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Subsections

• U,V-data display
• Flagging Requirements

Data Display and Editing

The order of calibration, data display and editing is not fixed in VLBI. In many cases flagging is done within the self-cal and mapping cycle, after a first fringe fit, but applying a-priori flags is often the first thing done after data loading.

In the area of continuum data inspection a good model for functionality is provided by the DIFMAP package. We hope that AIPS++ can come up with a similarly quick and intuitive way of inspecting and editing data.

U,V-data display

In general VLBI has a strong demand for powerful tools to display the data. Because of the large number of visibilities, each composed of many IF bands and spectral channels, a lot of the time can be involved in checking the data. A list of functionality that is expected in this area is given below.

• display of data aggregated in various ways (e.g. averaged over a number of spectral channels).
• displaying amplitudes and phases baseline by baseline

• displaying estimates of amplitude bias in amplitude plots

• displaying both closure quantities: closure amplitude and phase
• taking arbitrary cuts (e.g. circular, radial or a user-defined locus) through the u,v-plane interactively

• setting windows in space andor time interactively
• expanding aggregates (e.g. clicking on an averaged multi-channel visibility to show the component spectrum).

• plotting of spectra and correlation functions (for different phase centers)

• display of fringe rate spectra (AIPS equiv: FRPLT)
• display of model data against observed data, for diagnostic purposes it should be possible to treat simulated data in a similar way

Flagging Requirements

Flagging will start with incorporating telescope based information that is based on the log information. It is often augmented with a-priori flags provided manually by the astronomer. In the calibration and imaging cycle, further flagging is performed.

• flagging should be reversible, with the ability to store flagging information and apply this on the fly
• multiple level flagging to cater for different levels of severity of problems or different source of information
• flagging on the basis of monitorobserving log data and tape motion
• flagging from ``consistency check'' information, in particular redundancy, where possible, or crossing-points in the u,v-plane

• flagging based on autocorrelation spectra
• ``intelligent'' automated flagging for large datasets (e.g. based on amplitude excursions, polarization)

• baseline by baseline display and editing (including multiple, simultaneous baselines)

• antenna based display and flagging (by interactively selecting baselines that involve a suspect antenna)

• display of T_sys, rate and delay data together with visibility data per interferometer
• allow the display of flagged u,v data in a different color along with the data and model