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Several optical ‘tricks’ have been used to obtain high spectral resolution and efficiency despite the large size of the telescope and the 1 arcscec sky aperture of the instrument, like superimposing the beams in order to minimize the size of the echelle grating.
The 220000 spectral resolution specified for the spectrograph requires a 3 x 1 echelle mosaic, since the largest echelle master that can be ruled has a ruled length of 408 mm (16 inch) and a width of up to 306 mm (12 inch).
The paper describes the design of the mosaic as well as the various phases of its assembly and alignment. We also introduce the mounting of the mosaic inside the mount in order to guaranty the long term stability ESPRESSO requires. We address the packing and conditioning of the mosaic for the transport to Chile, which has been proven to sustain extremely strong shock, without causing misalignment in the mosaic. Finally a short summary of the instrument performances is presented.
An overview of the mid-infrared spectro-interferometer MATISSE: science, concept, and current status
The instrument consists in a warm optical system (WOP) accepting four optical beams and relaying them after a dichroic splitting (for the L and M- and N- spectral bands) to cold optical benches (COB) located in two separate cryostats. The Observatoire de la Côte d’Azur is in charge of the WOP providing the spectral band separation, optical path equalization and modulation, pupil positioning, beam anamorphosis, beam commutation, and calibration. NOVA-ASTRON is in charge of the COB providing the functions of beam selection, reduction of thermal background emission, spatial filtering, pupil transfer, photometry and interferometry splitting, additional beam anamorphosis, spectral filtering, polarization selection, image dispersion, and image combination. The Max Planck Institut für Radio Astronomie is in charge of the operation and performance validation of the two detectors, a HAWAII-2RG from Teledyne for the L- and M- bands and a Raytheon AQUARIUS for the N-band. Both detectors are provided by ESO. The Max Planck Institut für Astronomie is in charge of the electronics and the cryostats for which the requirements on space limitations and vibration stability resulted on very specific and stringent decisions on the design.
The integration and test of the COB: the two cryogenic systems, including the cold benches and the detectors, have been conducted at MPIA in parallel with the integration of the WOP at OCA. At the end of 2014, the complete instrument was integrated at OCA. Following this integration, a period of interface and alignment between the COB and the WOP took place resulting in the first interference fringes in the L-band during summer 2015 and the first interference fringes in the N-ban in March 2016.
After a period of optimization of both the instrument reliability and the environmental working conditions, the test plan is presently being conducted in order to evaluate the complete performance of the instrument and its compliance with the high-level requirements. The present paper gives the first results of the alignment, integration and test phase of the MATISSE instrument.
The respective test setup was designed in collaboration between PTB and the CRIRES+ consortium. The PTB provided optical radiation sources and calibrated detectors for each wavelength range. With this setup, it is possible to measure the absolute efficiency of the gratings both wavelength dependent and polarization state dependent in a wavelength range from 0.9 μm to 6 μm.
One of the most challenging systems in this cryogenic channel involves the Cooling System. Due to the highly demanding requirements applicable in terms of stability, this system arises as one of the core systems to provide outstanding stability to the channel. Really at the edge of the state-of-the-art, the Cooling System is able to provide to the cold mass (~1 Ton) better thermal stability than few hundredths of degree within 24 hours (goal: 0.01K/day).
The present paper describes the Assembly, Integration and Verification phase (AIV) of the CARMENES-NIR channel Cooling System implemented at IAA-CSIC and later installation at CAHA 3.5m Telescope, thus the most relevant highlights being shown in terms of thermal performance.
The CARMENES NIR-channel Cooling System has been implemented by the IAA-CSIC through very fruitful collaboration and involvement of the ESO (European Southern Observatory) cryo-vacuum department with Jean-Louis Lizon as its head and main collaborator. The present work sets an important trend in terms of cryogenic systems for future E-ELT (European Extremely Large Telescope) large-dimensioned instrumentation in astrophysics.
MUSE is composed of several subsystems which are under the responsibility of each institute. The Fore Optics derotates and anamorphoses the image at the focal plane. A Splitting and Relay Optics feed the 24 identical Integral Field Units (IFU), that are mounted within a large monolithic structure. Each IFU incorporates an image slicer, a fully refractive spectrograph with VPH-grating and a detector system connected to a global vacuum and cryogenic system. During 2012 and 2013, all MUSE subsystems were integrated, aligned and tested to the P.I. institute at Lyon. After successful PAE in September 2013, MUSE instrument was shipped to the Very Large Telescope in Chile where that was aligned and tested in ESO integration hall at Paranal. After, MUSE was directly transported, fully aligned and without any optomechanical dismounting, onto VLT telescope where the first light was overcame the 7th of February, 2014.
This paper describes the alignment procedure of the whole MUSE instrument with respect to the Very Large Telescope (VLT). It describes how 6 tons could be move with accuracy better than 0.025mm and less than 0.25 arcmin in order to reach alignment requirements. The success of the MUSE alignment is demonstrated by the excellent results obtained onto MUSE image quality and throughput directly onto the sky.
This course explains the basic principles required for the design of a cryogenic system. It introduces the main laws to evaluate the heat load on a cryostat. The course provides a detailed process on how to design a cryogenic instrument and introduces the various means of cryogenic cooling. This course, in contrast to traditional cryogenic courses, directly addresses the case of ground-based astronomy, and is based on more than 30 years of experience designing and building instruments for one of the most important astronomical institutes. The course shows a number of real examples including a few mistakes and solutions on how to avoid them. The course also addresses the basics of vacuum technology, and reviews the various evacuation systems available today. A specific chapter is also dedicated on outgassing and how to reduce it.
A growing part of ground based astronomical instruments are dedicated to near infrared observations. This means always increasing need to deal with mechanism and optics operating in vacuum and cryogenic environment. This course explains the main difference between an instrument operated at ambient temperature in air and an instrument operated under vacuum and at cryogenic temperature. The course presents a set of technical solutions which have been developed in order to deal with the constraints of this specific environment. The course addresses a parts on pure mechanics with a number of example of mechanisms including lessons learned over the time. The second part discusses optomechanical problems encountered with the differential expansion coefficient and give also practical example of stress free mounting for optical components. This is based on more than 30 years of experience designing and building instruments for one of the world's most important astronomical institutes.
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