Instrument Subsystem Status

Ca H&K Spectrometer

• Throughput requirement met by calculation

  • measurement deferred to on-sky

• Met all other requirements

• Trouble with trigger signal to start exposures has meant it has not been in regular use

• On-sky throughput measurement still TBD

  • requires testing of HK ADC within FIU

• Continued troubleshooting of trigger signal

• On-sky throughput tests

  • part of FIU HK-arm ADC alignment tests

Calibration Unit

• Could not fully test the Calibration Unit at SSL since compensator motors had very long lead and were not in-hand.

• Calibration Unit was set into a state that allowed use but was not the final configuration.

• New plan is to not use motors but purchase filters with higher wedge-angle tolerances. 

• This will make for a simpler system going forward (and one easier to maintain with 4 fewer motors involved and no look-up table to maintain)

• There have been issues with Photron lamps and power supplies:

  • Photron no longer makes Th-Ar lamps

  • One (of the four) KPF Photron power supplies failed (for no apparent reason)

• Going forward KPF will use Green Scientific lamps and power supplies

  • Initial Green Scientific lamp failed quickly, but the second one has lasted longer

Servicing mission items:

• install filters with higher wedge-angle tolerances

LFC

• LFC availability was sparse.  A combination of sub-optimal thermal variations in the high-bay (10’s of degrees F thermal variation over 12 hours) and incomplete software automation precluded extended operation of the LFC at SSL.

• Comb has been operational but there has been significant down-time due to Menlo hardware and software issues.

• Flux in blue orders (< 500 nm) is intermittent and the bluest orders (445-480 nm) is missing from nearly all spectra.

• Occasional help with installing hardware (i.e. PCF fiber modules)

• Monitoring LFC control software to maintain performance has proven to be time-intensive

Etalon

• Was not available for tests at SSL.

• Current etalon has been used regularly though the Doppler stability is not well tested over long periods because the other testing sources have had irregular availability during the past month or so. Initial results are promising on the < 1 day timescale.

• However etalon light source (SuperK) is failing or moving out of alignment

• Troubleshoot SuperK-to-etalon alignment (underway)

• Secure a replacement SuperK and a separate spare

• Assess Doppler stability of the etalon with comparison to the LFC

Cryostats/CCDs

• Fully passed majority of requirements

  • Some requirements were just missed but deemed OK.

• Fringing was significantly worse than requirement, plan was to correct in software

• Low-level illumination pattern on CCDs seen from ion pumps. This increases the effective dark current and limits faint-object performance.

• Some fixed-noise patterns on CCDs caused by insufficient grounding

• A new charge Transfer Efficiency (CTE) issue on one quadrant of Green CCD

• Fringing pattern still present

• Ion pump issue still present

• Grounding straps to be attached between Archon and vacuum chamber (underway)

• Change readout mode on Green CCD to avoid CTE issue

• Investigate ways to minimize fringing impact within DRP

• Hardware fix for ion pump issue during servicing mission

Environmental Control System

• Vacuum Chamber met requirements

• Thermal enclosure not designed/built

• Thermal enclosure to be installed later this year

• Temperatures in KPF Alley are more variable (~0.5 C) than expected based on pre-installation measurements.

Servicing mission items:

• Install thermal enclosure

• bring linear potentiometers online (these provide bench position feedback)

• bring gate valve position feedback online

Exposure Meter

• Throughput requirement met by calculation

  • measurement deferred to on-sky

• Met all other requirements

• In regular use

• Exposure termination based on signal-to-noise ratio feature not yet implemented.

• Develop software for signal-to-noise based exposure termination.

• Test using the Exposure Meter in an automated way to terminate an exposure at the correct signal-to-noise ratio.

• Determine on-sky throughput (and compare to main spectrometer)

Fiber Injection Unit

• Optical performance and alignment requirements met

• Centering stars on fibers is difficult to measure and likely not meeting the requirements

• ADC performance is difficult to measure precisely and is likely not meeting the requirements

• FVCs have been more challenging to use than expected

• Prisms within Science arm ADC appear to not be set correctly.

• Detailed discussion in https://keckobservatory.atlassian.net/wiki/spaces/KPF/pages/1537441840 and https://keckobservatory.atlassian.net/wiki/spaces/KPF/pages/1537671297

• Fiber centering and science ADC performance are not meeting spec.

• A path forward for resolving these issues needs to be identified. An external system for calibrating the ADC positions may be preferable to the on sky methods we have been using.

Optical Fibers

• All requirements met

• Backup Simultaneous Cal fiber was damaged during installation. There are no current plans to build a replacement.

Agitator

• Was not tested at SSL

• In regular use

• Quantify agitator performance via “agitator on” vs. “agitator off” test.

Instrument Control Software

• Nearly all dispatchers written (only exposure meter, LFC, and etalon TBC)

• Minimal alarms in place

• All dispatchers now operational

• “testall” script in regular use

• Alarm system fully functional with important alarms in place

• Archon has occasional trigger-signal issues

• Backup computer is installed at summit but not operational (needs OS installed)

• Potential need for help troubleshooting Archon trigger signal issue

• Installation of backup computer

• Add more alarms for various telemetry items

Observing GUI

• Sketches and plans but no code before PSR

• In regular use

• Two areas still need some effort:

  • tip/tilt control and status GUI

  • automated exposure meter control of exposures

• Full integration with Data Services Initiative (DSI) is still pending

Spectrometer

• Throughput requirement met by calculation

  • measurement deferred to on-sky

• Met all other requirements

• Fiber block in reformatter is slightly out of alignment

• Green channel focus is soft in one corner of CCD

• Flat field fiber system needs slight realignment

• Throughput matches model except at bluest end of full bandpass

  • could be a symptom of incorrect ADC correction

• Servicing mission items:

  • fiber block re-alignment

  • Green channel focus adjustment

  • flat field fiber re-alignment

SoCal

• Not included within PSR scope

• Fully funded and now part of the KPF system

• Installed at Keck and in regular use

• Some dispatcher details to finalize

• Continue working towards a more automated start-up and close-down

• Continue working towards a balance between time spent on daytime Cals and SoCal observing

LN2 Autofill System

• Original LN2 cart and LN2 transfer plumbing was complete

• Initial tests showed major heat losses within transfer plumbing and GN2 back-pressure issues which negatively impacted dewar fills, and introduced significant thermal transients in the spectrometer

• System was re-designed to correct these issues

• Autofill system now in regular use, and KPF dewars are filled from supply dewars located in K2 machinery room

• Need an automated, daily check that fills have completed successfully and sends out alerts if not.

• Swapping 180 liter supply dewars every other day represents unanticipated labor.

• Maintenance of LN2 plumbing (vac lines, solenoids)

• Potential need to purge KPF LN2 lines if ice accumulation issue has not been solved.