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| EPOXI | |
|---|---|
| Name | EPOXI |
| Mission type | Planetary science, comet exploration, exoplanet photometry |
| Operator | NASA / Jet Propulsion Laboratory |
| Mission duration | Extended mission of Deep Impact spacecraft |
| Spacecraft | Reused Deep Impact probe |
| Launch mass | 650 kg (approximate) |
| Launch | 2005 (original) |
| Launch site | Cape Canaveral Space Force Station |
| Manufacturer | Ball Aerospace / Aerojet / Max-Planck-Institut für Sonnensystemforschung |
EPOXI EPOXI was a NASA extended-mission program that combined two investigations—an extrasolar planet characterization campaign and a comet flyby—using the repurposed Deep Impact spacecraft originally associated with Comet Tempel 1 and the Stardust and Rosetta era of small-body exploration. The initiative linked resources from NASA and the Jet Propulsion Laboratory to pursue high-precision photometry of extrasolar planet transits and a close encounter with a short-period comet, leveraging heritage from missions such as Galileo (spacecraft), Cassini-Huygens, and NEAR Shoemaker. The program integrated observational goals from institutions including Harvard-Smithsonian Center for Astrophysics, Space Telescope Science Institute, and international partners involved in planetary science campaigns.
The EPOXI concept arose as an efficient reuse of the Deep Impact bus after its primary Deep Impact objective at Comet Tempel 1 and aligns with priorities identified by panels like the Decadal Survey and the NASA Office of Planetary Science. The combined mission comprised two primary components: EPOCh (Extrasolar Planet Observation and Characterization), which coordinated with Kepler Mission follow-up efforts and ground-based programs at Mauna Kea Observatories, and DIXI (Deep Impact eXtended Investigation), which executed a flyby of a new comet drawing on encounter strategies used by NEAR Shoemaker and Deep Space 1. EPOXI operations involved collaboration with Arecibo Observatory teams for navigation support, science planning with the European Space Agency, and scheduling against opportunities from Hubble Space Telescope and Spitzer Space Telescope campaigns.
The spacecraft was the Deep Impact flyby/impactor bus repurposed with the original High Resolution Instrument (HRI) and Medium Resolution Instrument (MRI) optical systems, sharing heritage with imagers from Voyager 2 and Mars Reconnaissance Orbiter. The HRI comprised a 30-cm aperture telescope paired with a broadband visible CCD and filter wheel, while the MRI provided context imaging similar in concept to the cameras on NEAR Shoemaker. A visible-light spectrometer and dust-impact sensors complemented the payload, enabling comparative analyses with instruments on Stardust and Rosetta. Onboard systems for attitude control, powered by reaction wheels and hydrazine thrusters, were managed using navigation software influenced by Deep Space 1 and Galileo (spacecraft) guidance heritage.
Although EPOXI’s primary DIXI target was a comet, mission planning referenced trajectory opportunities involving outer-planet assists and small-body flybys analogous to gravity assists used by Voyager 2 at Neptune and flybys of 243 Ida by Galileo (spacecraft). Early mission analyses examined potential encounters with main-belt asteroids and trans-Neptunian object windows similar to campaigns by New Horizons and Hayabusa. The spacecraft’s extended timeline required coordination with planetary ephemerides maintained by JPL Horizons and input from teams experienced with close approaches to bodies like Eros and Itokawa.
EPOCh performed space-based photometric monitoring of known extrasolar planet systems to measure transit timing variations, albedo, and atmospheric signatures, coordinating data with Kepler (spacecraft), Hubble Space Telescope, and ground networks at Palomar Observatory and La Silla Observatory. Targets included hot Jupiters and transiting systems discovered by programs like Wide Angle Search for Planets and teams associated with Harvard-Smithsonian Center for Astrophysics radial velocity surveys. The mission applied calibration techniques developed in the Kepler Mission and the Spitzer Space Telescope exoplanet program, enabling comparisons with models by groups at University of Arizona and University of California, Berkeley focused on planetary atmosphere retrievals and phase-curve analyses.
DIXI repurposed the impactor-era heritage to perform a close flyby of a short-period comet, using encounter planning methods similar to Deep Impact and observation strategies employed by Giotto and Rosetta. The objective was to image the nucleus morphology, map coma structure, and characterize dust and gas composition with context from spectroscopic comparisons to datasets from VIRTIS on Rosetta and mass-spectrometer results from Giotto. The team included investigators from University of Maryland, Max-Planck-Institut für Sonnensystemforschung, and University of Colorado Boulder who synthesized flyby imagery with laboratory spectral libraries and dynamical models.
Mission operations were conducted from the Jet Propulsion Laboratory flight operations facility, employing ground stations in the Deep Space Network and scheduling coordinated observation windows with Hubble Space Telescope and Spitzer Space Telescope to maximize simultaneous coverage. Trajectory design used gravity assists and deep-space maneuvers similar to those implemented for Cassini and New Horizons, and relied on navigational inputs from the Deep Space Network, optical navigation against star catalogs like Hipparcos and 2MASS, and perturbation modeling developed at JPL. Teams executed targeting burns, attitude sequences, and downlink plans consistent with procedures refined during the Deep Impact primary mission.
EPOXI produced high-precision light curves of transiting extrasolar planet systems that informed atmospheric models developed at institutions such as Caltech, MIT, and Princeton University, and contributed to constraints on albedo and phase-curve variability comparable to findings from Spitzer and Hubble. The DIXI comet flyby yielded nucleus imagery and coma morphology data that advanced comparative planetology efforts alongside datasets from Rosetta, Stardust, and Deep Impact. Legacy impacts include methodological innovations in spacecraft reuse and mission extension policy adopted by NASA and influence on later missions like Lucy (spacecraft) and OSIRIS-REx, as well as data archived in repositories maintained by NASA Planetary Data System and analyzed by research groups at University of Arizona and Brown University.
Category:NASA spacecraft Category:Planetary science missions