Chandra Announcement: PIMMS Update for ACIS Subarrays

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Tingle, Evan

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Jan 30, 2026, 9:26:57 AMJan 30

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Chandra Announcement: PIMMS Update for ACIS Subarrays

We have updated the PIMMS tool within the Chandra Proposal Planning Toolkit to resolve an issue with pileup calculations for ACIS subarrays. Previously, PIMMS incorrectly defaulted to a 3.2 second frame time regardless of user-defined chip counts or subarray sizes. The update ensures that using the "Calculate" option for Frame Time correctly reflects the nominal subarray frame time and provides accurate pileup estimates. Proposers who have recently used the PIMMS tool with user-defined chip counts or subarray sizes for future proposals should consider recalculating frame times.