;+ ; NAME: ; GET_TIMING ; PURPOSE: ; Determine time offsets [msec] from center of each observing cycle, for ; each sample and channel within the sample. ; CATEGORY: ; OVRO APC TIME ; CALLING SEQUENCE: ; msoff = get_timing(pol,header,cfg,obseq) ; INPUTS: ; pol A byte array giving the polarization state ; for each channel and each observing sequence entry. ; The polarization is coded as 0 = RCP, 1 = LCP, 3 = LIN ; header The HEADER structure corresponding to the data. ; cfg The CONFIG structure corresponding to the data. ; obseq The OBSEQ structure corresponding to the data. ; OPTIONAL (KEYWORD) INPUT PARAMETERS: ; ROUTINES CALLED: ; OUTPUTS: ; msoff A long array of size [NCHAN,NFRQ,NPOL] giving the time offsets ; [msec] for each sample and each channel within the sample, ; relative to the center of a cycle. ; COMMENTS: ; Timing is complicated for OVSA data, since we have only three correlators ; and do time-multiplexing of baselines, frequencies and poln. Thus, each datum ; is obtained at slightly different times within a cycle. To keep careful ; track of timing, it is necessary to have the information provided by this ; routine. Note that if a particular frequency/baseline/poln combination is ; measured twice in a cycle (the usual case) then the time indicated in MSOFF ; is the center time between the two measurements. ; SIDE EFFECTS: ; RESTRICTIONS: ; MODIFICATION HISTORY: ; Written 03-Apr-2001 by Dale Gary ; 14-Dec-2001 DG ; Changed to reflect new 2 and 4 polarization flags, used for ; 2m TP channels to indicate that data should be saved in RCP and ; LCP channels as well. ;- function get_timing,pol,header,cfg,obseq nant = header.nant ; Number of antennas nchan = nant^2 ; Number of data channels nbl = (nchan-nant)/2 ; Number of baselines nndw = 1 + header.ndbw + header.nfgw ; Number of non-data words in sample if (keyword_set(ndon)) then offidx = where(*obseq.pnd eq 1) $ else offidx = where(*obseq.pnd eq 2) hp = (*obseq.pharm)(offidx) hpx = hp(sort(hp)) ; Intermediate step--sort the harmonics hlist = hpx(uniq(hpx)) ; Form a list of uniq harmonics hlist = hlist(sort(hlist)) ; Sort in ascending order nfrq = n_elements(hlist) nfp = n_elements(offidx) ; fp = hp*0.2 poln = pol(nndw:*,offidx) nsamp = obseq.nx ; Number of samples in one cycle data = fltarr(nchan,nfp) smldata = fltarr(nchan,nfrq,3) ; Get index of active antennas IANTS (e.g. [1,2] => [0,1], [4,5,6] => [2,3,4] antlist = [1,2,4,5,6,7,8] ; Translation from antenna number to index aa = header.aatab(where(header.aatab ne 255)) iants = intarr(nant) for i = 0, nant-1 do begin iants[i] = where(antlist eq aa[i]) endfor ; Nant x nant matrix of time offsets for each channel, in msec, ; and corresponding channel offsets. Also FG pointer array. msoff = (choff = intarr(nant,nant)) for i = 0, nant-1 do begin for j = 0, nant-1 do begin msoff[i,j] = cfg.msoff(iants[i],iants[j]) choff[i,j] = header.lchoff(iants[i],iants[j]) endfor endfor ; Due to a bug in FASAR (CPC program) the channels for baseline 46 and 56 ; were swapped. This was fixed on day 303 of 1999, but prior data must ; have their channels swapped before analysis. NB: All data before this ; date were taken in 5-element mode, so it is okay to give explicit indexes. if (header.tls.yrday lt 1999.303) then begin choff(4,2) = 28 choff(4,3) = 26 choff(2,4) = 28 choff(3,4) = 26 endif ; Form array representing the indexes of upper part of matrix upper = intarr(nbl) k = 0 for i = 0, nant-2 do begin for j = i+1, nant-1 do begin upper[k] = i*nant+j k = k + 1 endfor endfor choff(upper) = choff(upper)+1 ; Trick to put cos channel numbers into choff cycledur = nsamp*cfg.sampintms ; Duration of a cycle, in msec tsample = indgen(nsamp)*cfg.sampintms ; Time offsets [msec] corresponding ; to each sample in one cycle ; Shift by 1/2 cycle so that TSAMPLE is relative to middle of the cycle tsample = tsample-cycledur/2 tsample = tsample(offidx) ; Reduce to only "good" samples ; Create a parallel flag array with zeroes smlflag = byte(data)*0 ; Start with all zeroes ; More complicated POLN flags now--0 => RCP, 1=> LCP, >1=>LIN, but ; for small dishes, as a way to keep full time resolution of data, ; use 2=> put LIN also into RCP, 4=> put LIN also into LCP rcpflag = (lcpflag = (linflag = smlflag + 1)) ; Parallel arrays for each poln, all set to 1 notr = where(poln ne 0 and poln ne 2) if (notr(0) ne -1) then rcpflag(notr) = 0 ; Set non-RCP to 0 notl = where(poln ne 1 and poln ne 4) if (notl(0) ne -1) then lcpflag(notl) = 0 ; Set non-LCP to 0 noti = where(poln le 1) ; Small dish total power are flagged with -3 for I, so use abs(poln) if (noti(0) ne -1) then linflag(noti) = 0 ; Set non-LIN to 0 ; Create a flag array parallel to smldata (reuse SMLFLAG variable) smlflag = bytarr(nchan,nfrq,3) ; Create a time array parallel to smldata smltime = lonarr(nchan,nfrq,3) toff = msoff(sort(choff)) ; Loop over each "good" sample, doing the 25 channels all at once ; for each sample for i = 0, nfp-1 do begin ; Index into smldata for frequency fidx = where(hlist eq (*obseq.pharm)(offidx(i))) ; Accumulate sums into appropriate columns of smldata array smlflag(*,fidx,0) = smlflag(*,fidx,0) + rcpflag(*,i) smlflag(*,fidx,1) = smlflag(*,fidx,1) + lcpflag(*,i) smlflag(*,fidx,2) = smlflag(*,fidx,2) + linflag(*,i) ; Determine time offsets corresponding to each sample/channel smltime(*,fidx,0) = smltime(*,fidx,0) + (tsample(i)+toff)*rcpflag(*,i) smltime(*,fidx,1) = smltime(*,fidx,1) + (tsample(i)+toff)*lcpflag(*,i) smltime(*,fidx,2) = smltime(*,fidx,2) + (tsample(i)+toff)*linflag(*,i) endfor ; Do average of smldata, according to how many good values were ; summed in each array location smltime = smltime/(smlflag>1) ; Contains average time for each element of SMLDATA return,smltime end