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Área de Instrumentación
NAHUAL Mechanical ConceptCurrent Status
F. Javier FuentesInstituto de Astrofísica de Canarias
September 02 2008
Área de InstrumentaciónF. Javier FuentesInstituto de Astrofísica de Canarias 2
It is the idea a part of the Nahual Consortium has about the present state and desired future development of the mechanical architecture of the instrument.
It is just a proposal for discussion. It is fully opened to all the ideas, comments, suggestions,… Nahual is a very complex instrument and it is not an easy task to put it on the best design path.
It is the input to the mechanical WBS and schedule proposals. They will be presented and discussed on session 4 this meeting.
What this talk is?
Área de InstrumentaciónF. Javier FuentesInstituto de Astrofísica de Canarias 3
Spectral Domain: 1 – 2.4 µm
Spectral Resolution > 50.000
Radial Velocity Accuracy: 1 m/s (1 hr to days/months/years)
Simultaneous Wavelength Calibration
No moving parts
Science RequirementsMain Mode
Área de InstrumentaciónF. Javier FuentesInstituto de Astrofísica de Canarias 4
Spectral Domain: 0.9 – 2.5 µm
Spectral Resolution 500 to 61.000
Long Slit / Image Slicer
AO needed on some modes
Wavelength Tuning
Cold mechanisms needed to change between configurations
To be implemented ONLY if they are compatible with the Main Mode architecture/functionality/operation
Science RequirementsOptional Modes
Área de InstrumentaciónF. Javier FuentesInstituto de Astrofísica de Canarias 5
Working Temperature < 100 K (cryogenic environment)
Image Stability 0.1 to 0.01 pixel
According the Radial Velocity Error Budget (TBD)
Specified values according similar instruments
Temperature Stability in the Cold Bench < 0.01 K
According the Zemax-Ansys Instrument Model (TBD)
Specified values according similar instruments
Time Stability 1 hr to years
According the Calibration Procedure (TBD)
No Cold Mechanisms involved
Located in the GTC Nasmyth platform
Mechanical Functional BaselineMain Mode
Área de InstrumentaciónF. Javier FuentesInstituto de Astrofísica de Canarias 6
GIANO @ TNG
Spectral Range: 0.9 – 2.5 µm (cryogenic)
Spectral Resolution > 46.000
RV accuracy < 10 m/s (< 0.1 K)
PRVS @ GEMINI
Spectral Range: 0.9 – 1.8 µm (not fully cryogenic)
Spectral Resolution > 70.000
RV accuracy < 3 m/s long-term (< 1 m/s goal)
Similar Instruments
Área de InstrumentaciónF. Javier FuentesInstituto de Astrofísica de Canarias 7
SPIROU @ CFHT
Spectral Range: 0.9 – 2.4 µm (cryogenic)
Spectral Resolution > 50.000 (70.000 goal)
RV accuracy < 1 m/s (< 0.01 K)
HARPS @ 3.6 m Telescope
Spectral Range: visible (non-cryogenic)
Spectral Resolution > 120.000
Long-term RV accuracy < 1 m/s (< 0.01 K)
Similar Instruments
Área de InstrumentaciónF. Javier FuentesInstituto de Astrofísica de Canarias 8
Optical Layout. Main Mode
Echelle
Cross Disperser
FP1
FP2
OAP1-OAP2
OAP3
Camera
Detector
Área de InstrumentaciónF. Javier FuentesInstituto de Astrofísica de Canarias 9
Sizes of Optical Components
Element Clear aperture (mm)
FP1 ~ 2 x 2
OAP1 , OAP2 109
ECHELLE 109 x 220
FLD1 ~ 10 x 10
FP2 ~ 2 x 2
OAP3 109
CROSS DISP 109
DETECTOR (HAWAII-2) 36.8
Área de InstrumentaciónF. Javier FuentesInstituto de Astrofísica de Canarias 10
Mechanical Layout. Fractal Proposal
Área de InstrumentaciónF. Javier FuentesInstituto de Astrofísica de Canarias 11
Auxiliary Module. Fractal Proposal
Área de InstrumentaciónF. Javier FuentesInstituto de Astrofísica de Canarias 12
Calibration Module. Fractal Proposal
Integrating sphere and lamps
Gas cell
Cryostat window
IR camera
Área de InstrumentaciónF. Javier FuentesInstituto de Astrofísica de Canarias 13
System architecture.Present status
Mechanical architecture proposed by Fractal is partially driven by the cryogenic Auxiliary Module (Optional Mode) configuration, as well as the configuration/position of the Calibration Module
