Accumulate NDRs

So far we have worked with sub-exposures. Each sub-exposures collects the signal incoming after the end of the collection of the previous sub-exposure, as indicated in the following figure from Sub-Exposures:

Now we want to accumulate the subsequent sub-exposures of the same exposure, building the ramp. This means that, starting from the first sub-exposure of the ramp, all the successive are equal of themselves plus the previous one. If an exposure is made of \(N\) sub-exposure, we have

\[Sub_0 = Sub_0\]

But then for every other sub-exposure on the same ramp

\[Sub_i = Sub_i + Sub_{i-1}\]

This is handled by AccumulateSubExposures, which overwrites the input cached dataset with the new one.