HIRES Processing

HIRES • Software Tool • Past

HIRES employs the Maximum Correlation Method (MCM) (H.H. Aumann, J.W. Fowler and M. Melnyk, 1990,AJ, 99,1674) to construct (resolution-enhanced) coadded images. HIRES images may be requested from IPAC using the e-mail based data request system. 

There are some rules of thumb for choosing good HIRES targets. Often examination of the results of a HIRES request will suggest that the data would benefit from re-processing with slightly different processing options set. In this case, a new HIRES request for the revised processing can be submitted. Options which are not explicitly mentioned in the request form can be written in as "Special Instructions". 

 HIRES is a three-step process: 

A program called SNIPSCAN is used to retrieve the raw survey data. The IRAS raw scan data are known as CRDD (Calibrated, Reconstructed Detector Data) and the full set of survey CRDD is stored in a FITS table format merged with the pointing (boresight) information. The collection of the raw data in FITS table format is known as the Level 1 Archive. A program called AOCRDD is used in place of SNIPSCAN to retrieve raw AO (Additional Observation or pointed mode) data. AOs are described briefly under IRAS spacecraft and mission strategy. 

A program called LAUNDR is used to clean up the CRDD. 

A program called YORIC applies the MCM algorithm to the LAUNDR'd data. For HIRES, YORIC is iterated, progressively reconstructing a better model of the sky. In default processing YORIC is iterated 20 times. 

As of March 31, 1993, HIRES is AC calibrated. The IRAS detectors exhibited dwell-time dependent responsivity changes, especially at 12 µm. This is the IRAS data feature known as the "AC/DC effect". Previous IRAS image products have been calibrated on the DC scale, which is correct for structures on spatial scales greater than 30'. The AC scale gives flux densities commensurate with the Point Source Catalog (PSC2) for point sources.

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