That said, I wouldn't be surprised if some known launches also contained some unknown payloads. Stealth technology on a satellite would probably thwart detection in space well enough.
Stealth is great for radar, but even the B-2 can be spotted pretty easily via the Mk 1 eyeball. Satellites also have to have radiators, which limits what you can manage.
It has a visual cloaking device too. It isn't terribly complicated. The bottom of the aircraft is a particular color. If you fly at an altitude that the sky above is the same color as the bottom of your plane, people on the ground cannot see you. So a tiny camera pointed up can be used to calibrate the altitude to best hide.
Also see counterillumination, a trick used by many sea creatures to hide from things below them. I doubt the B2 uses this but the military has studied it as an option in the past.
https://www.thedrive.com/the-war-zone/29543/the-visible-hist...
> Modern stealth aircraft, such as the F-117 Nighthawk attack jet and B-2 Spirit bomber, are painted in matte black or dark grey and are flown at night to limit their visual signature.
Can't really do that in space; you've got a day/night cycle ever 90 minutes or so.
The F117 is black and only flew at night, at lower levels. The bottom of the B2 isn't actually black, more a dark grey with a bit of blue in it. And the top of the aircraft is more sea blue than black at most angles. Someone thought long and hard about those colors, about not just painting it all black like the F117.
It sure heats up fast, though. Radiating enough heat not to roast the electronics is already an issue for satellites with shiny coatings to keep heat from the sun out.
There's a good, detailed explanation of how hard stealth in space is at https://worldbuilding.stackexchange.com/questions/23313/stea....
There've been efforts towards stealthier craft. https://en.wikipedia.org/wiki/Misty_(satellite)
The ISS is way bigger than a highly classified satellite, but I'd guess a lot of nation states have way better capability than some guy with a telescope in his back yard in New Zealand.
I giggled.
I bet you could make a satellite look like a stray screw or fleck of paint with enough effort. Careful geometry and surface design can reduce the radar cross section to a tiny fraction; some ultrablack coating and judicious heat rejection could make it look effectively invisible to optical and IR. Power with an RTG to avoid glints and radar scatter from solar panels.
And I'm sort of geeking out thinking about how you could misdirect observers about the payload's path— release a very shiny dummy payload, and then release the real thing some time before or after. Or pull a Millennium Falcon gambit and release the actual payload from a disposed fairing or stage when no one's looking...
There was some speculation over that approach with the failed launch of the Zuma satellite. https://en.wikipedia.org/wiki/Zuma_(satellite)
This confidence in agencies and funding is puzzling to me.
[0] https://www.electronics-notes.com/articles/antennas-propagat...
[1] https://en.wikipedia.org/wiki/Meteor_burst_communications
https://www.theatlantic.com/technology/archive/2016/06/mappi...