Matthew Townson's Outputs (27)

Optical sparse telescope arrays and scintillation noise (2023)
Journal Article
Hartley, K. E., Farley, O. J. D., Townson, M. J., Osborn, J., & Wilson, R. W. (2023). Optical sparse telescope arrays and scintillation noise. Monthly Notices of the Royal Astronomical Society, 526(1), 1235-1245. https://doi.org/10.1093/mnras/stad2835

Fresnel propagation of starlight after it passes through high altitude turbulence in the Earth’s atmosphere results in random fluctuations of the intensity at ground level, known as scintillation. This effect adds random noise to photometric measurem... Read More about Optical sparse telescope arrays and scintillation noise.

First On-Sky Demonstration of a Scintillation Correction technique using Tomographic Wavefront Sensing (2023)
Journal Article
Hartley, K. E., Farley, O. J., Townson, M. J., Osborn, J., & Wilson, R. (2023). First On-Sky Demonstration of a Scintillation Correction technique using Tomographic Wavefront Sensing. Monthly Notices of the Royal Astronomical Society, 520(3), 4134-4146. https://doi.org/10.1093/mnras/stad420

Scintillation noise significantly limits high precision ground-based photometry of bright stars. In this paper we present the first ever on-sky demonstration of scintillation correction. The technique uses tomographic wavefront sensing to estimate th... Read More about First On-Sky Demonstration of a Scintillation Correction technique using Tomographic Wavefront Sensing.

Demonstrating 24-hour continuous vertical monitoring of atmospheric optical turbulence (2023)
Journal Article
Griffiths, R., Osborn, J., Farley, O., Butterley, T., Townson, M. J., & Wilson, R. (2023). Demonstrating 24-hour continuous vertical monitoring of atmospheric optical turbulence. Optics Express, 31(4), 6730-6740. https://doi.org/10.1364/oe.479544

We report what is believed to be the first example of fully continuous, 24-hour vertical monitoring of atmospheric optical turbulence. This is achieved using a novel instrument, the 24-hour Shack-Hartmann Image Motion Monitor (24hSHIMM). Optical turb... Read More about Demonstrating 24-hour continuous vertical monitoring of atmospheric optical turbulence.

FAST: Fourier domain adaptive optics simulation tool for bidirectional ground-space optical links through atmospheric turbulence (2022)
Journal Article
Farley, O., Townson, M., & Osborn, J. (2022). FAST: Fourier domain adaptive optics simulation tool for bidirectional ground-space optical links through atmospheric turbulence. Optics Express, 30(13), 23050-23064. https://doi.org/10.1364/oe.458659

Free space optical links between the ground and space may be severely degraded by atmospheric turbulence. Adaptive Optics, a technique allowing partial correction of this degradation, is beginning to see use in the field with the potential to achieve... Read More about FAST: Fourier domain adaptive optics simulation tool for bidirectional ground-space optical links through atmospheric turbulence.

Astrosat: forecasting satellite transits for optical astronomical observations (2021)
Journal Article
Osborn, J., Blacketer, L., Townson, M. J., & Farley, O. J. (2022). Astrosat: forecasting satellite transits for optical astronomical observations. Monthly Notices of the Royal Astronomical Society, 509(2), 1848-1852. https://doi.org/10.1093/mnras/stab3003

The impact of large-scale constellations of satellites, is a concern for ground-based astronomers. In recent years there has been a significant increase in the number of satellites in low-Earth orbit and this trend is set to continue. The large numbe... Read More about Astrosat: forecasting satellite transits for optical astronomical observations.

ELT-scale elongated LGS wavefront sensing: on-sky results (2021)
Journal Article
Bardou, L., Gendron, E., Rousset, G., Gratadour, D., Basden, A., Bonaccini Calia, D., …Vidal, F. (2021). ELT-scale elongated LGS wavefront sensing: on-sky results. Astronomy & Astrophysics, 649, Article A158. https://doi.org/10.1051/0004-6361/202038330

Context. Laser guide stars (LGS) allow adaptive optics (AO) systems to reach greater sky coverage, especially for AO systems correcting the atmospheric turbulence on large fields of view. However LGS suffer from limitations, among which is their appa... Read More about ELT-scale elongated LGS wavefront sensing: on-sky results.

Adaptive Optics pre-compensated laser uplink to LEO and GEO (2021)
Journal Article
Osborn, J., Townson, M., Farley, O., Reeves, A., & Mata Calvo, R. (2021). Adaptive Optics pre-compensated laser uplink to LEO and GEO. Optics Express, 29(4), 6113-6132. https://doi.org/10.1364/oe.413013

We present the results from a Monte Carlo computer simulation of adaptive optics (AO) pre-compensated laser uplink propagation through the Earth’s atmospheric turbulence from the ground to orbiting satellites. The simulation includes the so-called po... Read More about Adaptive Optics pre-compensated laser uplink to LEO and GEO.

