[Lordsandwhich]

I was always under the assumption that with Radar images that it didn't rely on a light source as technically the radar is the source. So that the impression that there is a light an dark side was based purely on the motion towards and away from the receiver.

But, you have pointed out something interesting and that would appear to indicate other wise. The clear rotation independent of source already shows that I am wrong on that.

Apparently I don't understand this very well.

[RachelF]

You are correct, the "light" is the transmitted radar pulse from Goldstone, not from the sun.

They do all sorts of fancy signal processing to get this sort of resolution.

Because radar power received goes down with 1/(distance^4), the inverse square law, squared, this is hard to do at astronomical distances.

The power level differential between transmitted and received power can be in the order of ~10^15.

Goldstone transmits a 500kW radio pulse but will probably get nanowatts back, which is amplified millions of times by the big dish, amplifiers and signal processing.

[radicalbyte]

This thread is very confused.

There are two things: the radar images are created with radio waves emitted by the radar installation. The second thing is that the visualisation shows a light source. They are unrelated to each other. I assume that the light source was added during rendering of the film and that it approximates the sun.

[TorKlingberg]

I don't think the visualisation shows any light source. The radar reflection from the asteroid just looks like it is "lit up"

[ceejayoz]

The radar is the light source, just like shining a flashlight during the night at something.

The actual solar illumination of the asteroid at the time was likely significantly different from what we see in these images.