The correlator operator sits in front of this bank of computer screens at the correlator console. With these computers the operator can start and stop the tapes and watch the screens as well as the drives as the data is being correlated. The data on the monitors concerns time synchronization, power levels, and correlator output. At times there may be problems with tapes that were not recorded correctly, or hardware or software concerns that will show up on the computer screens as well. The whiteboard behind the console is used for keeping track of problems with the 24 drives.

The astronomical data gathered during an observation are digitized, recorded on magnetic tape, and sent to the Array Operations Center to be correlated. The reels in this photograph are glass, 14 inches in diameter, and hold 18,000 feet of tape that is only 16 microns thick. One inch of the tape can hold as much data as is normally saved on a 3.5 inch floppy disk. There are 24 of these tape drives (located along the left wall in the panoramic view). All of the tapes for a single experiment are put on the drives, synchronized, and played in unison. The correlator (below), using a complex mathematical computation called fast Fourier Transform, combines all of the data from all of the antennas, simulating a single telescope 5,000 miles wide.

All of the information from the large tapes is compiled and put on a "DAT"(Digital Audio Tape) which is then sent to the primary investigator in the observation. That scientist will then analyze (or "reduce") the data to produce a map or an image similar to the ones featured in our Image Gallery.

< Back

To the Array side >

Copyright © 2009 Associated Universities, Inc.
The National Radio Astronomy Observatory is a facility of the National Science Foundation operated under cooperative agreement by Associated Universities, Inc.