The NEOWISE Post-Cryo Data Release products were generated using data taken during the mission's Post-Cryo survey phase. This phase covers the time following the exhaustion of solid hydrogen in the WISE payload inner cryogen tank, when the detectors and optics gradually warmed until they reached a stable equilibrium temperature near 73.5 K (VIII.1.a.i). During this time, WISE's W1 and W2 detectors continued to acquire high quality imaging data with sensitivities close to that during the mission's cryogenic survey phases. The W3 and W4 detectors were fully saturated by the thermal emission from the warming telescope.
WISE scanned approximately 70% of the sky during the Post-Cryo survey phase continuing with the same strategy that was used during the full cryogenic survey. WISE scanned along lines of constant ecliptic longitude from near one ecliptic pole to near the other pole with a scan rate close to the orbital rate of 3.8 arc-minutes/second in order to always point away from the Earth. Each semi-circular track from ecliptic pole to ecliptic pole is called a scan. During each scan WISE took a frameset every 11 seconds. Each Post-Cryo frameset contains two images, one for each of the W1 and W2 bands, both observing the same 47x47 arc-minute square patch of sky.
The Post-Cryo Releases include the Single-exposure images (Level 1b) and a Database of all source detections extracted on the Single-exposure images. This database is useful to recover the individual flux measurements and positions of solar system objects identified by the WISE Moving Object Pipeline System. It can also be used as a resource to learn more about inertial objects that are found in the WISE All-Sky Release Catalog, such as flux variability and/or proper motion. The Single-exposure images and source database include all of the Single-exposure image data, regardless of frame quality.
The 2013 Post-Cryo Release products are based on second-pass processing of the Post-Cryo image data that incorporated calibrations and algorithms that were optimized for the performance of the warm detectors and telescope. The 2013 Release products supersede those of the July 2012 Post-Cryo Preliminary Release that were based on very early first-pass processing that was largely still tuned for the cryogenic payload performance. Users should always defer to the 2013 Post-Cryo Release data products.
The Post-Cryo Data Releases do not include the coadded Atlas Images and deep source extractions that are part of the All-Sky and 3-Band Cryo Releases.
|Figure 1 - Galactic projection sky plot showing the average raw frameset depth-of-coverage in 14'x14' spatial bins during the WISE Post-Cryo survey phase. Colors encode the average depth-of-coverage indicated by the key on the left side of the diagram.|
Last Updated: 2013 May 20