Applications of Montage - Quality Assurance

Our customers have exploited the capabilities of Montage in generating scientific products, underpinning quality assurance of data products, deploying data access services, analyzing data, and in deriving educational and public outreach products.

Montage has been used by SWIRE and GLIMPSE to support quality assurance of that data. SWIRE has used Montage as a fast re-projection and co-addition engine to build sky simulations at a common spatial sampling that model the expected behavior of the sky, including galaxies, stars and cirrus. These simulations have been used to validate the processing pipeline and source extraction. Predictions of the expected source populations and appearance of the sky have been used to plan the observing strategy (Lonsdale et al. 2003).

As part of their quality assurance program, GLIMPSE has used Montage deliver mosaics of their entire survey region at 2MASS J (1.25 µm), H (2.2 µm), and K (2.2 µm ) and MSX 8 µm. These mosaics provide quicklook comparisons for quality assurance of the IRAC mosaics.

2MASS 3-color composite image created to provide quicklook comparisons for quality assurance of GLIMPSE data: a 0.5 x 0.5 degree field centered at l=284.3 and b=-0.32. Credit: NASA/JPL-Caltech/E.Churchwell (Univ. of Wisconsin)

The Cosmic Evolution Survey (COSMOS) used Montage to validate the scientific content of the image mosaics of the 2 square degree survey area measured with the Advanced Camera for Surveys (ACS) on board the Hubble Space Telescope. The mosaics were created with the Image Reduction and Analysis Facility (IRAF) at STScI. Montage offers flexibility in rectifying the background emission - it can compute a background model by minimizing image overlap differences (mBgModel), or simply "force" a flat background onto the mosaic (mFlattenExec). The flexibility proved in important in understanding the character and origin of background emission. In addition, mFixNaN identified pixel values set to not-a-number (NaN) and correct them.

IRSA routinely uses mImgtbl in its archive ingestion process to verify that the FITS headers of images delivered to the archive are complete, and that the images contain a complete specification of image footprints on the sky; that is, the full WCS specification. Used in tandem with the open-source fverify syntax checker, part of the FTOOLS FITS analysis distribution, mImgtbl is a powerful tool for validating the structure and content of FITS files. IRSA also uses mJPEG and mSubset to verify that images at different wavelengths measured with a common instrument are co-registered.