Formally the software allows both channel and energy rebinning of the response to an arbitrary grid. This is terrible; instead, ResponseMatrix should have methods that rebin channels the normal way, and rebin energy ONLY using the methods allowed by the ftools (https://heasarc.gsfc.nasa.gov/docs/software/ftools/headas/ftrbnrmf.html)
Formally the software allows both channel and energy rebinning of the response to an arbitrary grid. This is terrible; instead, ResponseMatrix should have methods that rebin channels the normal way, and rebin energy ONLY using the methods allowed by the ftools (https://heasarc.gsfc.nasa.gov/docs/software/ftools/headas/ftrbnrmf.html)