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Mission to Antarctic

Mission to Antarctic. PhD: first year Ing. Alberto Riva Prof. Aldo Treves, Dott. Filippo Maria Zerbi. Summary. The IRAIT-AMICA project The AMICA camera Design of AMICA Evolution of project. The IRAIT-AMICA project WHAT IS THE SCIENCE?. Infrared astronomy

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Mission to Antarctic

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  1. Mission to Antarctic PhD: first year Ing. Alberto Riva Prof. Aldo Treves, Dott. Filippo Maria Zerbi

  2. Summary • The IRAIT-AMICA project • The AMICA camera • Design of AMICA • Evolution of project

  3. The IRAIT-AMICA projectWHAT IS THE SCIENCE? • Infrared astronomy • From near to medium infrared (1-28 microns) • Ground based astronomy • Costs lower than space astronomy • Long time surveys • Polar “night”

  4. The IRAIT-AMICA projectWHY ANTARCTICA? • ATMOSPHERE • Infrared windows at 3, 10 microns • Low background emission • Good seeing • TEMPERATURE • Mean temperature -50°C • Max -30°C, Min -90°C • CLIMATE • Low precipitations • Negligible humidity

  5. The IRAIT-AMICA projectWHERE? • DOME C CONCORDIA (Ita-Fra) • Antarctic plateau • 3500 m a.s.l. • 4000 m barometric quote

  6. The IRAIT-AMICA projectIRAIT • IRAIT (InfraRed Antarctic Italian Telescope) • Aperture = 80 cm • F# = 21,165 • Curvature primary mirror = 480 cm • Secondary wobbled

  7. The AMICA camera WHAT IS AMICA? • AMICA (Antarctica Multiband Infrared Camera) • Two channels • From 1 to 5 microns • From 5 to 28 microns • Inaf – PNRA • Teramo – Padova – Brera (Merate)

  8. The AMICA camera WHAT IS THE TASK? • Map the infrared tramsission in the 1-28 microns band • Perform long observation of interesting bodies • Make surveys of the sky in the infrared band

  9. The AMICA camera WHAT ARE THE CONSTRAINTS? • TECHNICAL • CLIMATICS • LOGISTICS

  10. The AMICA camera TECHNICAL CONSTRAINTS • Two detectors, operated at very low temperature • NIR (1-5microns) detector at 30K (Raytheon CRC – 463 InSb 256256 array) • MIR (5-28 microns) detector at 7K (DRS MF – 128 SiAs BIB 128x128 array) • Reliability of materials and systems • Electronic part and system • Motorized functions

  11. The AMICA camera CLIMATIC CONSTRAINTS • VERY LOW TEMPERATURE • Materials • Sealings • DIAMOND DUST • Protections • DARKNESS DURING WINTER • About 6 months of unaccessibility • BAROMETRIC QUOTE OF 4000 m • Low or negligible natural convection

  12. The AMICA camera LOGISTICS CONSTRAINTS • LIMITED ON SITE WORKSHOP CAPABILITIES • Optical facilities • Transportation facilities • LIMITED ON SITE TECHNICIAN CAPABILITIES • Mechanics • Optics • LIMITED ON SITE SUPPLIES • Power limited • Materials availability

  13. The AMICA camera WHAT ARE THE DESIDERATA? • Best efficiency at 3 and 10 microns • Field of view as larger as possible • Minimal aberrations • Full band coverage from 1 to 28 microns with high efficiency • At least 12 filter positions

  14. Design of AMICAWHICH IS THE PHILOSOPHY? • REFLECTIVE ELEMENTS • HOMOTHETIC SHRINKING • MINIMUM NUMBER OF MOTORIZED FUNCTIONS • INTERNAL MOTORS • COMPACTNESS AND LIGHTNESS • TWO DETECTORS, ONE CHANNEL PER EXPOSURE

  15. Design of AMICATHE STARTING POINT

  16. Design of AMICATHE ALTERNATIVES • Double channel with a toggling element • THREE ALTERNATIVES

  17. Design of AMICAALTERNATIVE A

  18. Design of AMICAALTERNATIVE B

  19. Design of AMICAALTERNATIVE C

  20. Design of AMICAEVALUATION – LAYOUT • A) 40x60 cm:7 mirrors 4aspherics symmetric • B) 40x50 cm: 6 mirrors 3 aspherics not symmetric • C) 20x45 cm: 5 mirrors 4 aspherics symmetric

  21. Design of AMICAEVALUATION – SPOTS • A) 15m RMS30 m GEO final f#  6.5 • B) 30 m RMS75 m GEO final f#  13 • C) 40 m RMS90 m GEO final f#  10.3

  22. Design of AMICAEVALUATION – MOVEMENTS • A) 2 axial rotations • B) 1 axial rotation and 1 mirror to extract • C) 2 axial rotations

  23. Design of AMICAEVALUATION • All the alternatives present advantages and disadvantages • Aspheric mirrors are difficult to produce • Some difficulties in alignment operations

  24. Design of AMICATHE INNOVATIVE IDEA

  25. Design of AMICASUMMARY OF ADVANTAGES • 2 active mirrors, commercial • Compactness (as the alternative C) • Detectors very near • 1 filterwheel compact

  26. Design of AMICATHE QUALITY OF THE SPOTS

  27. Design of AMICATECNICAL DATA • NIR • field of 2.29 arcmin squared • samples of Airy disc with 4 pixels (30x30 microns each) at the wavelength of 3.426 microns; 0.54 arcsec/pixel; 256x256 pixels • MIR • field of 2.86 arcmin squared • samples of Airy disc with 4 pixels (75x75 microns each) at the wavelength of 8.57 microns; 1.34 arcsec/pixel; 128x128 pixels

  28. EVERYTHING SEEMS GOOD BUT?

  29. Evolution of projectPROBLEMS ON THE FUTURE • Producing this nice toy is not so simple • Temperature of 7K of MIR detector to mantain for 6 months continuosly • External temperature • Cryocooler and pump are not designed for theese conditions

  30. Evolution of project POSSIBLE ROADS • In order to solve problems of electronic parts and sealing materials we can encapsulate all the system (camera, pump, cryocooler, electronic devices) into a rack mantained in pressure and at some degrees above 0°C • But this seems to present higher costs in term of power (Watt on total budget) and weight (Kilograms that can be loaded on the telescope)

  31. Evolution of project POSSIBLE ROADS • We would prefer to mantain the camera at room (antarctic) temperature • Advantage • Less power requested to the cryocooler • Problems • Urgent need to study the cryo-dynamic of the system, with particular attention to the cryocooler and the path of the cold finger

  32. Evolution of project OTHER TASKS • Mirrors, coating • Tolerances • Turbolences to the telescope • Site inspection at DOME C • PRODUCTION!!!!

  33. MY ROLE: past • Responsible of the optical subsystem of AMICA • Designer of the optical system (solutions A,B,C and final one)

  34. MY TASK: future • Study and design the solutions to the problem presented (mainly cryocooling, and procurement of the optical elements) • Improve the astronomical background of my knowledge

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