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Data Reduction

Visitors coming for data reduction in Grenoble will find a number of hardware and software changes.

Concerning the hardware, 16 GBytes of disk space have been recently added to the workstation dedicated to Plateau de Bure data reduction. A second, more powerful, HP-J280 workstation with 24 GBytes of storage will be added soon. Real-time archiving is now done on CD-ROMs rather than DATs, significantly reducing the time required to load the original data set.

To fully benefit from the CD-ROM archiving, the CLIC program has been modified to handle the data and the calibration parameters in two separate files. The data file is never modified, and can reside in a read-only file system like a CD-ROM. Operation is transparent for the user. The original DAT archive is progressively converted to CD-ROMs.

A new calibration procedure has been written. The new procedure utilizes the SIC Window interface, and greatly simplifies and speeds up data reduction. ``Automatic'' calibration is even possible on good quality data. The procedure handles dual-frequency projects by phase-referencing the 1.3 mm data to the 3 mm ones.

Based on this procedure, and capitalizing on the experience gained with the interferometer, we are studying a method to pre-calibrate the data at the Plateau de Bure.

The ``Calibration CookBook'' is under revision to include a more comprehensive description of the new calibration facilities.