Survey
* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
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 –From near to medium infrared (1-28 microns) Ground based astronomy –Costs lower than space astronomy Long time surveys –Polar “night” The IRAIT-AMICA project WHY 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 The IRAIT-AMICA project WHERE? DOME C CONCORDIA (Ita-Fra) – Antarctic plateau – 3500 m a.s.l. – 4000 m barometric quote The IRAIT-AMICA project IRAIT IRAIT (InfraRed Antarctic Italian Telescope) Aperture = 80 cm F# = 21,165 Curvature primary mirror = 480 cm Secondary wobbled 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) 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 The AMICA camera WHAT ARE THE CONSTRAINTS? TECHNICAL CLIMATICS LOGISTICS The AMICA camera TECHNICAL CONSTRAINTS Two detectors, operated at very low temperature – NIR (1-5microns) detector at 30K (Raytheon CRC – 463 InSb 256256 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 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 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 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 Design of AMICA WHICH IS THE PHILOSOPHY? REFLECTIVE ELEMENTS HOMOTHETIC SHRINKING MINIMUM NUMBER OF MOTORIZED FUNCTIONS INTERNAL MOTORS COMPACTNESS AND LIGHTNESS TWO DETECTORS, ONE CHANNEL PER EXPOSURE Design of AMICA THE STARTING POINT Design of AMICA THE ALTERNATIVES Double channel with a toggling element – THREE ALTERNATIVES Design of AMICA ALTERNATIVE A Design of AMICA ALTERNATIVE B Design of AMICA ALTERNATIVE C Design of AMICA EVALUATION – LAYOUT A) 40x60 cm: 7 mirrors 4 aspherics symmetric B) 40x50 cm: 6 mirrors 3 aspherics not symmetric C) 20x45 cm: 5 mirrors 4 aspherics symmetric Design of AMICA EVALUATION – SPOTS A) 15m RMS 30 m GEO final f# 6.5 B) 30 m RMS 75 m GEO final f# 13 C) 40 m RMS 90 m GEO final f# 10.3 Design of AMICA EVALUATION – MOVEMENTS A) 2 axial rotations B) 1 axial rotation and 1 mirror to extract C) 2 axial rotations Design of AMICA EVALUATION All the alternatives present advantages and disadvantages Aspheric produce Some mirrors are difficult to difficulties in alignment operations Design of AMICA THE INNOVATIVE IDEA Design of AMICA SUMMARY OF ADVANTAGES 2 active mirrors, commercial Compactness Detectors 1 (as the alternative C) very near filterwheel compact Design of AMICA THE QUALITY OF THE SPOTS Design of AMICA TECNICAL 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 EVERYTHING SEEMS GOOD BUT? Evolution of project PROBLEMS 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 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) 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 Evolution of project OTHER TASKS Mirrors, coating Tolerances Turbolences to the telescope Site inspection at DOME C PRODUCTION!!!! MY ROLE: past Responsible of the optical subsystem of AMICA Designer of the optical system (solutions A,B,C and final one) 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