11.1.4 Imaging Sensitivities

Plotted in Figure 11-6 below are HIPO first-light sensitivities for several representative cases. These figures assume that the FLITECAM dichroic beamsplitter is not installed. The upper figures correspond to occultations by Pluto or Triton while the lower two are for the case of a very faint occulting object. The left and right figures are for 0.5 sec and 50 ms integrations, respectively.Each figure shows S/N for no filter (dichroic only) and for the 0.675 um dichroic plus standard Sloan filters. The dichroic transition is assumed to occur from 0.57 and 0.67 μm.

HIPO sensitivities

Figure 11-6: Plotted here are the anticipated sensitivities for HIPO for several representative occultation scenarios.

The deviation of S/N from a square root dependence is mostly due to shot noise on the occulting object in the upper left figure, about equally shot noise on the occulting object and read noise in the upper right figure, about equally shot noise on the sky and read noise in the lower left figure, and read noise in the lower right figure. Once the aluminized tertiary mirror is available read noise will only be significant in the lower right figure. The improved final SOFIA pointing stability will increase sensitivity for sky-limited events and improve discrimination from nearby bright objects (e.g. Neptune for a Triton occultation).

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