Kepler & TESS Exoplanet Transit Surveys
NASA's Kepler Space Telescope (2009–2018) and Transiting Exoplanet Survey Satellite (TESS, 2018–present) use ultra-precise space-based CCD photometry to monitor hundreds of thousands of stars simultaneously for periodic planetary transit dips. Kepler performed a deep 4-year demographic census in Cygnus-Lyra that proved planets outnumber stars, while TESS scans nearly the entire sky to find transiting planets around the nearest, brightest stars suitable for JWST spectroscopy.
Physical Mechanism & Dynamics
Kepler stared continuously for 4 years at a single 115-square-degree field in Cygnus and Lyra (~150,000 main-sequence stars) with a 0.95-meter Schmidt telescope, achieving ~20 ppm photometric precision over 6.5 hours—sensitive enough to detect Earth-sized planets at 1 AU. After two reaction wheels failed in 2013, the repurposed K2 mission used solar radiation pressure balance to survey 20 ecliptic fields.
In contrast, TESS uses four wide-field 10.5-cm f/1.4 cameras in a resonant 13.7-day Lunar-assisted high Earth orbit to tile 24° × 96° sectors across >90% of the sky. TESS targets stars 30–100× brighter than Kepler's sample, enabling ground-based radial velocity mass measurements and JWST atmospheric characterization.
Quantitatively, this mechanism is governed by Transit Signal-to-Noise Ratio across N_tr Transits (SNR_transit = [ (R_p / R_★)² / σ_CDPP ] · √N_tr). σ_CDPP is the Combined Differential Photometric Precision over the transit duration; Kepler achieved σ_CDPP ≈ 20–30 ppm for V = 12 solar-type stars.
Transit Signal-to-Noise Ratio across N_tr Transits
SNR_transit = [ (R_p / R_★)² / σ_CDPP ] · √N_trσ_CDPP is the Combined Differential Photometric Precision over the transit duration; Kepler achieved σ_CDPP ≈ 20–30 ppm for V = 12 solar-type stars.
Quantitative Benchmarks & Parameters
| Parameter / Observable | Measured Value / Scale | Method & Context |
|---|---|---|
| Kepler & K2 planet yield | >3,300 confirmed exoplanets | Primary Cygnus-Lyra field + 19 K2 campaigns |
| TESS sky coverage | >93% of the entire sky | 24° × 96° four-camera sectors (27.4 days per sector) |
| Kepler 6.5-hr precision | ~20–30 ppm (Sun-like stars) | Required to detect 84 ppm Earth-Sun transits |
| Average planets per star | >1.0 planet per Milky Way star | Completeness-corrected Kepler occurrence rates |
Observational Evidence & How Scientists Know
Kepler discovered that the most common planets in the galaxy with periods <100 days are super-Earths and sub-Neptunes (1.2–3.5 R_⊕)—a class entirely absent from our Solar System—and revealed the photoevaporative Fulton radius valley at 1.8 R_⊕.
Across reference datasets (NASA Exoplanet Archive), quantitative benchmarks for kepler & tess exoplanet transit surveys are anchored by: Kepler & K2 planet yield (>3,300 confirmed exoplanets, via Primary Cygnus-Lyra field + 19 K2 campaigns); TESS sky coverage (>93% of the entire sky, via 24° × 96° four-camera sectors (27.4 days per sector)); Kepler 6.5-hr precision (~20–30 ppm (Sun-like stars), via Required to detect 84 ppm Earth-Sun transits); Average planets per star (>1.0 planet per Milky Way star, via Completeness-corrected Kepler occurrence rates).
Uncertainties, Systematics & Open Questions
Determining the true occurrence rate of temperate rocky planets in 1-year orbits around Sun-like stars (η_⊕, currently estimated at ~0.1–0.3) awaits ESA's PLATO mission (24 cameras), which will combine long-baseline transits with asteroseismic host-star ages.
Real Astronomical Benchmarks & Cross-Domain Links
Cygnus & Lyra (Kepler Field)
Primary 115 deg² sky region monitored continuously by Kepler for 4 years
TRAPPIST-1 e
Transiting temperate planet observed by K2, Spitzer, and JWST
Transit Photometry & Spectroscopy
Physical measurement principles of Kepler and TESS
Guided Learning Path
Related Concepts, Methods & Explorers
Scientific Sources & Provenance
- NASA Exoplanet Archive (2026-10-01 snapshot) — Akeson, R. L., et al. 2013, PASP, 125, 989; NASA Exoplanet Archive (IPAC/Caltech). Archive / Reference ↗
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