7.1 Summary of the Observing Program

In this section, we summarize the basic steps followed to design a Spitzer observing program that uses the SL module to construct a low resolution spectral map of the Ring Nebula, a planetary nebula located at RA = 18:53:35.16, DEC = +33:01:43.2 (J2000). The design process for this example is presented in more detail in the remainder of this chapter.

• Target Selection and Duplication Check: Checking the Reserved Observations Catalog using Leopard shows that the target does not already have approved or completed Spitzer observations using IRS. Thus, a new observing proposal using IRS will have no conflicts as specified in the Spitzer Duplicate Observations Rules. See §7.2 for additional details.

• Slit Orientation and Timing Constraints: The ``Calculate Position Angle'' function in Spot's Visibility Windows window is used to determine the subset of the Spitzer visibility windows during which the IRS SL slit position angle is within $\pm10^{\circ}$ of perpendicular to the major axis of the Ring Nebula. These timing constraints are then recorded in an AOR Timing window. See §7.4 for additional details.

• Laying Out the Spectral Map: Spot's visualization tool is used to overlay slit templates for a given AOR configuration onto an image of the target. This allows determination of the optimum spectral map layout parameters that achieve the observational goals. The layout is controlled by specifying a number of steps of a given size in each direction parallel or perpendicular to the long axis of the slit. For the spectral map of the Ring Nebula, we specify 2 parallel steps of size $51^{\prime \prime }$ and 11 perpendicular steps of size $3\hbox{$.\!\!^{\prime\prime}$}6$ (i.e., the width of the SL slit) for each of the 1st and 2nd order subslits of the SL module. This produces a closely sampled map. See §7.7.3 for additional details.

• Filling in the IRS Spectral Mapping Mode AOT: In addition to timing constraints and map layout parameters, the individual ramp durations and numbers of map and/or ramp cycles must be specified. Although only one mapping cycle will be performed, two ramp cycles will be obtained at each pointing position in the map. This will facilitate combining the individual spectra at each map pointing in order to improve signal-to-noise ratio (S/N) and to provide redundancy against cosmic ray hits. In addition, the ``2MASS Selection'' function is used to configure a moderate accuracy, Blue IRS peak-up on HD 175291, a K type star with $V=8.3$ mag. The estimated duration for the spectral mapping observation does not exceed the 3-hour time limit for an IRS AOR. See §7.7, §7.7.2, and §7.7.3 for additional details.