Manosque, 25 February 2003

University of Durham Astronomical Instrumentation GroupAstronomical Instrumentation Group

NGST IFU Prototype

Slit/Pupil Mirror Design

Manosque, 25 February 2003

University of Durham Astronomical Instrumentation GroupAstronomical Instrumentation Group

Original Design

• Both Pupil and Slit mirrors required raster grinding to produce freeform surfaces in monolithic substrate

• Full tolerance analysis and specification produced

Pupil Mirror

Slit Mirror

Manosque, 25 February 2003

University of Durham Astronomical Instrumentation GroupAstronomical Instrumentation Group

Interim Design

• IFU re-designed to eliminate need to use raster (freeform) grinding

• Compromise in output slit performance (each “slitlet” focuses in different position in focal plane)

• Considered easier by LFM to manufacture

Manosque, 25 February 2003

University of Durham Astronomical Instrumentation GroupAstronomical Instrumentation Group

Interim Design – Pupil Mirror

• Pupil Array Design– Zerodur Substrate– Monolithic

Construction– Toleranced– Full Specification

produced– Cost Estimate

~€12,000

Manosque, 25 February 2003

University of Durham Astronomical Instrumentation GroupAstronomical Instrumentation Group

Interim Design – Pupil Mirror

• Slit Design– Construction as for

pupil mirror– Fully Toleranced and

specification produced– Cost estimate

~€12,000

Manosque, 25 February 2003

University of Durham Astronomical Instrumentation GroupAstronomical Instrumentation Group

Issues With Manufacture

• Development of Raster Grinding of Zerodur still in early stages of development

• Proposed a “simplified” IFU design to use line contact method of grinding

• IFU re-designed to accommodate line contact method of manufacture (but…)

Manosque, 25 February 2003

University of Durham Astronomical Instrumentation GroupAstronomical Instrumentation Group

Issues Still Remaining• Steps between Pupil/Slit

facets will cause problems when grinding (unable to control quality/shape of surface close to step)

• Either:– Larger gaps between facets– Modified grinding wheel

(experimental)

Manosque, 25 February 2003

University of Durham Astronomical Instrumentation GroupAstronomical Instrumentation Group

Line Contact Grinding (Spherical)

Manosque, 25 February 2003

University of Durham Astronomical Instrumentation GroupAstronomical Instrumentation Group

Line Contact Grinding (Toroidal)

Manosque, 25 February 2003

University of Durham Astronomical Instrumentation GroupAstronomical Instrumentation Group

Raster Grinding

Manosque, 25 February 2003

University of Durham Astronomical Instrumentation GroupAstronomical Instrumentation Group

Grinding Setup (Line Contact)

Manosque, 25 February 2003

University of Durham Astronomical Instrumentation GroupAstronomical Instrumentation Group

Manosque, 25 February 2003

University of Durham Astronomical Instrumentation GroupAstronomical Instrumentation Group

Rougness Measurement (test Component)

Ra=10nm

Manosque, 25 February 2003

University of Durham Astronomical Instrumentation GroupAstronomical Instrumentation Group

Interferometry (test component)

• This should have a picture of the interferometry data however including it crashes my laptop

• Aperture 4mm x 6mm• Spherical – ROC = 66.2mm• PV : 0.174• rms : 0.023

Manosque, 25 February 2003

University of Durham Astronomical Instrumentation GroupAstronomical Instrumentation Group

Next Stages (Zerodur Optics)

• Produce spherical “proof of concept” monolithic mirror

• Toroid production tests• Tackle issue of stepped facets• Produce line contact ground

components• Develop raster grinding techniques

Manosque, 25 February 2003

University of Durham Astronomical Instrumentation GroupAstronomical Instrumentation Group

Timescale For Development

• To develop repeatable/reliable process for production of monolithic components in Zerodur (line contact method with steps between facets)

– not possible before August 03• This gives a problem with IFU

schedule

Manosque, 25 February 2003

University of Durham Astronomical Instrumentation GroupAstronomical Instrumentation Group

Proposal

• Develop IFU system with replacement metal (Aluminium) Pupil and Slit arrays

• Perform all warm/vibration tests with metal components – replace with Zerodur when techniques fully developed

• Durham shall provide metal components (already have much experience with GNIRS IFU)

• Pursue Zerodur components in parallel

Manosque, 25 February 2003

University of Durham Astronomical Instrumentation GroupAstronomical Instrumentation Group

GNIRS IFU Slit Mirror

Manosque, 25 February 2003

University of Durham Astronomical Instrumentation GroupAstronomical Instrumentation Group