Pluto Kuiper Express
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The Pluto Kuiper Express mission was a space mission designed to flyby the Pluto–Charon system and at least one other large object in the Kuiper belt beyond Pluto's orbit. Originally designated the Pluto Fast Flyby, it was scheduled to reach Pluto by 2012 or 2013. The mission was cancelled for budgetary reasons, but later replaced by the similar New Horizons mission.
The timing of the mission was important, as it would have passed Pluto shortly before the planet's atmosphere froze, which it does for a considerable period of the planet's orbit. The mission's main objectives would have been to map the planet's surface and examine the double system's geology and geomorphology, as well as determining the composition of Pluto's atmosphere. This last task would have been considerably more difficult after the start of atmospheric freezing. Scientific equipment on board would have included visible light imaging systems, infrared and ultraviolet spectrometers, and an ultrastable oscillator (USO) for use in a radio occultation experiment.
The spacecraft was to have been a simple hexagonal prism shaped structure weighing some 220 kg, powered by radioisotope thermal generators (RTGs) similar to those used on the Galileo and Cassini missions. On-board control and data collection would have been maintained by a 1.5 MIPS RISC-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 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 Zond probes to study the Plutonian atmosphere. This plan was later abandoned.
The Pluto Express was predicted to be launched in 2001, but it really was ready in late 2004. The spacecraft was to have been launched via either a Delta rocket or the Space Shuttle, most likely in December 2004. Had that come to be, the only option would have been to use a Delta rocket, as the Shuttle fleet was grounded after the Columbia disaster. The course would have been initially via Jupiter, where the planet's gravity well would have been used to increase the probe's velocity via a gravity assist. The closest approach distance to Pluto would have been about 15,000 km at 17-18 km/s, so as to allow for 1 km resolution mapping. After passing Pluto, the spacecraft would have used its imaging camera to search for Kuiper Belt objects.
- New Horizons: NASA's Pluto-Kuiper Belt Mission, The Johns Hopkins University Applied Physics Laboratory
- Pluto Kuiper Express, NASA-National Space Science Data Center