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Survey and Observing Strategy

  WIRE mission planning includes a three-part survey strategy:

Part 1: The moderate-depth survey.
The goal of this survey is to maximize the number of high-redshift systems detected by WIRE. About 60% of the survey time will be spent on this survey. Cumulative exposure times on each field will range from 15 to 75 minutes, set by the exposure time for which the background noise is about 3 times the confusion noise.

Part II: The deep, confusion-limited survey.
The goal of this survey is to obtain a large (> 2000 galaxies) sample with the largest lookback time at a given luminosity. About 30% of the survey time will be spent on the deep survey. The cumulative exposure times will be several hours, with the background noise roughly equal to the confusion noise.

Part II: The ultra-deep, confusion-distribution measurement.
The first goal of this survey is to measure the level of number counts ten times fainter than WIRE can detect discrete sources. A second goal is to constrain the infrared background. About ten percent of the primary observing time will be spent on a few ultra-deep fields, with cumulative exposure times per field of 24 hours or more.

Observing Strategy

The first step in the observing strategy is to select about 50 survey "areas", each about 1.5x1.5 sq degrees (3x3 WIRE fields). Then, each field will be observed during a single orbit segment of about ten minutes in duration, while the target is close to the zenith. During each segment, about eight 56 second WIRE exposures will be taken, with a small slew or "dither" of about 1 arcminute in between. This stare-and-dither technique will allow accurate estimation of instrumental offsets and diffuse foreground emission so they can be subtracted from the data. The final step will be to return to each WIRE field at least once to accumulate sufficient exposure time and to detect moving or variable sources.



Last Updated: 9/3/97