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 25A to perform several upgrades. This will involve warm up of the detectors. The work is expected to be completed during the Keck I pier repair shutdown in March and April, so no additional off sky time will be needed.

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.

  • Detector Noise: After servicing mission 2 in November of 2024, additional pattern noise has been present on the detectors. This severaly increases the effective read noise of the system and damages sensitivity. The noise is 4-5 times the nominal value. This is expected to be addressed during servicing mission 3 in March of 2025.
  • Detector Cooling Systems: The CCR currently cooling the green detector has been unstable resulting in the occasional temperature transient. These transients vary in magnitude from a few mK to 10s of K. This is expected to be addressed during servicing mission 3 in March of 2025. The red side is unaffected.
  • Detector Errors: 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.
  • Tip Tilt Corrections: The tip tilt stage X-axis has degraded once again (as of 2024 Aug 22) and we are not making fast tip tilt corrections in X. Troubleshooting is underway.
  • Ca H&K Detector: The CA H&K detector is operational.
  • Double Star Observations: Operational.
  • Etalon: Operational and providing the expected flux.
  • LFC: Is operating normally.
  • Simultaneous Calibration (SimulCal): Simultaneous calibrations are supported. Observers have the option of manually specifying the ND filters to balance the calibration flux or using the AutoNDFilters option in the OB to have an algorithm set the filters based on the KPF ETC, the target parameters in the OB, and a reference calibration brightness value. See the Nighttime Calibrations page for more info.
  • Exposure Meter Terminated Exposures: The control system supports exposure meter terminated exposures (ExpMeterMode: control in the OB), however we are still documenting 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.