Timeline: Kepler space telescope

Kepler’s launch was delayed by eight months due to budget cuts and consolidation at NASA.

The project was delayed again by four months due to fiscal problems; the high-gain antenna was changed from a gimballed design to a fixed design to reduce cost and complexity, at the cost of one observation day per month.

The Kepler observatory was launched aboard a Delta II rocket from Cape Canaveral Air Force Station, Florida.

The telescope cover was jettisoned in preparation for observations.

Kepler took its first light images (first astronomical images after launch).

The Kepler science team concluded that further refinement of the telescope’s focus would significantly increase scientific return.

Focus was successfully optimized by moving the primary mirror 40 micrometers toward the focal plane and tilting it by 0.0072 degrees.

Kepler completed its commissioning phase and began its planet-search operations.

The spacecraft entered safe mode due to a processor reset; operations were later resumed.

Kepler successfully sent its first science data to Earth.

A second safe mode event occurred, again triggered by a processor reset; Kepler resumed normal operations on July 3.

NASA held a press conference on early mission science results, reporting that Kepler had confirmed the previously known transiting exoplanet HAT-P-7b and was performing well enough to discover Earth-size planets.

The cause of the June and July safing events was determined to be a low-voltage power supply that provided power to the RAD750 processor.

The Kepler project publicly released light curves of stars dropped from the planet-search target list because they were too variable in brightness for transit detection.

Kepler’s first main mission results were announced (early results emphasized short-period planets, as expected).

Part of the focal plane transmitted anomalous data, indicating a problem with the MOD-3 module (covering two of Kepler’s 42 CCDs).

Kepler released data publicly for all but 400 of ~156,000 target stars; 706 targets from the first data set had viable exoplanet candidates (from Earth-size to larger than Jupiter).

A letter to NASA clarified that analysis of then-current Kepler data did not support claims that Kepler had already found Earth-like planets, addressing a common misunderstanding in media coverage.

Kepler mission data began being used in the citizen science project Planet Hunters, enabling volunteers to search for transits in light curves.

The Kepler team announced analysis of data taken between May 2 and September 16, 2009, identifying 1,235 planetary candidates orbiting 997 host stars, including candidates potentially in the habitable zone.

Kepler announced 2,326 planetary candidates, including increased counts of Earth-size and super-Earth-size candidates, and candidates in habitable zones under more stringent criteria.

Kepler announced the first Earth-size exoplanets, Kepler-20e and Kepler-20f, orbiting the Sun-like star Kepler-20.

The Kepler mission was approved for extension through fiscal year 2016 (though this depended on the spacecraft’s remaining reaction wheels).

One of Kepler’s four reaction wheels (wheel 2) failed, reducing redundancy for precise pointing.

NASA announced completion of Kepler’s primary mission and the start of an extended mission.

The discovery of 461 additional exoplanet candidates was announced, bringing the candidate total to 2,740 potential planets orbiting 2,036 stars.

A white dwarf in the KOI-256 system was reported to bend the light of its companion red dwarf (a gravitational lensing effect).

A second reaction wheel (wheel 4) failed, ending Kepler’s original three-wheel precision pointing capability and halting collection of new primary-mission science data.

NASA announced it had given up trying to fix the two failed reaction wheels and called for alternative mission proposals using the spacecraft’s remaining capabilities.

The K2 “Second Light” mission concept was presented, proposing observations of different fields near the ecliptic and continued exoplanet and astrophysics studies with reduced precision.

Scientists announced confirmation of 715 new exoplanets using the “verification by multiplicity” statistical method, enabling faster validation of many candidates in multi-planet systems.

Kepler collected data from “Field 0” as a testing run for the K2 mission concept.

NASA approved extending the Kepler mission as the K2 mission.

K2 observations began as the spacecraft shifted to campaigns targeting different fields near the ecliptic.

NASA reported that K2 had completed Campaign 1 and that Campaign 2 was underway.

NASA announced K2’s first confirmed exoplanet, the super-Earth HIP 116454 b, found in engineering data (with radial-velocity follow-up needed because only a single transit was observed).

NASA announced the 1,000th confirmed Kepler exoplanet; among newly confirmed planets were several found in habitable zones, including Kepler-438b, Kepler-442b, and Kepler-452b.

Kepler observations captured a Type Ia supernova, KSN 2011b, including pre-explosion data useful for studying supernova light curves and potentially dark energy.

NASA announced the discovery of Kepler-452b, a near-Earth-size confirmed exoplanet orbiting in the habitable zone of a Sun-like star.

During a scheduled contact, Kepler was found in emergency mode; it was transitioned to safe mode, then point-rest state, and returned to science operations on April 22, shortening the first half of K2 Campaign 9.

NASA verified 1,284 new exoplanets found by Kepler, the mission’s single largest planet finding announcement; nine of these were reported to orbit in their stars’ habitable zones.

NASA announced a K2 mission extension of three additional years beyond the expected exhaustion of on-board fuel in 2018.

Kepler’s distance from Earth was reported as about 0.917 AU (137 million km) as it continued in an Earth-trailing heliocentric orbit.

NASA roused the spacecraft from sleep mode, applied a modified configuration to address thruster-related pointing degradation, and began collecting data for the 19th observation campaign.

After Kepler ran out of fuel, NASA announced the telescope would be retired; the spacecraft was shut down the same day, ending its nine-year service (2009–2018).

Kepler was deactivated with a “goodnight” command sent from the mission control center at the Laboratory for Atmospheric and Space Physics.

As of August 2022, Kepler’s totals were reported as 2,711 confirmed exoplanets and 2,056 exoplanet candidates remaining to be confirmed (reflecting continued validation work after mission end).