I was referring to this part.
And 99.965% absorption is still visible in a bright light.
"The Worlds Blackest Black vs The Worlds Brightest Flashlight (32,000 lumen)—Which Will Win?"
https://www.youtube.com/watch?v=AaFdCvnV8PM
To summarize, the flashlight wins, and it's reasonable to expect the effect would be the same with a laser and sensitive detection equipment.
That isn't Vantablack as such though, is it? Afaik, Vantablack proper requires a specific application process [1], which I've mentally envisaged as being something akin to growing diamonds in a lab on a substrate, or applying flocking to materials.
I'd be quite curious to know what the reflectivity would be like on some clever coating consisting of vertically-laid carbon nano tubes, etc.
[1] - https://www.surreynanosystems.com/vantablack/applying-vantab...
The USAF figured out how to detect such satellites back in the 1980s.[1] The Ground-based Electro-Optical Deep Space Surveillance (GEODSS) looks at the sky with three 40-inch telescopes per site. This automatic system has a big star catalog, and can detect when something blocks its view of a star. The telescopes are some distance apart, and so they can see time differences between something occulting a star and compute range. The multiple telescopes allow disambiguating problems such as clouds, aircraft, and birds.
If something looks interesting enough, one of the telescopes is switched to laser mode, and a laser flash is used to illuminate the target. Even black objects reflect some light.
GEODSS was the first fully computerized telescope system, and it generated far more usable data than film-based systems. One of the old GEODSS sites was used to look for near-earth asteroids for years, and found most of the known ones. Now, of course, everybody has multi-megapixel imagers on telescopes and enough computer power to analyze the results.
[1] https://en.wikipedia.org/wiki/United_States_Space_Surveillan...