Primary Mirror Replacement Project Documentation

Created: 08/02/10 by EF
Updated: 07/29/13 by EF

The FLWO 1.2m telescope is an essential tool for CfA scientists studying time variable phenomena including transiting exoplanets and supernovae despite the fact that the primary mirror has deteriorated seriously. About 30% of the primary's surface is visibly damaged to the naked eye, and much of the surface is revealed to be defective in optical tests. If we do nothing, the telescope will be unusable in a few years. We therefore proposed to replace the 1.2m primary with a newly cast and polished mirror made by the Steward Observatory Mirror Laboratory (SOML) from the same Ohara E6 borosilicate glass used for the MMT, Magellan, LBT, and GMT primary mirrors.

Even with the deteriorated optics, the 1.2m has been oversubscribed significantly. A properly functioning telescope will have much higher sensitivity due to better image quality, higher reflectivity, and considerably lower scattering. This increased sensitivity together with upcoming support for automated scheduling and observing will open attractive new opportunities.

Current Science: examples

Future Science

Replacement Plans


As of 09/29/11, the completion of the mirror had slipped to the end of December 2011, due to a failure in the polishing machine at COS. The machine is now repaired, tested and operational.
The mirror is now generated and ground to the "best fit sphere" as described here (pdf, 2.5MB).

As of January 2012, the completion of the mirror had been extended to May 2012. The causes of this delay are the inefficiency of the original setup and the personnel resources that were available. Currently, these have been increased and the process has been streamlined significantly so it is much more efficient. There is light at the end of the tunnel.
The latest report from SOML shows that the aspherizing is progressing well, as described here (pdf, 280KB).

As of April 2012, the completion of the mirror had been extended again, to June 2012.
The latest report from SOML shows that the aspherizing is complete and polishing has started, as described here (pdf, 917KB).

July 2013
After several delays from problems with the polishing equipment at COS, we have determined that the mirror is in full compliance with our requirements. The document that demonstrates compliance is here (pdf, 1.4MB).
The mirror is scheduled for aluminization at the "Sunnyside" UA facility in Tucson on 07/31/13. We will swap it in during the first week or so of the August 2013 shutdown.
Picture Gallery for the Project