A STEP 400 Technical development status

Transcription

1 A STEP 400 Technical development status ARENA workshop, Catania, 17 sept 08 Authors: J.B. Daban (1), C. Gouvret (1), A. Agabi (1), T. Guillot (2), F. Fressin (2), L. Abe (1), N. Crouzet (2), Y. Fanteï-Caujolle (1), S. Peron (1), S. Ottogalli (1), J.P. Rivet (2), F.X. Schmider (1), F. Valbousquet (6), P.E. Blanc (3), M. Dugué (1), A. Roussel (1), P. Assus (1), Y. Bresson (1), A. Blazit (1), E. Bondoux (1), Z. Chatilla (1), A. Le Van Suu (3), M. Merzougui (3), E. Fossat (1), H. Rauer (4), A. Erikson (4), F. Pont (5), S. Aigrain (5), N. Tothill (5). Affiliation: (1) Laboratoire FIZEAU, UNS/OCA, Nice - France (2) Laboratoire CASSIOPEE, UNS/OCA, Nice - France (3) Observatoire de Haute-Provence, France (4) Deutsches zentrum für Luft und Raumfahrt, Germany (5) Exeter Observatory, Exeter, United Kingdom (6) Optique et Vision, Antibes, France

2 Outline: Project partners Tech Specs Optical design Mechanical design Focal Box thermal issues Mount and Dome Schedule

3 A STEP is supported by: A STEP consortium:

4 Main Tech Specs (1) FoV: 1 x 1, and scale: ~ 1 arcsec / pixel Science spectral band: nm. PSF size and shape: size: 2 pix < FWHM < 3 pix all over the FoV. aspect: ~ Gaussian, no sharpen edges, no central hole. energy spread: 97.7% of the energy inside a 3 on-axis FWHM diameter circle. 35 to 90% of the energy inside a 1 on-axis FWHM diameter circle. Energy in 1 pixel around the PSF peak must be between 4% and 50% of the total PSF energy.

5 Main Tech Specs (2) PSF uniformity over the FoV: Variation of the PSF energy inside a 3 on-axis FWHM diameter circle must be < 1.3%. Variation of the PSF energy inside a 1 on-axis FWHM diameter circle must be < 70%. Flux stability: Flux variation in a 3 on-axis FWHM diameter circle should be less than 0.1% for one hour. Image position stability: goal 0.2 pix, maximum 2 pix for 2 hours. Duty cycle: 90% of clear sky time, minimum 75%. Temperature: operating range: -40 C to -80 C variation speed: up to 20 C / day

6 Optical design (1) Newtonian 40cm, F/D 4.6, 42% central obscuration Focal Box including: double window, M3 dichroïc plate, corrector, science detector, M4 mirror, guiding detector. Science CCD: 4Kx4K pixels (36x36mm) at 0.2mm behind focus M2 Double window M1 M3 Corrector Science CCD Focal Box M4 Guiding CCD Designed by C. Gouvret

7 Optical design (2) PSF uniformity over the FOV irradiance relative 1 0,9 0,8 0,7 0,6 0,5 0,4 0,3 0,2 Instrument Coupes PSF de profiles PSF dans (w/o le champ seeing) 0 x x x x x0.5 0, position X (µm) C. Gouvret

8 Optical design (3) Mirrors coating: Al vs Ag Voie science Science path Voie guidage Guiding path flux sortant / flux incident 0,7 0,6 0,5 0,4 0,3 0,2 0,1 Ag Al flux sortant/flux incident 0,7 Aluminium protégé 0,6 Melles Argent protégé 0,5 SESO 0,4 Argent protégé OCA 0,3 Al(180) protégé OCA 0,2 Al(210) protégé OCA 0,1 Aluminium protégé Melles Argent protégé SESO Argent protégé OCA Al(180) protégé OCA Al(210) protégé OCA wavelength longueur d'onde (nm) wavelength longueur d'onde (nm) C. Gouvret

9 Optical design (4) Some positioning specifications Sub-assemblies M1 lateral position (XY) M2 position (XYZ) Focal box alignment (at the entrance window) (XY) Focal box focus (at the entrance window) (Z) Optics in focal box Double window alignment (XY) Double window focus (Z) M3 position (XYZ) Corrector position (XYZ) Accuracy: +/- 0.5mm Accuracy: +/- 0,25mm Accuracy: +/- 0.5mm Accuracy: +/- 0.1mm Accuracy: +/- 0.1mm Accuracy: +/- 0.1mm Accuracy: +/- 0.25mm Accuracy: +/- 0.25mm Stability: +/- 0.05mm Stability: +/- 0.05mm Stability: +/- 0.05mm Stability: +/- 0.1mm Stability: +/- 0.01mm Stability: +/- 0.01mm Stability: +/- 0.01mm Stability: +/- 0.01mm

10 Mechanical design (1) Serrurier structure Carbon fiber bars Invar sleeves Aluminium alloys parts Carbon fiber covering Instrument weight: 95Kg

11 Mechanical design (2) Structure finite element analysis Bending analysis in telescope positions

12 Thermal expansion analysis with T= 30 C ~150µm defocus at Focal Box entrance window Need of autofocus device on the science CCD

13 Mechanical design (3) Estimated performances compared with the specs: energy spread in the PSF: energy inside a 3 x FWHM diameter circle: E > 98.6% spec: E > 97.7% energy inside a 1 FWHM diameter circle: 55% < E < 66%, spec: 35% < E < 90% energy in 1 pixel around the PSF peak: 6.9% < E < 12%, spec: 4% < E < 50% PSF uniformity over the FOV: variation of the PSF energy inside a 3 x FWHM diameter circle: 0.3%, spec: < 1.3% variation of the PSF energy inside a 1 x FWHM diameter circle: 17%, spec: < 70% flux variation due to mechanical bending and thermal expansion of the telescope: variation in a 3 x FWHM diameter circle: < 0.06% for one hour, spec: < 0.1%

14 Mechanical design (4) M1 Barrel

15 Aluminium lateral stops Invar arms

16 Mechanical design (5) M2 Spider

17

18 Focal Box thermal solution (1) The issue is: How to keep the sensitive parts (cameras, dichroïc coating) at comfortable temperature without making: instrument seeing thermal distortion of lenses? Dichroïc coating needs T >-40 C M2 Cameras shutters needs T >0 C Cameras and signal converters electronic needs T >-10 C

19 Focal Box thermal solution (2) Outer T : -80 C -40 C Dichroïc s room T order: -20 C Fused silica (low CTE) Shutters T order: +5 C Cameras room T order: -10 C

20 Mount and Dome (2) Dome Galactica 12ft

21 Schedule of the next months Technical studies are done except the mechanical design of the Focal Box (September-October 2008). Optics manufacturing: Primary mirror: done Secondary mirror and other optics: delivery in December 2008 / January 2009 Mechanics manufacturing: Telescope mechanical assembly: December 2008 Focal box assembly: February 2009 Instrument Software: delivery in February 2009 On sky tests at Nice Observatory: March July 2009 Shipping to Dome C: August 2009

22 See you in ~1.5 year at dome C for A STEP 400 FIRST LIGHT