OK, so, I'm reading an article on the Chinese balloon(s) that got shot down, and I'm not expecting much, but the person writing the story neglects to understand the most basic aspects of the technology in question.
Here is the bit:
………
The spy balloon that overflew the continental U.S. in February had sophisticated reconnaissance capabilities, possibly including "synthetic aperture radar," which can see at night and penetrate clouds, topsoil, and thin materials.
First, all radars of certain frequencies can penetrate clouds, topsoil, and thin materials.
That's why you have thing like "Ground penetrating radar."
What "synthetic aperture radar" (SAR) does is create higher resolution images.
Radar resolution is a function of two things, the frequency of the radar, and the size of the antenna.
What SAR does is that it takes multiple images from a moving platform, and then uses the radar returns from different locations and processes them to create an return that has the higher resolution of a larger antenna.
It simulates having a larger aperture (antenna), hence the name.
It's just radar, and apart from the increased resolution, it does not do anything different from any other radar.
For f%$#'s sake, SAR has its own Wiki Page!
It would have taken 15 minutes to understand the basics of what the technology does, and does NOT do:
Synthetic-aperture radar (SAR) is a form of radar that is used to create two-dimensional images or three-dimensional reconstructions of objects, such as landscapes.[1] SAR uses the motion of the radar antenna over a target region to provide finer spatial resolution
than conventional stationary beam-scanning radars. SAR is typically
mounted on a moving platform, such as an aircraft or spacecraft, and has
its origins in an advanced form of side looking airborne radar
(SLAR). The distance the SAR device travels over a target during the
period when the target scene is illuminated creates the large synthetic antenna aperture (the size
of the antenna). Typically, the larger the aperture, the higher the
image resolution will be, regardless of whether the aperture is physical
(a large antenna) or synthetic (a moving antenna) – this allows SAR to
create high-resolution images with comparatively small physical
antennas. For a fixed antenna size and orientation, objects which are
further away remain illuminated longer - therefore SAR has the property
of creating larger synthetic apertures for more distant objects, which
results in a consistent spatial resolution over a range of viewing
distances.
To create a SAR image, successive pulses of radio waves are transmitted to "illuminate" a target scene, and the echo of each pulse is received and recorded. The pulses are transmitted and the echoes received using a single beam-forming antenna, with wavelengths
of a meter down to several millimeters. As the SAR device on board the
aircraft or spacecraft moves, the antenna location relative to the
target changes with time. Signal processing
of the successive recorded radar echoes allows the combining of the
recordings from these multiple antenna positions. This process forms the
synthetic antenna aperture and allows the creation of higher-resolution images than would otherwise be possible with a given physical antenna.[2]
This sh%$ ain't rocket science, just stop phoning it in.