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 was re-observed. During Year 4 (July 2021-September 2022; 16 sectors), parts of the northern ecliptic hemisphere were re-observed, and a 240° swath of the ecliptic was observed for the first time. During Year 5, the northern hemisphere survey was completed and a new southern survey began. 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.

Precise Contact Times

For those interested in a prediction of when TESS will be observing in a particular orbit or sector, a .csv file has been provided to list the ground contact times that define the beginnings and ends of TESS observations based on downlink schedules. This file includes information for past orbits and sectors as well as the scheduled start and stop times for the next few sectors and is provided here. This file only accounts for the times of ground contacts and does not include information about any past interruptions in observations. (You may have to clear your cache to get the latest version of this file).

Precise Data Accumulation Times

For those interested in knowing precisely when TESS was collecting FFI data, a .csv file has been provided that contains the exact range of times during which FFI observations were made: it can be found here. The data in this file is based entirely on precisely when FFI data were collected and, as such, accounts for interruptions in observations. (You may have to clear your cache to get the latest version of this file).

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.

Table of Momentum Dumps

A table of the FFI and 2-minute cadence numbers (along with UTC, TJD, and spacecraft time) affected by momentum dumps can be downloaded here. With the onset of Extended Mission 2 and the use of apogee contacts, there will no longer be momentum dumps during observations: the one momentum dump during the orbit will occur during the apogee contact. (You may have to clear your cache to get the latest version of this file).

Overlay of Year 1-4x pointings in ecliptic coordinates (upper image) and celestial coordinates (lower image). Maps for individual years and individual ecliptic sectors are shown below.

Current Status

TESS is in Orbit 142, Sector 67. Observations of Sector 67 will continue through July 29, 2023.

(image shamelessly borrowed from tasoc.dk)

Observations of Two-Minute Cadence Targets through Sector 46

The images below are plots of all targets observed at two-minute cadence through Sector 46: 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.

Sector Pointings for Years 1-6

The details of TESS spacecraft orientation for Years 1-6 are given on the pages for each of the years: Year 1, Year 2, Year 3, Year 4, Year 5, and Year 6. Each page contains a table of pointing for each sector: the columns are Sector number, Start and End dates of Sector, then (RA, dec, roll) in degrees (J2000) of the spacecraft and four camera boresights. Note: All future values are provisional and may be changed, although there are currently no plans to do so.

The full table of Year 1-7 pointings, at higher precision than what is shown below, can be downloaded here. Note that the pointings for Years 6 and 7 are preliminary and may change.

Year 1

Observations during Year 1 comprised Sectors 1-13. For each of these sectors, the instrument boresight was pointed at an ecliptic declination of -54°.

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 was pointed at +54° ecliptic latitude. During Sectors 14-16 and 24-26, the boresight was pointed at +85° ecliptic latitude, to avoid 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 was re-observed. For each of these sectors, the instrument boresight was pointed at an ecliptic declination of -54°.

Year 4

Observations during Year 4 comprises Sectors 40-55. In contrast to Years 1-3, Year 4 comprises 16 observing sectors. Year 4 began with Sectors 40-41 in the Northern hemisphere, pointings roughly equivalent to those of Sectors 14 and 15, at an ecliptic latitude of +85°. In Sectors 42-46, the spacecraft was rotated by 90° in order to observe the ecliptic. 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.

Year 5

Observations during Year 5 comprises Sectors 56-69. During Year 5, the second scan of the Northern ecliptic hemisphere will be completed (Sectors 56-60), and a new scan of the Southern hemisphere will begin (Sectors 61-69). The ecliptic latitude at which the spacecraft boresight is pointed will be shifted by 1.5° and the instrument field-of-view will be rotated by 1.5° in order that regions of the sky not covered in the first four years of the mission can be observed (these regions are caused by the gaps between CCDs in each camera, and they are most prominently seen at 18° and 54° latitude and at the ecliptic poles).

Year 6

Observations during Year 6 comprises Sectors 70-83. Year 6 will begin with three sectors on the ecliptic (Sectors 70-72), followed by a new scan of the Northern hemisphere will begin (Sectors 73-83). The ecliptic latitude at which the spacecraft boresight is pointed will be shifted by 1.5° and the instrument field-of-view will be rotated by 1.5° in order that regions of the sky not covered in the first four years of the mission can be observed (these regions are caused by the gaps between CCDs in each camera, and they are most prominently seen at 18° and 54° latitude and at the ecliptic poles).