sci23021 — Announcement

Gemini Mirror Status: 31 March 2023

April 18, 2023

Update 31 March 2023

We are happy to report that the Gemini North primary mirror repair team has reached another important milestone. On Friday 24 March the team attached a new lateral support attachment pad on the primary mirror, replacing the one removed by REOSC a few weeks ago. We are closely monitoring the temperature and position of the attachment pad while the epoxy cures over the next 8 days.

The team has been preparing for this step for the last several weeks, including dress rehearsals of attaching the pad in the correct location within tolerance, additional simulations and tests for maintaining the correct temperature of the glass and metal, and preparation of witness samples.

This week the team is conducting an internal readiness review for the primary mirror stripping, coating, and reinstallation. This work is planned to begin on 17 April. Our current schedule has our return to science operations in mid-May. 

Continuing updates will be posted on both the NOIRLab and Gemini websites.

Update 16 March 2023

An update from the Gemini Observatory Director, Jen Lotz, on the status of the Gemini North primary mirror.

I am very pleased to report that the glass surrounding the chipped region of the Gemini North primary mirror is now repaired! Despite challenging weather conditions on Maunakea, Safran-REOSC was able to finish the grinding and polishing of the damaged regions of the primary mirror.

The REOSC team members have performed their final birefringence tests, which help determine the optical properties of the material, and confirmed that the stress has been released. The Gemini/NOIRLab team has performed the initial inspections of their work and is very happy with the results.

We still need to re-attach the replacement lateral pad, complete the mirror coating, reassemble the telescope, and perform a series of checkouts before returning to nighttime operations. 

Continuing updates will be posted on both the NOIRLab and Gemini websites. 

Update 27 February 2023

The Safran–REOSC team will arrive in Hilo this week and start the on-site repair work for the Gemini-North primary mirror. We anticipate that the repairs, re-attachment of the lateral pad, and additional reviews will take around 4 weeks. Once the repairs are determined to be successful, we will complete the M1 stripping, coating, and reassembly of the telescope. This is planned to take another approximately 4 weeks. Our current schedule has the return of Gemini North to science operations by the end of April.

Update 25 January 2023:

The Observatory now has a signed agreement in place with Safran-REOSC for the preparatory work, glass repair, and lateral-pad removal for the primary mirror at Gemini North and Safran-REOSC has begun their preparatory work. Our current schedule has the return to science operations in late March/early April barring unforeseen delays, consistent with our previous update. 

Further updates will be posted at both the NOIRLab and Gemini websites. 

Update 22 December 2022:

The NOIRLab Gemini North recovery team has made significant progress with preparations for repair work on the primary mirror. The Gemini North Primary Mirror Independent Review Board met on 12 December and endorsed the new Gemini mirror handling procedures, which is a key milestone for the return to science operations. The repair plan includes: a series of preparatory tests, safety procedures, and environmental control during the repairs; removal of the lateral pad next to the damaged area; glass repair work; replacement of the lateral actuator pad; and post-repair assessment and tests.

An updated estimate of when Gemini North will return to night-time science operations is the end of March or early April 2023. Given this updated schedule, the Observatory is planning to delay the Gemini South telescope shutdown and primary mirror coating, originally planned for April 2023, to ensure that at least one Gemini telescope is available to the community, particularly during the next potential LIGO run.

We remain confident that Gemini North will recover fully from this incident and look forward to observations with a newly coated mirror in the near future. 

Further updates will be posted at both the NOIRLab and Gemini websites. 

Update 1 December 2022:

The Observatory has progressed significantly on the plan to repair the Gemini North primary mirror and return to night-time operations. More thorough inspections of the mirror have not found any additional damage, and confirm that the damage is limited to a small area on the outer edge of the mirror. We anticipate repairs to be completed in January and a return to night-time operations sometime in February, barring unforeseen delays due to weather or other factors. Further updates will be posted here

Original Announcement:

On Thursday 20 October 2022 the 8.1-meter primary mirror of the Gemini North telescope, part of the International Gemini Observatory and operated by NSF’s NOIRLab, suffered damage to two areas of its outer edge in a section that is outside the area collecting light for observations. There were no injuries associated with this event. 

While moving the primary mirror in preparation for stripping its reflective protected silver coating, it contacted an earthquake restraint on the facility’s wash cart, chipping the edge. A stop-work order was issued immediately and a thorough investigation by NOIRLab, Gemini, and external experts has begun to determine what happened and what is needed to repair the mirror. 

A comprehensive lessons-learned report will also be prepared to prevent similar events in the future. An Independent Review Board, chaired by Jim Oschmann, will review and approve the results of the investigation.

This process will proceed at a deliberate and careful pace; our primary concern is the safety of our staff. The timescale for Gemini North’s return to operations will be determined by the findings of the investigation and the repair plans. 

We will provide further updates as they become available. 

More information 

NSF’s NOIRLab(National Optical-Infrared Astronomy Research Laboratory), the US center for ground-based optical-infrared astronomy, operates the International Gemini Observatory(a facility of NSFNRC–CanadaANID–ChileMCTIC–BrazilMINCyT–Argentina, and KASI–Republic of Korea), Kitt Peak National Observatory (KPNO), Cerro Tololo Inter-American Observatory (CTIO), the Community Science and Data Center (CSDC), and Vera C. Rubin Observatory(operated in cooperation with the Department of Energy’s SLACNational Accelerator Laboratory). It is managed by the Association of Universities for Research in Astronomy (AURA) under a cooperative agreement with NSF and is headquartered in Tucson, Arizona. The astronomical community is honored to have the opportunity to conduct astronomical research on Iolkam Du’ag (Kitt Peak) in Arizona, on Maunakea in Hawai‘i, and on Cerro Tololo and Cerro Pachón in Chile. We recognize and acknowledge the very significant cultural role and reverence that these sites have to the Tohono O'odham Nation, to the Native Hawaiian community, and to the local communities in Chile, respectively.



Jennifer Lotz
Director, Gemini Observatory

Charles Blue
Public Information Officer
T: +1 202 236 6324


About the Announcement



Gemini North telescope - side view

International Gemini Observatory/NSF’s NOIRLab/AURA/J. Pollard