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Knowledgebase: MIPS
Why can't I derive the 24 um saturation values in Table 2.7 (from the MIPS Instrument Handbook) by sticking either 0 or large background levels into Table 2.8?
Posted by z-James Colbert on 04 December 2008 01:30 PM
Trying to compare Tables 2.7 and 2.8 is like comparing apples and oranges. The values for truly (ideal) cases are in Table 2.7. The formulae in Table 2.8 actually describe the general case, which includes a combination of point and background flux, so they break down in the limiting cases. Further complicating matters, Table 2.8 also has incorporated into it subframes that are part of the observing sequence AND the impact of some substitution of values for point sources -- there is a half-second data frame taken at the beginning of the observing sequence, and we can use the first difference to substitute in values for *point sources* that are saturated later in the exposure. This doesn't work for extended sources, so far as we know from our testing to date. The values in Table 2.7 are meant to be single-point values, plain vanilla, with nothing hidden. The values in Table 2.8 are a better approximation to reality, a mixture of point and background sources, subframes that are part of the observing sequence, and the use of some of these subframes to substitute saturated pixels.