Changes to dimmconfig files

The $STARLINK_DIR/share/smurf directory contains a set of dimmconfig...lis files that define "pre-canned" sets of configuration parameters for use with MAKEMAP. Some changes have been made to these files recently, partly to tidy them up and make them more user-friendly, but also to incorporate some new parameter values that have been found to give better results in the majority of cases.

The most important changes that you need to be aware of are:

1. The dimmconfig.lis file now uses MAPTOL to specify the convergence criterion rather than CHITOL. 
2. The value of 850.FLT.FILT_EDGE_LARGESCALE provided by dimmconfig_bright_extended.lis has changed from 300 to 600 arc-seconds. The 450 value remains unchanged at 600 arc-seconds.
3. The dimmconfig_bright_extended.lis file now inherits values from  dimmconfig.lis instead of dimmconfig_bright.lis. This means that the modified values previously provided by dimmconfig_bright.lis for COM.CORR_TOL, COM.GAIN_ABSTOL, COM.GAIN_TOL, DCTHRESH and NOISECLIPHIGH are no longer inherited by dimmconfig_bright_extended.lis. Consequently the new dimmconfig_bright_extended.lis will perform more aggressive rejection of bad values than the old version.

Other less important changes are:

1. The descriptions of individual parameters that previously were in dimmconfig.lis have been moved into $SMURF_DIR/smurf_makemap.def. This is the file that defines the complete list of all legal parameters for makemap and their default values. These description are also included in an appendix in SUN/258.
2. Parameters that are mainly intended for experimental use by makemap developers have been removed entirely from dimmconfig.lis but are still defined in the smurf_makemap.def file.
3. The prologues of the main dimmconfig files have been standardised.
4. Experimental dimmconfig files have been moved into a subdirectory called "experimental" within $STARLINK_DIR/share/smurf.

Multiple masks revisited

I have today made another change to the way that multiple masks are handled, and I have modified the previous post "Using Multiple Masks" to reflect it.

Previously, multiple masks were always combined by taking the union of the source regions. Now, the intersection of the source regions may instead be used by setting the xxx.ZERO_UNION parameter to zero (i.e. false), where "xxx" is AST, FLT or COM. Note, the default is still to use to use the union.

This can be useful, for instance, if a basic SNR mask allows bright structures to develop near the edges - intersecting the SNR mask with a ZERO_LOWHITS mask will reduce the SNR mask to exclude the edge regions.

Automated removal of bad-baseline spectra from ACSIS/HARP time series

I presented the following poster at November's ADASS Conference, describing the methods I added to the ORAC-DR REDUCE_SCIENCE_NARROWLINE and REDUCE_SCIENCE_GRADIENT recipes to detect and remove `wobbly' and noisy spectra. It shows some examples of the then identified forms of interference and example results.  Since then an additional form---ringing---came to light from looking at more data, and is shown in the latest JCMT Newsletter 34. I'll discuss that in a further blog.

Go here for the full-sized PDF.

SCUBA-2 papers on arxiv

Three papers describing the performance of SCUBA-2 have been accepted for publication. They can be found on arxiv at the following links:

SCUBA-2: The 10000 pixel bolometer camera on the James Clerk Maxwell Telescope
Holland et al. 2013 MNRAS
http://arxiv.org/abs/1301.3650

SCUBA-2: iterative map-making with the Sub-Millimetre User Reduction Facility
Chapin et al 2013 MNRAS
http://arxiv.org/abs/1301.3652

SCUBA-2: on-sky calibration using submillimetre standard sources
Dempsey et al 2013 MNRAS
http://arxiv.org/abs/1301.3773

MAKEMAP default method

When running MAKEMAP, you indicate the method it is to use by setting the METHOD parameter on the command line. In the past, if you failed to do this you would be prompted for a value for METHOD, with the suggested default of "REBIN". I've changed this so that METHOD will now default to "ITERATE" and you will no longer be prompted if it is not specified on the command line.

So note, if for any reason you want to use the "REBIN" method, you will now need to indicate this by adding "METHOD=REBIN" to the command line.

A significant bug using multi-chunked data

Today I have found and fixed a bug that could seriously upset the MAKEMAP "maptol" convergence test when used with data that has been split into more than one chunk. Basically, the map at the end of the first iteration on each new chunk was compared with the final map from the previous chunk, rather than with a blank map full of zeros. The effect of this could be to produce spurious values for the "normalized map change" reported at the end of each iteration, and thus cause the iterative loop to be left prematurely. 

Change to way config files work

With today's cutting-edge starlink, configuration parameters work slightly differently in cases where a value is assigned to a parameter twice. For instance, if you config file holds

450.flt.filt_edge_largescale=600
flt.filt_edge_largescale=500

then previously the value 600 would have been adopted when processing 450 um data. With the new changes, the value 500 will be adopted instead. That is, unqualified values now take priority over qualified values.

This will be most relevant if your config file inherits from another config file (which almost all do), in which parameters are specified with qualifiers. Previously, in order to override such a value in your own config, you needed to include the wavelength. But now, you no longer need to include the wavelength.

These changes have been installed at Hilo. To use them at your locally, you will need to rsync from Hilo.