= Changes/atlod = ||atlod || || || || || ||Item || Complexity || Research || Milestone || Time || ||[wiki:Changes/atlod#SYSCALRecordChanges Sampler Statistics] || easy || none || 6 || 1d || ||[wiki:Changes/atlod#SYSCALRecordChanges Storage Of SYSCAL Data] || moderate || some || 6 || 2*5d|| ||ApplyingXYPhaseCorrections|| easy || little || 6 || 5d || ||[wiki:Changes/atlod#DataSizeLimits Data Size Limits] || easy || little || 6 || 2d || ||FlaggingWithinATLOD - basics|| easy || little || 6 || 5d || ||MoreSelectionOptions || easy || little || 6 || 5d || ||IdentifyParentWindow || moderate || some || 8 || 2*5d || ||[wiki:Changes/atlod#FlaggingWithinATLOD Flagging Within ATLOD] - autoflagging || moderate || some || 9 || 4*5d || == SYSCAL Record Changes == The SYSCAL records will change from their current form. SamplerStatistics:: Not present in CABB data; do not execute flagging or "samcorr" code. StorageOfSYSCALData:: AT correlator data format holds 24 scalar values of Tsys (6 antennae * 2 polarizations * 2 IFs) written into every integration, and 12 (6 ant. * 2 IFs) of XYPhase.[[BR]] [[BR]] In the new system there will likely be a spectrum of each, in the form of autocorrelations. Tsys is formed from the XX and YY polarisations of the autocorrelations, with the noise diode on and off; XYPhase from the XY (or its conjugate, YX) with the diode on and off.[[BR]] [[BR]] Deciding what to do here in terms of data representation requires discussions with WarwickWilson. Making changes here has flow on effects to other tasks that use Tsys or XYPhase. CABB data will include autocorrelation for both ON and OFF phases of the switched noise diode.[[BR]] ATLOD will calculate[[BR]] Tsys(f) = OFF(f) * Tcal(f) / ( ON(f) - OFF(f) )[[BR]] for each of the XX and YY polarization products. In the equation above 'f' is the frequency.[[BR]] Tcal(f) will be included in the RPFITS file once per scan.[[BR]] ATLOD will also calculate[[BR]] XYPhase(f) = arg( XYPhase_ON(f) - XYPhase_OFF(f) )[[BR]] ATLOD will record in the Miriad data TsysX(f), TsysY(f) and XYPhase(f). Input option 'noauto' will determine whether autocorrelation spectra are kepts. ApplyingXYPhaseCorrections:: At present atlod applies the XYPhase during filling. Nothing else (except maybe [http://www.atnf.csiro.au/computing/software/miriad/doc/atxy.html atxy]) uses them. So we can compute the corrections, apply them and drop the XYPhase information, during ATLOD? May need to order the RPFITS data stream so that autocorrelations come before cross-correlations (and after SYSCAL records), so that the corrections for the cross-correlation can be computed before reaching the cross-correlations. We will need to carry Tsys info along but may be able to do it more compactly than storing the autocorrelations themselves.[[BR]] [[BR]] Research needed: The phase values computed on a per channel basis will be noisy, and applying them will just introduce noise. We need to understand how much smoothing across frequency will be needed. Need to do some experiments to understand the sequence of events in reading in a file. == Data Size Limits == Research needed: check for size limits on the data dimensions - number of windows, channels, etc == Identify Parent Window == Each spectral window output by the correlator can have some [wiki:Glossary/ZoomBands ZoomBands] defined. We think that it will be necessary to keep track of each window's parent window. There should only be 0 or 1 parents. Research needed: Whether it is necessary to keep track of the children of a particular band is unclear. == Flagging Within ATLOD == [http://www.atnf.csiro.au/computing/software/miriad/doc/atlod.html atlod] does a qualitatively different type of flagging to other parts of Miriad; it drops data from the output instead of just marking it as bad. There are two possible types of flagging-related changes. * basic things like removal of [wiki:Glossary/Birdies birdies] - there are likely to be some new ones.[[BR]] Research needed: locations of birdies; will there be new types of flags on scans that indicate bad data? * Possibly using the [Glossary/AutoCorrelations autocorrelations] to flag data affected by interference. == More Selection Options == People will want to atlod just a subset of the data, not the whole thing. This requires more selection options than is available with 'ifsel'. Research needed: need to list out the types of datasets that are likely to be written and then decide what the "sub-selectable" elements are. [/trac/miriad4cabb Wiki Home]