Leave a Comment Realuminization of the MMT’s primary mirror has been deferred until summer 2016. Two factors guiding this decision were the state of the current coating and the status of a full-scale aluminizing test chamber being assembled at FLWO basecamp. Read more.
Recent measurements of the current aluminum coating show that it has only dropped in reflectivity by less than 1.5% since 2010. This is less than the 3.0% drop that is generally used as the criterion for recoating. The MMTO’s cleaning schedule likely helped maintain the high reflectivity. A blemished region of the coating that was contaminated with Mylar fumes during the 2010 shot remains, but reflectivity in that region has continued to improve considerably with every contact wash.
A full-scale test of the MMT’s aluminization process is necessary because of several changes made since the 2010 coating. Although the test chamber is coming along nicely, it would not be ready for a full-scale test before the scheduled shutdown this summer.
Given the state of the current coating and the status of the test chamber, the safest and most prudent decision was to wait one more year before recoating.