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Next: Development plan Up: The Generic Instrument: IV Specifications and Development Plan Previous: Imaging and Image Processing

Subsections

Priorities for development

While the previous sections reflect the specifications for AIPS++ functionality in the area of synthesis processing, the priorities for development are not given. In this section, I discuss these priorities.

Completion of MEGI design

Cornwell and Wieringa (1996) describe the design of the MEGI. The following have yet to be completed:

1.: Scalar version for e.g. RR alone or RR and LL only.
2.: Full persistence of objects
3.: Optimization for speed, including gridding and Fourier transformation
4.: Cross-calibration

NFRA

NFRA wants to use AIPS++ for data analysis for the new WSRT on-line system TMS. TMS is expected to debut in August 1996. NFRA needs a commitment from AIPS++ to support such use of AIPS++. As outlined by Jan Noordam, the priorities are:

1.: AIPS++ port to HP/UX
2.: Fill to AIPS++ Synthesis MeasurementSet from WSRT data format
3.: Simple calibration, editing and imaging of WSRT data, controllable from TMS
4.: Polarized sky models including XX,YY,XY and YX as well as the standard I,Q,U,V
5.: Parametrized source components. Initially only for existing calibrator models.
6.: Subtraction of known sources from coherences
7.: Simple data statistics: averages, rms, etc.
8.: Visualization of coherence data

ATCA

Mark Wieringa outlined priorities for ATCA calibration :

1.: A Solver for bandpass and gain using the parallel hand correlations.
2.: A Solver for polarization leakage, gain and optionally source polarization using all four correlations.
3.: Selfcal Solvers using either single Stokes (I) correlation data or multiple correlations.
4.: A Corrector for each of bandpass, leakage and antenna/i.f.-gain and a versioning scheme for either the Correctors or their underlying tables.

There is no specific ``drop-dead'' date attached to these priorities since Miriad currently can be used.

BIMA

Peter Teuben (1996) has outlined the special needs of BIMA.

1.: Support for time-sliced fashion polarization measurements, measuring circular polarization (LR and RL) with a quarter-wave plate. See also Wright (1995a) for a discussion on some of the possibilities.
2.: Deconvolution of mosaiced fields, including pointing corrections. Also adding single dish data to interferometry data.
3.: VLBI: BIMA regularly participates in mm VLBI experiments. The phased array data are currently processed offline using standard VLBI techniques (Mark-xxx, ref. xxx), and whenever AIPS++ will provide VLBI data processing, BIMA should be able to use them without any major problems.
4.: Heterogenous array elements.
5.: Unusual correllator modes: The correlator can be configured in many modes, and produces DSB data with a small (< 8) number of windows with different settings of the IF. An interesting method to calibrate DSB data is to use the generally much slower varying gain ratio (phase difference and amplitude ratio).
6.: Offline phase corrections, using total power measurements (see Wright 1995b), examplify one of the many ways in which calibration needs to be flexible.

MIRIAD employs a very general visibility file format, where correlations (both cross- and auto) are tagged with a rich set of (name based) variables. Variables can be multi-dimensional of any of the basic types (variables can change dimension in a dataset, in principle even type). Obviously, like in the FITS community, these variables need to be registered and their meaning clarified. Currently MIRIAD knows about 95 variables. Although it would be ideal that the telescope data be directly written in native AIPS++ format, for the foreseeable future, a conversion program will be used.

VLA

A mail message from Michael Rupen dated Sept 19, 1995, gives the following priorities for VLA software development.

1.: Interpolating bandpass solutions.
2.: Ionospheric corrections from GPS.
3.: D-term self-calibration (with and without time-variability).
4.: Mosaicing.
5.: High dynamic range imaging (Briggs' NNLS algorithm)
6.: Automated flagging.

In general, NRAO will use whatever system is appropriate to acheive a given functionality. In some cases, AIPS is still the chosen route, whereas in others AIPS++ is preferred. The first and second items are being addressed within AIPS.

VLBI

Tony Beasley has summarized the special requirements for VLBI:

1.: High precision quantities
2.: Version typing to allow tracking of e.g. interferometer models used
3.: Multi-file datasets (greater than 2 Gbyte and perhaps spread over many disks)
4.: Variable and possibly unequal integration times
5.: Provision for tied arrays
6.: Diversity of antenna mounts
7.: ``In the beam'' phase referencing

In addition, tasks for the following will be needed:

1.: Data readers for various formats
2.: Sophisticated model for correlator effects e.g. decorrelation, state-count corrections.
3.: Absolute amplitude calibration is more important than in connected element interferometry. There are various approachs, all of which must be supported.
4.: Fringe fitting, both antenna and baseline-based.
5.: External data calibration
6.: Phase-cal information
7.: Polarization calibration, including all known calibration algorithms
8.: Velocity correction for fringe-rotation
9.: Pulsar binning and gating
10.: Source fitting

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