Group f is from 2019-08-23 to the end of 2020, when APOLLO observations
were transferred away from UC San Diego.  Group f is marked by the
installation of a new detector (30 micron elements) that performs better
and therefore takes more advantage of the Absolute Calibration System
(ACS).  This group should be appended to the latest versions of groups a,
b, c, d, and e.