Project status of the Robert Stobie spectrograph near infrared instrument (RSS-NIR) for SALT

Wolf, Marsha J.; Mulligan, Mark; Smith, Michael P.; Adler, Douglas P.; Bartosz, Curtis; Bershady, Matthew A.; Buckley, D.; Burse, Mahesh; Chordia, Pravin; Clemens, J. C.; Garot, Kristine; Indahl, Briana L.; Jaehnig, Kurt P.; Koch, Ron J.; Mason, William P.; Mosby, Gregory; Nordsieck, K. H.; Percival, J. W.; Punnadi, Sujit; Ramaprakash, A. N.; Schier, Jan; Sheinis, Andrew; Smee, Stephen A.; Thielman, Donald J.; Werner, Mark W.; Williams, T. B.; Wong, Jeffrey P.

doi:10.1117/12.2056736

Cited by 6 publications

(4 citation statements)

References 5 publications

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“…The throughput of the best existing moderate and low-resolution spectrographs are 50 -60 percent (for example, FOCAS/Subaru 13 , OSIRIS/GTC 14 , RSS/SALT 15 ) and the efficiencies of even the best existing echelle-spectrometers HARPS 16 and PEPSI 17 still do not exceed 10 percent. Respectively, the low-moderate resolution spectrographs have spectral resolution of 1000 when only limiting optical range can be observed (at lesser resolution the whole range is covered, at higher resolution these can not cover all the visible range), the echelle-spectrographs may cover the whole range with spectral resolution from 10000 and notably higher.…”

Section: Discussionmentioning

confidence: 99%

Design and optimization of a dispersive unit based on cascaded volume phase holographic gratings

et al. 2017

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We describe a dispersive unit consisting of cascaded volume-phase holographic gratings for spectroscopic applications. Each of the gratings provides high diffractive efficiency in a relatively narrow wavelength range and transmits the rest of the radiation to the 0 th order of diffraction. The spectral lines formed by different gratings are centered in the longitudal direction and separated in the transverse direction due to tilt of the gratings around two axes. We consider a technique of design and optimization of such a scheme. It allows to define modulation of index of refraction and thickness of the holographic layer for each of the gratings as well as their fringes frequencies and inclination angles. At the first stage the gratings parameters are found approximately using analytical expressions of Kogelnik's coupled wave theory. Then each of the grating starting from the longwave sub-range is optimized separately by using of numerical optimization procedure and rigorous coupled wave analysis to achieve a high diffraction efficiency profile with a steep shortwave edge. In parallel such targets as ray aiming and linear dispersion maintenance are controlled by means of ray tracing. We demonstrate this technique on example of a small-sized spectrograph for astronomical applications. It works in the range of 500-650 nm and uses three gratings covering 50 nm each. It has spectral resolution of 6130-12548.Obtaining of the asymmetrical efficiency curve is shown with use of dichromated gelatin and a photopolymer. Change of the curve shape allows to increase filling coefficient for the target sub-range up to 2.3 times.

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Section: Discussionmentioning

confidence: 99%

Design and optimization of a dispersive unit based on cascaded volume phase holographic gratings

et al. 2017

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“…To mitigate this shortfall and to overcome challenges we faced in polishing earlier generations of bare fiber IFUs, e.g., SparsePak (Bershady et al 2004), HexPak (Wood et al 2012) and Pak (Eigenbrot & Bershady 2018), we have developed a custom polishing arm for use with an off-the-shelf Ultra Tec Polisher to enable precise polishing of fiber end terminations to be used in astronomical applications. The arm was developed to facilitate a more deterministic approach to polish v-groove blocks and the IFU for the SALT NIR Spectrograph (Sheinis et al 2006;Wolf et al 2014, *mps@astro.wisc.edu 2018; Smith et al 2018). The intension is that the features of the new arm would enable polishing procedures to be established and retained over time.…”

Section: Introductionmentioning

confidence: 99%

Development and characterization of a precisely adjustable fiber polishing arm

Smith

Chattopadhyay

Hauser

et al. 2020

Advances in Optical and Mechanical Technologies for Telescopes and Instrumentation IV

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The development of bare fiber or air-gapped microlens-fiber coupled Integral Field Units (IFUs) for astronomical applications requires careful treatment of the fiber end-faces (terminations). Previous studies suggest that minimization of fiber end face irregularity leads to better optical performance in terms of the diminishing effect of focal ratio degradation. Polishing has typically been performed using commercial rotary polishers with multiple gradually decreasing grit sizes. These polishers generally lack the ability to carefully adjust angular position and polishing force. Control of these parameters vastly help in getting a repeatable and controllable polish over a variety of glass/epoxy/metal matrices that make up integral filed units and fiber slits.A polishing arm is developed to polish the fiber terminations (IFU, mini-bundles and v-grooves) of the NIR Fiber System for the RSS spectrograph at SALT. The polishing arm angular adjustments ensure the correct position and orientation of each termination on the polishing surface during the polish.Various studies have indicated that the fiber focal ratio also degrades if the fiber end face comes under excessive stress. The polishing arm is fitted with a load cell to enable control of the polishing force. We have explored the minimal applicable end stress by applying different loads while polishing.The arm is modular to hold a variety of fiber termination styles. The polishing arm is also designed to access a fiber inspection microscope without removing the fiber termination from the arm. This enables inspection of the finish quality at various stages through polishing process.

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“…3 In addition, numerous ground based observatories world-wide utilize these arrays, e.g in MMIRS of the Multiple Mirror Telescope and Magellan observatories, 4 Keck's MOSFIRE, 5 EMIR of the Gran Telescopio Canarias, 6 and RSS-NIR of the Southern African Large Telescope. 7 The newest near infrared focal plane arrays from Teledyne, the H4RG-10, have been developed for the Wide Field InfraRed Space Telescope (WFIRST) and represent a natural evolution to higher resolution (to a 4096 x 4096 pixel array) and performance from the H2RG. 8,9 However, there are some key differences.…”

Section: Introductionmentioning

confidence: 99%

Operation of a H4RG-10 in the NASA Goddard Astrophyiscs Divison IR detector lab testbed

Mosby

Rauscher

Kutyrev

2018

High Energy, Optical, and Infrared Detectors for Astronomy VIII

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Future space and ground based missions in the near infrared are planning to or will utilize the next generation of Teledyne's HxRG detectors, the HgCdTe 4K x 4K array (H4RG). The science cases of such missions will require optimal stability and noise performance. To assess the detailed performance of the H4RG, we have developed a small single detector testbed in NASA Goddard's Astrophysics Division IR detector lab. The testbed operates a H4RG array inside a large dewar using a room temperature Leach controller. The dewar will include two integrating spheres with controlled apertures using NIR LEDs as light sources as well as a calibrated photodiode to precisely measure flux. We present preliminary results of a banded H4RG-10 array on the bench. In the near future, we plan to use the test bed to investigate the specific origins of electronic noise in the test bed, persistence, and other flux dependent nonlinearities.

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Project status of the Robert Stobie spectrograph near infrared instrument (RSS-NIR) for SALT

Cited by 6 publications

References 5 publications

Design and optimization of a dispersive unit based on cascaded volume phase holographic gratings

Design and optimization of a dispersive unit based on cascaded volume phase holographic gratings

Development and characterization of a precisely adjustable fiber polishing arm

Operation of a H4RG-10 in the NASA Goddard Astrophyiscs Divison IR detector lab testbed

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