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The Wide-field Infrared Survey Explorer at IPAC |
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3-Band Cryo Data Release June 29, 2012 |
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The Wide-field Infrared Survey Explorer (WISE; Wright et al. 2010) 3-Band Cryo Data Release contains 3.4, 4.6 and 12 μm (W1, W2 and W3) image and extracted source data that were acquired following the exhaustion of solid hydrogen in the satellite's payload outer cryogen tank. WISE surveyed 30% of the sky between 6 August and 29 September 2010 UTC while the detectors continued to be cooled by the hydrogen ice in the inner cryogen tank. The telescope warmed from the 12 K maintained during the main mission to 45 K. During the 3-Band Cryo survey phase, the 3.4 and 4.6 μm detectors operated with nearly the same sensitivity as during the full cryogenic survey. Higher operating temperatures and elevated thermal emission from the warming telescope reduced the sensitivity of the 12 μm measurements and fully saturated the 22 μm detector.
The WISE 3-Band Cryo Data Release products include an Atlas of 5,649 match-filtered, calibrated and coadded image sets and a Source Working Database containing positions and 3-band photometry for over 261 million sources detected on the Atlas Images. A guide to the format, content, characteristics and cautionary notes for the 3-Band Cryo Release products is provided in section VII of the WISE All-Sky Release Explanatory Supplement.
The WISE All-Sky Data Release that includes data taken during the mission's full cryogenic phase remains the best compendium of sources of mid-infrared emission over the entire sky. Because the 3-Band Cryo observations were an independent, second-epoch measurements of 30% of the sky, the 3-Band Cryo Release Atlas and Source Database are best used as resources with which to learn more about objects found in the All-Sky Release Atlas and Catalog, such as proper motion, flux variability over six month timescales, and confirmation of faint, marginally detected sources. In addition, the 3-Band Cryo observations fill in some of the low coverage gaps in the All-Sky Release products.
Please include this acknowledgment in any published material that makes use of WISE data products.
Research using WISE Release data is eligible for proposals to the NASA ROSES Astrophysics Data Analysis Program.
WISE imaged approximately 30% of the sky in the W1, W2 and W3 bands
simultaneously with multiple, independent exposures during its 3-Band Cryo
survey phase. The Release area covers two large regions
bounded approximately by the ecliptic longitude ranges:
Exposure times were 7.7 sec in W1 and W2. The W3 exposure time
was 8.8 sec at the beginning of the 3-Band Cryo phase and was
then reduced to 4.4 sec, 2.2 sec, and finally 1.1 sec as the thermal
emission from the telescope increased. As illustrated in Figure 1, the
survey scanning strategy resulted in 12 to 13 exposures of
each point on the ecliptic plane. Coverage increases to over 1000 exposures
at the ecliptic poles.
Individual 3-Band Cryo exposures that met minimum requirements for
image quality and noise levels were combined to form the Image Atlas and
Source Working Database. The localized decreases in coverage in
small areas seen in Figure 1 are the result of exclusion of lower quality
exposures. Additionally, coverage depth was artificially capped at
approximately 160 exposures near the ecliptic poles for processing
runtime and memory usage requirements.
A plot of the approximate differential area as a function of the average
W1 exposure depth-of-coverage realized in the 3-Band Cryo Release Atlas
and Source Working Database is shown in Figure 2. The peak near 12 coverages
corresponds the ecliptic plane.
Pixel-level frame effective coverage information is provided in the
WISE Image Atlas depth-of-coverage maps.
The following service can be used to determine if a location or object is
contained within one of the 5,649 3-Band Cryo Data Release Tiles:
The WISE 3-Band Cryo Image Atlas is comprised of 5,649
4095x4095 pixel @1.375"/pix FITS format image sets.
One image set is produced for each predefined Atlas Tile. The
1.564°x1.564° Atlas Tiles are built on an equatorial projection
and are distributed in 119 iso-declination bands with 238 Tiles on
the celestial equator and six Tiles in the |δ|=89.35°
declination band. Tiles overlap by 180" in RA and Dec on the equator, and
the RA overlap increases towards the equatorial poles.
Each Atlas Image set consists of:
The headers of each Atlas Image provide WCS information to convert pixel to
equatorial coordinates and photometric zero points for calibration
of relative photometry.
See section VII.2.b of the WISE
3-Band Cryo
Release Explanatory Supplement for more information about the content
and format of the Image Atlas.
The WISE 3-Band Cryo Source Working Database contains the attributes
for 261,418,479 point-like and resolved sources detected on the
3-Band Cryo Atlas Intensity images.
CAUTION: The 3-Band Cryo Source Database
is not a highly reliable, well-vetted list of mid-infrared sources
like the WISE
All-Sky Release
Source Catalog.
The Database contains both detections of real astrophysical objects, as well
as spurious extractions of image artifacts and transient pixel events such as
noise excursions, and redundant detections of objects in the Atlas Tile
overlap regions.
As a result, the 3-Band Cryo Source Database is best used as a resource
for learning more about objects found in the WISE All-Sky Release
Source Catalog.
Attributes included for each entry in the Source Database include:
Relative photometric calibration for WISE source photometry is made using
measurements of a network of calibration standard stars near the ecliptic
poles. The WISE bandpasses and relative spectral response curves
are available
in Section IV.4.h.v of the
WISE All-Sky Release Explanatory Supplement.
See section VII.2.a of the WISE
Explanatory Supplement for more information about the content and
format of the 3-Band Cryo Source Working Database.
In addition to the Image Atlas, Source Working Databse and Explanatory
Supplement, the WISE 3-Band Cryo Release includes several ancillary
data products.
See sections VII.2.c-j of the
WISE 3-Band Cryo
Release Explanatory Supplement for more information about the content
and format of each of the Ancillary Products.
The WISE 3-Band Cryo Release data products can be accessed
via the on-line and machine-friendly services of the
NASA/IPAC Infrared
Science Archive (IRSA). IRSA services are VO compatible.
See section VII.1.c of the WISE
3-Band Cryo Release Explanatory Supplement for a complete description of how
to access WISE data products.
Please include the following in any published material that makes use of the
WISE data products:
"This publication makes use of data products from the Wide-field Infrared
Survey Explorer, which is a joint project of the University of California,
Los Angeles, and the Jet Propulsion Laboratory/California Institute of
Technology, funded by the National Aeronautics and Space Administration."
Thank you very much.
Sky Coverage
Figure 1 - Equatorial Aitoff projection sky map showing
the average number of individual Single-exposures
within 14´ × 14´ spatial bins going into the WISE 3-Band Cryo
Release Atlas and Source Working Database.
Colors encode different frame depths-of-coverage as specified by the legend
on the left.
Figure 2 - Differential area in Atlas Image pixels
(1 pix covers 1.9 arcsec2) as a function of average W1 frame
depth-of-coverage in the 3-Band Cryo Atlas and Source Database,
computed from the depth-of-coverage maps.
Image Atlas
Figure 3 - (left, top row) W1, W2 and W3
intensity images, (left, center row)
depth-of-coverage maps, and (left, bottom row)
uncertainty maps for
the Atlas Tile 0450p605_ab31 that contains
the center of the W5 star formation region (IC1848). The color scale on the
bottom of the
grid refers to the depth-of-coverage maps.
(above) 3-color composite intensity image
for this same Tile, with W1 mapped to blue, W2 to green, and W3 to red.
Source Working Database
Ancillary Products
Data Access
Standard Acknowledgment for Use of WISE Data in Publications
Last update - 2013 March 21
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