arXiv subjects

Stefan Kuiper

Publications and source records attributed to Stefan Kuiper.

8 recordsLinked to original sources

arXiv2026

Facility integration of the NASA IRTF adaptive secondary mirror

IRTF-ASM-1 has been functioning well since its first light in 2024. This adaptive secondary mirror (ASM) was primarily developed to be an on-sky demonstration of the new hybrid variable reluctance actuator technology at the NASA Infrared Telescope Facility (IRTF). However, due to its physical robustness and our previous demonstrations of sensitivity enhancements with the ASM, we are interested in using it to optimize telescope image quality on a nightly basis. This will directly benefit science observations. However, as IRTF does not currently have adaptive optics expertise, we have been developing the system to be used with minimal human intervention. We present our progress in developing software for active optics mode with IRTF-ASM-1 using the single conjugate, facility 2x2 Shack-Hartmann wavefront sensor Felix. We also present techniques for removing low-order, large amplitude non-common path aberrations between Felix and our science instruments.

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arXiv2026

Progress report on the integration of the IRTF adaptive secondary mirror

IRTF-ASM-1 is the first on-sky adaptive secondary mirror using the hybrid variable reluctance (HVR) actuators developed by the Netherlands Organization for Applied Scientific Research (TNO). Since its first light in April 2024, the ASM has continued to work consistently well with no hardware issues. The primary purpose of IRTF-ASM-1 is to serve as a demonstration of the HVR actuator technology, both in terms of verifying its robustness and testing calibration methods that are relevant to larger ASMs. However, as the ASM has proven to be easy to handle and reliable in its performance, we are moving toward integrating the ASM for long-term use at IRTF. We present closed loop results with the ASM and IRTF's off-axis facility wavefront sensor FELIX. Correcting the first seven Zernike modes through coma at 90-180 Hz, we are able to enhance the seeing by a factor of 1.8 in FWHM under 0."5 seeing conditions. We also performed the first science observations with the ASM in "static" mode and demonstrated that we can improve the throughput of IRTF's slit spectrograph by approximately a factor of 2, although this requires good reference slopes in FELIX. In the near future, we plan to optimize the calibration of reference slopes in FELIX and streamline the software so that the system can be operated by a non-AO expert.

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arXiv2024

In-lab and On-sky Closed-loop Results of Adaptive Secondary Mirrors with TNO's Hybrid Variable Reluctance Actuators

We performed closed-loop lab testing of large-format deformable mirrors (DMs) with hybrid variable reluctance actuators. TNO has been developing the hybrid variable reluctance actuators in support for a new generation of adaptive secondary mirrors (ASMs), which aim to be more robust and reliable. Compared to the voice coil actuators, this new actuator technology has a higher current to force efficiency, and thus can support DMs with thicker facesheets. Before putting this new technology on-sky, it is necessary to understand how to control it and how it behaves in closed-loop. We performed closed-loop tests with the Shack-Hartmann wavefront sensor with three large-format deformable mirrors that use the TNO actuators: DM3, FLASH, and IRTF-ASM-1 ASM. The wavefront sensor and the real-time control systems were developed for the NASA Infrared Telescope Facility (IRTF) and the UH 2.2-meter telescope ASMs. We tested IRTF-ASM-1 on-sky and proved that it meets all of our performance requirements. This work presents our lab setup for the experiments, the techniques we have employed to drive these new ASMs, the results of our closed-loop lab tests for FLASH and IRTF-ASM-1, and the on-sky closed-loop results of IRTF-ASM-1 ASM.

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arXiv2024

First laboratory and on-sky results of an adaptive secondary mirror with TNO-style actuators on the NASA Infrared Telescope Facility

We are developing an adaptive secondary mirror (ASM) that uses a new actuator technology created by the Netherlands Organization for Applied Scientific Research (TNO). The TNO hybrid variable reluctance actuators have more than an order of magnitude better efficiency over the traditional voice coil actuators that have been used on existing ASMs and show potential for improving the long-term robustness and reliability of ASMs. To demonstrate the performance, operations, and serviceability of TNO's actuators in an observatory, we have developed a 36-actuator prototype ASM for the NASA Infrared Telescope Facility (IRTF) called IRTF-ASM-1. IRTF-ASM-1 provides the first on-sky demonstration of this approach and will help us evaluate the long-term performance and use of this technology in an astronomical facility environment. We present calibration and performance results with the ASM in a Meniscus Hindle Sphere lens setup as well as preliminary on-sky results on IRTF. IRTF-ASM-1 achieved stable closed-loop performance on-sky with H-band Strehl ratios of 35-40% in long-exposure images under a variety of seeing conditions.

