  The first six months of flight data from the Multiband Imaging Photometer for
Spitzer (MIPS) were used to test MIPS reduction algorithms based on extensive
preflight laboratory data and modeling. The underlying approach for the
preflight algorithms has been found to be sound, but some modifications have
improved the performance. The main changes are scan mirror dependent flat
fields at 24 micron, hand processing to remove the time dependent stim flash
latents and fast/slow response variations at 70 micron, and the use of
asteroids and other sources instead of stars for flux calibration at 160 micron
due to a blue ``leak.'' The photometric accuracy of flux measurpements is
currently 5%, 10%, and 20% at 24, 70, and 160 micron, respectively. These
numbers are expected to improve as more flight data are analyzed and data
reduction algorithms refined.
