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B. 2-D Bias Properties


Figure 3 shows two bias frames obtained at detector temperatures of T ~ +10 degrees C (upper panel) and T ~ -10 degrees C (lower panel). Note that in the warmer bias, there are many hot columns, but that these columns are no longer problematic in the cooler bias. This is further evidence to support the notion that one should not use the system unless T < -10 degrees C.

  • Figure 3: A bias obtained at T ~ +10 degree C (upper panel) and one obtained at T ~ -10 degrees C (lower panel).

    Figure 4 shows a set of bias ratio frames. In each case the denominator is a frame with T ~ -20 degrees C. The numerator frames have temperatures of T ~ +20 degrees C (Fig. 4a), +10 degrees C (Fig. 4b), 0 degrees C (Fig. 4c), and -10 degrees C (Fig. 4d). The display range is smaller for the second set of images (the contrast is higher). Note that there is significant 2-D structure in all the ratio frames except the last one. Thus, both the small- and large-scale 2-D structure of the bias of our detector have significant temperature dependence above T ~ -10 degrees C. One is unlikely to obtain useful scientific data for detector temperatures higher than this.

  • Figure 4: Ratios of bias frames at a range of temperatures divided by a bias obtained at T ~ -20 degrees C. Temperatures as follows: a) T ~ +20 degrees C; b) T ~ +10 degrees C; c) T ~ 0 degrees C; d) T ~ -10 degrees $ C.


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    Updated: 2005 September 21 [pbe]