W. M. Keck Observatory | Go Astronomy

Keck pairs two 10-meter telescopes on Maunakea, each with a mirror of 36 hexagonal segments

The W. M. Keck Observatory runs two optical and infrared telescopes, Keck I and Keck II, near the summit of Maunakea on Hawaii Island. Each primary mirror is 10 m across and made of 36 hexagonal segments. The instruments now in service are MOSFIRE, DEIMOS, HIRES, KCWI, LRIS, NIRC2, NIRES, NIRSPEC, OSIRIS, ESI and the Keck Planet Finder (KPF).

Results announced in 2026 include the youngest exoplanet yet found in Keck data (16 September), the host galaxy of the most distant fast radio burst (8 October) and a third galaxy without dark matter (16 June).

The California Association for Research in Astronomy (CARA), a 501(c)(3) nonprofit, operates Keck for its partners Caltech, the University of California and NASA, which joined in October 1996; the University of Hawaii also allocates time. Howard B. Keck of the W. M. Keck Foundation gave $70 million in 1985 for Keck I, and private construction grants totaled more than $140 million. Keck I saw first light on 24 November 1990 with nine of its 36 segments and began science in May 1993; Keck II followed in October 1996. The Keck Interferometer combined the two telescopes on an 85 m baseline until it was discontinued in mid-2012.

The telescopes stand at 4,145 m (13,600 ft) among the Maunakea Observatories, beside Subaru and Gemini North. Hurricane Lala passed south of Hawaii Island in mid-August 2026; Keck found no significant damage to the telescopes, but its liquid-nitrogen-cooled instruments warmed up, HIRES for the first time in more than two decades, and the Center for Maunakea Stewardship cleared trees and two mudslides to reopen emergency access. See the W. M. Keck Observatory listing, the largest optical telescopes and more observatories in Hawaii.

Each Keck segment is 1.8 meters of Zerodur, held in place to 4 nanometers

Each segment is 1.8 m across, 7.5 cm (3 in) thick and weighs about 880 lb (0.4 metric tons), cut from Zerodur glass-ceramic. Schott made the blanks. Itek Optical Systems was fabricating segments by 1988, and Tinsley Laboratories polished Keck segments by stressed mirror polishing, the method Jerry Nelson developed: the blank is bent opposite to its final off-axis shape, polished to a simple sphere, then released so it springs into the right asphere. The telescope has a focal length of 17.5 m on an altazimuth mount, with about 270 metric tons of steel and more than 300 metric tons in each telescope.

The Active Control System keeps the 36 segments acting as one mirror. Capacitive edge sensors read at 100 Hz, actuators move in steps of 4.18 nm at 2 Hz, and the surface holds to 4 nm. A Shack-Hartmann Phasing Camera System checks alignment after segment exchanges and about once a month. The makers of the edge sensors and actuators are not publicly named.

Segments rotate out every other month for a fresh aluminum coat

Keck technicians exchange segments every other month and recoat them in-house, laying about 120 nm of aluminum in a 10 ft vacuum chamber; a new coat is about 17% more reflective. The maker of the chamber is not publicly named. After about 20 years of thermal cycling, cracks appeared near the support points, where Invar fittings are bonded to the Zerodur, and a repair project covers all 84 segments in the fleet, spares included. Simpson Gumpertz & Heger ran the finite element analysis of the repaired supports.

Component	Supplier	Country	Role	Status	Note
Primary mirror segment blanks, Zerodur glass-ceramic	Schott	Germany	Manufacturer	In service	Blanks delivered on schedule per 1988 status paper
Primary mirror segment fabrication	Itek Optical Systems	US	Manufacturer	In service	Lexington MA facility per Wikipedia
Mirror segments by stressed mirror polishing	Tinsley Laboratories	US	Manufacturer	In service	Source does not say how many segments or when
Finite element analysis of repaired segment supports	Simpson Gumpertz & Heger (SGH)	US	Designer	Delivered	Analysis of whiffletree and radial supports; repair vendor not named
KPF Zerodur bench CTE measurement and echelle/camera mount machining	Schott	Germany	Manufacturer	In service	-

Lasers make artificial guide stars so adaptive optics can sharpen Keck's images

Adaptive optics (AO) measures how the atmosphere blurs a star and reshapes a deformable mirror hundreds of times a second to undo it. A laser tuned to sodium lights a guide star in the upper atmosphere wherever astronomers need one. Keck II has used laser guide star AO for science since 2004, first with a 15 W dye laser; in December 2015 a TOPTICA laser with a Raman fiber amplifier from MPB Communications (MPBC) replaced it.

