New change as of 12 March 2002
______________________________

ACS_READ has been modified to read ACS data processed by OPUS.
The routine now supports three output orientations for WFC and HRC data:

Orientation 1) Raw Format: The position for each amplifier is in the
	lower left corner.  As shown

	..... .....
	..... .....
	..... .....
	C.... D....
	..... .....
	..... .....
	..... .....
	A.... B....

Orientation 2) data into a format as though one were looking at the
detector.
	This was previously the default format output by ACS_READ.

	C.... ....D
	..... .....
	..... .....
	..... .....
	..... .....
	..... .....
	..... .....
	A.... ....B

Orientation 3) Output orientation for the OPUS pipeline.

	A.... ....B
	..... .....
	..... .....
	..... .....
	..... .....
	..... .....
	..... .....
	C.... ....D

The default output format (when reading both prelaunch or postlaunch data)
is controlled by the system variable !prelaunch.

	!prelaunch = 0        use Orientation 3 (OPUS)
	!prelaunch = 1        use Orientation 2 (prelaunch default)

The output format can be overridden by using the following keyword
parameters
to acs_read.

	/raw          - use orientation 1
	/prelaunch    - use orientation 2
	/postlaunch   - use orientation 3

or alternately you can use the keyword rotate to give the orientation

	rotate = 1    - use orientation 1
	rotate = 2    - use orientation 2
	rotate = 3    - use orientation 3

For example:
-----------

	all of the following would give orientation number 1:
		acs_read, 'j8a604agq_raw.fits', h, d, /raw
		acs_read, 'j8a604agq_raw.fits', h, d, rotate = 0


	all of the following would give orientation number 2:
		acs_read, 'j8a604agq_raw.fits', h, d, /prelaunch
		acs_read, 'j8a604agq_raw.fits', h, d, rotate = 1
		!prelaunch = 1
		acs_read, 'j8a604agq_raw.fits', h, d

	all of the following would give orientation number 3:
		acs_read, 'j8a604agq_raw.fits', h, d, /postlaunch
		acs_read, 'j8a604agq_raw.fits', h, d, rotate = 2
		!prelaunch = 0
		acs_read, 'j8a604agq_raw.fits', h, d

	The default value for !prelaunch in the ACS startup file
	will be set to 0.  This means if you do not specify any
	orientation, you will get the OPUS orientation.

For SBC data, the output orientation is identical in all cases.

The calling sequence of ACS_READ is:

	ACS_READ, id, h, d, hudl, udl, heng1, heng2

where
    id is the entry number in the prelaunch data catalog, the prelaunch
	filename, or the postlaunch file name (eg. 'j8a604agq_raw.fits')
    h is the header for the science data
    hudl - is the a header constructed from the UDL.  For postlaunch data
    	it is extracted from the _spt file (eg. 'j8a604agq_spt.fits').
	If this file is not present in the same directory as the raw data
	file, this output header will not be populated.
    udl - binary UDL vector
    heng1, heng2 - engineering snaphot headers at the beginning and end
        of the exposure.  These also are only defined if the _spt file
	is present for postlaunch data.


For post-launch data: hudl, heng1, and heng2 are constructed from the UDL
vector in the SPT file by the same software that was used to construct the
headers for the prelaunch data.  An additional keyword output, HSPT, can be
used to get the header for the _spt file.  For example:

	acs_read, 'j8a604agq_raw.fits', h, d, hspt=hspt

The HSPT header contains the support schedule information, the onboard
ephemeris model parameters, proposal information, and exposure information
extracted from the UDL by OPUS.

Also for postlaunch data, the following keywords that were present in the
prelaunch headers are added to the primary header by ACS_READ.

FOLDPOS   /Fold Mechanism Position
CALDOOR   /Cal Door Position Select
WSHUTPOS  /W shut RESolver POS
HSHUTPOS  /H shut RESolver POS
WFOCPOS   /Wfc corctr FoCuS POS
WINNPOS   /Wfc corctr INNer POS
WOUTPOS   /Wfc corctr OUTer POS
HFOCPOS   /Hrc corctr FoCuS POS
HINNPOS   /Hrc corctr INNer POS
HOUTPOS   /Hrc corctr OUTer POS
OVER_AC   /Physical Overscan AC
OVER_BD   /Physical Overscan BD
OVER_V    /Virtual Overscan Per Amp
MCPVOLT   /SBC MAMA MCP VOLTAGE
FIELDVLT  /SBC MAMA FIELD VOLTAGE
MFIFOVR   /Number of SBC MAMA Overflow Events



--------------------------------------------------------------------

Installation note:

ACS_READ now requires the following files to be located in the directory
specified by the environment variable JAUX.

	acs_ess.txt      acs_filter.txt    tdfd.an

These files are the same ones used by acs_acquire.


The line:
	defsysv,'!prelaunch',0

should be added to the IDL startup file to create the !prelaunch system
variable.  The location of you current IDL startup file can be found
bye typing:

	echo $IDL_STARUP