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Subsections


14.23 Footprint Matrices for PHT-P and C 


Description Parameter:	 none 
Processing Level:	 none, service to observer
Usage in processing:	 N/A 
File Type: 		 FITS Image
File names:		 PP2FOOTP, PP3FOOTP, PC1FOOTP, PC2FOOTP

Using a model for the primary mirror, secondary mirror and tripod, the theoretical point spread function (PSF) was obtained assuming a given wavelength. By convolving the PSF with the geometrical properties of the apertures and detectors, synthetic footprints or beam profiles were derived for each filter. The footprints are monochromatic assuming the reference wavelength of the filter. The footprint matrices give at each listed position the fraction of the total power in the PSF falling on the aperture or pixel if the geometrical centre of the aperture or pixel is placed at position (0,0). The matrices are aligned with the spacecraft Y and Z-directions.

The high degree of asymmetry found in the measured P1 beam profiles cannot be explained with the present model. It has been decided to postpone the release of synthetic P1 footprints until a refined understanding of the P1 beams is available.

The footprint matrices can be used for accurate photometry in maps, e.g. for extracting accurate point source fluxes from an underlying extended component or in crowded fields.


14.23.1 Product PP2FOOTP: PHT-P2 footprint matrices

NAXIS = 4
TYPE = R*4 


AXIS Length  Description
1    2 	     Filters (20, 25$\mu $m 
2    14      Apertures (Change Wheel position)
3    87      Y-direction - $2''$ steps for apertures $<\,18''$ 
	     $3''$ steps for apertures $\geq\,18''$
4    87      Z-direction - $2''$ steps for apertures $<\,18''$ 
	     $3''$ steps for apertures $\geq\,18''$


14.23.2 Product PP3FOOTP: PHT-P3 footprint matrices

NAXIS = 4
TYPE = R*4 


AXIS	 Length	Description
1 	 2 	Filters (60, 100$\mu $m 
2 	 14 	Apertures (Change Wheel position)
3 	 87 	Y-direction - $2''$ steps for apertures $<\,52''$
		$10''$ steps for apertures $\geq\,18''$
4 	 87 	Z-direction - $2''$ steps for apertures $<\,18''$
		$10''$ steps for apertures $\geq\,18''$


14.23.3 Product PC1FOOTP: PHT-C100 footprint matrices

NAXIS = 3
TYPE = R*4 


AXIS	Length	Description
1 	7 	Filters (C100, in wheel position order)
2 	35 	Y-direction - $7.5''$ steps
3 	35 	Z-direction - $7.5''$ steps


14.23.4 Product PC2FOOTP: PHT-C200 footprint matrices

NAXIS = 3
TYPE = R*4 


AXIS	Length	Description
1 	5 	Filters (C200, in wheel position order)
2 	35 	Y-direction - $15''$ steps
3 	35 	Z-direction - $15''$ steps

next up previous contents index
Next: 14.24 Relative System Responses Up: 14. Calibration-G Products Previous: 14.22 Colour Corrections
ISO Handbook Volume IV (PHT), Version 2.0.1, SAI/1999-069/Dc