Transcript Mission to Antartic

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 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
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) 15m 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