Neptune Orbiter

Neptune Orbiter was a proposed NASA unmanned planetary spacecraft to explore the planet Neptune. It was envisioned that it would be launched sometime around 2016 and take 8 to 12 years to reach the planet; however, NASA's website no longer lists any possible launch date. The Neptune Orbiter concept would have answered many questions about the nature of the planet.

Its objective was to study Neptune's atmosphere and weather, its ring system, and its moons, particularly Triton. The California Institute of Technology proposed one mission plan in 2004, while the University of Idaho and Boeing proposed an alternative approach in 2005.

Neptune Orbiter's primary mission was to go into orbit and perform scientific studies of the planet. The mission concept was first proposed to NASA in 2005. It was proposed to use a launch rocket similar to the Delta IV or Atlas V. The orbiter's trajectory was to use one Venus gravity assist, and a Jupiter gravity assist before arriving at Neptune. The length of time from launch until Neptune arrival was estimated to be 10.25 years.

Just prior to arriving, the orbiter would release its two atmospheric probes, which would transmit data before aerocapture. Then, it would begin Neptune orbit insertion by aerocapture. After adjusting its orbit to its planned science orbit, the orbiter would carry out studies of Neptune, its rings, atmosphere, weather, and its natural satellites. The main phase of the science operations would have taken from 3 to 5 years with a possible extension lasting 3 more years.

In 2008, the mission was removed from NASA's possible future missions list. According to NASA's 2010 budget, funding to missions to the outer Solar System was aimed at the future Europa Jupiter System Mission. The remaining budget was allocated to ongoing undertakings such as Cassini–Huygens, Juno, and New Horizons, with the Neptune system not being part of any official considerations.

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