Last night I was observed as data for the ALFALFA survey. The observer wrote all about it here. This morning, before I even had a chance to get used to being data, I started being transferred from Arecibo (warm and sunny) to Cornell University (not so warm and sunny). It takes a while for me to arrive fully – during the night I grew by about 1 Gb per hour, so there is a lot of me to travel along the internet trunks from Puerto Rico to Ithaca.
Finally, there’s a whole copy of me in Ithaca. I find out that I’m considered Level 0 data right now. The first thing that is going to happen to me is that I’ll be processed to become Level 1 data. This process actually takes a while, but the first part will happen today.
The first thing that happens is I’m calibrated. This is where I go from being in units measured by the telescope (a ‘temperature’) to units used by astronomers (the Janksy). Since a calibrator of known signal was fired every ten minutes last night during the observing, the records of the calibrator can be used to convert from telescope units to the flux units of interest.
After I’m calibrated, it’s time for ‘bpd’. This step is a bandpass correction. The filter on the telescope that allows the frequencies of interest through isn’t exactly flat. During this step, any frequency-dependent response I may have is removed. My fluxes are scaled so that the same signal strength on the sky corresponds to the same flux in the data file.
Now I’ll wait for the next step, flagging, after which I’ll be Level 1 data.