Automated wind velocity profiling from adaptive optics telemetry (2019)
Journal Article
Laidlaw, D. J., Osborn, J., Morris, T. J., Basden, A. G., Gendron, E., Rousset, G., …Wilson, R. W. (2020). Automated wind velocity profiling from adaptive optics telemetry. Monthly Notices of the Royal Astronomical Society, 491(1), 1287-1294. https://doi.org/10.1093/mnras/stz3062

Ground-based adaptive optics (AO) systems can use temporal control techniques to greatly improve image resolution. A measure of wind velocity as a function of altitude is needed to minimize the temporal errors associated with these systems. Spatio-te... Read More about Automated wind velocity profiling from adaptive optics telemetry.

AOtools - a Python package for adaptive optics modelling and analysis (2019)
Journal Article
Townson, M., Farley, O., Orban de Xivry, G., Osborn, J., & Reeves, A. (2019). AOtools - a Python package for adaptive optics modelling and analysis. Optics Express, 27(22), 31316-31329. https://doi.org/10.1364/oe.27.031316

AOtools is a Python package that is open-source and aimed at providing tools for adaptive optics users and researchers. We present version 1.0, which contains tools for adaptive optics processing, including analysing data in the pupil plane, images a... Read More about AOtools - a Python package for adaptive optics modelling and analysis.

Efficient implementation of pseudo open loop control for adaptive optics on Extremely Large Telescopes (2019)
Journal Article
Basden, A., Jenkins, D., Morris, T., Osborn, J., & Townson, M. (2019). Efficient implementation of pseudo open loop control for adaptive optics on Extremely Large Telescopes. Monthly Notices of the Royal Astronomical Society, 486(2), 1774-1780. https://doi.org/10.1093/mnras/stz918

Closed-loop adaptive optics systems which use minimum mean square error wavefront reconstruction require the computation of pseudo open loop wavefront slopes. These techniques incorporate a knowledge of atmospheric statistics which must therefore be... Read More about Efficient implementation of pseudo open loop control for adaptive optics on Extremely Large Telescopes.

Optimizing the accuracy and efficiency of optical turbulence profiling using adaptive optics telemetry for extremely large telescopes (2018)
Journal Article
Laidlaw, D. J., Osborn, J., Morris, T. J., Basden, A. G., Beltramo-Martin, O., Butterley, T., …Wilson, R. W. (2018). Optimizing the accuracy and efficiency of optical turbulence profiling using adaptive optics telemetry for extremely large telescopes. Monthly Notices of the Royal Astronomical Society, 483(4), 4341-4353. https://doi.org/10.1093/mnras/sty3285

Advanced adaptive optics (AO) instruments on ground-based telescopes require accurate knowledge of the atmospheric turbulence strength as a function of altitude. This information assists point spread function reconstruction, AO temporal control techn... Read More about Optimizing the accuracy and efficiency of optical turbulence profiling using adaptive optics telemetry for extremely large telescopes.

Representative optical turbulence profiles for ESO Paranal by hierarchical clustering (2018)
Journal Article
Farley, O., Osborn, J., Morris, T., Sarazin, M., Butterley, T., Townson, M., …Wilson, R. (2018). Representative optical turbulence profiles for ESO Paranal by hierarchical clustering. Monthly Notices of the Royal Astronomical Society, 481(3), 4030-4037. https://doi.org/10.1093/mnras/sty2536

Knowledge of the optical turbulence profile is important in adaptive optics (AO) systems, particularly tomographic AO systems such as those to be employed by the next generation of 40-m class extremely large telescopes. Site characterization and moni... Read More about Representative optical turbulence profiles for ESO Paranal by hierarchical clustering.

Generating artificial reference images for open loop correlation wavefront sensors (2018)
Journal Article
Townson, M., Love, G., & Saunter, C. (2018). Generating artificial reference images for open loop correlation wavefront sensors. Monthly Notices of the Royal Astronomical Society, 479(2), 1595-1602. https://doi.org/10.1093/mnras/sty1362

Shack–Hartmann wavefront sensors for both solar and laser guide star adaptive optics (with elongated spots) need to observe extended objects. Correlation techniques have been successfully employed to measure the wavefront gradient in solar adaptive o... Read More about Generating artificial reference images for open loop correlation wavefront sensors.

