Solar Probe Plus
Artist's concept of NASA's Solar Probe Plus
|Operator||NASA / Applied Physics Laboratory|
|Mission duration||< 10 years|
|Flyby of||Venus (V7)|
|Satellite of||The Sun|
|Altitude||~5,900,000 km (3,700,000 mi)|
|Orbital period||88 days|
Solar Probe Plus or Solar Probe+, previously NASA Solar Probe, is a planned robotic spacecraft to probe the outer corona of the Sun. It will approach to within 8.5 solar radii (0.034 astronomical units or 5.9 million kilometers or 3.67 million miles, roughly 1/8 of the perihelion of Mercury) to the 'surface' (photosphere) of the Sun. The project was announced as a new mission start in the fiscal 2009 budget year. On May 1, 2008 Johns Hopkins University Applied Physics Laboratory announced it will design and build the spacecraft, on a schedule to launch it in 2015. The launch date has since been pushed back to 2018.
Trajectory and mission 
Early conceptual designs for the Solar Probe mission used a gravity assist maneuver at Jupiter to cancel the orbital angular momentum of the probe launched from Earth, in order to drop onto a trajectory close to the Sun. The Solar Probe Plus mission design simplifies this trajectory by using multiple gravity assists at Venus, to incrementally decrease the orbital perihelion to achieve multiple passes to approximately 8.5 solar radii, or about 6,000,000 km (3,700,000 mi).
The mission survives the harsh environment near the Sun, where the incident solar intensity is approximately 520 times the intensity at Earth orbit, by the use of a solar shadow-shield. The solar shield, at the front of the spacecraft, is made of reinforced carbon-carbon composite. The spacecraft systems, and the scientific instruments, are located in the penumbra of the shield. The primary power for the mission will be by use of a dual system of photovoltaic arrays. A primary photovoltaic array, used for the portion of the mission outside of 0.25 AU, is retracted behind the shadow shield during the close approach to the Sun, and a much smaller secondary array powers the spacecraft through closest approach. This secondary array uses pumped-fluid cooling to maintain operating temperature.
As the probe passes around the Sun, it will achieve a velocity of up to 200 km/s (120 mi/s) at that time making it the fastest manmade object ever, almost three times faster than the current record holder, Helios II.
Scientific goals 
- Determine the structure and dynamics of the magnetic fields at the sources of solar wind.
- Trace the flow of energy that heats the corona and accelerates the solar wind.
- Determine what mechanisms accelerate and transport energetic particles.
- Explore dusty plasma near the Sun and its influence on solar wind and energetic particle formation.
See also 
- List of vehicle speed records
- Advanced Composition Explorer (ACE), launched 1997, still operational.
- Solar Orbiter, 45 Rs
- STEREO (Solar TErrestrial RElations Observatory), launched 2006, still operational.
- WIND (spacecraft) launched 1994, still operational.
- Applied Physics Laboratory (19 November 2008). Feasible Mission Designs for Solar Probe Plus to Launch in 2015, 2016, 2017, or 2018 (.PDF). Johns Hopkins University. Retrieved 2010-02-27.
- Tony Phillips. "NASA Plans to Visit the Sun". NASA. Retrieved 30 September 2010.
- M. Buckley (2008-05-01). "NASA Calls on APL to Send a Probe to the Sun". Johns Hopkins University Applied Physics Laboratory. Retrieved 30 September 2010.
- M. Buckley (2012-03-05). "NASA Solar Study Mission Moves to Next Design Stage". Johns Hopkins University Applied Physics Laboratory. Retrieved 12 March 2012.
- "Solar Probe Plus: A NASA Mission to Touch the Sun:". JHU/APL. 4 September 2010. Retrieved 30 September 2010.
- G.A. Landis, P. C. Schmitz, J. Kinnison, M. Fraeman, L. Fourbert, S. Vernon and M. Wirzburger, "Solar Power System Design for the Solar Probe Mission," AIAA Paper-2008-5712, International Energy Conversion Engineering Conference, Cleveland OH, 28-30 July 2008.
- Kerri Beisser (10 February 2011). "Solar Probe Plus: Mission Overview". JHU/APL. Retrieved 10 February 2011.
|Wikimedia Commons has media related to: Solar Probe +|
- Solar Probe Plus at the Johns Hopkins Applied Physics Laboratory
- Official NASA Solar Probe project homepage
- Solar Probe Plus Mission Engineering Study Report
- NASA - Heliophysics Research
- Explorers and Heliophysics Projects Division (EHPD)