I would assume stealth aircraft are rather hard to clearly image with a Synthetic-aperture radar satellite. But the point was more about cutting down on the number of satellites you need to worry about. You can’t exactly hide the fact a satellite is sending out radar for imaging.
Stealth for jets isn't primarily designed for plan view. (Referring to radar cross section isn't just a generic use of the term for "detectable area of return".)
Even if it was stealthy from above, it would be easy to identify and defeat, especially on the ground: just look for the plane-shaped area without a ground return.
Or separately, a pair of co-orbital following satellites would entirely defeat all (publicly known) radar stealth (with the transmitter offset from the receiver). The US admittedly has similar pairs of these for "scientific purposes". I assume the military/IC have access or have their own.
And synthetic aperture radar can be disguised such that its nearly indistinguishable from background noise. It's one of the features that makes it superior to old school dish radar. That's not even a secret. It's currently deployed throughout the military: ground, sea, and air. Space based platforms probably had it first.
In terms of disguising synthetic aperture radar that’s much harder with a satellite which needs to send out a strong signal to hit stuff at 300+ miles and then bounce back to another detector at 300+ miles. Especially when there is such a limited number of easily tracked satellites to be concerned with.
10x distance requires 100x the signal.
When it comes to being stealthy from above, jets bank to turn. Pilots can handle much higher g loads vertically than horizontally.
> And synthetic aperture radar can be disguised such that its nearly indistinguishable from background noise
So the transmit power is the same as background noise and you can still get useful radar pictures out of it?
Amazing. I roughly know you can recover repeating signals that are below the noise floor, but still amazing.
See: https://en.m.wikipedia.org/wiki/Spread_spectrum along with cryptographically randomized frequency hopping, you would not be able to figure out when there is an actual signal rather than noise.
Picture a point source frequency hopping different collars of visible light on your wall. There are real limits to how many photons it can send before it becomes really obvious.
As satellites need to detect returns bounced off the ground hundreds of miles away they have some hard minimums for high resolution images vs aircraft or ground stations. 10x distance needs 100x the signal.
If the surrounding area where the plane is parked is coherent (which pavement and concrete usually is) then you will see an incoherent region in the SAR imagery where the plane resides which would be quite suspicious.
You can jam it (if you know the right frequencies) and you can also passively blow it out with a big corner reflector, which tends to result in a very bright spot and loss of surrounding detail.
Synthetic-aperture radar is making the Earth’s surface watchable 24/7 https://www.economist.com/technology-quarterly/2022/01/27/sy...