IRIS2 Data Reduction - Filename meanings

A full description of the various suffices attached to processed versions of the data is available from the ORAC-DR home page (link is external) for imaging (link is external) and spectroscopic (link is external) data. For imaging reduction, you will probably be most interested in the mosaicing output, which have filenames of the form


where yyyymmdd is the UT date of the file, n is the first frame number of the group of images which go into making up the mosaic pattern, and a is the sub-mosaic number. Thus, for a 9 point jitter on 28 July 2002 UT beginning with frame 21, a reduced sub-mosaic will be created after frame 29 has been obtained, and will be called gi20020728_21_mos_0.sdf, as well as a "grand mosaic" gi20020728_21_mos.sdf. If the 9 point jitter pattern is then repeated immediately (i.e. the value of npatt in the Observing Sequence is >1), then a new sub-mosaic gi20020728_21_mos_1.sdf will be created after frame 38, and then added to the existing grand mosaic gi20020728_21_mos.sdf. Note that the effective exposure time of any sub-mosaic is the same as each of the component frames, i.e., if each frame consists of 10 coadds of 5 seconds each, then the counts in each sub-mosaic are normalised to 5 seconds. However, the grand mosaic formed from adding 3 sub-mosaics will be normalised to the equivalent of 15 seconds exposure time.

For spectroscopy reduction, the raw images (_mraw) have their known bad pixels masked (_bp), then their variance array is updated for read-noise and gain (_rnv, _pov). Spectra taken with the Sapphire_240 grism are flipped laterally (_reo), so that wavelength increases with pixel number. They are then flatfielded (_ff) if requested, and an approximate wavelength scale applied (_wce). (Object  - Sky) pairs are co-added to make the group giyyyymmdd_nn.sdf files. A cross-cut in the spatial (y) axis is produced (_ypr), and an optimal extraction (_oes) is performed about the strongest positive and negative peaks found there. The negative beam is inverted, cross-correlated with the positive beam, then shifted before co-adding (_sp). The co-added beams are then normalised to a 1 second integration time (_nsp), before division by the rectified standard star spectrum (_dbs). Lastly, the spectrum is flux-calibrated based on the known magnitude and spectral type of the standard (_fc), then lightly smoothed and negative pixels clipped (_fcs) to assist with autoscaling of the display.