The WMAP format

The WMAP is the primary image and requires the standard image keywords. Downstream software will likely require both the primary and the secondary (WCSTY#P='PHYSICAL') WCS keywords.

• OPTIC1 - the X-coordinate position of the optical axis in detector coordinates.
• OPTIC2 - the Y-coordinate position of the optical axis in detector coordinates.
• WMREBIN - the rebinning factor from detector pixels to WMAP bins (this should be the single axis binning factor eg a binning factor of 4 puts 16 detector pixels into each WMAP bin).
• CDELT1 - the X-axis increment for each WMAP bin in detector units.
• DDELT1 - the original X-axis increment
• CDELT2 - the Y-axis increment for each WMAP bin in detector units.
• DDELT2 - the original Y-axis increment
• CRVAL1 - the coordinate position of the X-axis reference pixel.
• CRVAL2 - the coordinate position of the Y-axis reference pixel.
• CRPIX1 - the X-axis reference pixel.
• DRPIX1 - the original X-axis reference pixel
• CRPIX2 - the Y-axis reference pixel.
• DRPIX2 - the original Y-axis reference pixel
• CTYPE1 - the name of the X-axis in the WMAP.
• CTYPE2 - the name of the Y-axis in the WMAP.
• CUNIT1 - the unit for the X-axis in the WMAP.
• CUNIT2 - the unit for the Y-axis in the WMAP.
• WCSTY1P- PHYSICAL
• WCSTY2P- PHYSICAL
• CTYE1P - Source of X-axis.
• CTYE2P - Source of Y-axis.
• CRPIX1P- X-axis reference pixel.
• CRPIX2P- Y-axis reference pixel.
• CRVAL1P- Coordinate of X-axis reference pixel in original image.
• CRVAL2P- Coordinate of Y-axis reference pixel in original image.
• CDELT1P- X-axis increment
• CDELT2P- Y-axis increment
• BLANK - the null value used in the WMAP to indicate a bin outside the selected region (usually -1).

It should also include the standard OGIP keywords :

HDUCLASS= 'OGIP    '           / Format conforms to OGIP/GSFC conventions
HDUCLAS1= 'IMAGE   '           / Extension contains an image
HDUCLAS2= 'WMAP    '           / Extension contains a weighted map
HDUVERS = '2.0.0   '           / Header version
HDUDOC  = 'OGIP/96-001'        / OGIP memo describing format