9.4.1 ISSA

Select ``ISSA'' and you will get the dialog box shown in Figure 9.2.

Figure 9.2: Retrieving an image from ISSA.

Our whole region will fit in one retrieval of an ISSA image; Spot limits ISSA image retrievals to between $1^{\circ}$ and $12.5^{\circ}$, with a default value of $5^{\circ}$. We can select more than one wavelength, and we can select whether or not these images are opened in one frame (with an option to cycle through them interactively) or in separate frames. Here, we choose all of them, $12$, $25$, $60$, and $100 \; \mu {\rm m}$, put all plots in a single frame, $5^{\circ}$ on a side, no zoom. Using Spot, it is possible to combine three of these wavelengths together into an RGB composite image. When Spot has retrieved the images, you will note that there are now large black arrows and a slider bar in the upper right; see Figure 9.3. This is how you can flip between images loaded into the same window. If you load fewer than four images into the same window, then the slider only includes those images as options.

Figure 9.3: Flipping between $12$, $25$, $60$, and $100 \; \mu {\rm m}$ images.

The default color table is black and white; to better see gradations, we can change the color table. Click on the color grid button (looks vaguely like a Rubik's Cube) which has now appeared on the right of the image window, to obtain the window shown in Figure 9.4. From the color table pull-down menu, we pick ``a trip around a color cube,'' click ``apply color to all plots,'' then click Apply and OK.

Figure 9.4: Color table selection.