The Variance Maps have patterns.

We investigated the variance maps for different stages/processing:

• chip (md)
• warp (md)
• stack (md and sas)

There are periodic patterns associated with warp and stack, which are not associated with chip.

Here is a zoom of one of the unconv.wt.fits for SAS footprint: (stack_Id= 336346). You can see an odd periodic background. The yellow circles are the false detections.

Here is a zoom of one of the unconv.wt.fit stacks for a recent MD refstack, it not quite as strange, but still, there is an underlying odd, periodic background.

Chip stage does not have this background (click to zoom in)

chip

chip.wt

Warp stage (for the same chip) has a very strange background for the weight map (click to zoom in)

warp

warp.wt