; Load the SDFITS.
filein,"data/TGBT22A_503_02.raw.vegas"
; Check what was observed.
summary
; The first two scans, 60 & 61, are part of an OnOff scan,
; the next two, 62 & 63, are part of a Nod scan, and the
; next one is a Track scan using frequency switching.
; The pattern repeats five times, for different sources.
; We'll treat them as one source in this example.
; Lets start with the frequency switched observations.
; By default, the central beam, beam 1, will track the 
; source.
getfs,64,fdnum=0
; There are hints of something, lets smooth a bit to bring 
; it out from the noise.
gsmooth,5,/decimate
; A beautiful detection of ammonia!
; Lets process all the frequency switched scans to increase
; the signal-to-noise ratio.
; We will process all Track scans and put them in the accumulator
; so we can average them latter.
; Freeze the plotter to speed things up.
freeze
for s=64,84,5 do begin & getfs,s,fdnum=0 & gsmooth,5,/decimate & accum & endfor
unfreeze
; Average the accumulated spectra.
ave
; Smooth a bit more.
gsmooth,5,/decimate
; That looks better, but there is a residual "baseline".
; Select a range around the line and use these channels to
; fit a polynomial and remove the baseline.
; First, lets find out which channels are free of line emission.
setxunit,"Channels"
chan
; Channels 300 to 750 and 870 to 1290 cover the line free channels
; around the line.
nregion,[300,750,870,1290]
; Before proceeding with the fit, copy the spectrum to a different
; data container (10) in case we need to go back.
copy,0,10
; Lets see how different order polynomials would do.
nfit,7
bshape
; Not too bad, but maybe it is overfitting (How would we know if 
; GBTIDL does not give us something like a Chi squared, or a 
; Bayesian Information Criterion ?).
nfit,5
bshape
; Maybe a bit better.
nfit,3
bshape
; Definitely not.
; Lets use the order 5 polynomial.
nfit,5
bshape
; Actually apply the baseline correction.
baseline
; Limit the x range so it looks better.
setx,300,1200
; This could go in your fridge door!
; Put it somewhere for latter use.
copy,0,10
; Same but now for the other polarization.
; Clear the accumulator.
sclear
freeze
for s=64,84,5 do begin & getfs,s,fdnum=0,plnum=1 & gsmooth,5,/decimate & accum & endfor
unfreeze
ave
gsmooth,5,/decimate
; Again, the baseline is not flat.
; We do not really need to re-issue all of these commands.
setxunit,"Channels"
chan
nregion,[300,750,870,1290]
nfit,5
baseline
setx,300,1200
copy,0,11
; Average the two polarizations.
copy,10,0
accum
copy,11,0
accum
ave
; Save this for later analysis.
; But use velocity instead of channel number.
velo
write_ascii,"outputs/W3_IF_0.ascii"
; Now, focus on the Nod scans.
; getnod seems to be broken for the KFPA ¯\_(ツ)_/¯
; We'll have to use getsigref instead.
; For the Nod scans, the nodding was between beams 3 and 7
; (this is defined during the observations, and I do not know
; if there is an easy way of knowing this by looking at the SDFITS.
; I had to look at the AstrID logs).
; Remember that beam 1 is fdnum=0, so beam 3 is fdnum=2.
sclear
for s=62,82,5 do begin & getsigref,s,s+1,fdnum=2 & gsmooth,5,/decimate & accum & endfor
ave
gsmooth,5,/decimate
; That looks way better than the frequency switched one!
; Save it, but to a SDFITS file, just for fun.
velo
fileout,"outputs/W3_IF_0_Nod.fits",/new
keep
; Since in each other Nod scan the source is in beam 7 we can increase the signal-to-noise
; by also adding this data. Notice we flip the scan order.
sclear
for s=62,82,5 do begin & getsigref,s+1,s,fdnum=6 & gsmooth,5,/decimate & accum & endfor
ave
gsmooth,5,/decimate
keep
; No idea how to close the file :)
fileout,"none.fits"
; Now lets look at them together.
filein,"outputs/W3_IF_0_Nod.fits"
gettp,62
freeze
gettp,63
oshow
; The continuum is different, but the line profiles look consistent.
; After you do the same for the rest of the spectral windows,
; you can use your favorite ammonia fitter to figure out the
; source properties.
; For the OnOff scans we can use getps.
getps,60,fdnum=0,plnum=0