VII. 3-Band Cryo Data Release

2. 3-Band Cryo Data Products

The WISE 3-Band Cryo Data Release products are comprised of data taken during the mission's 3-Band Cryo survey phase. This phase covers the time following the exhaustion of solid hydrogen in the WISE payload outer cryogen tank, while the detectors and telescope were still cooled by the inner cryogen tank. During this time, WISE's W1, W2 and W3 bands were operational and continued to acquire useful data, but the W4 detector was saturated by thermal emission from the warming telescope. The sensitivity achieved in the W1 and W2 bands was similar to that during the full cryogenic mission phase. The W3 measurement sensitivity was degraded and decreased steadily during the 3-Band Cryo phase because of the increasing telescope temperature and decreasing exposure times.

WISE scanned approximately 30% of the sky during the 3-Band 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 3-Band Cryo frameset contains three images, one for each of the W1, W2 and W3 bands, with all bands observing the same 47x47 arc-minute square patch of sky. Images within each frameset were rejected and not included in the higher level data products if they were streaky due to spacecraft acceleration or if scattered Moon light was too strong, a problem that was worse at long wavelengths.

The highest level data products are the:

1. co-added Image Atlas, which has been match filtered to maximize signal-to-noise, and
2. Source Working Database of over 261 million detections made on the Atlas Images with signal-to-noise ratio greater than approximately 3.5 in at least one WISE band.

The lower-level data products included in the release are the Single-exposure images (Level 1b) and a Database of all the object detections on the Single-exposure image. This database is very useful for variability studies. The Single-exposure images and object detection database include lower quality frames that were not used for making the higher level products.

• Range of Observation Dates Represented in the 3-Band Cryo Release:


• 2010 August 6 10:35:04 UTC to 2010 September 29 18:39:37 UTC


• Number of Scans and Single-Exposures Represented in the 3-Band Cryo Release:


• Scans:    1,643


• Single-Exposures:


• Total number acquired in all scans:    392,879


• Number of framesets used in Multiframe Processing after quality and dynamic filtering to construct the Image Atlas and Source Working Database (see VII.4):



W1	379,310
W2	377,845
W3	348,291




• Number of 1.564°x1.564° Atlas Tiles Included in the 3-Band Cryo Release:    5,649


• Area Covered by the 3-Band Cryo Release:
• Ecliptic longitude ranges covered by 3-Band Cryo scans:     42.2°<λ<98.0° and 228.5°<λ<281.7°
• Nominal area covered by the 3-Band Cryo Release Products :



Table 1

Product	W1 (deg2)	W2 (deg2)	W3 (deg2)
Image Atlas and Source Working Database	12,564	12,566	12,317
Single-Exposure Images and Source Database	12,776	12,776	12,776



• Effective area covered as a function of Single-exposure depth-of-coverage in each band (see VII.5.a):



Figure 1- W1	Figure 2- W2	Figure 3 - W3
Cumulative histograms showing the effective area of the 3-Band Cryo Release Atlas as a function of Single-exposure depth-of-coverage in each band.



• Sky Maps
  

  Figure 4 - Aitoff galactic projection showing a 3-color composite mosaic of the 5,649 3-Band Cryo Release Atlas Images. Galactic north is towards the top and galactic longitude increases to the left. Blue is W1, green is W2 and red is W3.

  Figure 5 - Hammer galactic projection showing a grey-scale source count map of unique 3-Band Cryo Release Source Working Database entries that are detected in W1 with signal-to-noise ratio >5, and that are not flagged as a spurious detection of artifacts, and that are not redundant detections in the Tile overlap regions. Counts are computed in 0.2°x0.2° spatial bins. The full range is 0 to 1075 bin-1 (0 to 26,875 deg-2). Galactic north is towards the top and galactic longitude increases to the left.

  
  
  

Last Updated: 2012 July 11