A new cryogenic layout, only shaped by the Main Mode configuration (according the science requirements), is under study
The space around the entrance window is very crowded. The configuration and position of the Calibration Module will be optimized after the Main Mode architecture is established
The feasibility of the Optional Modes will be studied after the Main Mode architecture is established
Área de InstrumentaciónF. Javier FuentesInstituto de Astrofísica de Canarias 14
Mechanical Layout. Main Mode
Área de InstrumentaciónF. Javier FuentesInstituto de Astrofísica de Canarias 15
Mechanical Layout. Main Mode
Área de InstrumentaciónF. Javier FuentesInstituto de Astrofísica de Canarias 16
Cryogenics concept. Present status
The design of Nahual will be based on Giano’s highly stable cryogenics concept. Recent cold tests of Giano show an actively controlled temperature stability better than 0.01 K for short periods of time (~2 hours). Long-term stability remains to be tested.
Results from Giano, as well as the implications for Nahual, will be presented within other talk this meeting.
Same idea (to adapt the Giano’s cryogenics concept) is being considered by the Spirou’s team (at the Observatoire Midi-Pyrénées)
Área de InstrumentaciónF. Javier FuentesInstituto de Astrofísica de Canarias 17
Cryogenics concept. Design status (I)
LN2 will be an integral part of the optical bench to guarantee a close contact between LN2 and the bench surface.
LN2 temperature will be maintained stable by controlling the pressure of the N2 boiling gas down to 1 mbar (TBC)
Detailed concepts of the cold shield (to attain an isothermal environment in the optical bench) and the intermediate shield (or shields), using thick aluminium plates and MLI blankets (10 to 30 layers), will be presented in this meeting.
Área de InstrumentaciónF. Javier FuentesInstituto de Astrofísica de Canarias 18
Cryogenics concept. Design status (II)
A detailed steady-state thermal model, predicting a density of radiation better than 0.8 W/m2 , has been developed for this configuration.The model will be presented and commented within other talk this meeting. Proposals to avoid hot-spots will be also presented.
A vibration-free pulse-tube cooler will be used, if needed, to cool the detector and the vacuum getter (down to 10 K)
Área de InstrumentaciónF. Javier FuentesInstituto de Astrofísica de Canarias 19
Cryogenics concept. Giano design
Área de InstrumentaciónF. Javier FuentesInstituto de Astrofísica de Canarias 20
Cryogenics development
A collaborative framework is under discussion between the interested groups (presently Arcetri, IAC and UL) to share the tasks to design, manufacture, integrate and test a cryostat for Nahual. This will allow to identify the final temperature stability that can be reached with the Nahual configuration during long periods of time (as requested in the science requirements).
The private companies involved in the design and manufacturing of Giano (Studio Tomerelli and Criotec Impianti) would participate in the development of Nahual cryogenics as far as it is possible.
The schedule and detailed task sharing will be discussed during this meeting.
Área de InstrumentaciónF. Javier FuentesInstituto de Astrofísica de Canarias 21
Support Trusses concept
The following alternatives are being studied for the trusses supporting the cold bench:
Giano’s isostatic hexapod
Same concept, but using flexures/flexural pivots at the interfaces
G-10 isostatic or hyperstatic supports. Flat plates of cylinders
Use of titanium instead of stainless steel
A detailed analysis of alternatives will be presented within other talk this meeting
Área de InstrumentaciónF. Javier FuentesInstituto de Astrofísica de Canarias 22
Cryogenic wheel mechanisms
Wheel design could be based on proven concept from existing instruments