2023-2024 / SPAT0067-1

Atmospheric and adaptive optics


15h Th, 5h Pr

Number of credits

 Master in space sciences (120 ECTS)2 crédits 


Olivier Absil

Language(s) of instruction

English language

Organisation and examination

Teaching in the second semester


Schedule online

Units courses prerequisite and corequisite

Prerequisite or corequisite units are presented within each program

Learning unit contents

Atmospheric optics is the study of optical effects induced by the Earth atmosphere on light propagating from distant sources. Of particular concern to astronomers is atmospheric turbulence, which limits the performance of ground-based telescopes. The past two decades have seen remarkable progress in the capabilities and performance of adaptive optics (AO) systems. These opto-mechanical systems actively compensate for the blurring effect of the Earth's turbulent atmosphere. By sensing, and correcting, wavefront distortion introduced by atmospheric index-of-refraction variations, AO systems can produce images with resolution approaching the diffraction limit of the telescope at near-infrared wavelengths.

In this course, we detail the physical processes and fundamental equations of atmospheric optics that are most relevant to astronomy, and discuss the techniques used to characterize atmospheric turbulence. The fundamentals of AO are then introduced, including a description of wavefront sensing techniques, deformable mirrors, laser guide stars, and closed-loop control systems. We describe the AO error budget, and introduce the various flavours of advanced AO systems that have been developed over the last 20 years. The principles of each are outlined, the performance and limitations are examined, and a few notable applications of AO-assisted imaging are discussed (extrasolar planets, circumstellar disks, galactic center, etc).

Learning outcomes of the learning unit

This course aims to give an overview of the properties of atmospheric turbulence, to show how it affects the quality of astronomical images, and to describe how it can be corrected for using adaptive optics techniques. At the end of the course, the student will be able to understand and describe the successive deformations of a wave front from its entrance in the Earth atmosphere down to its measurement at the focus of a telescope equipped with adaptive optics. The course will give sufficient knowledge to embark in more advanced projects related to state-of-the-art ground-based astronomical imaging.

Prerequisite knowledge and skills

This course requires a basic knowledge of geometrical and physical optics. This is the reason why we suggest to also follow PHYS0048-3 (Coherent and incoherent optics, Instrumental optics I), although this is not mandatory. A brief introduction to physical optics will be given at the start of the course.

Planned learning activities and teaching methods

Theoretical part: lectures based on two main review articles (Roddier et al. 1981 on atmospheric turbulence, Hickson et al. 2016 on adaptive optics). A slideshow will be used and made available to the students.
Practical part: critical review of a recent research paper in the field of atmospheric or adaptive optics, 10-min presentation of a summary of that paper, and discussion.

Mode of delivery (face to face, distance learning, hybrid learning)

Face-to-face course

Additional information:

Recordings of the lectures can be made available to the students, if necessary.

Recommended or required readings

The slideshow used during the lectures will be made available to the students, as well as the two review articles on which the lectures are based.
Further recommended reading: "Principles of adaptive optics, 3rd edition" (Robert K. Tyson, 2012, CRC Press).

Exam(s) in session

Any session

- In-person

oral exam

Other : Presentation of a scientific paper to the class.

Additional information:

The evaluation will be carried out in two parts:

- an oral exam where the students will be asked to answer two questions on the theoretical lectures, randomly drawn from a list of questions submitted to the students a few weeks in advance,

- a presentation of the research article proposed to the student, followed by some questions and a discussion with the class.

The oral exam will count for 2/3rd and the homework for 1/3rd of the final grade.

Work placement(s)

Organisational remarks and main changes to the course


- Teacher: Dr Olivier Absil, F.R.S.-FNRS Senior Research Associate (olivier.absil@uliege.be)
- Secretary: Ms Nicole Massin (N.Massin@uliege.be)

Association of one or more MOOCs