Chapter 1: Introduction to CHEOPS

The CHEOPS (CHaracterising ExOPlanet Satellite) telescope, developed by the European Space Agency (ESA), has recently achieved a significant milestone by capturing its inaugural images of the universe, yielding results that exceeded initial expectations. Launched on December 18, 2019, via a Soyuz rocket, this satellite is designed to bridge the gap between earlier exoplanet-hunting missions and the advanced research efforts to be conducted by the upcoming James Webb Space Telescope and the Earth-based Extremely Large Telescope currently in construction in the Atacama Desert, Chile. While CHEOPS is not tasked with discovering new exoplanets, its primary role is to refine existing targets, transforming them into prime candidates for in-depth studies.

The initial image captured by CHEOPS showcases a star selected as a target, situated 150 light-years away in the constellation of Cancer. The image, measuring approximately 1000x1000 pixels, reveals that each pixel represents a minuscule angle of around 0.0003 degrees (1 arcsecond) in the sky. The fainter stars visible in the background enhance the context of the primary target. Notably, the star appears deliberately defocused, a design choice that allows CHEOPS to accumulate light from all pixels surrounding the star, thus achieving optimal photometric precision.

As the image was received, it brought immense joy to space enthusiasts and provided significant reassurance to the consortium of ESA researchers and scientists from the Universities of Bern and Geneva, who operate the telescope. Willy Benz, Professor of Astrophysics at the University of Bern and Principal Investigator of the CHEOPS mission, remarked, “The first images were crucial in confirming that the telescope's optics had survived the launch intact. When the initial images appeared, it was clear we had a functioning telescope.”

The research team is now focused on evaluating the telescope's performance over the next two months through extensive testing. Initial results appear promising. David Ehrenreich, CHEOPS project scientist at the University of Geneva, stated, “We will conduct a detailed analysis of additional images to ascertain the exact level of accuracy CHEOPS can achieve across various scientific parameters.”

Section 1.1: Defocusing for Precision

Interestingly, while the first images from CHEOPS are better than anticipated, they are not sharper. The telescope has been intentionally defocused to disperse light across multiple pixels, which helps mitigate any disturbances affecting the satellite. This approach is key to achieving high photometric precision. “The blurred images we received are smoother and more symmetrical than we expected from laboratory measurements,” noted Benz.

High precision is crucial for CHEOPS, as it aims to detect minute variations in a star's brightness when an orbiting exoplanet transits in front of it. This method, known as photometry or the transit method, necessitates exceptional sensitivity due to the significant size difference between stars and their orbiting planets. A prime example is the observation of Mercury transiting across the Sun.

The highlighted speck in the image represents Mercury, illustrating how even a small fraction of light can be obscured during its transit. CHEOPS will make these observations from hundreds to thousands of light-years away.

By employing the transit technique, astronomers can not only detect the presence of an exoplanet but also gather information about its characteristics. CHEOPS will primarily focus on measuring the size of exoplanets, which correlates with the brightness dip observed during transits. “The initial analyses are encouraging and serve as a boost for the team,” concluded Benz.

Chapter 2: Conclusion

The successful capture of images by the CHEOPS telescope marks a significant advancement in the study of exoplanets, offering new insights and opportunities for future exploration.