Tests have been undertaken at Sira on the dispersion of CHRIS. The results are shown plotted in Figure 1 together with a 5 th order polynomial curve that is the best least square fit to the measurements. The measurement were taken at 20.2

C, a shift will be expected due to launch and temperature changes.
Figure 2 shows a plot of the difference between the measured data and the 5 th
order polynomial. The differences are very small and can probably be accounted for largely by experimental error. If desirable, a slightly better fit can be obtained by dividing the curve into two sections and fitting 5 th
order polynomial curves to each of these separately.
Table 1 lists the relevant coefficients for a polynomial of the form:

= A
0
+A
1 n+A
2 n
2
+A
3 n
3
+A
4 n
4
+A
5 n
5 where

is the wavelength in nm and n is the array row number.
WAVELENGTH
RANGE (nm)
400 – 640
640 – 1050
400 – 1050
A
5
A
4
2.35573 x 10 -8 -6.62753 x 10 -6
-5.90263 x 10 -8 3.35818 x
10 -5
-6.21248 x 10 -9 3.54053 x
10 -6
A
3
A
2
A
1
A
0
7.71120 x 10 -4 -3.17521 x 10 -
2
1.82870 380.835
-7.15930 x 10 -3 7.50379 x 10 -1 -36.0441 1081.93
-5.20920 x 10 -4 4.27704 x 10 -2 -.0464701 396.140
Table 1 Polynomial coefficients to fit the wavelength calibration curves

WAVELENGTH CALIBRATION
1100.00
1000.00
900.00
800.00
700.00
600.00
500.00
400.00
0 20 40 60 80 100
COLUMN NUMBER
120 140 160
Fig. 1 Plot of wavelength calibration data and best fit 5 th
(T=20.2

C)
order polynomial
180
10.00
9.00
8.00
7.00
6.00
-3.00
-4.00
-5.00
-6.00
-7.00
-8.00
-9.00
-10.00
5.00
4.00
3.00
2.00
1.00
0.00
-1.00
-2.00
300.00
DEPARTURE OF MEASURED WAVELENGTHS FROM VALUES PREDICTED BY
POLYNOMIAL EQUATION
400.00
500.00
900.00
1000.00
600.00
700.00
WAVELENGTH nm
800.00
1100.00
Fig.2 Difference between measured data and best-fit polynomial – blue triangles are for a single polynomial and red dots for two polynomials