Transiting Exoplanet Survey Satellite

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Transiting Exoplanet Survey Satellite
Transiting Exoplanet Survey Satellite artist concept (transparent background).png
Artist concept of TESS
Mission type Space observatory
Operator NASA / MIT
Mission duration Planned: 2 years
Spacecraft properties
Bus LEOStar-2
Manufacturer Orbital Sciences
Launch mass 350 kg (772 lb)
Dimensions 3.7×1.2×1.5 m (12.1×3.9×4.9 ft)
Power 400 watts
Start of mission
Launch date August 2017[1]
Rocket Falcon 9 v1.1
Launch site Cape Canaveral SLC-40
Contractor SpaceX
Orbital parameters
Reference system Highly elliptical
Regime High Earth
Semi-major axis 240,000 km (150,000 mi)
Eccentricity 0.55
Perigee 108,000 km (67,000 mi)
Apogee 373,000 km (232,000 mi)
Period 13.7 days
TESS logo (transparent bg).png

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.[5][6]


NASA announced on December 16, 2014, that TESS will be launched in August 2017 on a SpaceX Falcon 9 v1.1 rocket from the Cape Canaveral Air Force Station. The total value of the contract is US$87 million.[1]

Mission concept[edit]

Once launched, the telescope would conduct a two-year all-sky survey program for exploring transiting exoplanets around nearby and bright stars.[5][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's sensitive cameras in a stable temperature range.

Orbital dynamics[edit]

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[edit]

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[edit]

The sole instrument on TESS is a package of four wide-field-of-view CCD cameras. Each camera features a low-noise, low-power 16.8 megapixel CCD detector created by the MIT Lincoln Laboratory. Each has a 24° × 24° field of view, a 100 mm (4 in) effective pupil diameter, a lens assembly with seven optical elements, and a bandpass range of 600 to 1000 nm.[9]

TESS spacecraft[edit]

TESS uses an Orbital Sciences LEOStar-2 satellite bus, capable of three-axis stabilization using four hydrazine thrusters plus four reaction wheels providing better than three arc-second fine spacecraft pointing control. Power is provided by two single-axis solar arrays generating 400 watts. A Ka-band dish antenna will provide a 100 Mbit/s science downlink.[9][10]

Scientific objectives[edit]

The survey will focus on G- and K-type stars with apparent magnitudes brighter than magnitude 12.[11] Approximately 500,000 stars will be studied, including the 1,000 closest red dwarfs,[12] across an area of sky 400 times larger than that covered by Kepler.[9] TESS is predicted to discover more than 3,000 transiting exoplanet candidates, including those which are Earth sized or larger.[9] 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.[13]


  1. ^ a b Beck, Joshua; Diller, George H. (December 16, 2014). "NASA Awards Launch Services Contract for Transiting Exoplanet Survey Satellite" (Press release). NASA. Retrieved December 17, 2014. 
  2. ^ "NASA FY 2015 President's Budget Request Summary" (PDF). NASA. March 10, 2014. 
  3. ^ Chandler, David (March 19, 2008). "MIT aims to search for Earth-like planets with Google's help". MIT News. 
  4. ^ Brown, Dwayne (September 29, 2011). "NASA Selects Science Investigations For Concept Studies" (Press release). NASA. 
  5. ^ a b Harrington, J. D. (April 5, 2013). "NASA Selects Explorer Investigations for Formulation" (Press release). NASA. 
  6. ^ "NASA selects MIT-led TESS project for 2017 mission". MIT News. April 5, 2013. Retrieved April 6, 2013. 
  7. ^ Ricker, George R. (June 26, 2014). "Discovering New Earths and Super-Earths in the Solar Neighborhood". SPIE Astronomical Telescopes + Instrumentation. June 22–27, 2014. Montréal, Quebec, Canada. doi:10.1117/2.3201407.18. 
  8. ^ Keesey, Lori (July 31, 2013). "New Explorer Mission Chooses the 'Just-Right' Orbit". NASA. 
  9. ^ a b c d "TESS: Transiting Exoplanet Survey Satellite". NASA. October 2014. FS-2014-1-120-GSFC. Retrieved December 17, 2014. 
  10. ^ "TESS: Discovering Exoplanets Orbiting Nearby Stars". Orbital Sciences. 2014. FS011_13_2998. Retrieved December 17, 2014. 
  11. ^ Seager, Sara (2011). "Exoplanet Space Missions". Massachusetts Institute of Technology. Retrieved April 7, 2013. 
  12. ^ Zastrow, Mark (May 30, 2013). "Exoplanets After Kepler: What’s next?". Sky & Telescope. Retrieved December 17, 2014. 
  13. ^ Gilster, Paul (March 26, 2008). "TESS: All Sky Survey for Transiting Planets". Centauri Dreams. Tau Zero Foundation. 

External links[edit]