11.4 Visualizing Your Target

Visualizing your target with respect to the background, and the required image retrieval to support this has been discussed above in detail (e.g., §9.4), but Spot has some extra features for Solar System objects that merit review. Here we will not walk through retrieving images in detail, since that is covered in earlier chapters (and in the Spot manual). We will use ISSA images since we are planning MIPS observations of this object, and the long-wavelength background is likely to matter.

From the Images menu, we select ISSA, and ask for all four wavelengths in one frame; see Figure 11.2. After clicking OK, Spot will ask what date we would like to visualize, and the number of data points to be distributed along the orbital arc. For purposes of this example, we pick ``2004 Jul 30'', and 100 points; see Figure 11.3. Finally, then, we get the images and tracks shown in Figure 11.4. The tracks show Pholus' position as a function of time, as seen from Spitzer. Note that because Spitzer tracks in linear segments, if a given source track has significant curvature during a planned AOR, the observation may need to be broken up into smaller AORs. Visualizing the orbital track of your object in Spot can help you determine whether an observation will need to be split into multiple AORs.

Figure 11.2: Retrieving an image from ISSA.

Figure 11.3: Picking the date to visualize.

Figure 11.4: Pholus orbital track visualization in all four ISSA bands.

If we click on the tiny red-and-blue table icon associated with the Pholus orbital track overlay in one of the ISSA images, we produce the window in Figure 11.5, which lists the specific dates associated with each of the points in Figure 11.4.

Figure 11.5: Pholus point identifications.

The controls in this window do several things to the overlay in the corresponding ISSA window. ``Hide All Points'' or ``Show All Points'' turns off and on the points in the overlay. ``Show All Dates'' or ``Hide All Dates'' turns on and off the dates associated with the specific points in the overlay. The next option, a pull-down menu, refers to the symbols used in the points in the overlay. ``Point color'' allows the user to select the point color in several different ways (``swatches,'' ``HSB,'' and ``RGB,'' just like in Adobe Photoshop or the Gimp). Similarly, ``Line Color'' allows us to choose the color of the track, and ``Hide Path'' or ``Show Path'' turns the track off and on. ``Save Table'' writes the object's position information as a function of time to an ASCII file. The individual entries for each point can be turned off and on, temporarily highlighted with a different color and symbol (``Hi'' column checkboxes), have its shape changed, and have its individual date notation turned off or on. Most of these features will be useful for us in a moment as we consider background contamination.