TESS Observations

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. Details of the observations during the first 4+ years of the mission, including spacecraft pointings, can be found below.

Precise Observation Times

The timing of TESS observations and ground contacts can be found in the TESS Operations Calendar. At each perigee, there are two LAHO (low-altitude housekeeping operations) contacts.  Science observations stop 10 minutes before the beginning of the first LAHO and resume 5 minutes before the end of the second LAHO.  The times of LAHO contacts are generally determined 3 months in advance.  The times of LAHO contacts can change, although this happens relatively rarely.

A .csv file that contains the accurate start and stop times of past sectors, along with predicted start and stop times for subsequent sectors, can be found here.

Target Lists

The lists of targets observed at two-minute cadence can be found on the Target Lists page. The pages for individual sectors can be reached using the pull-down menu under Observations.

Overlay of Year 1-4+ pointings in ecliptic coordinates (upper image) and celestial coordinates (lower image).

Current Status

TESS is currently observing in Orbit 79, Sector 36.  Sector 36 will be observed through March 19.

Starting with Orbit 73, the average observing time per orbit has dropped to 12 days, as opposed to the 13 days per orbit through Sector 32.  This is a consequence of natural evolution of the TESS orbit through the Kozai mechanism combined with the schedule of contacts for downlinks at perigee. The average of 12 days per orbit will persist through Sector 37.  Scattered light levels continue to be low and restricted to periods near perigee through Sector 35.

Observations of Two-Minute Cadence Targets for Years 1+2

The images below are plots of all targets observed at two-minute cadence through Sector 26: at left, in celestial coordinates, and at right, in ecliptic coordinates. The dots are color-coded to indicate the number of sectors each target was observed.

Year 2

Observations during Year 2 comprised Sectors 14-26. During Year 2, the northern ecliptic hemisphere was observed. During sectors 17-23, the instrument boresight will be pointed at +54° ecliptic latitude. During Sectors 14-16 and 24-26, the boresight were pointed at +85° ecliptic latitude, due to excessive contamination by stray Earth- and moonlight in cameras 1 and 2 in the nominal +54° orientation.

Year 3

Observations during Year 3 comprised Sectors 27-39. During Year 3, the southern ecliptic hemisphere will be re-observed.  For each of these sectors, the instrument boresight will be pointed at an ecliptic declination of -54°.

Year 4+

Observations during Year 4+ comprises Sectors 40-55. Year 4+ will begin with Sectors 40-41 in the Northern hemisphere, pointings roughly equivalent to those of Sectors 14 and 15, at an ecliptic latitude of +85°. Sectors 42-46 are ecliptic pointings.  Sectors 47-55 are Northern hemisphere pointings at ecliptic latitude of +54°, with Sectors 52 and 53 shifted north to +85° to avoid scattered light in cameras 1 and 2.