G Release Notes—V4.1

The main changes are improvements to polarimetry, aperture photometry, and Fabry-Perot reductions; several new recipes; and support for Magellan Classic Cam, VLT NACO, and Gemini NIRI instruments.

G.1 New recipes

BRIGHT_POINT_SOURCE_NCOLOUR

Reduces a multi-colour bright-point-source photometry observation.

BRIGHT_POINT_SOURCE_NCOLOUR_APHOT

Reduces a multi-colour bright-point-source photometry observation and performs aperture photometry.

BRIGHT_POINT_SOURCE_CATALOGUE

Reduces a bright-point-source photometry observation, producing a catalogue of all sources in the field.

BRIGHT_POINT_SOURCE_TELE

Reduces a bright-point-source photometry observation, using telescope offsets for registration.

BRIGHT_POINT_SOURCE_TELE_APHOT

Reduces a bright-point-source photometry observation, using telescope offsets for registration, and performs aperture photometry.

DIFFERENCE_STATS

Calculates statistics for Michelle darks in a pairwise manner.

JITTER_SELF_FLAT_CATALOGUE

Reduces a “standard jitter” photometry observation using object masking, and produces a catalogue of all sources in the field.

JITTER_SELF_FLAT_NCOLOUR_APHOT

Reduces a multi-colour “standard jitter” photometry observation using object masking, and performs aperture photometry.

LAMP_FLAT

Creates and files imaging flat fields derived from a calibration lamp for ISAAC and NACO.

POL_QU_FIRST_NOD_CHOP

Reduces a Michelle chopped and nodded polarimetry observation, where waveplate angle iterates in pairs at each jitter position. Its purpose is to form the $Q$,$U$ Stokes parameters as quickly as possible, hence offer more-accurate polarimetry than integrating at four waveplate angles before nodding.

G.2 Modified recipes

• The UIST ARRAY_TESTS calculates the dark current and readnoise in four regions equally divided along the $X$-axis. The recipe reports the quality of each statistic compared with normal operating parameters.
• FP, FP_JITTER, and FP_JITTER_NO_SKY   May allow scaling of the various components in the formula to create the reduced data, if other external calibrations are available, defaulting to the previous behaviour.
• MAKE_BPM   No longer applies an existing bad pixel mask and creates unwanrted variance.
• REDUCE_DARK   Permits averaging of darks of the same exposure time. The dark frame name now includes the exposure time. This does not apply to instruments whose darks only have a group identifier of 0, namely IRCAM, UFTI, and UIST.
• SKY_FLAT and SKY_FLAT_MASKED   These can now process multi-coloured observations.
• SKY_FLAT_FP   Applies a mask beyond the etalon’s transmitted circular region on the detector. The circle’s centre is either determined through the new fpcentre calibration, or it is determined using profiles of the surrounding ring.

G.3 Global changes

The main changes from a user perspective were as follows.

