===========================================================================

NOTE: This file describes COSMOS HST/WFPC2 data for Cycle 12 (top section)
and Cycle 13 (bottom section).

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===========================================================================
COSMOS HST/WFPC2 Data                                           Version 1.1
===========================================================================

The Cosmic Evolution Survey (COSMOS) is an HST Treasury Project to survey
a 2 square degree equatorial field, centered on RA=10:00:28.6 and
DEC=+02:12:21.0, using the ACS camera. The project also incorporates major
commitments from other observatories around the world, including the VLA
radio telescope, ESO's VLT in Chile, ESA's XMM X-ray satellite, and the
Japanese 8-meter Subaru telescope in Hawaii.

These data represent the first public release of the COSMOS observations
from the WFPC2 instrument on HST, obtained as parallel exposures to the
primary ACS observations. Included in this release are 222 pointings located
primarily in the central square degree of the survey, observed using the
F300W (U-band) filter.

The key characteristics of these data:

	Instrument:		HST Wide Field/Planetary Camera 2 (WFPC2)
	Dates of observations:	Cycle 12 (Jul 2003 - Jun 2004)
	Observing time:		4 exposures / 1 orbit / pointing
	Filter:			F300W (U-band)
	Area:			~0.5 sq deg (*non-contiguous*)
	Resolution:		0.10"/pixel (mosaic), 0.05"/pixel (PC chip)

The data products available here include:

	(1) drizzled, flux calibrated, astrometrically correct images from
	    the mosaic of all 4 WFPC2 chips, at a resolution of 0.1"/pixel
	(2) drizzled, flux calibrated, astrometrically correct images from
	    only the PC1 chip, at a resolution of 0.05"/pixel

The image files follow a standard naming scheme where, for example:

	wfpc2_U_mos_100135+0215_11.fits

refers to an HST/WFPC2 U-band (F300W) mosaic image centered at RA=10:01:35
and DEC=+02:15, version 1.1. The WFPC2 data are provided in two forms: a
mosaic of all four chips, in which the higher-resolution PC chip has been
binned ("_mos_" in file name), as well as a full-resolution image from just
the PC chip ("_pc1_" in file name).

IMPORTANT: Note that because these data are "parallel" HST observations,
and because the WFPC2 instrument has a smaller field of view than the ACS
instrument (~160" chevron versus 202" square), these data do NOT form a
contiguous map of the COSMOS survey area. They do, however, sample regions
throughout the survey area.

[March 2005]
Note: The WFPC2 data require several corrections to the FITS headers.
Please note that some fits readers will not be able to read these
files until they are updated with fixes headers.  For this reason, 
these image data are not being served through the search engine Atlas.
Header keyword problems are regarding the CCRVAL1 and CCRVAL2 keys
which have 7 instead of 8 characters before the "=" sign.  Also,
the CD matrix has lower case exponentials instead of upper case.

Further information may be obtained from the main COSMOS web page:

	http://cosmos.astro.caltech.edu/

===========================================================================

January 3, 2004
pls@astro.caltech.edu


===========================================================================
COSMOS HST/WFPC2 Data                                           Version 1.2
===========================================================================

The Cosmic Evolution Survey (COSMOS) is an HST Treasury Project to survey
a 2 square degree equatorial field, centered on RA=10:00:28.6 and
DEC=+02:12:21.0, using the ACS camera. The project also incorporates major
commitments from other observatories around the world, including the VLA
radio telescope, ESO's VLT in Chile, ESA's XMM X-ray satellite, and the
Japanese 8-meter Subaru telescope in Hawaii.

These data represent the second public release of the COSMOS observations
from the WFPC2 instrument on HST, obtained as parallel exposures to the
primary ACS observations. Included in this release are 171 pointings,
observed using the F450W (B-band) filter.

The key characteristics of these data:

	Instrument:		HST Wide Field/Planetary Camera 2 (WFPC2)
	Dates of observations:	Cycle 13 (Jul 2004 - Jun 2005)
	Observing time:		4 exposures / 1 orbit / pointing
	Filter:			F450W (B-band)
	Area:			~0.5 sq deg (*non-contiguous*)
	Resolution:		0.10"/pixel (mosaic)

The data products available here include:

	(1) drizzled, flux calibrated, astrometrically correct images from
	    the mosaic of all 4 WFPC2 chips, at a resolution of 0.1"/pixel

The image files follow a standard naming scheme where, for example:

	wfpc2_B_100135+0215_mos_12.fits

refers to an HST/WFPC2 B-band (F450W) mosaic image centered at RA=10:01:35
and DEC=+02:15, version 1.2. These WFPC2 data are provided in only one form:
a mosaic of all four chips, in which the higher-resolution PC chip has been
binned ("_mos_" in file name).

It should be noted that this release is different from the first COSMOS
release of WFPC2 data from the cycle 12 observations: those data were taken
in the U band. While they were provided in two forms, both a mosaic and
the unbinned full-resolution image from the PC1 chip, those data include
many fewer sources and therefore have significant astrometry problems.
These new data, being in the B-band, have improved astrometry in their
full mosaic form. We will not officially release the full-resolution PC1
chip form of these new data, nor the few fields of cycle 13 data that were
taken in the U band. Of course, all of these data can be obtained in their
raw and on-the-fly reduced forms from the MAST archive.

IMPORTANT: Note that because these data are "parallel" HST observations,
and because the WFPC2 instrument has a smaller field of view than the ACS
instrument (~160" chevron versus 202" square), these data do NOT form a
contiguous map of the COSMOS survey area. They do, however, sample regions
throughout the survey area.

Further information may be obtained from the main COSMOS web page:

	http://cosmos.astro.caltech.edu/

===========================================================================

December 1, 2005
pls@astro.caltech.edu