The Preliminary CatWISE catalog consists of 900,849,014 sources over the entire 
sky selected from WISE and NEOWISE survey data at 3.4 and 4.6 microns (W1 and 
W2) collected from 2010 to 2016. This dataset includes four times as many 
exposures and spans over ten times as large a time baseline as the AllWISE 
catalog. CatWISE adapts AllWISE software to measure the sources in co-added 
images created from six month subsets of these data, each representing one 
coverage of the inertial sky, or epoch. The catalog includes the measured motion
of sources in 8 epochs over the 6 year span of the data. From comparison to 
Spitzer, the SNR 5 Vega magnitude limits in fields out of the Galactic plane and
at low ecliptic latitude (corresponding to lower WISE coverage depth) are 
W1=17.5 and W2=16.4, vs. W1=16.9 and W2=15.9 for AllWISE. From comparison to 
Gaia, the motions are ten times more accurate than those from AllWISE. 

This PrelimREADMEIRSA.txt file contains minimal information to help
users access the Preliminary catalog, and was written on 2019 August
21. The web page https://catwise.github.io contains the latest updates
to CatWISE information.

The Preliminary CatWISE catalog is available as a contributed data set
through a user-friendly web interface
(https://irsa.ipac.caltech.edu/applications/Gator/) at the Infrared
Science Archive (irsa.ipac.caltech.edu). The catalog is also available
as a set of gzipped ascii files in IPAC table format at NERSC
(https://portal.nersc.gov/project/cosmo/data/CatWISE/prelim). Note
that 81 NULL glat values in the NERSC files have been updated in the
IRSA database.
 
The information in the Preliminary CatWISE catalog is similar to that
in the AllWISE catalog. There are 186 formatted columns of information
about each source, with the column format and description specified
here:

https://irsa.ipac.caltech.edu/data/WISE/CatWISE/gator_docs/catwise_colDescriptions.html. 

Additional information about most of the columns is available via the AllWISE
Explanatory Supplement (http://wise2.ipac.caltech.edu/docs/release/allwise/expsup/index.html).


Preliminary CatWISE catalog sources are required to:
 
1) be "primary" in their tile (i.e. be from the tile where that source is 
furthest from the tile edge) 

and

2) have W1 SNR >= 5 with no identified artifacts (a value of 0 for the 
"ab_flags" in the W1 part (left character) of column 178) 

or

have W2 SNR >= 5 with no identified artifacts (a value of 0 for the "ab_flags" 
in the W2 part (right character) of column 178).

A catalog of rejected sources is also available at IRSA and NERSC.

Additional information about the "primary" designation and the artifact flags is
given in the Preliminary CatWISE catalog overview paper (https://catwise.github.io/CatWISEoverview2019may14.pdf)