ISSA Explanatory Supplement IV. ANALYSIS RESULTS C. Point Spread Function

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 Figure IV.C.1(a) Contour Plot of Point Spread Function for a 12 µm Source, Contoured from 0.0 to 13.6, Interval 0.8 larger largest
The selected point sources (see §IV.B) were used to study the ISSA point spread function (PSF). The full widths at half maximum (FWHM) of these point sources were measured from ISSA data which had been interpolated to 0.15' sample spacing using a sinc function of 1.5' period apodized with a cosine to a full width of 12 zero crossings. Contour plots of interpolated point spread functions are shown in Figures IV.C.1(a)-(d). Note that there is some noncircularity evident. The short axes of the PSFs, when discernible, line up with the predominant scan direction. Table IV.C.1 lists the measured FWHMs of the point spread functions in both the long and short dimensions. These measurements indicate that the resolution of the ISSA is 4' to 5', depending on the orientation of the long axis of the image. This spatial resolution is consistent with expectations based on the binning algorithm used to produce the ISSA images.
 Figure IV.C.1(b) Contour Plot of Point Spread Function for a 25 µm Source, Contoured from 4.0 to 11.6, Interval 0.4 larger largest

 Figure IV.C.1(c) Contour Plot of Point Spread Function for a 60 µm Source, Contoured from 0.0 to 18.0, Interval 1.0 larger largest

 Figure IV.C.1(d) Contour Plot of Point Spread Function for a 100 µm Source, Contoured from 0.0 to 12.0, Interval 0.8 larger largest

Table IV.C.1 Point Spread Function Dimensions
IRAS NameField Flux
(Jy)
FWHM
(arcmin)
12 µm 10521+7208 414 35.6 3.7× 4.8
15448+3828 355 37.0 3.7× 4.9
17133+3651 357 48.2 3.6× 5.3
05174-3345 102 27.3 3.6× 4.7
03040-8013 3 26.2 3.6× 4.7
25 µm 20427-8243 9 12.6 3.6× 4.6
01452-8026 3 20.8 4.5× 4.9
17329+5359 383 21.4 3.6× 5.3
04330-6307 28 12.1 3.5× 3.9
02238-5947 26 12.1 3.8× 4.6
60 µm 08354+2555 316 24.3 3.7× 4.2
00163-1039 162 6.9 2.7× 3.9
04315-0840 169 33.5 3.5× 4.6
23488+2018 270 17.0 3.2× 5.2
100 µm 13183+3423 322 24.4 4.5× 4.8
10565+2448 319 14.3 4.6× 5.2
23488+2018 270 21.0 5.2× 6.1
09320+6134 397 20.1 4.8× 5.2

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