What signal to noise ratio is reached in a one orbit exposure (2000 seconds) observing Jupiter's aurora in Ly- using the SBC and F122M filter?
The equation from the Section , "Emission Line Source" can be used to calculate the expected count rate. The aurora is variable, up to ~100kR. The value of (QT) for the SBC+F122M filter at 1216 Ć is 0.0009, from inspection of Figure 10.106. For a surface brightness of 40kR = 1.22x10-12 erg/cm2/second/arcseconds2 ( See <$patatext for conversion), the total counts per pixel are given by the following calculation:
2.23x101 2* 0.009 * 1.22x10-12 * 1216 * (0.032)2 * 2000 = 61.0.
The background contributions are the detector dark of 1.2x10-5 counts/pixel/second (which can be ignored in this case) and a sky background which is dominated by geocoronal Lyman-. During the daytime, the geocoronal background is 20kR, or 30.5 counts, while at night the background drops to one tenth of this, or 3.05 counts.
Finally, we calculate the signal to noise ratio for a 2 x 2 pixel resolution element: in the daytime,
= 12.7, while at night,
= 15.2
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