Optical turbulence profiling with Stereo-SCIDAR for VLT and ELT (2018)
Journal Article
Osborn, J., Wilson, R., Sarazin, M., Butterley, T., Chacon, A., Derie, F., …Townson, M. (2018). Optical turbulence profiling with Stereo-SCIDAR for VLT and ELT. Monthly Notices of the Royal Astronomical Society, 478(1), 825-834. https://doi.org/10.1093/mnras/sty1070

Knowledge of the Earth’s atmospheric optical turbulence is critical for astronomical instrumentation. Not only does it enable performance verification and optimisation of existing systems but it is required for the design of future instruments. As a... Read More about Optical turbulence profiling with Stereo-SCIDAR for VLT and ELT.

On-sky demonstration of matched filters for wavefront measurements using ELT-scale elongated laser guide stars (2017)
Journal Article
Basden, A., Bardou, L., Bonaccini-Calia, D., Buey, T., Centrone, M., Chemla, F., …Vidal, F. (2017). On-sky demonstration of matched filters for wavefront measurements using ELT-scale elongated laser guide stars. Monthly Notices of the Royal Astronomical Society, 466(4), 5003-5010. https://doi.org/10.1093/mnras/stx062

The performance of adaptive optics systems is partially dependent on the algorithms used within the real-time control system to compute wavefront slope measurements. We demonstrate the use of a matched filter algorithm for the processing of elongated... Read More about On-sky demonstration of matched filters for wavefront measurements using ELT-scale elongated laser guide stars.

Correlation Wavefront Sensing and Turbulence Profiling for Solar Adaptive Optics (2016)
Thesis
Townson, M. J. (2016). Correlation Wavefront Sensing and Turbulence Profiling for Solar Adaptive Optics. (Thesis). Durham University. Retrieved from https://durham-repository.worktribe.com/output/1647300

Turbulence velocity profiling for high sensitivity and vertical-resolution atmospheric characterization with Stereo-SCIDAR (2016)
Journal Article
Osborn, J., Butterley, T., Townson, M., Reeves, A., Morris, T., & Wilson, R. (2017). Turbulence velocity profiling for high sensitivity and vertical-resolution atmospheric characterization with Stereo-SCIDAR. Monthly Notices of the Royal Astronomical Society, 464(4), 3998-4007. https://doi.org/10.1093/mnras/stw2685

As telescopes become larger, into the era of ∼40 m Extremely Large Telescopes, the high-resolution vertical profile of the optical turbulence strength is critical for the validation, optimization and operation of optical systems. The velocity of atmo... Read More about Turbulence velocity profiling for high sensitivity and vertical-resolution atmospheric characterization with Stereo-SCIDAR.

Turbulence profiling for adaptive optics tomographic reconstructors (2016)
Presentation / Conference Contribution
Laidlaw, D. J., Osborn, J., Wilson, R. W., Morris, T. J., Butterley, T., Reeves, A. P., …Morel, C. (2016, July). Turbulence profiling for adaptive optics tomographic reconstructors

Improved shift estimates on extended Shack–Hartmann wavefront sensor images (2015)
Journal Article
Townson, M., Kellerer, A., & Saunter, C. (2015). Improved shift estimates on extended Shack–Hartmann wavefront sensor images. Monthly Notices of the Royal Astronomical Society, 452(4), 4022-4028. https://doi.org/10.1093/mnras/stv1503

An important factor which affects performance of solar adaptive optics (AO) systems is the accuracy of tracking an extended object in the wavefront sensor. The accuracy of a centre-of-mass approach to image shift measurement depends on the parameters... Read More about Improved shift estimates on extended Shack–Hartmann wavefront sensor images.

Characterising daytime atmospheric conditions on La Palma (2015)
Journal Article
Townson, M., Kellerer, A., Osborn, J., Butterley, T., Morris, T., & Wilson, R. (2015). Characterising daytime atmospheric conditions on La Palma. Journal of Physics: Conference Series, 595, Article 012035. https://doi.org/10.1088/1742-6596/595/1/012035

Day-time turbulence profiles are important for the next generation of Solar Telescopes, which will be equipped with multi conjugate adaptive optics systems. We measured daytime turbulence profiles above La Palma from 17th to 19th September 2013 using... Read More about Characterising daytime atmospheric conditions on La Palma.

Phase A AO system design and performance for MOSAIC at the ELT
Presentation / Conference Contribution
Morris, T., Basden, A., Calcines-Rosario, A., Dohlen, K., Dubbeldam, C., El Hadi, K., Fitzsimons, E., Fusco, T., Gendron, É., Hammer, F., Jagourel, P., Jenkins, D., Morel, C., Morris, S., Rousset, G., Townson, M., Vola, P., & Younger, E. (2018, June). Phase A AO system design and performance for MOSAIC at the ELT. Presented at Adaptive Optics Systems VI: SPIE Astronomical Telescopes + Instrumentation 2018, Austin, Texas

MOSAIC is a mixed-mode multiple object spectrograph planned for the ELT that uses a tiled focal plane to support a variety of observing modes. The MOSAIC AO system uses 4 LGS WFS and up to 4 NGS WFS positioned anywhere within the full 10 arcminute EL... Read More about Phase A AO system design and performance for MOSAIC at the ELT.

