The sun is the most massive object in our solar system, accounting for 99.8% of the entire mass of the system. Still, we really don't understand it. The various probes are to study and learn more about our life giving star.

Hear the sounds of a solar flare (X17.2) as recorded by University of Iowa Professor and Space Physicist Don Gurnett using NASA's Cassini spacecraft (enroute to Saturn) on October 28, 2003.

• Pioneer 5 (USA) 11 March 1959. Pioneer 5 was designed to provide the first map of the interplanetary magnetic field. It functioned for 106 days. It is still in solar orbit.
• Pioneer 6 (USA) 16 December 1965. Measured solar wind and the Sun's magnetic field. Still in solar orbit. Still active.
• Pioneer 7 (USA) 17 August 1966. Monitored solar wind and cosmic rays. Still in solar orbit.
• Pioneer 8 (USA) 13 December 1967. Collected solar radiation data. Still in solar orbit. Still active.
• Pioneer 9 (USA) 8 November 1968. Collected solar radiation data. Still in solar orbit.
• Pioneer E (USA) 27 August 1969. Destroyed by range safety due to first stage hydraulics failure.
• Explorer 49 (RAE 2,  Radio Astronomy Explorer) (USA) 10 June 1973. Solar physics mission in lunar orbit 15 June 1973.
• Helios 1 (Helios-A) (USA/Germany-FRG)  10 December 1974. Still in solar orbit. Came within 47 million km of the sun.
• Helios 2 (Helios-B) (USA/Germany-FRG)  16 January 1976. Came within 43 million km of the sun.
• SMM (Solar Maximum Mission) (USA)  14 February 1980. Stayed in Earth orbit, but studied solar flares. Re-entered 2 December 1989.
• Ulysses(International Solar Polar Mission, Solar Polar) (ESA)  6 October 1990. Went by Jupiter (February 1992) so that it could swing around and go into a polar solar orbit. First craft to pass over the poles of the sun (south pole in mid-1994, north pole in mid-1995).
• Solar-A (Yohkoh) (Japan)  30 August 1991. Japanese mission to study solar flares from Earth orbit.
• SOHO (Solar & Heliospheric Observatory) (ESA/USA)  12 December 1995. European solar observatory in solar orbit.
• Genesis ( Genesis Solar Wind Sample Return) (USA)   8 August 2001. This robotic probe will park for 2˝ years about a million miles away to collect samples of the solar wind which will then be returned to Earth in 2004. Total material collected will be equivalent to about 8 grains of salt.
• Stereo-A, Stereo-B (USA)  26 October 2006. These are identical satellites which orbit the sun, Stereo-A(head) of the Earth and Stereo-B(ehind) the Earth. They will create stereo images of the sun used to predict Coronal Mass Ejections headed for the Earth.