When observers want to use fast read mode, we should first make sure it is reasonable to use. First, fast read mode is not compatible with cadenced observing – an RV taken by KPF in fast read mode will have an arbitrary offset to and RV taken of the same star in normal read mode. Thus, fast read mode really only makes sense for observations which are complete within a single night (or small number of nights) such as astroseismology or RM measurements.

Split Nights: Fast and Normal

We need to develop a policy for split nights. Changing modes induces a thermal transient which affects subsequent RV measurements, so we should avoid this unless it is well motivated scientifically.

Procedures

If a night (or portion of a night) is fast read mode, we need to take the normal set of daily calibrations as normal (in normal read mode) to maintain our knowledge of the instrument. In addition to the normal calibrations we need to switch in to fast read mode and take a set of calibrations. This is probably best done after regular scheduled cals are finished (usually around 5:30pm HST) and before sunset. This can be a very narrow time window at some times of year.

To change modes use kpfSetReadModeFast or kpfSetReadModeNormal as appropriate.

Then run the cals using kpfRunCalOB -f /kroot/rel/default/data/obs/kpf/FastReadoutCals.yaml