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Spectral response function mapping to detect Earth twins
Lead Supervisor: David Buscher, Department of Physics

Brief summary
The project aims to test a new idea for interferometric wavelength calibration of EPRV spectrographs by building a prototype system and testing it in the laboratory. The new idea uses a broadband light source to illuminate the spectrograph through a Fourier-transform spectrograph (FTS) arrangement. Fourier analysis of the spectra seen for different values of the optical path difference in the FTS will allow high-precision measurement of the spectral response of each pixel.

Importance of the area of research concerned
The detection of ``Earth twins'' – rocky planets orbiting at radii of order 1au around solar-type stars – will be one of the major stepping-stones in our search for life in the Universe. One of the most promising avenues to make these detections is to use extreme precision radial velocity (EPRV) spectrographs to detect the minute (10 cm/s) stellar reflex Doppler signals caused by the Earth twin. Ongoing advances in wavelength calibration using laser frequency combs and disentangling the effects of stellar activity features mean that this goal is now within reach. This research aims at addressing the problem of calibrating the wavelength of each individual pixel in an EPRV spectrograph – something that even laser combs are not currently able to do – in order to help reach the 10 cm/s goal needed for Earth twin detection.

What will the student do?
The student will build a Michelson interferometer in the laboratory and use this to feed light into a test spectrograph. They will develop software in Python to control the interferometer and to analyse the data from the interferometer and the spectrograph. The student will use the results of this analysis to determine how well the system works and recommend future improvements to the system design.

Zhao, Lily L., David W. Hogg, Megan Bedell, and Debra A. Fischer. ‘Excalibur: A Nonparametric, Hierarchical Wavelength Calibration Method for a Precision Spectrograph’. The Astronomical Journal 161, no. 2 (January 2021): 80.

Charsley, Jake M., Richard A. McCracken, Derryck T. Reid, Grzegorz Kowzan, Piotr Maslowski, Ansgar Reiners, and Philipp Huke. ‘Comparison of Astrophysical Laser Frequency Combs with Respect to the Requirements of HIRES’. In Proc. SPIE, 10329:103290Y. International Society for Optics and Photonics, 2017.

Thompson, Samantha J., Didier Queloz, Isabelle Baraffe, Martyn Brake, Andrey Dolgopolov, Martin Fisher, Michel Fleury, et al. ‘HARPS3 for a Roboticized Isaac Newton Telescope’. In Proc. SPIE, 9908:99086F. International Society for Optics and Photonics, 2016.

Requirements as to the educational background of candidates that would be suitable for the project
This project requires a degree in Physics or related discipline. It would suit students with a background in optics, computer control of hardware, and data analysis.

You can find out about applying for this project on the Leverhulme Centre for Life in the Universe widening participation PhD Studentships page.