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 PrelimREADME.txt file contains minimal information to help users access the
Preliminary catalog, and was written on 2019 June 5. The web page 
https://catwise.github.io contains the latest updates to CatWISE information.

The Preliminary CatWISE catalog is available here 
(https://portal.nersc.gov/project/cosmo/data/CatWISE/prelim) 
and will also soon become available via the Infrared Science Archive 
(https://irsa.ipac.caltech.edu) as a contributed data set.
 
The Preliminary CatWISE catalog here is separated into 18,240 gzipped ascii 
files in IPAC table format, one for each of the same number of spatially 
overlapping tiles, using the same equatorial coordinate grid as for WISE and 
unWISE. The 50 tiles nearest the ecliptic poles used slightly different
processing, and their file names contain the string "opt0_2018" and do not
have an underscore ("_") separating the date and time stamp in the name. All
other file names contain the string "opt1_2019" and have an underscore
separating the date and time stamp in the name. All file names begin with an 
8 character string of form:

rrrrsddd

where rrrr is the decimal right ascension and sddd is the signed declination of 
the tile center to 0.1 degrees, in J2000. The WISE tile lookup service at 
https://irsa.ipac.caltech.edu/applications/WISETiles/ 
provides a useful tool for identifying the tile(s) containing a coordinate.

For example, the brown dwarf Gliese 570D, at RA 14h57m16.2s, or 224.3175 in 
decimal form, and declination -21d22m16s, will be found in the file with the 
prefix 2243m213.

The files are organized here into 359 directories, one for each decimal degree 
of right ascension from 0 to 358 (there are no tiles beginning with 359). For 
example the file containing Gliese 570D is in 
https://portal.nersc.gov/project/cosmo/data/CatWISE/prelim/224.

Each catalog file contains typically 50,000 rows, one per source, with 
information similar to that in the AllWISE catalog 
(http://wise2.ipac.caltech.edu/docs/release/allwise/expsup/index.html).

There are 186 formatted columns of information about each source, with the 
column format and description specified in the file prelimcwcat.sis20190511.txt.
Additional information about most of the columns is available via the AllWISE 
Explanatory Supplement.

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).

Sources that do not meet these criteria go into the reject file for their tile, 
so there are also 18,240 gzipped ascii reject files in IPAC table format, in the
same decimal RA directory as their corresponding catalog file. (Note that an
initial version of the files, ending in "a0.tbl.gz", did not apply the first 
criterion, and only sources failing the second were put in those reject files. 
The correct versions now provided here end in "a1.tbl.gz".) Reject files 
typically contain 8,000 sources, although near the celestial poles this can 
reach over 30,000 due to large tile overlap. Reject files have one additional 
column (for a total of 187) indicating if the source is "primary" in its tile. 
The column format and description are specified in the file 
prelimcwrej.sis20190511.txt. Catalog and reject file names for a given tile 
generally differ only in having the letters "cat" or "rej" as appropriate.

Additional information about the "primary" designation and the artifact flags is
given in the Preliminary CatWISE catalog overview paper, which is available at 
https://catwise.github.io.