The Launch of TESS

On 18 April 2018, the Transiting Exoplanet Survey Satellite, commonly known as TESS, was launched into space to begin its ambitious mission of mapping the heavens. This deployment represented a shift in the methodology of planetary discovery, moving away from the deep-field observations of its predecessors to a more comprehensive approach. By focusing its sensors on the brightest and closest stars in the sky, the mission aimed to create a vast catalogue of worlds that could be studied in greater detail by other observatories. The launch served as a critical step in the ongoing effort to understand the diversity of planetary systems existing beyond our own solar system.

The primary objective of this mission was to conduct an all-sky survey designed to identify transiting exoplanets. A transit occurs when a planet passes directly in front of its host star, causing a subtle, periodic dip in the star's brightness that can be detected by sensitive instruments. By monitoring these fluctuations across the entire celestial sphere, the satellite provided astronomers with a wealth of data regarding the size, orbital period, and atmospheric potential of distant planets. This systematic survey was intended to fill significant gaps in our knowledge of how common Earth-sized or larger planets are within our immediate galactic neighbourhood.

Within the broader history of space telescopes, the arrival of this mission offered a new perspective on the distribution of planetary bodies. While earlier telescopes often peered into distant, narrow regions of space, the strategy here was to cast a wide net across the brightest stars visible from Earth. This approach ensured that the discovered planets would be prime candidates for follow-up observations, as their proximity allows for more rigorous analysis of their chemical compositions and physical characteristics. By prioritising nearby systems, the project established a foundation for future research that relies on the accessibility of these newly identified targets.

The mission focuses on surveying the brightest stars in the sky to identify planets that are well-positioned for detailed follow-up study by ground-based and space-based observatories.

The technical success of the launch allowed the satellite to enter a stable orbit, which was essential for the long-term stability required for continuous observation. Maintaining a steady gaze at specific sectors of the sky for weeks at a time enabled the detection of planets with shorter orbital cycles, which are often the most straightforward to characterise. This operational rhythm was carefully calibrated to maximise the volume of data returned to researchers, ensuring that the mission could effectively scan both the northern and southern hemispheres. The resulting stream of information has provided a clearer picture of the architecture of planetary systems orbiting various types of stars.

As part of the wider sequence of space exploration, the deployment of this satellite highlights the evolution of our search for life and planetary formation. It connects the foundational discoveries of the early 21st century with the more specialised investigations of the present day. By providing a broad census of exoplanets, the mission has allowed the scientific community to refine its models of how planets form and evolve over time. This work remains a cornerstone of contemporary astrophysics, bridging the gap between theoretical predictions and the empirical reality of the thousands of worlds now confirmed to exist in our galaxy.