MMTS Hectospec Archive of News and Status:

• October 28, 1998:

The Central Engineering MMTS web page has been launched.  A general description of the fiber positioner and spectrograph assemblies, as well as, an overview of the science objectives  is included.  Project status and news items will be periodically updated on this page.  An archive of old news items will also be accessible from here.

Where are we now?  (This will be a bit long-winded since this is our first update.)

The Hectospec fiber positioner subassemblies are coming together.  We've been assembling items for testing in pretty much the same sequence in which they were designed.  In general, the subassemblies will be put together in the MMT Instrumentation Lab at Porter Exchange where a functional test will be performed  prior to moving each subassembly to the lab at 160 Concorde Avenue for more detailed calibration and further testing.  Final assembly, integration, and test of the Hectospec fiber positioner assembly will occur at 160 Concorde Avenue.

• The prototype gripper assembly has been put together and tested with excellent results.  The primary concern with this design is the ability of the gripper to repeatably place a button on the focal surface from a lifted position at any orientation of the fiber positioner assembly.  We tested the assembly in our lab at 160 Concorde Ave in Cambridge and found that the gripper was able to hold position repeatability to less than 1 um (.00004").  Our error budget allows 5 um for this process.  These tests were performed using a centroiding algorithm with a backlit optical fiber and a CCD camera.
 
• The prototype two axis gimbal assembly has been put together and tested with excellent preliminary results.  Our design uses two Newport Corp. linear actuators which we are transferring from operation under a Newport Corp. controller to being able to run under the Hectospec motion control system (Delta Tau PMAC).  Testing under Newport Control exhibited motion repeatability at ~ 1 um.  This is in line with our overall assembly and alignment budget for all axes of 8 um.  Servo tuning of the actuators under PMAC control is under way.  Gimbal repeatability testing will continue after the actuators have been tuned satisfactorily.
 
• The prototype Z axis assembly has been put together mechanically and will be tested just as soon as the electrical cabling is complete - next week.
 
• The X-Y translation assemblies are in the final stages of fabrication.
 
• The fiber positioner support structure is in the final stages of fabrication at American Process Equipment Company -APEC (Hingham, MA).  The final machining of the lower support structure is complete and has passed our in plant inspection on 10/15/98 (Warren Martell and Ed Hertz).  The mounting flange support is expected to be through final machining late next week with an inspection to follow.  APEC will then complete the final assembly operations, machining of the fine flange guides, painting, and a final inspection prior to shipment of the complete support structure to SAO at the end of November.  The work is proceeding slowly, but the quality and the attention to detail has been excellent!
 
Once we receive the support structure at our lab at 160 Concorde, we will begin assembly of the X-Y translation assemblies to the support structure and the real fun will start.

The spectrograph assembly is also moving toward completion.  The major optical mounts except the CCD Dewar and Fiber Shoe assemblies have been fabricated and have gone through a preliminary fit check.  The filter changer assembly will be a spin-off of the design prepared for the Hectochelle spectrograph.  Completion of the configuration of the fiber run has taken precedence at this point in the design.  The Hectospec spectrograph will be assembled in the MMT Instrumentation Lab at Porter Exchange.
 

The assemblies required for test, handling, and storage are nearing completion.  We determined many months ago that we would require a fixture which simulated the MMT in terms of it's mounting stiffness and mounting geometry in order to adequately calibrate and test the Hectospec.  This Telescope Simulator took on a life of its own as we determined that it would be used for all of SAO's focal plane instruments planned for the converted MMT.  The simulator is complete and fully functional in our lab at 160 Concorde Avenue.  We also determined that we would need a handling and storage cart for the Hectospec and decided to combine these efforts into one assembly - the instrument cart.

• The Telescope Simulator was built in several parts.  The Gimbal Assembly, which maintains the 72" diameter bolt circle for mounting all focal plane instruments and a .001" mounting surface flatness was fabricated by Framingham Welding and Engineering Corporation (Framingham, MA).  The Test Stand Assembly and various spacers which allow instruments to be raised (or lowered) and to be manually rotated for ease of assembly and testing were fabricated by Prime Machine (Salt Lake City, UT).  All of the lead counterweights were fabricated by I. Broomfield & Son (Providence, RI).  D & S Manufacturing (Southwick, MA) fabricated the counterweight support posts.  We have, with the help of Harnum Industries (Wilmington, MA), who specialize in rigging services, assembled the Telescope Simulator in the lab at 160 Concorde Avenue.  It has been tested and operated and works as planned.
   
• The instrument cart has been fabricated at APEC (Hingham, MA) and final inspection has been successfully completed.  APEC continues to hold the cart because it will be used for final shipment of the fiber positioner support structure also being fabricated at this facility.