LATE PROJECT: Non-invasive atmospheric monitoring not only for large observatories

Advisor: Jan Ebr or Michael Prouza (IP CAS)

Funding: Fully funded

Website: https://www.fzu.cz/en/research/research-topics/instruments-atmospheric-calibration-astroparticle-experiments

Contact: ebr@fzu.cz

This is a late project added after application deadline. If you are interested, please contact the project advisor on the email above.

The knowledge of the state of the atmosphere is a necessary condition for the operation of any optical observatory. The Prague team is currently involved in atmospheric monitoring at the sites of two large optical experiments in astroparticle physics – the Pierre Auger Observatory operated in Argentina and the Cherenkov Telescope Array (CTA) being built in Chile and the Canary Islands. Unlike in the case of large traditional astronomical observatories, where the most closely monitored variables of the atmospheric conditions are flow turbulence (seeing) and water vapor content, the main challenge for the operation of the astroparticle experiments requires is the knowledge of the momentary aerosol load above the detector [1]. This value is easily measured using laser-based methods, but as extensive usage of lasers interferes with the operation of the primary detectors, other, non-invasive methods are highly valuable.

The Prague team has been developing methods for non-invasive atmospheric monitoring for over a decade. The primary tools for this monitoring are small robotic telescopes (known as FRAMs) which determine the transparency of the atmosphere using stars as reference light sources. The first FRAM telescope, located at the Pierre Auger Observatory, has been regularly used for the monitoring of clouds in the field of view of the fluorescence telescopes of the Observatory. Recently, a novel method to use the stellar photometry obtained by the FRAMs for precision aerosol measurements has been developed and refined to a precision comparable with state-of-the-art methods in the field [2]. It will serve as a tool to both characterize aerosol climatology at future sites of optical experiments (such as CTA) and to provide real-time data on atmospheric transparency during the operation of such experiments [3].  Three FRAMs were already constructed and shipped to both CTA sites Chile and La Palma, an additional FRAM for the Pierre Auger Observatory is being built.

There are numerous research directions possible within the FRAM project. Large amount of data have been obtained and are waiting to be processed. The methods are still being actively improved and broadened to further applications, such as the study of horizontal inhomogeneities of aerosols or the wavelength-dependence of the scattering. Data from different telescopes of different sizes are available for studies of the most efficient hardware choices. A large archive of “incidental” astronomical data taken during the atmospheric measurements is been kept and offers the potential for numerous discoveries. Perhaps most importantly, concrete opportunities exist for collaboration with other groups doing atmospheric monitoring at the relevant experiments, at the European Southern Observatory (including the currently built largest optical telescope in the world, E-ELT) and in meteorology and climatology. On top of all that, the Prague group also operates two Sun/Moon Photometers [4] (which use a similar idea to the FRAM, but with the Sun and the Moon as light sources) and is collaborating with top experts on the analysis of this data.

We offer an experimentally focused PhD. position. The student would contribute to the analysis of atmospheric monitoring data from FRAM telescopes and participate in the further development of analysis methods for the data. Depending on the capabilities, motivation and initiative of the student, a vast variety of applications across various fields can be explored.

References:

[1] B. Keilhauer for the Pierre Auger Collaboration: Atmospheric Monitoring at a Cosmic Ray Observatory - a long-lasting endeavour, EPJ Web Conf. 197 (2019) 02001.
[2] J. Ebr et al.: A New Method for Aerosol Measurement using Wide-field Photometry, submitted to AJ - https://arxiv.org/abs/2101.03074 .
[3] J. Ebr et al. for the CTA consortium: Atmospheric calibration of the Cherenkov Telescope Array, PoS ICRC2017 (2018) 833.
[4] J. Juryšek for the CTA consortium: Sun/Moon photometer for the Cherenkov Telescope Array - first results, PoS(ICRC2017)853 .