KAPA turns one laser into four guide stars on Keck I

The Keck All-sky Precision Adaptive optics (KAPA) project, funded by NSF Mid-Scale Innovations award AST-1836016, put a 20 W TOPTICA Raman-fiber amplifier laser on the Keck I elevation ring, replacing a Nasmyth-mounted laser from Lockheed Martin Coherent Technologies, and split it into four guide stars for laser tomography. Sources give the asterism radius as 6.35 arcseconds (KAPA design page) and 7.6 arcseconds (2024 SPIE paper). KAPA saw first light on 4 December 2025 with about a 20% gain in K-band Strehl ratio over a single laser, entered science verification on 31 January 2026 and finished commissioning on 10 May 2026, though it is not yet supported for routine nights. It includes a facility that reconstructs the point spread function from AO telemetry.

HAKA gives Keck II a mirror of 2,844 actuators

The HAKA upgrade swaps Keck II's 349-actuator Xinetics deformable mirror for a 2,844-actuator mirror from ALPAO, and its Shack-Hartmann wavefront sensor goes from 20 x 20 to 60 x 60 subapertures. Work began on 2 February 2026 with a 16-week shutdown of Keck II AO; the loops first closed on 28 March 2026, reaching a K-band Strehl ratio above 55% in 0.65-arcsecond seeing, with science set to resume on 23 May 2026. A 2024 SPIE paper gave ALPAO delivery as December 2024 in its text and 2026 or 2027 in its schedule table; installation came in February 2026.

A GPU controller replaced the FPGA brains of both AO systems

Microgate led a new real-time controller with Swinburne University of Technology and the Australian National University, moving from the FPGA controller in use since 2007 to GPUs. It saw first light in 2021 and was released for science on Keck I in late 2023 and Keck II in early 2024. Its wavefront sensors use OCAM2K EMCCD cameras from First Light Imaging.

Component	Supplier	Country	Role	Status	Note
Keck II laser guide star laser	TOPTICA Photonics	Germany	Manufacturer	In service	Named as TOPTICA/MPBC; replaced 15 W dye laser Dec 2015
Keck II laser guide star laser Raman fiber amplifier	MPB Communications (MPBC)	Canada	Manufacturer	In service	Named as TOPTICA/MPBC
KAPA 20 W Raman-fiber amplifier laser on Keck I elevation ring	TOPTICA Photonics	Germany	Manufacturer	In service	Split into four guide stars; KAPA verification done May 2026
Former Keck I sum-frequency guide star laser	Lockheed Martin Coherent Technologies	US	Manufacturer	Delivered	Nasmyth-mounted; replaced by TOPTICA laser for KAPA
KAPA asterism generator behind the secondary	OMP	Not stated by source	Manufacturer	In service	Company full name not given
GPU-based AO real-time controller, both telescopes	Microgate	Italy	Integrator	In service	Consortium lead; first light 2021
Real-time controller computation engine	Swinburne University of Technology	Australia	Designer	In service	Microgate consortium member
Real-time controller development	Australian National University	Australia	Designer	In service	Microgate consortium member
KAPA four-laser infrastructure contract	Microgate	Italy	Integrator	Delivered	Not yet fully supported for routine nights as of May 2026
Original Keck II 349-actuator deformable mirror	Xinetics	US	Manufacturer	Delivered	Replaced by HAKA in 2026
HAKA 2844-actuator deformable mirror for Keck II	ALPAO	France	Manufacturer	In service	Loops first closed 28 Mar 2026
Keck II MEMS deformable mirror	Boston Micromachines	US	Manufacturer	In service	Source names it as Boston MEMS DM

The Keck Planet Finder aims to measure stellar wobbles below 30 centimeters a second

The Keck Planet Finder, designed and built at the UC Berkeley Space Sciences Laboratory, finds planets by the radial velocity (RV) wobble they cause in their stars, with a goal below 30 cm/s. It was installed in late 2022 and commissioned in early 2023. Its parts come from across the industry: STA4850 CCDs and Archon controllers from Semiconductor Technology Associates (STA), cameras from Winlight Systems, Zerodur bench work by Schott, a 31.6 grooves/mm echelle master from Richardson Gratings, a laser frequency comb from Menlo Systems with 20 GHz repetition, and isolators from Minus K Technology. In 2026 the green detector read noise was about 10 electrons and the red about 4.3.

KPF has been offline since early April 2026, when a vacuum turbo pump failed catastrophically and put dust and debris on all its optics. A Failure Review Board is at work; no return date is set, and Keck expects several months.

KCRM and HISPEC extend Keck's spectroscopy to the red and the infrared

KCRM, the red arm of the Keck Cosmic Web Imager built at Caltech, covers 560 to 1,080 nm and saw first light on 4 June 2023 on the Turtle Nebula (NGC 6210); NSF, the Mt. Cuba Astronomical Foundation and an anonymous donor funded it. HISPEC, from the Caltech Exoplanet Technology Lab, is a diffraction-limited fiber-fed spectrograph for Keck II behind HAKA, covering 0.98 to 2.46 microns at a resolution of about 100,000, with a twin, MODHIS, planned for the Thirty Meter Telescope. Its first light was slated for 2026, but as of November 2026 Caltech still lists it as being built and no first light has been announced.

