Implementation and performance of the metrology system for the multi-object optical and near-infrared spectrograph MOONS

Drass, H.; Vanzi, L.; Torres-Torriti, Miguel; Dünner, Rolando; Shen, Tzu‐Chiang; Belmar, Francisco; Dauvin, Lousie; Staig, Tomas; Antognini, Jonathan; Flores, Mauricio; Luco, Yerko; Béchet, Clementine; Boettger, D.; Beard, S. M.; Montgomery, David; Watson, Stephen; Cabral, Alexandre; Hayati, Mahmoud; Abreu, Manuel; Rees, Phil; Cirasuolo, M.; Taylor, W. D.; Fairley, Alasdair

doi:10.1117/12.2232654

Cited by 4 publications

(3 citation statements)

References 1 publication

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“…The new surveys are usually equipped fiber position monitoring camera to achieve closed-loop control of the fiber position, e.g., PFS (Wang et al 2016), MOONS (Drass et al 2016) and DESI (Baltay et al 2019). LAMOST currently uses an open-loop controlled fiber positioning system.…”

Section: Introductionmentioning

confidence: 99%

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A New Fiber Detection Method for LAMOST Based on the Front-illuminated Method

Zhou¹,

Zhang²,

Lv³

et al. 2022

Res. Astron. Astrophys.

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The double revolving fiber positioning technology is one of the key technologies for the success of The Large Sky Area Multi-Object Fiber Spectroscopic Telescope (LAMOST). The accuracy of fiber positioning will directly affect the observation efficiency of LAMOST. To achieve higher fiber positioning accuracy, the original open-loop controlled fiber positioning system urgently needs to be upgraded into a closed-loop control system. The fiber detection is the most important part of the closed-loop controlled fiber positioning system. Back-illuminated detection method is usually used to detect the fiber position by directly detecting the light spot generated at the fiber end in the multi-fiber spectral surveys. In this paper, we introduce a new method to measure the fiber position based on the image of the front-illuminated LAMOST focal plane. The front-illuminated image does not require lighting devices inside the spectrograph, it could reduce the instability and light pollution in the spectrograph end. Our method measures the fiber position by fitting the profile of the fiber pinhole with a 2D Gaussian function. Series of tests show that the relative position measurement precision of the front-illuminated method is about 0.12 arcsec, and the method could have the same accuracy as the back-illuminated method once the system bias is calibrated by a simple radial correction function. The new method satisfies the requirement of LAMOST fiber detection accuracy and could be used in the closed-loop fiber control system.

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Section: Introductionmentioning

confidence: 99%

“…The fiber detection in the multi-fiber spectral surveys usually use two methods of illumination: back-illuminated method (Wang et al 2016;Hörler 2018;Baltay et al 2019) and frontilluminated method (Drass et al 2016). The back-illuminated method is a direct detection method.…”

Section: Introductionmentioning

confidence: 99%

A New Fiber Detection Method for LAMOST Based on the Front-illuminated Method

Zhou¹,

Zhang²,

Lv³

et al. 2022

Res. Astron. Astrophys.

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“…Each FPU will be compensated to improve the positioning accuracy according to the differences between the detected position and the expected position. New multi-fiber spectral surveys are all equipped with fiber monitoring camera systems, e.g., DESI (Baltay et al 2019), MOONS (Drass et al 2016) and PFS (Wang et al 2016).…”

Section: Introductionmentioning

confidence: 99%

LAMOST Fiber Positioning Unit Detection Based on Deep Learning

Zhou

Lv²,

Li³

et al. 2021

PASP

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The double revolving fiber positioning unit (FPU) is one of the key technologies of The Large Sky Area Multi-Object Fiber Spectroscope Telescope (LAMOST). The positioning accuracy of the computer controlled FPU depends on robot accuracy as well as the initial parameters of FPU. These initial parameters may deteriorate with time when FPU is running in non-supervision mode, which would lead to bad fiber position accuracy and further efficiency degradation in the subsequent surveys. In this paper, we present an algorithm based on deep learning to detect the FPU’s initial angle using the front illuminated image of LAMOST focal plane. Preliminary test results show that the detection accuracy of the FPU initial angle is better than 2.°5, which is good enough to distinguish those obvious bad FPUs. Our results are further well verified by direct measurement of fiber position from the back illuminated image and the correlation analysis of the spectral flux in LAMOST survey data.

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Novel Fiducial Fiber Scanning Measurement Method Based on a Polar Coordinate System for LAMOST

Zhang¹,

Chen²,

Liu³

et al. 2023

PASP

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The multiobject fiber-fed spectrograph is the core scientific instrument for large-scale spectroscopic surveys. For closed-loop control of fiber positioning, fiber metrology systems are implemented in numerous fiber-fed spectrographs. The position accuracy of the fiducial fiber in the focal plate directly affects the performance of the fiber metrology system. However, there are currently no suitable methods and devices for measuring the fiducial fibers with high accuracy in the Large Sky Area Multi-Object Fiber Spectroscopic Telescope (LAMOST). To solve this problem, this study proposed a novel online scanning measurement method for fiducial fibers in which a scanning camera was set up in front of the focal plate, and the rotation and translation movements of the focal plate were combined to set a polar coordinate measurement system. First, the pole and polar axis of the polar coordinate frame were determined, and the compensation values of the polar radius and angle of the polar coordinate of the fiducial fibers were solved in the field of view of the scanning camera. A prototype measurement platform was set up to verify the feasibility and scientific validity of the method. Experiment results show that the polar radius accuracy of the proposed method met the measurement requirements. The X–Y measurement accuracy can be further improved when a higher-precision rotary stage is adopted. Thus, the difficulties in online accurate measurement for fiducial fibers can be tackled by the proposed method with good operability in LAMOST.

show abstract

Implementation and performance of the metrology system for the multi-object optical and near-infrared spectrograph MOONS

Cited by 4 publications

References 1 publication

A New Fiber Detection Method for LAMOST Based on the Front-illuminated Method

A New Fiber Detection Method for LAMOST Based on the Front-illuminated Method

LAMOST Fiber Positioning Unit Detection Based on Deep Learning

Novel Fiducial Fiber Scanning Measurement Method Based on a Polar Coordinate System for LAMOST

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