Day 1, continued:
Last time I talked about my initial processing. Part of this was the ‘bpd’ process in which I was bandpass corrected. I have a few pictures that I thought I would share.
The first picture is from before I was bandpass corrected. You can see that the response (vertical axis, measured in temperature) varies with frequency (the channel number). Ideally, I should have the same response everywhere so that it’s easy to tell how strong a signal is, no matter what channel it falls in. You can see that the bandpass edges are particularly bad and my response falls off quickly. In order to have the best data quality possible, the bandpass response needs to be divided out; areas of high response are weighted down and areas of low response are weighted up. Now, I don’t want to lose any of my information which means we have to be a little careful. That strong response you see in the middle is real – it’s hydrogen in our own Galaxy! I don’t want to lose that, so we interpolate around the Galactic hydrogen, fitting a smooth function over the extent of the signal.
This is a picture of me after I’ve been bpd-ed. You can see that my response is now flat across all channels and that the Galactic hydrogen is still visible. This means I’m all ready to go for the next step.