Pluto Kuiper Express

The Pluto Kuiper Express mission, originally designated the Pluto Fast Flyby, was designed to fly by and make studies of the planet Pluto and its satellite Charon in 2012 and fly on to encounter one or more of the large bodies in the Kuiper belt beyond the orbit of Pluto. It was cancelled for budgetary reasons, and a new mission to Pluto and the Kuiper Belt called New Horizons replaced it.

Pluto Kuiper Express' major science objectives were to:

1. characterize the global geology and geomorphology of Pluto and Charon
2. map the composition of Pluto's surface
3. determine the composition and structure of Pluto's atmosphere.

The mission was intended to reach Pluto before the tenuous Plutonian atmosphere can refreeze onto the surface as the planet recedes from the Sun. Studies of the double planet system would have begun 12-18 months prior to closest approach.

Spacecraft and subsystems

The overall structure of the spacecraft was to be an aluminum hexagonal bus with no deployable structures. Of the total 220 kg mass of the spacecraft, only about 7 kg would have consisted of science instruments. Power would have been provided by radioisotope thermal generators (RTGs) similar in design to those used on earlier missions (e.g., Galileo or Cassini). It was planned to use spare RTGs from Cassini. Communications would have been via a fixed, 1.47 m high-gain antenna employing an X-band uplink receiver and downlink transponder. Pointing control would have been maintained by a wide-field star tracker and a set of three solid-state rate sensors. The on-board computer was to have been a 1.5 MIPS RISC-based system capable of processing a science data stream of 5 Mbit/s. The solid-state data storage system was to be capable of storing 400 MB in both compressed and uncompressed formats. Data storage capacity and transmission rates would allow the transmission of 1+ gigabit of science data over a one year period. Planned experiments for the spacecraft included a multi-color visible light imaging system, an infrared mapping spectrometer, an ultraviolet airglow and solar occultation spectrometer, and a radio occultation experiment utilizing an ultrastable oscillator (USO) and the on-board telecommunications system.

There was originally a study of a potential cooperative effort with Russia involving the inclusion of Zond probes, to study the Plutonian atmosphere. Strawman experiments for the probe included either a mass spectrometer or a retarding potential analyzer, an atmospheric imager, and an accelerometer. The Zond would separate from the flyby spacecraft about 30 days prior to closest approach and relay data prior to impact on Pluto. This possibility no longer looks feasible.

Mission profile

Launch of the Pluto Kuiper Express spacecraft was to be on either a Delta rocket or from the Space Shuttle, tentatively scheduled for December 2004. It was planned for the spacecraft to obtain a gravity assist from Jupiter in April to June 2006 to obtain sufficient velocity to fly by Pluto in December 2012. To accomplish the mission goal of 1 km resolution mapping, the closest approach distance would have been about 15,000 km. The flyby velocity would have been 17-18 km/s. The infrared spectrometer required a spatial resolution of 5-10 kilometers per pixel. Studies of Pluto's neutral atmosphere would have determined the mole fractions of nitrogen, carbon monoxide, methane and other gases to at least the one percent level. Data would have been transmitted back to Earth for a year following the flyby. After the flyby the spacecraft would have continued on to the Kuiper Belt where it would have used its imaging camera to search for Kuiper Belt objects. If a good flyby candidate had been found, trajectory maneuvers could have been made to allow close approach and study of the object.

External links

• http://nssdc.gsfc.nasa.gov/database/MasterCatalog?sc=PLUTOKE