Transiting Exoplanet Survey Satellite
Artist concept of TESS
Operator NASA
Mission type Space observatory
Launch date 2017[1]
Mission duration 2 years
Orbits High Earth orbit
Orbital elements
Semimajor axis 240,000 km (150,000 mi)
Eccentricity 0.55
Apoapsis 373,000 km (232,000 mi)
Periapsis 108,000 km (67,000 mi)
Orbital period 13.7 days

The Transiting Exoplanet Survey Satellite (TESS) is a planned space telescope for NASA's Explorer program, designed to search for extrasolar planets using the transit method.

The primary mission objective for TESS is to survey the brightest stars near the Earth for transiting exoplanets over a two-year period. The TESS project will use an array of wide-field cameras to perform an all-sky survey. It will scan nearby stars for exoplanets. With TESS, it will be possible to study the mass, size, density and orbit of a large cohort of small planets, including a sample of rocky worlds in the habitable zones of their host stars. TESS will provide prime targets for further characterization by the James Webb Space Telescope, as well as other large ground-based and space-based telescopes of the future.

Previous sky surveys with ground-based telescopes have mainly picked out giant exoplanets. In contrast, TESS will examine a large number of small planets around the very brightest stars in the sky. TESS will record the nearest and brightest main sequence stars hosting transiting exoplanets, which will forever be the most favorable targets for detailed investigations.[2]

Led by the Massachusetts Institute of Technology with seed funding from Google,[3] TESS was one of 11 proposals selected for NASA funding in September 2011, down from the original 42 submitted in February of that year.[4] On April 5, 2013, it was announced that TESS, along with the Neutron star Interior Composition ExploreR (NICER), had been selected for launch in 2017.[1][5]


TESS will be launched by a NASA Launch Services (NLS) II Medium Class Launch Vehicle to be provided by NASA Kennedy Space Center.[6]

Mission concept

Once launched, the telescope would conduct a two-year all-sky survey program for exploring transiting exoplanets around nearby and bright stars.[1][7] TESS would be equipped with four wide-angle telescopes and charge-coupled device (CCD) detectors, with a total size of 67 megapixels. Science data, which are pixel subarrays around each of up to 10,000 target stars per field, are transmitted to Earth every two weeks for analysis. Full-frame images with an effective exposure time of two hours are transmitted to the ground as well, enabling astrophysicists to search the data for an unexpected, transient phenomenon, such as the optical counterpart to a gamma-ray burst.

TESS will carry out the first space-borne all-sky exoplanet transit survey, covering 400 times as much sky as any previous mission, including Kepler. It will identify thousands of new planets in the solar neighborhood, with a special focus on planets comparable in size to the Earth. TESS will be in a special orbit, one that is not too close, and not too far, from both the Earth and the Moon. As a result, every two weeks TESS will approach close enough to the Earth for high data-downlink rates, while remaining above the planet's harmful radiation belts. This special orbit will remain stable for decades, keeping TESS' sensitive cameras in a stable temperature range.

Orbital dynamics

In order to obtain imagery from both locations in both northern and southern hemispheres of the sky, TESS will utilize a lunar resonant orbit called P/2, a never-before-used orbit. This highly elliptical orbit can be stable; the mission apogee can be timed to keep the craft away from the Moon, which acts as a destabilizing agent. The majority of the orbit is spent well outside the Van Allen belts, to avoid damage to TESS. Every 13.7 days at its orbit's perigee, TESS will downlink the data it has collected during the orbit to Earth over a period of approximately 3 hours.[8]

Mission overview

All-sky, two year photometric exoplanet discovery mission:

TESS will tile the sky with 26 observation sectors:

  • At least 27 days staring at each 24° x 96° sector.
  • Brightest 100,000 stars at 1-minute cadence.
  • Full frame images with 30-minute cadence.
  • Map Northern hemisphere in first year.
  • Map Southern hemisphere in second year.
  • Sectors overlap at ecliptic poles for sensitivity to smaller and longer period planets in JWST Continuous Viewing Zone (CVZ).
  • Stable 2:1 resonance with Moon’s orbit.
  • Thermally stable and low-radiation.

TESS observes from unique High Earth Orbit (HEO):

  • Unobstructed view for continuous light curves.
  • Two 13.7 day orbits per observation sector.
  • Stable 2:1 resonance with Moon’s orbit.
  • Thermally stable and low-radiation.

TESS science instrument

Four wide field-of-view CCD cameras. Each of the four cameras has:

  • 24° x 24° Field-of-View.
  • 100 mm effective pupil diameter.
  • Lens assembly with 7 optical elements.
  • Athermal design.
  • 600 nm – 1000 nm bandpass.
  • 16.8 Megapixel, low-noise, low-power, MIT Lincoln Lab CCID-80 detector.

The TESS telescopes will provide photometric precision of 200 ppm in 1 hour on an I=10 star, with systematic noise sources <60 ppm/hr.

TESS spacecraft

Heritage Orbital LEOStar-2 spacecraft bus:

  • Three-axis stabilized pointing, with ≤3 arc-sec performance.
  • Two-headed star tracker; four-wheel zeromomentum system.
  • 400W single-axis articulating solar array.
  • Passive thermal control.
  • Mono-propellant propulsion system.
  • Ka-band 100 Mbit/s science downlink.

Scientific objectives

The survey will focus on G- and K- type stars with apparent magnitudes brighter than 12.[9] Approximately 500,000 of these stars would be studied, including the 1,000 closest red dwarfs. TESS is predicted to discover 1,000 - 10,000 transiting exoplanet candidates which are Earth-sized or larger, with orbital periods of up to two months. These candidates could be later investigated by the Automated Planet Finder telescope, the HARPS spectrometer and both the future ESPRESSO spectrometer and James Webb Space Telescope. The development team at MIT has suggested that the first manned interstellar space missions may be to planets discovered by TESS.[10]

TESS is designed to:

  • Monitor 500,000 nearby stars for planets
  • Focus on Earth and Super-Earth size planets
  • Cover 400X larger sky area than Kepler
  • Span stellar spectral types of F5 to M5


  1. ^ a b c "NASA Selects Explorer Investigations for Formulation".  
  3. ^ Chandler, David (2008-03-19). "MIT aims to search for Earth-like planets with Google's help". MIT News. 
  4. ^ "NASA Selects Science Investigations For Concept Studies" (Press release). NASA. 2011-09-29. 
  5. ^ "NASA selects MIT-led TESS project for 2017 mission". MITnews. Retrieved 2013-04-06. 
  6. ^ Launch Vehicle
  7. ^ Ricker, George R. (26 June 2014). "Discovering New Earths and Super-Earths in the Solar Neighborhood". SPIE Astronomical Telescopes + Instrumentation. 22–27 June 2014. Montréal, Quebec, Canada.  
  8. ^ "New Explorer Mission Chooses the 'Just-Right' Orbit".  
  9. ^ Seager, Sara (2011). "Exoplanet Space Missions". Sara Seager. Massachusetts Institute of Technology. Retrieved 2013-04-07. 
  10. ^ Gilster, Paul (2008-03-26). "TESS: All Sky Survey for Transiting Planets". Centauri Dreams.  

External links