I have been trying to figure out recently why people don’t understand what IR detector data looks like, given that we have examples and studies and in a few cases specifications of what we’ll get from JWST, and examples and analysis of NICMOS, Spitzer and some Keck data. My wife explained it to me, and then I looked at the numbers. She’s right, and I wanted to publicly thank her.
We have some simulated data, a cutout of which is shown here, that gives you the general idea of what the data will look like if it’s pretty good. Jay Anderson (STScI) did this simulation.
That picture is 1 percent bad pixels, which is pretty good. For the roughly 4 megapixel NIRCam, you’d expect to get 40,000 bad pixels, before you add any cosmic rays. That means one in every hundred pixels is a bad one. It could be one in 50. And still, that’s pretty good.