What is TESS?
The Transiting Exoplanet Survey Satellite (TESS) is a space-based astronomical observatory designed to discover exoplanets orbiting bright, nearby stars using the transit method.
It is a successor to the Kepler mission, with a stronger focus on nearby and easily observable planetary systems.
Launch and Agency
- Launched: April 2018
- Launch Vehicle: Falcon 9
- Developed by: NASA (with MIT as the lead academic partner)
- Mission Type: Astrophysics / Exoplanet exploration
Primary Objective
- To identify transiting exoplanets, especially:
- Earth-sized and Super-Earth planets
- Planets orbiting bright and nearby stars
- Enable follow-up studies of exoplanet atmospheres using advanced telescopes like JWST.
How TESS Works (Transit Method)
- Continuously monitors the brightness of stars.
- Detects periodic dips in brightness when a planet passes in front of its host star.
- From these dips, scientists infer:
- Planet size
- Orbital period
- Distance from the star
Survey Strategy
- The sky is divided into 26 observation sectors.
- Each sector is observed for ~27 days.
- Covers ~85% of the entire sky, unlike Kepler which focused on a narrow region.
- Gives special attention to stars within 300 light-years.
Orbit of TESS
- Highly elliptical Earth orbit
- Orbital period: 13.7 days
- Stable, low-radiation environment → longer mission life and precise observations
Key Achievements
- Discovered thousands of exoplanet candidates (called TOIs – TESS Objects of Interest)
- Confirmed many rocky and potentially habitable planets
- Identified targets suitable for atmospheric analysis
- Contributed significantly to:
- Exoplanet demographics
- Stellar astrophysics
- Transient astronomical events
Importance of TESS
- Shifts focus from detection to characterisation
- Builds a catalog of nearby planetary systems
- Strengthens the global search for habitable worlds
- Complements:
- Kepler (depth-focused)
- JWST (atmospheric analysis)
- Ground-based observatories
Limitations
- Less sensitive to:
- Very small planets around faint stars
- Long-period planets far from their stars
- Requires ground-based and space-based confirmation missions
