ATST Site Impact Workshop August 11-12, 2005

1
ATST Site Impact WorkshopAugust 11-12, 2005

• M1 Assembly / Coating Plans
• Ron Price

2
M1 Assembly - Site Impact

• M1 Support System
• Science requirements define pointing within 10
  of horizon (zenith angle of 80)
• Haleakala site data indicates that some of the
  best seeing occurs during the early morning hours
  when the sun is at 70 - 80 zenith angle.
• M1 surface figure does not currently meet 32 nm
  rms surface figure requirements at these high
  zenith angles.
• M1 Thermal Control
• Haleakala has a significantly lower diurnal
  temperature excursion compared to other sites
  this makes the M1 thermal control somewhat
  easier.

3
M1 Orientation at 80 Zenith Angle
4
M1 Support System

• Current Status
• The baseline M1 support system does not meet the
  32 nm rms M1 optical surface performance
  requirements at the high zenith angles.
• Recent analysis completed by Dan Hofstadter shows
  that the M1 optical surface figure is around
  40-45 nm rms at 80 zenith angle with a 75mm
  thick substrate.

5
M1 Support System, cont.

• Future Plans
• Analysis and optimization is being continued by
  Myung Cho on the M1 lateral and axial support
  system to improve performance at high zenith
  angles.
• Lateral Support is being optimized to provide
  best possible optical surface figure at vertical
  position, with degradation likely at zenith
  pointing position.
• Will have horizon pointing acceptance test at M1
  Assembly vendor to verify performance.
• As M1 thermal control analysis continues, may
  consider going from 75mm back to 100mm thickness
  to improve optical surface figure at high zenith
  angles.

6
Coating Plans Site Impact

• Air Force is planning to construct a coating
  facility (AFMCF) that will be attached to the
  existing AEOS building
• Discussions between Air Force and ATST began in
  late 2004 both have similar requirements
• AEOS M1 3.67 meter
• ATST M1 4.24 meter
• Air Force wants to support ATST they are
  planning a 5 meter coating chamber to accommodate
  the ATST 4.24 meter M1 substrate

7
Coating Plans, cont.

• Detailed coating / M1 handling scenarios were
  developed by G. Poczulp (NOAO Coating Lab) to
  better define possible interface with AFMCF
• Two basic scenarios
• ATST M1 is transported to AFMCF and is
  stripped/cleaned/coated
• ATST M1 is stripped/cleaned at ATST facility and
  transported to AFMCF for coating
• On-going discussions with AF personnel.

8
Coating Plans-Future Activities

• AFMCF is not certain to be built AF is going
  through budget reviews and dealing with
  environmental issues
• ATST is maintaining a complete M1 coating
  facility in the baseline support and operations
  building
• ATST will maintain contact with AF personnel