Component	Supplier	Country	Role	Status	Note
ORKID opto-mechanics	OMP	Not stated by source	Manufacturer	In service	Company full name not given
Keck Planet Finder design and build	UC Berkeley Space Sciences Laboratory	US	Integrator	In service	Built with Caltech; offline since April 2026 turbo pump failure
KPF camera optics, opto-mechanics and reformatter	Winlight Systems	France	Manufacturer	In service	Fabricated, assembled and aligned both cameras
KPF echelle grating master, 31.6 grooves/mm	Richardson Gratings	US	Manufacturer	In service	Source names Richardson
KPF reformatter fiber block	Femtoprint	Switzerland	Manufacturer	In service	-
KPF laser frequency comb	Menlo Systems	Germany	Manufacturer	In service	20 GHz repetition rate; bought as a black-box system
KPF solar calibrator mount with sun sensor	EKO Instruments	Japan	Manufacturer	In service	STR-22G
KPF Fabry-Perot etalon	Macquarie University	Australia	Designer	In service	-
KPF telescope fiber wrap section	igus	Germany	Manufacturer	In service	Triflex TRL-40
KCRM red arm of the Keck Cosmic Web Imager	Caltech	US	Integrator	In service	With Keck and UCO/Lick engineering; first light 4 June 2023
HISPEC fiber-fed infrared spectrograph for Keck II	Caltech Exoplanet Technology Lab	US	Designer	In production	First light slated for 2026 per Caltech; still "being built", no first light announced as of Nov 2026
OCAM2K EMCCD wavefront sensor cameras	First Light Imaging	France	Manufacturer	In service	Replaced SciMeasure cameras
ORKID CMOS camera	Andor	UK	Manufacturer	In service	ORKID operating from 2023
KPF STA4850 science CCDs	Semiconductor Technology Associates (STA)	US	Manufacturer	In service	Green read noise about 10 e- in late 2025
KPF Archon CCD controllers	Semiconductor Technology Associates (STA)	US	Manufacturer	In service	Lakeshore named only as possible future heater control
KPF CM-1 vacuum-compatible bench isolators	Minus K Technology	US	Manufacturer	In service	Source names Minus K
KPF solar calibrator weatherproof enclosure	Fornax Mounts	Hungary	Manufacturer	In service	-

Observers run Keck from Waimea while four pipelines deliver science data overnight

All Keck observing is remote, from rooms in the Kohala Wing at the headquarters in Waimea (Kamuela) or from approved sites on the mainland; observers no longer work at the summit, where an observing assistant runs the telescope. Under the Data Services Initiative, four pipelines (KCWI, MOSFIRE, DEIMOS and KPF) deliver science-grade data to the Keck Observatory Archive (KOA) in near real time during the night.

Since February 2026 NIRC2 has used "Fast and Furious" focal-plane image sharpening, a gain of about 10% in relative K-band Strehl ratio. No production use of AI or machine learning at Keck is confirmed in the sources found.

Keck's lease on Maunakea expires in 2033, and a new state authority takes over the summit on 1 December 2029

The University of Hawaii has held the master lease for the Maunakea summit since 1968, and the current telescope leases expire in 2033. If the Maunakea Stewardship and Oversight Authority (MKSOA) does not extend or renew them, the observatories must be decommissioned and the land restored. No new lease had been issued as of February 2026, and uncertainty over long-term leases was linked to the cancellation of the $500 million replacement for the Canada-France-Hawaii Telescope.

HB 2592 (Act 53), signed by Governor Josh Green on 27 May 2026, moved the transfer of all University of Hawaii rights and duties to MKSOA from 2028 to 1 December 2029. The authority must adopt a management plan before 30 June 2028 and have it operating by 1 December 2029; if it misses those deadlines, management reverts to the university. The law lets MKSOA extend existing leases before the transfer, but its board chair said there are no current plans to do so.

On 5 November 2026 a University of Hawaii Regents committee voted unanimously for plan amendments that would allow decommissioned observatory sites to be reused; the full Board has not yet voted. The university's 2022 master plan named five sites for decommissioning.

Visitors can watch Keck I from a summit gallery, but the road to it has strict rules

The Summit Visitor Gallery is open daily from 10 am to 2:30 pm, with a view of Keck I and two restrooms; no tours or bookings are listed. The headquarters at 65-1120 Mamalahoa Hwy in Waimea (Kamuela) holds public events such as "Shadow the Scientists" evenings.

Maunakea rules apply to every summit trip. Stop for 30 minutes at the Visitor Information Station at 9,200 ft to acclimatize; a four-wheel-drive vehicle is required above it. Children under 13, pregnant visitors and people with heart or respiratory conditions should not go higher. The summit is open from 30 minutes before sunrise to 30 minutes after sunset, and stargazing is allowed only below Park 2.