| Astrophysics (Index) | About |
NASA's Pioneer programs from the 1960s to the 1990s, included about 15 spacecraft, focused on solar system exploration, including the Moon, Venus (Pioneer 12 and 13), space weather, and the outer solar system.
Two identical spacecraft, Pioneer 10 and Pioneer 11 were devoted to the outer solar system, both of which were boosted to speeds beyond the Sun's escape velocity, and will continue out through the interstellar medium. Each of the two carried the following instruments:
Pioneer 10 was launched in 1972, flew by Jupiter in 1973, the mission terminated in 1997 when it was about 67 AU from the Sun, the final signal successfully received was in 2003 at about 80 AU, and calculations place its current (February 2026) position at about 140 AU.
Pioneer 11 was launched in 1973, flew by Jupiter in 1974 and Saturn in 1979, the final signal successfully received was in 1997 at about 44 AU, and calculations place its current (February 2026) position at about 117 AU.
The Pioneer anomaly was an oddity in the speeds of Pioneer 10 and 11 as they passed through and beyond the outer planets: they appeared to be moving slower than expected. This was eventually ascribed to more thermal emission toward the direction they were heading than toward other directions.