• Updated and expanded documentation, featuring the new recipes and instrument-data supported, more on the “Features of the Primitives”, and a new appendix listing the file prefixes.
• Added support for Magellan Classic Cam imager, and the ESO NACO instrument in imaging mode. These have only processed a few nights data exercising a few recipes. The NACO pipeline would certainly benefit from more data.
• Upgraded support for the Gemini NIRI instrument from pre-alpha to alpha, through more-thorough header translations, adjusting the nominal WCS to an actual one, setting the saturation levels, tested aperture photometry within a 3-arcsec aperture of thermal data. It’s still a work in progress, but it should be possible to process non-thermal data too given a sequence of frames matching a standard sequence.
• Incorporated eStar (intelligent-agent) calls in in five recipes, including the two new recipes which make an inventory of the sources such as BRIGHT_POINT_SOURCE_CATALOGUE.
• The IRIS2 ARRAY_TESTS has been improved. The mode, speed, and readnoise are written to the calibration log and reported.
• Several recipes in the BRIGHT_POINT_SOURCE JITTER_SELF_FLAT families and CHOP_SKY_JITTER have two additional steps: one to correct for residual bias variations along columns, and the other to correct for field distortion. For most instruments these are null, but not for ISAAC, where both are applied; and NACO, where the bias striping is removed.
• The ISAAC sky co-ordinate system is tied to the undistorted grid co-ordinates rather than than the distorted grid. This means that measured sky positions for sources will not be misplaced by the distortion. IRIS2 now corrects its world co-ordinate system for spatial distortion, but the pixel grid is not resampled.
• Improved central-source registration and corrected the world co-ordinate system associated with polarimetry products. The latter includes allowance for the bifurcation in the Wollaston prism, and the left-handed sky co-ordinates of UIST (by flipping the raw data and WCS headers). Enlarged the extracted target and sky regions for UIST.
• Combining sources in NOD_CHOP recipes revamped, using the chop and nod offsets to decide upon the visibility of an image. Thus it can now cope with just one positive-negative image pair.
• Centroid hunting allows for the source to be just outside the initial search box, and should lead to better registration of single sources and photometry, when the source is not placed at the nominal location (such as shifted instrument apertures at UKIRT).
• The option to clean small blemishes using a 15$\times$15 box filter during flat creation is now accessible from recipes, say when invoking _FLAT_FIELD_MASKED_GROUP_.
• Object masking reports the detection threshold read from the EXTRACTOR parameter file rather than a hardwired value.
• For ESO data CHOP_SKY_JITTER allows the last frame to be of the target. Fixed a bug where the normalised sky frames were flat-fielded prior to object masking instead of flattening the frames with masked deviant pixels.
• Fixed a bug in determining a consistent set of sky levels for CHOP_SKY_JITTER in multiple recipe iterations.
• Fixed a bug where exposure time was not integrated in the grand mosaic of EXTENDED recipes. The the start and end times and airmasses are also updated in the grand mosaic’s headers. The mosaic’s WCS is set to the SKY by default.
• Allow polarimetry recipes to work with angles of 0, 45, 90, and 135 degrees. This permits the circular polarisation to be determined from the Stokes images. Appropriately named flats for 90 and 135 degrees are created where necessary.
• There is a new polrefang calibration to correct the measured polarisation angles to position angle, allowing for instrumental alignment. The index file may be created manually to overide the default calibrations.
• The default near-infrared polarisation selection criteria have changed. The maximum polarisation threshold is increased from 50% to 75%. The standard deviation is relaxed to 10%. There is a new criterion where the minimum intensity must be at least three standard deviations above zero. The binning size is increased from 3 to 5 and its value is reported.
• The polarimetry-parameter images now have their world co-ordinates set to SKY, so plots will be annotated with equatorial co-ordinates.
• More intermediate frames are tidied at the end of recipes, notably in CHOP_SKY_JITTER.
• Improved header translations for ISAAC, such as offering fallback translations if the primary keyword is absent, setting cumulative offsets to zero for the first jitter position, recognising different observation-type values, and improved the test for the source to be a standard for ESO data. More headers are tested for a waveplate angle leading to greater robustness when the polarimetry recipes are released. These improvements were based upon experience of more data from a longer range of epochs.
• ORACUT now set for selection of calibrations of INGRID and ESO data. Michelle’s ORACTIME is now in decimal UT days.
• The changed Michelle headers are supported.
• Michelle reductions adapted to handle the nod iterator used in observation preparation.
• UIST uses separate flat calibrations for imaging and spectroscopy.
• The KAPVIEW display recognises a boolean key keyword. If set to true (1), it places a key, such as the colour table, besides the graphic.

The main changes from a programmer perspective were as follows.

• Much of the ISAAC code applies generally to ESO instruments. There are new ESO/ directories for recipes and primitives. These directories are ahead of the instrument-specific directories in the search path for the recipe and primitive source code. ORAC::Frame::ESO and ORAC::Group::ESO modules from which instrument-specific frame and group methods are sub-classed.
• Sigma-clipping is allowed for certain combination methods during mosaic formation via a new SIGMA argument. There is also a new ZERO argument to permit optional zero-point shifts between contributing frames. While the default continues to apply intensity offsets, Fabry-Perot wavelength mosaics set ZERO to false.
• There is a new POLARIMETRY argument for some of the registration primitives.
• In aperture photometry primitives the centroid search boxsize is now decoupled from the aperture size via a BOXSIZE argument.
• LAMP is a new value for internal header ORAC_OBSERVATION_TYPE to support internal lamps used to make flats.
• The handling of the filters and standards’ catalogues has been redesigned in the photometry primitives to be be more transparent and to make it easier to use multiple catalogues of standards. A waveband is interchanged rather than a column index.
• _CALC_STOKES_ has a boolean DEBIAS argument to control the application of the statistical-bias correction.
• _CALC_STOKES_NOD_CHOP_ has a new boolean CENTROID argument, whose valued is passed to _COMBINE_CHOPPED_SOURCE_.