is about trying to identify transient phenomena that are captured in single exposures. No software in the world can undo the harm if hardware and physics don't allow for it.
Adeldor t1_jahsf9s wrote
You speak of misinformation, then misrepresent what I wrote with this:
> You are attempting to create an impression that there is no problem, and that everything has been or will be mitigated. [emphasis added]
In fact I wrote:
> There will be effects, but they are in general minor, or there are mitigating actions being taken now ... [emphasis added]
I neither wrote nor implied "no problem" and "everything has been or will be mitigated." Those are your words. Further, I provide the links for everyone to read the full releases in context, in an explicit attempt to avoid the very sin you seem to imply I'm committing.
Regardless, constellations are here now. Their worth has been proven, Starlink at least and professional observatories are working together to share the sky, and astronomy is not facing an existential threat, per that click-bait headline.
FlingingGoronGonads t1_jahtzyv wrote
I'll leave it to the alert reader to actually read the quotes we both provided. The only thing I will say to you about your "in general minor" harms that have no potential for mitigation (and I have provided a source for that statement already):
If observatories are literally unable to carry out part or all the mission objectives for which they are designed (like searching for Atira-type asteroids, which must be searched for at twilight because they orbit the Sun closer than Earth does), you have an interesting definition of the word "minor".
EDITED TO ADD: This comment has been up for hours and stands at a mere minus-2. I'm disappointed in you Musk worshippers, you're off your game here. I suppose I could keep fielding clueless anti-science comments like dern_the_hermit's below all day, but I'm done with this thread. For people that actually want to understand science and the problems that satellite swarms present, please remember that observatories and photometers are not just taking one-off snapshots - they're often taking data over a certain period of time to build up a light curve (a graph of change in brightness versus time), to give just one example. Tearing out gaps in a curve means loss of data that can be irretrievable, especially when an object is doing something unexpected. You can't mathematically reconstruct something that is non-repeatable!
dern_the_hermit t1_jaj4p4r wrote
It's just bonkers to suggest observatories can't observe because a portion of some pictures is lost.
FlingingGoronGonads t1_jaj6mwh wrote
What happens when the actual object you're trying to observe is blotted out with an adjacent satellite streak? Vera Rubin will be taking short exposures - lots of them. Wide-field surveys need the sky to be open because, you know, they're looking for unknown sources, or need to see if known sources are doing unexpected things. Why is that difficult to understand?
dern_the_hermit t1_jaj8btq wrote
> What happens when the actual object you're trying to observe is blotted out with an adjacent satellite streak
Take another picture. Pictures are cheap.
FlingingGoronGonads t1_jaj8v7t wrote
Sure, chuckles, loss of data is no big deal. Especially when you know ahead of time that the transient object/behaviour you're looking for means that the light source has no guarantee of being at the same brightness or position next exposure.
Musk fanatics are forever betraying their ignorance of science. Bye-bye, troll.
dern_the_hermit t1_jaj9367 wrote
Insults are completely inappropriate.
> loss of data is no big deal
It's not necessarily an existential threat, is the point. Let's stayed focused and on-topic here.
[deleted] t1_jajabmp wrote
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