Loading Data and Computing an Image

Name of Progam: SwanImageTool.pro

This program loads a SWAN data set stored under the FITS format.

The main variables are described at the following link:

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The list of tasks performed by the program is the following:

• The program loads and converts the Swan Observation data stored in the FITS file.

• The program loads the SOHO orbit datafile and the motor coordinate correction files.

• The program applies motor coordinate corrections to the data to account for measured offsets.

• The program computes a flatfield correction to compensate for Pixel Response Non-Uniformity.

• If data from both sensors are present (full-sky images), the programme computes the +Z/-Z cross calibration factor. Data of the -Z sensor are converted to equivalent +Z sensor count rate. Throughout the mission the +Z sensor has been used as a reference for the instrument calibration.

• The program computes an image in a chosen coordinate system. The size and step size of the image can be chosen.

The output of the program is a set of images. If data from both sensors are present, there will be an image for the +Z sensor and an image for the -Z sensor.

The results are stored in a 3-dimension variable like that:

COUPOFF = FLTARR( N1, N2, 2)

The first 2 dimensions N1 et N2 correspond to the size of the image.

It is defined for N1-1 longitude values and N2 latitude values. The N1-1 line is used to define the limits of the image.

The array given by COUPOFF(0:N1-2,0:N2-1,0) contains the image obtained from the data.

The array COUPOFF(0:N1-2,0:N2-1,1) contains the statistical error associated to the image.

Spatial coordinates of the point (i,j) are given by:

longitude(i,j) = lonmin + (i+0.5) $\times$ londel

latitude(i,j) = latmin + (j+0.5) $\times$ latdel

The limits of the image are given by

lonmin = COUPOFF(N1-1,0,1)

londel = COUPOFF(N1-1,1,1)

latmin = COUPOFF(N1-1,2,1)

latdel = COUPOFF(N1-1,3,1)

lonmax = lonmin + (N1-1) $\times$ londel

latmax = latmin + N2 $\times$ latdel