It’s been a while since I last engineered something where thermals were a consideration, but this just doesn’t feel right.
Making blank spots in the sky between the observer and the observed is something I suspect won't really be an improvement. It likely to make the problem less noticable (eg. no more b-roll of streaks in the sky to upset people) and, probably, more of a challenge to mitigate.
So if the satellite is simply blocking light, in the worst case, it will block the light of a star, maybe for a few milliseconds(?) dimming the star in the final picture by a minuscule amount.
This might still be problematic (influencing spectroscopy? dimming the star slightly, influencing some measurements there?) but probably still better than potentially mixing in light from a difference source (?)
also, black coating is old news. very old news. and musk said he didn't consider for starlink because he doesn't have to pay for something that doesn't make money directly for himself. so this whole discussion is pointless.
> "...researchers demonstrate how Vantablack® 310 – an ultra-black coating developed by University of Surrey spinout Surrey NanoSystems, co-authors of the paper..."
The equilibrium temperature of a polished aluminum surface at 1AU from the sun is 416K, hot enough to melt polyethylene and at least weaken many of the relevant aerospace plastics like the PET in mylar film.
Painting polished aluminum black drastically raises emissivity along with the lowered reflectivity, and brings its behavior closer to a blackbody.
So does allowing aluminum to oxidize, which it does almost instantaneously in atmosphere. So it's not like it's going to change anything drastically.
The reason this seems like it should change things a lot is that you're used to convectively cooled matte surfaces on Earth, where emissivity and radiative cooling is a less relevant factor and the only significant effect of painting something black is primarily that it absorbs more energy.
But that is NOT the temperature of something in LEO. You're ignoring everything else that adds energy to the system. Friction from collisions with atomic oxygen, down to heating up to temperatures as hot as 530 Kelvin just entirely dependent upon orientation to the sun.
Can I get some of that for my target gun sights?
Visual isn't the only concern, either. https://observatoiredeparis.psl.eu/starlink-satellites-a-thr...
Astronomers don't look first and then aim their cameras, and most interesting features (essentially all of them) require long exposures, which would make this problem a slight, one-time variance in brightness.
>Dr Noelia Noel, Senior Lecturer, PhD in Astrophysics
Is this a joke article?
She is from Argentina. Both are common given names and family names here. Neither is in the top 10 list, but they are not unusual to cause surprise. I'd recommend to avoid using both together to avoid nasty online comments.
> Astha Astha
She is from India. Astha is a common given name there. It looks like it's common in some areas to have only a given name and no family name. I guess in some form she was had to fill a family name and decided to repeat the given name instead of using NULL.
Link to the classic article by patio11: "Falsehoods Programmers Believe About Names" (2010) https://www.kalzumeus.com/2010/06/17/falsehoods-programmers-... (a few HN discussions, in particular https://news.ycombinator.com/item?id=21492464 | 150 points | Nov 2019 | 144 comments)
(Though I'd rather anodize the thing black imperfectly if it helps avoid paint flecks becoming orbital debris)
Remove convection/conduction as heat transfer methods, and you end up with two numbers dictating radiative balance:
Percent reflectivity in the bands it's exposed to
Percent emissivity in the bands it's emitting
The balance between these dictates temperature, and they're generally inversely correlated. Mirrors are good reflectors, but very poor emitters.