TESS will identify planets ranging from Earth-sized to gas giants like Jupiter. The main focus is to find small planets with host stars that are 10-100 times brighter than those surveyed during the Kepler mission. Planets that have bright host stars are easier to study. Really the only time we can get a good look at planets like these is when they pass in front of their host star. Therefore, the brighter the star the better.
The prime objective of TESS is to observe bright stars. To do this TESS will maintain a unique high Earth orbit. It will have an unobstructed view in a stable thermal environment with low radiation. To observe the stars TESS will use four identical cameras. Each camera will look at a sector of space for 27 days. Each sector covers a 24˚ x 24˚ area. With the four cameras pointed in different directions, they will observe four sectors at a time.
After 27 days have passed the craft will rotate to observe four new sectors. It will continue in this fashion for a year completing a 360˚ view of the southern hemisphere of space around the Earth. In the second year, it will observe the northern hemisphere. When the mission is complete TESS will have observed the surrounding space in all directions.
What they hope to find
By observing more than 200,000 stars over two years they are expecting to find more than 1,500 exoplanets. This will include more than 1000 planets smaller than Neptune and dozens that are the size of Earth. The goal is to build a catalog of planets for further study with the James Web Space Telescope and ground based techniques.
Details about the spacecraft and its mission are in the infographic below.