The Pioneer spacecraft were designed to explore our solar system and study the outer planets, including Jupiter, Saturn, and beyond. They were also the first spacecraft to collect data on the solar wind, cosmic rays, and magnetic fields in interplanetary space.
The Pioneer spacecraft were launched with a speed of around 32,000 miles per hour (51,500 km/h), but their speed has decreased over time due to the gravitational pull of the planets they have passed. As of 2021, the Pioneer 10 spacecraft is travelling at a speed of approximately 27,000 miles per hour (43,000 km/h), while Pioneer 11 is travelling at around 24,000 miles per hour (39,000 km/h).
The Pioneer 10 spacecraft was the first to leave our solar system in 1983, reaching a distance of over 7.5 billion miles (12 billion km) from the Sun. As of 2021, Pioneer 10 is the farthest man-made object from Earth. Pioneer 11 followed a similar trajectory, and as of 2021, it has travelled over 4.6 billion miles (7.4 billion km) from the Sun.
The Pioneer spacecraft were launched in the direction of the ecliptic plane, which is the plane in which most of the planets orbit the Sun. This means that they are travelling in a southerly direction from Earth's perspective. However, since they have been affected by the gravitational pull of different planets, their exact cosmological direction is constantly changing.
The last communication with the Pioneer 10 spacecraft was in 2003, and the last communication with Pioneer 11 was in 1995. Both spacecraft are now considered to be inactive, although they are still travelling through space and transmitting data on their position and speed. NASA's Deep Space Network continues to track the Pioneer spacecraft and receive data from them, providing valuable information on the conditions in interstellar space.