In both grating and Fabry-Perot modes, scans are carried out at one of two standard
lengths of detector integration ramp, 0.25 s and 0.5 s. The total integration time per
spectral point is then achieved by varying the number of these ramps. It was
originally intended that spectra be scanned by carrying out a number of integrations at
each setting of the grating or Fabry-Perot until the total required integration time had
been built up. In order to minimise the low-frequency end of 
noise, however, a
fast-scanning mode was also implemented, in which only one integration was
performed at each position of the grating or Fabry-Perot, the total integration time
being built up by repeatedly scanning. This method is now recommended for all
observations because it avoids successive integration ramps being affected by the
same particle hit.