Instrument Status

KPF has been commissioned on sky, and is available for use. Many aspects of the instrument are still being optimized and the long term stability is still under evaluation. Short term stability looks excellent (exceeding the 50 cm/s target spec within a night) and we expect measures of the long term RV precision to become available as the DRP evolves.

A detailed summary of the instrument status was presented at the September 2023 Keck Science Meeting. The slides from that presentation are available in PDF format.

Important Notice: KPF will have a lengthy “servicing mission” during 24B to perform several upgrades. This will involve warm up of the optical bench. The expected timeline is to do this in November 2024. Details are still being worked out.

Subsystem Status

This is an attempt to summarize the status of various sub-systems of the instrument. Each sub-system name is color coded to indicate the status at a glance: green means functioning normally, orange means mostly normal, but with some caveats or minor issues, and red means the sub-system is compromised in some way.

  • Tip Tilt Corrections: The tip tilt stage was replaced in early June 2024 and is now working as expected.
  • Ca H&K Detector: Currently non-functional.
  • Double Star Observations: Recent modifications to the tip tilt system should enable double star observations. There is still learning curve as we figure out how to optimize source detection though, so be patient with the OAs while trying to do this. Remember that this is not the same as the MAGIQ guiding system, so your intuition there does not transfer to KPF.
  • Etalon: The etalon flux problem was fixed during the servicing mission in Feb 2024 and it is now provided the expected flux levels. We have not yet worked out an algorithm for recommending ND filter settings for a given observation to balance SimulCal five flux with science fiber flux, but the mode is available. We are still recommending that slew cals should be taken every hour.
  • LFC: Is operating normally. Standard exposure parameters are now ExpTime: 60, CalND1: OD 2.0, and CalND2: OD 0.1.
  • Detector Systems: The red and green detectors suffer from occasional “start state errors” in which the affected detector remains in the start phase and does not produce a useful exposure. The observing scripts now detect this occurrence, abort the current exposure (with read out) and start a fresh exposure on both cameras. No action is necessary on the part of the observer. This costs about a minute of time for this to happen, but the resulting data should be normal (unless another error occurs). The occurrence rate for these problems is 0.34% on the green detector and 0.22% on the red, so around one in every 180 exposures is affected by one of the two detectors experiencing this error.
  • Exposure Meter Terminated Exposures: The control system supports exposure meter terminated exposures (ExpMeterMode: control in the OB), however we are still verifying performance on sky.
  • Nod to Sky Observations: For observations which need a sky measurement other than the built in sky fibers, nodding away to a sky position can be accomplished manually by running separate OBs for the target and sky and asking the OA to offset the telescope as appropriate. We plan to build a separate Nod To Sky observing mode which will accomplish this within a single OB, but that is not yet ready.
  • Off Target Guiding: Not yet commissioned. Currently, the tip tilt system must be able to detect the science target in order to position it on the fiber.