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arXiv2023

V(WF)$^2$S: Very Wide Field WaveFront Sensor for GLAO

Adaptive optics is a technique mostly used on large telescopes. It turns out to be challenging for smaller telescopes (0.5~2m) due to the small isoplanatic angle, small subapertures and high correction speeds needed at visible wavelengths, requiring bright stars for guiding, severely limiting the sky coverage. NGS SCAO is ideal for planetary objects but remains limited for general purpose observing. The approach we consider is a compromise between image quality gain and sky coverage: we propose to partially improve the image quality anywhere in the sky instead of providing the diffraction limit around a few thousand bright stars. We suggest a new solution based on multiple AO concepts brought together: The principle is based on a rotating Foucault test, like the first AO concept proposed by H. Babcock in 1953, on the Ground Layer Adaptive Optics, proposed by Rigaut and Tokovinin in the early 2000s, and on the idea of Layer-oriented MCAO and the pupil-plane wavefront analysis by R. Ragazzoni. We propose to combine these techniques to use all the light available in a large field to measure the ground layer turbulence and enable the high angular resolution imaging of regions of the sky (e.g., nebulas, galaxies) inaccessible to traditional AO systems. The motivation to develop compact and robust AO system for small telescopes is two-fold: On the one hand, universities often have access to small telescopes as part of their education programs. Also, researchers in countries with fewer resources could also benefit from reliable adaptive optics system on smaller telescopes for research and education purposes. On the other hand, amateur astronomers and enthusiasts want improved image quality for visual observation and astrophotography. Implementing readily accessible adaptive optics in astronomy clubs would also likely have a significant impact on citizen science.

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arXiv2021

Developing Adaptive Secondary Mirror Concepts for the APF and W.M. Keck Observatory Based on HVR Technology

An Adaptive secondary mirror (ASM) allows for the integration of adaptive optics (AO) into the telescope itself. Adaptive secondary mirrors, based on hybrid variable reluctance (HVR) actuator technology, developed by TNO, provide a promising path to telescope-integrated AO. HVR actuators have the advantage of allowing mirrors that are stiffer, more power efficient, and potentially less complex than similar, voice-coil based ASM's. We are exploring the application of this technology via a laboratory testbed that will validate the technical approach. In parallel, we are developing conceptual designs for ASMs at several telescopes including the Automated Planet Finder Telescope (APF) and for Keck Observatory. An ASM for APF has the potential to double the light through the slit for radial velocity measurements, and dramatically improved the image stability. An ASM for WMKO enables ground layer AO correction and lower background infrared AO observations, and provides for more flexible deployment of instruments via the ability to adjust the location of the Cassegrain focus.

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arXiv2021

Performance of Large-Format Deformable Mirrors Constructed with Hybrid Variable Reluctance Actuators II: Initial Lab Results from FLASH

Advancements in high-efficiency hybrid variable reluctance (HVR) actuators are an enabling technology for building the next generation of large-format deformable mirrors, including adaptive secondary mirrors. The Netherlands Organization for Applied Scientific Research (TNO) has developed a new style of hybrid variable reluctance actuator that requires approximately seventy-five times less power to operate as compared to the traditional style of voice-coil actuators. We present the initial performance results from laboratory testing of TNO's latest 19-actuator prototype deformable mirror, FLASH. We report the actuator cross-coupling, linearity, hysteresis, natural shape flattening, and drift as measured with a Zygo interferometer and a set of four capacitive sensors. We also present results of the dynamic performance of the FLASH on sub-millisecond timescales to estimate the limits of this technology for high-contrast imaging adaptive optics. We confirm that this technology has strong potential for use in on-sky adaptive secondary mirrors without the need for active cooling.

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arXiv2020

Performance of Large-Format Deformable Mirrors Constructed with TNO Variable Reluctance Actuators

Advancements in making high-efficiency actuators are an enabling technology for building the next generation of large-format deformable mirrors. The Netherlands Organization for Applied Scientific Research (TNO) has developed a new style of variable-reluctance actuator that requires approximately eighty times less power to operate as compared to the traditional style of voice-coil actuators. We present the performance results from laboratory testing of TNO's 57-actuator large-format deformable mirror from measuring the influence functions, linearity, hysteresis, natural shape flattening, actuator cross-coupling, creep, repeatability, and actuator lifetime. We measure a linearity of 99.4 +- 0.33% and hysteresis of 2.10 +- 0.23% over a stroke of 10 microns, indicating that this technology has strong potential for use in on-sky adaptive secondary mirrors (ASMs). We summarize plans for future lab prototypes and ASMs that will further demonstrate this technology.

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