GeminiFocus October 2017 | Page 22

Figure 5 ( left ). How the shutter was immobilized . Simple , but effective .
Figure 6 ( right ). The Acquisition and Guidance unit , extracted from the heart of the telescope for maintenance .
The summit team ( led by Gemini North Mechanical Engineering Group , and supplemented with occasional help from the Science Operations Specialists group ) worked through their well-choreographed plan almost exactly to schedule . The weather largely cooperated , and after starting on July 10th , we were back on sky as planned on August 25th .
We expect work of this scale to produce some surprises , and one that came up late in the project was a 10- to 12-millimeter misalignment of the lower shutter . We ’ re still working to understand this . Until we ’ re certain , the lower shutter will be kept out of normal operations at night . Meanwhile , the upper shutter is working more smoothly than anyone can recall , and night-time operations are going well .
In parallel , we took advantage of the closed time to carry out essential maintenance on a wide variety of instruments and telescope systems . The work involved essentially all disciplines , from mechanical to instrumentation , and from electronics to software . We worked on all the following needs : maintenance of instrument optics , replacement of part of the mechanism for the Gemini Multi- Object Spectrograph on-instrument wavefront sensor , refurbishment of the Gemini Near-InfraRed Spectrometer cold heads and work on its filter wheel and focus mechanisms , and inspection of the helium hoses within the Cassegrain Rotator . We also carried out upgrades of various processors in the Enclosure Control System and made a lot of progress on our project to counter obsolescence in our real-time control systems .
Upgrading the Observatory Control Software
When it comes to observing ( and preparing for observing ), virtually everything Gemini and its users do relies on the Observatory Control Software ( OCS ) — most of which has been around for more than a decade and a half . The user software ( Observing Tool and Phase I Tool , referred to as OT and PIT , respectively ) are large Java packages that require users to download hundreds of megabytes per semester . New users find the organicallygrown OT over-complex and opaque . Even more youthful items , such as the PIT ( which was completely rewritten in 2012 ), have significant scope for improvement and better integration with other user tools , such as the integration time calculators .
At the business end , we store observation definitions in a very non-standard database , which does not scale well ; it also feeds a “ Sequence Executor ” ( which runs the telescope and instruments ) written in TCL / TK — now essentially a dead and unsupportable language .
October 2017 GeminiFocus