TESS observes the sky in sectors measuring 24° x 96°. Each sector is observed for two orbits of the satellite around the Earth, or about 27 days on average. The field-of-view is oriented along a line of ecliptic longitude with the instrument boresight generally pointing at ±54° ecliptic latitude, which centers Camera 4 on an ecliptic pole. By orienting the fields in this way, a 24° diameter region centered on the ecliptic pole can be observed for nearly a full year. During certain sectors in Year 2 and 4, the instrument boresight is pointed at +85° to avoid excessive scattered light in cameras 1 and 2. Because the fields-of-view are shifted north along a line of ecliptic longitude, the region near the ecliptic pole is still observed continuously.
During Year 1 of the mission (July 2018-July 2019), the southern ecliptic hemisphere was observed. During Year 2 of the mission (July 2019-July 2020), the northern hemisphere was observed. During Year 3 of the mission (July 2020-July 2021), the southern ecliptic hemisphere is being re-observed. During Year 4 (July 2021-September 2022; 16 sectors), parts of the northern ecliptic hemisphere will be re-observed, and a 240° swath of the ecliptic will be observed for the first time. During Year 5, the northern hemisphere survey will be completed and a new southern survey will begin. Details of the observations during the first 5 years of the mission, including spacecraft pointings, can be found below. Preliminary pointings for Year 6 are also listed.
Precise Observation Times
The timing of TESS observations and ground contacts can be found in the TESS Operations Calendar. Through Sector 55, there are two LAHO (low-altitude housekeeping operations) contacts at each perigee. Science observations stop 10 minutes before the beginning of the first LAHO and resume 5 minutes before the end of the second LAHO. Starting with Sector 56, there will be one LAHO contact at perigee and one HAHO (high-altitude housekeeping operations) contact at apogee: science observations will stop 10 minutes before each contact begins and resume 5 minutes before the contact ends.
The times of LAHO and HAHO contacts are generally determined 3 months in advance. The times of these contacts can change, although this happens relatively rarely.
A .csv file that contains the contact times that define the beginnings and ends of TESS observations for past orbits and sectors, along with predicted start and stop times for the next few sectors, can be found here.
NOTE: Beginning in September, 2022, there will be a single contact at orbit perigee and a single contact at orbit apogee. Thus, starting with Sector 55, the observation times are broken up into two segments per orbit.