HST/WFC3 ramp effect model based on charge trapping. Journal reference: Zhou et al. (2017)
The first three input parameters are the intrinsic count rate (in e/s)
time series, the time stamps of the exposures, and the exposure time (in seconds). For calculating
ramps for a group of pixels, crates should be the average count rates
of the pixels in the group. The next four parameters are the ones that need to be
optimized. trap_pop_s and trap_pop_f are the initial numbers of occupied
traps and dTrap_s and dTrap_f are charges trapped during the gaps between
orbits. trap_pop_s/trap_pop_f normally ranges from 0 to 100. dTrap_s
and dTrap_f are often close to 0 and normally less than 50. It will
return the count time sieries (in e) with ramp applied. You may also
check the doc-string for additional information.