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.

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: Starting in November of 2024, additional pattern noise has been present on the detectors. We have been working on eliminating the spurious nose, but we have been unable to completely remove it. As of late-April 2025 the read noise in the various amplifiers is between 12 and 13.5 electrons.
  • Detector Cooling Systems: Both detectors are now cooled with closed cycle refrigerators (CCRs). The green side CCR has some lingering problems and has very little overhead on maintaining temperature, but it is holding the detector at target temperature and the control system is maintaining better than the goal of 1 mK stability. Red side is performing well.
  • 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 detect this, 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. The occurrence rate is such that around one in every 180 exposures is affected by one of the two detectors experiencing this error.
  • Tip Tilt Corrections: The tip tilt axis are currently correcting as expected.
  • Ca H&K Detector: The CA H&K detector is operational.
  • Double Star Observations: Operational.
  • Etalon: Operational but with reduced flux which is imbalanced between red and green.
  • LFC: Operating normally.
  • Simultaneous Calibration (SimulCal): Simultaneous calibrations are supported.
  • Exposure Meter Terminated Exposures: The control system supports exposure meter terminated exposures, 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 available.
  • 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.