K2 mission

K2 mission. The K2 mission was a repurposed extension of the highly successful Kepler space telescope, operated by NASA after the failure of two of its four reaction wheels. This innovative second life, managed from the Ames Research Center, transformed the observatory into a versatile survey instrument, conducting photometric observations across multiple fields along the ecliptic plane. It continued the search for exoplanets while vastly expanding its scientific portfolio to include studies of stars, galaxies, and solar system objects, operating from 2014 until its final decommissioning in 2018.

Mission overview

Following the loss of a second reaction wheel in 2013, which ended the original Kepler mission's ability to maintain precise, continuous pointing at its original field in the constellations of Cygnus and Lyra, engineers devised a novel solution using solar radiation pressure. This technique allowed the crippled spacecraft to stabilize its pointing by balancing against the gentle pressure of sunlight, enabling a new mission dubbed K2. The mission was organized into a series of approximately 80-day observational "campaigns," each focusing on a different region of the sky along the ecliptic plane to keep the solar panels properly aligned. This operational shift, approved by the NASA Senior Review process in 2014, was led by the project team at Ball Aerospace & Technologies Corp. and the science office at Ames Research Center, with data archived at the Mikulski Archive for Space Telescopes.

Scientific objectives

The primary objective remained the detection of exoplanets, particularly those orbiting bright, nearby main-sequence stars like red dwarfs, using the transit method. However, the K2 mission's flexible pointing significantly broadened its scientific goals to include asteroseismology, the study of stellar interiors through oscillations, in diverse stellar populations like those in the open cluster M67 and the Hyades. It also conducted observations of active galactic nuclei, supernovae in distant galaxies, and objects within our own solar system, such as Trojan asteroids and trans-Neptunian objects. This wide-ranging program attracted proposals from the broader scientific community through a Guest Observer program, similar to those for the Hubble Space Telescope and the Spitzer Space Telescope.

Spacecraft and instruments

The K2 mission utilized the existing Kepler space telescope hardware, a 0.95-meter Schmidt camera photometer, with its primary instrument being a 42-CCD array creating a 115 square degree field of view. The spacecraft's pointing was controlled by its two remaining reaction wheels, with the solar radiation pressure from its panels providing a counter-balancing force about the spacecraft bus's roll axis. Key supporting systems included the high-gain antenna for communicating with the Deep Space Network and the photometer's sophisticated electronics, originally designed for the Kepler mission. The mission's success hinged on sophisticated new flight software developed by teams at Ball Aerospace & Technologies Corp. and NASA to manage the complex balancing act required for stable data collection.

Operations and discoveries

Operations involved 20 distinct campaigns, each targeting fields from the Pisces to Sagittarius constellations, yielding a vast dataset. Notable exoplanet discoveries included the TRAPPIST-1 system, a red dwarf host to seven Earth-sized worlds, and the super-Earth LHS 1140 b, located in the habitable zone. The mission also characterized the disintegrating planetesimal WD 1145+017 b, observed stellar variability in young associations like the Pleiades, and monitored the bright star Vega. Its data contributed to studies of Type Ia supernovae for cosmology and the internal structure of red giant stars, with results published in journals like The Astrophysical Journal and Nature.

End of mission and legacy

The K2 mission concluded on October 30, 2018, when the spacecraft finally exhausted its hydrazine fuel, rendering it unable to orient its antenna toward Earth for data transmission. NASA officially retired the spacecraft, leaving it in a safe heliocentric orbit. Its legacy includes the confirmation of over 500 exoplanets and the identification of thousands more candidates, providing crucial statistical data for missions like the Transiting Exoplanet Survey Satellite and the future James Webb Space Telescope. The mission demonstrated extraordinary engineering ingenuity, saving a flagship NASA asset and setting a precedent for adaptive space telescope operations that informed the development of subsequent observatories.

Category:NASA space telescopes Category:Exoplanet search projects Category:Spacecraft launched in 2009