Pluto Kuiper Express

Artist's impression ofPluto Kuiper Express encountering thePluto–Charon system
Names	Pluto Fast Flyby (1992–1995) Pluto Kuiper Express (1995–2000)
Mission type	Pluto flyby
Operator	NASA
Mission duration	Cancelled
Spacecraft properties
Launch mass	220 kg (490 lb)[1]
Payload mass	7 kg (15 lb)[1]
Power	228 watts
Start of mission
Launch date	December 2004
Rocket	Delta II orSpace Shuttle
Flyby ofJupiter
Closest approach	April–June 2006[1]
Flyby ofPluto
Closest approach	December 2012[1]
Distance	15,000 km (9,300 mi)
Transponders
Bandwidth	5-Mbit/s

Pluto Kuiper Express was an interplanetaryspace probe that was proposed byJet Propulsion Laboratory (JPL) scientists and engineers and under development byNASA. The spacecraft was intended to be launched to studyPluto and its moonCharon, along with one or more otherKuiper belt objects (KBOs). The proposal was the third of its kind, after thePluto 350 and a proposal to send aMariner Mark II spacecraft to Pluto.

Originally conceived asPluto Fast Flyby, and later briefly namedPluto Express, the mission was inspired by a 1991United States Postal Service stamp that branded Pluto as "Not Yet Explored". The project brought on JPL engineers and students from theCalifornia Institute of Technology and, later,Alan Stern and other scientists from the Pluto 350 project. While the project was initiated in 1992, the project's development phase was lengthy, spending nearly a decade in the proposal and funding stage. During planning, the mission was changed to include a Kuiper belt object flyby and re-christened thePluto Kuiper Express, after the discovery of numerous such objects beyondNeptune in the mid-to-late 1990s. NASA ultimately decided to cancel the mission in 2000, however, citing the project's expanding budget as the ultimate reason for the cancellation.^[2]

After the mission's cancellation, most of thePluto Fast Flyby team, including Stern, went on to developNew Horizons, a mission nearly identical toPluto Kuiper Express, for NASA'sNew Frontiers program. The spacecraft was successfully launched in January 2006, after a financial standoff with NASA and additional delays, and went on to perform the first ever flyby of the Pluto–Charon system in July 2015.

As proposed byJet Propulsion Laboratory (JPL) in 1992, the Pluto Fast Flyby mission was to be two craft weighing 150 kg (330 lb) each. The voyage from Earth to Pluto was to take seven or eight years, with a launch as early as 1998. The two craft would be timed to view different sides of Pluto. The budget for the mission was said to be no more than $400-million, with NASA administratorDaniel Goldin wholeheartedly supporting the proposal.^[3][4]

By 1995, the proposed mission was known as Pluto Express, and pre-project managerRobert Staehle of JPL suggested a budget "in the neighborhood of $300 million". At this point the mission was still to have been twin spacecraft, and it was hoped it could be launched in 1998.^[5] NASA tried to negotiate with Russia for use ofProton rockets to launch the spacecraft, in exchange for carrying Russian "Drop Zond" probes to Pluto.^[6] Another idea, emanating from theMax Planck Institute, would have had Germany contribute funding for the launch, in exchange for Pluto Express carrying a German probe to be dropped atIo during the Jupiter gravity assist.^[7]

The timing of the mission was important, as it would have passed Pluto shortly before itsatmosphere froze, which it was thought to do for a considerable part of its orbit. The mission's main objectives would have been to map Pluto's surface and examine the double system's geology and geomorphology, as well as determining the composition ofPluto's atmosphere. This last task would have been considerably more difficult after the start of atmospheric freezing. Scientific equipment on board would have includedvisible light imaging systems,infrared andultravioletspectrometers, and an ultrastable oscillator (USO) for use in aradio occultation experiment.

The spacecraft was to have been a simple hexagonal prism-shaped structure weighing some 220 kg (490 lb), powered byradioisotope thermal generators (RTGs) similar to those used on theGalileo andCassini missions. On-board control and data collection would have been maintained by a 1.5 MIPSRISC-based computer system capable of processing data at 5 Mbit/s. This would have allowed for the transmission of over one gigabyte of data over a one-year period. Communications would have been via a fixed 1.47 m (4.8 ft)high-gain antenna, directionally corrected using a wide-field star tracker. Early in the mission's planning there was suggestion of combining efforts with the Russian space agency and including small Drop Zond probes to study the Plutonian atmosphere. This plan was later abandoned.

The Pluto Express was predicted to be launched in 2001, but it was not ready until late 2004. The spacecraft was to have been launched via either aDelta rocket or theSpace Shuttle, most likely in December 2004. Had that happened, the only option would have been to use a Delta rocket, as the Shuttle fleet was grounded after theColumbia disaster. The course would have been initially viaJupiter, whosegravity well would have been used to increase the probe's velocity via agravity assist. The closest approach distance to Pluto would have been about 15,000 km (9,300 mi) at 17–18 km/s, so as to allow for 1.0 km (0.62 mi) resolution mapping. After passing Pluto, the spacecraft would have used its imaging camera to search forKuiper Belt objects.^[1]

In September 2000 NASA ceased work on the Pluto-Kuiper Express mission,^[8] although the agency said it was being "rethought and replanned", not scrapped. The mission's cost at that time was said by a NASA spokesperson to be an unaffordable $500 million (compared to an original budget of $350 million in 1999).^[9]

• New Horizons: NASA's Pluto–Kuiper Belt Mission, The Johns Hopkins University Applied Physics Laboratory
• Pluto Kuiper Express, NASA-National Space Science Data Center
• Cheng, Kenneth (July 18, 2015)."The Long, Strange Trip to Pluto, and How NASA Nearly Missed It".The New York Times.

• Proposed NASA space probes
• Missions to Pluto
• Cancelled spacecraft

• Articles with short description
• Short description is different from Wikidata
• Use mdy dates from August 2015