Optical design of the SuMIRe/PFS spectrograph

Pascal, Sandrine; Vivès, S.; Barkhouser, Robert H.; Gunn, James E.

doi:10.1117/12.2055738

Cited by 8 publications

(8 citation statements)

References 2 publications

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“…This is obtained for the nominal theoretical design, and it appears that the theoretical design is well within the specifications. The tolerance design (including manufacturing and alignment errors) meets also the specifications and is described in [4]. More details on the optical design and the optical performance (in particular the relationship between RMS spot size and EEE) can be found in [4].…”

Section: Expected Optical Performancementioning

confidence: 99%

Current status of the spectrograph system for the SuMIRe/PFS

et al. 2014

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The Prime Focus Spectrograph (PFS) is a new facility instrument for Subaru Telescope which will be installed in around 2017. It is a multi-object spectrograph fed by about 2400 fibers placed at the prime focus covering a hexagonal field-ofview with 1.35 deg diagonals and capable of simultaneously obtaining data of spectra with wavelengths ranging from 0.38 um to 1.26 um.The spectrograph system is composed of four identical modules each receiving the light from 600 fibers. Each module incorporates three channels covering the wavelength ranges 0.38-0.65 mu ("Blue"), 0.63-0.97 mu ("Red"), and 0.94-1.26 mu ("NIR") respectively; with resolving power which progresses fairly smoothly from about 2000 in the blue to about 4000 in the infrared. An additional spectral mode allows reaching a spectral resolution of 5000 at 0.8mu (red). The proposed optical design is based on a Schmidt collimator facing three Schmidt cameras (one per spectral channel). This architecture is very robust, well known and documented. It allows for high image quality with only few simple elements (high throughput) at the expense of the central obscuration, which leads to larger optics.Each module has to be modular in its design to allow for integration and tests and for its safe transport up to the telescope: this is the main driver for the mechanical design. In particular, each module will be firstly fully integrated and validated at LAM (France) before it is shipped to Hawaii. All sub-assemblies will be indexed on the bench to allow for their accurate repositioning. This paper will give an overview of the spectrograph system which has successfully passed the Critical Design Review (CDR) in 2014 March and which is now in the construction phase.PFS is composed on 4 main elements: the Prime Focus Instruments (PFI) which covers a field-of-view of 1.3deg with 2400 fiber positioners, the fiber system which relays the light captured by each PFI positioner to the Spectrograph System (SpS), described in this paper. The last element is the metrology camera (located at the Cassegrain focus of the telescope) which will verify the correct location of each PFI fiber positioner. *sebastien.vives@lam.fr; phone +33 (0)491 056 931

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Section: Expected Optical Performancementioning

confidence: 99%

Current status of the spectrograph system for the SuMIRe/PFS

et al. 2014

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“…A pair of 2k x 4k Hamamatsu CCDs comprise the detector array for the visible cameras. 2 For the near infrared (NIR) camera, which is the subject of this paper, the 1.7 µm cutoff Teledyne H4RG-15 Mercury-Cadmium-Telluride device is used. The H4RG is described in a recent paper by Blank.…”

Section: Introductionmentioning

confidence: 99%

The near infrared camera for the Subaru Prime Focus Spectrograph

et al. 2014

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We present the detailed design of the near infrared camera for the SuMIRe (Subaru Measurement of Images and Redshifts) Prime Focus Spectrograph (PFS) being developed for the Subaru Telescope. The PFS spectrograph is designed to collect spectra from 2394 objects simultaneously, covering wavelengths that extend from 380 nm -1.26 µm. The spectrograph is comprised of four identical spectrograph modules, with each module collecting roughly 600 spectra from a robotic fiber positioner at the telescope prime focus. Each spectrograph module will have two visible channels covering wavelength ranges 380 nm -640 nm and 640 nm -955 nm, and one near infrared (NIR) channel with a wavelength range 955 nm -1.26 µm. Dispersed light in each channel is imaged by a 300 mm focal length, f/1.07, vacuum Schmidt camera onto a 4k x 4k, 15 µm pixel, detector format. For the NIR channel a HgCdTe substrate-removed Teledyne 1.7 µm cutoff device is used. In the visible channels, CCDs from Hamamatsu are used. These cameras are large, having a clear aperture of 300 mm at the entrance window, and a mass of ∼ 250 kg.Like the two visible channel cameras, the NIR camera contains just four optical elements: a two-element refractive corrector, a Mangin mirror, and a field flattening lens. This simple design produces very good imaging performance considering the wide field and wavelength range, and it does so in large part due to the use of a Mangin mirror (a lens with a reflecting rear surface) for the Schmidt primary. In the case of the NIR camera, the rear reflecting surface is a dichroic, which reflects in-band wavelengths and transmits wavelengths beyond 1.26 µm. This, combined with a thermal rejection filter coating on the rear surface of the second corrector element, greatly reduces the out-of-band thermal radiation that reaches the detector.The camera optics and detector are packaged in a cryostat and cooled by two Stirling cycle cryocoolers. The first corrector element serves as the vacuum window, while the second element is thermally isolated and floats cold. An assembly constructed primarily of silicon carbide is used to mount the Mangin mirror, and to support the detector and field flattener. Thermal isolation between the cold optics and warm ambient surroundings is provided by G10 supports, multi-layer insulation, and the vacuum space within the cryostat.In this paper we describe the detailed design of the PFS NIR camera and discuss its predicted optical, thermal, and mechanical performance.

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“…The Prime Focus Spectrograph (PFS) [1] of the Subaru Measurement of Images and Redshifts (SuMIRe) project for Subaru telescope is developed by a large consortium over the world lead by the Japanese of IPMU divided into two main systems, a fiber positioner placed at the prime focus of SUBARU telescope and a spectrograph composed by four identical spectrographs feed by 600 fibers each. A spectrograph module [2] covers a spectral range between 380 to 1260nm splitted in 3channels, the blue, the red and the near infrared (NIR) one. A module, as shown on Figure 1 is fed by a pseudo slit placed at the focal plane of a Schmidt collimator, the beam is split into three channels by two dichroics followed the Schmidt corrector of the collimator and the Volume Phase Holographic Gratings (VPHG).…”

Section: Introductionmentioning

confidence: 99%

SUBARU prime focus spectrograph: integration, testing and performance for the first spectrograph

Madec¹,

Fur²,

Mignant³

et al. 2016

SPIE Proceedings

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The Prime Focus Spectrograph (PFS) of the Subaru Measurement of Images and Redshifts (SuMIRe) project for Subaru telescope consists in four identical spectrographs fed by 600 fibers each. Each spectrograph is composed by an optical entrance unit that creates a collimated beam and distributes the light to three channels, two visibles and one near infrared. This paper presents the on-going effort for the tests & integration process for the first spectrograph channel: we have developed a detailed Assembly Integration and Test (AIT) plan, as well as the methods, detailed processes and I&T tools. We describe the tools we designed to assemble the parts and to test the performance of the spectrograph. We also report on the thermal acceptance tests we performed on the first visible camera unit. We also report on and discuss the technical difficulties that did appear during this integration phase. Finally, we detail the important logistic process that is require to transport the components from other country to Marseille.

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Optical design of the SuMIRe/PFS spectrograph

Cited by 8 publications

References 2 publications

Current status of the spectrograph system for the SuMIRe/PFS

Current status of the spectrograph system for the SuMIRe/PFS

The near infrared camera for the Subaru Prime Focus Spectrograph

SUBARU prime focus spectrograph: integration, testing and performance for the first spectrograph

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