VII. 3-Band Cryo Data Release
d. Cautionary Notes
WISE 3-Band Cryo data products are subject to most of the same
limitations and exhibit the same features as the WISE All-Sky
Release Image and Source List data products.
We recommend that you begin by reviewing the Cautionary
Notes for the
Products before making use of the 3-Band Cryo Data Products.
The WISE survey data acquisition strategy, data processing and quality
assurance measures were all designed to yield data products of high
reliability and fidelity. However, the changing nature of the
payload and detectors during the 3-Band Cryo survey phase make it
difficult to produce calibrated products that have the same
uniformity and fidelity of the products generated from the full cryogenic
survey when the performance of the WISE payload was extremely stable.
This combined with the challenge of validating such a large
data set in a limited time result in a number of limitations and
problems that persist into the 3-Band Cryo Release products.
3-Band Cryo Release Supplement sections VII.1.d.i through VII.1.d.vi contain
descriptions of known features and limitations that pertain to WISE
3-Band Cryo Data Release products.
Section VII.1.d.i below contains a list of the most
important things that you should know about the Release products to make
the best use of them in your research. Click on any item in the list to
see a more detailed discussion.
Section VII.1.d.ii contains general
information that pertain to all of the 3-Band Cryo Release products.
Sections VII.1.d.iii and
VII.1.d.iv contain essential
information specific to the 3-Band Cryo Source Working Database
and Image Atlas.
Sections VII.1.d.iv and
contains Cautionary Notes for users who make use of the 3-Band Cryo
Single-exposure Source Database and Images.
The Known Solar System Object Possible Association List
is subject to the same limitations that apply to the All-Sky Release
that are described in I.4.d.iv.
You are strongly encouraged to read and familiarize yourself with
all of these Cautionary Notes before using the WISE 3-Band Cryo Release data
i. Top 10 (or so) Things You Should Know About the WISE 3-Band Cryo
Release Data Products
Click on the links below to read more detailed descriptions.
- The quality of
the WISE 3-Band Cryo Release data products is generally not as good as
that of the All-Sky Release products. Performance in the W1 and W2
bands is close that in the full cryogenic survey phase,
but the W3 performance is significantly
degraded because of increasing temperatures and reduced exposure
All-Sky Release Catalog and Atlas are the most complete and uniform
compendia of the mid-infrared sky. The WISE 3-Band Cryo Release Products
are most useful as a resource to learn more about objects found in the
All-Sky Release products, such as possible
flux variability, proper motion, and verification for very faint or
- The 3-Band Cryo Release
products do not contain any
measurements in the W4 (22 μm) band.
- The 3-Band Cryo observations
covered only 30% of the sky. See also
- There is a gap in the W3 coverage
during the 3-Band Cryo
survey when the W3 Single-exposure measurements began to saturate on
normal sky backgrounds before the exposure times could be reduced.
These W3 frames were omitted from Multiframe Pipeline processing
that produced the W3 Atlas Images and Source Working Database.
- The W3 band sensitivity
varied in a complex way during
the 3-Band Cryo period because of the increasing temperatures
and the reduced exposure times. 3-Band Cryo W3 Atlas Images were assembled
using Single-exposure images with very different depth and quality,
so depth-of-coverage in the Atlas Image cannot be used as a reliable proxy
for relative sensitivity. Use the 3-Band Cryo Atlas Image Uncertainty Maps
to account properly for the net sensitivity in W3.
- The 3-Band Cryo Source Working
Database is not a highly reliable, well-vetted list of mid-infrared sources
like the All-Sky Release Source Catalog. The 3-Band Cryo Database contains
detections of real astrophysical objects, as well as spurious extractions
of image artifacts and transient noise events, and redundant detections
of objects in the Atlas Tile overlap regions.
- The 3-Band Cryo Source Working
photometry measurements may be systematically fainter than measurements
in the All-Sky Release Source Catalog. This bias increases
towards fainter fluxes, and with increasing source density.
- The 3-Band Cryo Single-exposure
Images and Source Working
Database W3 calibrations have ±6%, time-dependent variations
with respect to the All-Sky Release calibrations. These variations
were compensated for during the construction of the 3-Band Cryo
Atlas Images and the Source Working Database.
- Saturated pixels and
sources may not be accurately flagged in the
3-Band Cryo Release image and extracted source databases
because of the loss of on-board saturated pixel encoding.
This results in erroneous flux measurements for saturated
sources and incorrect flagging of spurious detections of
by image artifacts from bright sources..
Last update: 2012 June 26