Photometry and Spectrum measurements of the Laser Guide Star beam emission at Observatorio del Roque de Los Muchachos with the Gran Telescope Canarias
Presentation / Conference Contribution
Lombardi, G., Calia, B., Centrone, M., Talavera, M. R. G., Morris, T., Pfrommer, T., Basden, A., Vidal, F., Gendron, E., Rousset, G., Mayers, R., Osborn, J., Reeves, A., Talbot, R., Townson, M., Lavers, A. C., & Postigoh, A. D. U. (2017, June). Photometry and Spectrum measurements of the Laser Guide Star beam emission at Observatorio del Roque de Los Muchachos with the Gran Telescope Canarias. Presented at Adaptive Optics for Extremely Large Telescopes 5, Tenerife, Canary Islands, Spain

In the past years ESO has built together with industry a transportable Laser Guide Star Unit (WLGSU) to test the laser technology while supporting some strategic experiments for the LGS-AO technologies. Since July 2016, the WLGSU has been installed a... Read More about Photometry and Spectrum measurements of the Laser Guide Star beam emission at Observatorio del Roque de Los Muchachos with the Gran Telescope Canarias.

Reducing the Field of View in Correlating Wavefront Sensors for Solar Adaptive Optics
Presentation / Conference Contribution
Townson, M. J., & Saunter, C. D. (2017, June). Reducing the Field of View in Correlating Wavefront Sensors for Solar Adaptive Optics. Presented at Adaptive Optics for Extremely Large Telescopes 5 (AO4ELT5), Tenerife, Canary Islands, Spain

Wavefront sensing for solar adaptive optics currently requires the use of extended-field Shack-Hartmann wavefront sensors. Such wavefront sensors suffer from a reduced sensitivity to high altitude turbulence due effects of measuring wavefront gradien... Read More about Reducing the Field of View in Correlating Wavefront Sensors for Solar Adaptive Optics.

Preliminary on-sky results of the CANARY experiment with an ELT-elongated sodium LGS
Presentation / Conference Contribution
Bardou, L., Gendron, E., Rousset, G., Gratadour, D., Basden, A. G., Bonaccini, D., Buey, T., Centrone, M., Chemla, F., Lombardi, G., Marchetti, E., Morris, T. J., Myers, R. M., Osborn, J., Townson, M. J., Vidal, F., & Reyes Garcia-Talavera, M. (2017, June). Preliminary on-sky results of the CANARY experiment with an ELT-elongated sodium LGS. Presented at Adaptive Optics for Extremely Large Telescopes 5, Tenerife, Canary Islands, Spain

We present on-sky results of wavefront sensing on an elongated LGS. These results are derived from observations made with the multi-object AO demonstrator CANARY on the William Herschel Telescope (WHT) in La Palma. The laser guide star is produced us... Read More about Preliminary on-sky results of the CANARY experiment with an ELT-elongated sodium LGS.

Correlation wavefront sensing for extended objects
Presentation / Conference Contribution
Townson, M. J., Love, G. D., Kellerer, A., & Saunter, C. D. (2016, July). Correlation wavefront sensing for extended objects. Presented at Adaptive Optics Systems V., Edinburgh

Daytime site characterisation of La Palma, and its relation to night-time conditions
Presentation / Conference Contribution
Townson, M., Kellerer, A., Osborn, J., Butterley, T., Morris, T., & Wilson, R. (2014, December). Daytime site characterisation of La Palma, and its relation to night-time conditions. Presented at Ground-based and Airborne Instrumentation for Astronomy V, Montréal, Quebec

This paper presents preliminary daytime profiles taken using a Wide-Field Shack-Hartmann Sensor at the Swedish Solar Telescope (SST), La Palma. These are contrasted against Stereo-SCIDAR data from corresponding nights to assess the validity of the as... Read More about Daytime site characterisation of La Palma, and its relation to night-time conditions.

The 24hSHIMM: a continuous day and night turbulence monitor for optical communications
Presentation / Conference Contribution
Griffiths, R., Osborn, J., Farley, O., Butterley, T., Townson, M., & Wilson, R. (2023, January). The 24hSHIMM: a continuous day and night turbulence monitor for optical communications. Presented at Free-Space Laser Communications XXXV, San Francisco, United States

We present the 24-hour Shack-Hartmann Image Motion Monitor (24hSHIMM), the first truly continuous, 24-hour optical turbulence monitor. Atmospheric optical turbulence is a significant limitation for free-space optical communications and other technolo... Read More about The 24hSHIMM: a continuous day and night turbulence monitor for optical communications.