April 5, 2013
NASA Celebrates 40th Anniversary Of Pioneer 11
[ Watch the Video: Pioneer 11 Animation and Archive Footage ]
Michael Harper for redOrbit.com — Your Universe Online
NASA is celebrating the 40th birthday of the Pioneer 11 spacecraft. For the past four decades, Pioneer has been hurtling through space, capturing satellite images of the planets Jupiter and Saturn. As its predecessor, Pioneer 10 had launched just over a year before and was the first spacecraft to not only leave the inner Solar System, but make the trip to Jupiter as well.
Pioneer 11, launched on April 5, 1973, surpassed its predecessor's achievements before it was ultimately lost in 1995.
According to a NASA tribute, the Pioneer 11 was originally intended only as a backup spacecraft for the Pioneer 10. The only difference between the two crafts was the addition of a Flux-Gate Magnetometer.
Following a successful fly-by of Jupiter by Pioneer 10, Pioneer 11 was rerouted mid-flight to expand on its predecessor's mission. Using Jupiter´s gravitational pull as a sling shot, the astronomers at NASA´s Ames Research Center in California directed Pioneer 11 towards Saturn.
The NASA tribute also remembers the discussion carried on internally about the path of Pioneer 11. The Ames team wanted to send it much closer to Jupiter than the 10 had gotten. Though this decision was opposed by several team members on the Pioneer 11 team, it ultimately did pass just 26,097 miles above Jupiter´s atmosphere, nearly 5 times closer than its predecessor, Pioneer 10, which passed by at about 124,000 miles.
As Pioneer 11 passed by Jupiter, it was able to photograph the poles and capture some very detailed shots of the famous Red Spot.
Still reeling from the debate about which path Pioneer 11 would take past Jupiter, the Ames astronomers again began to discuss which path the spacecraft would take on its voyage to Saturn. NASA's Voyager 1 and 2 missions were launched two years prior to Pioneer 11´s arrival at Saturn and were already heading towards the asteroid belt. As the Voyager duo cost much more than the Pioneer´s relatively simple makeup, some members of the team wanted to use 11 as a sort of a crash test dummy to ensure Voyager 1 wouldn´t be destroyed on its way to Saturn.
At the time, astronomers thought Saturn´s rings were filled with hazardous debris and materials, and wanted 11 to pass through first to test out the waters. Already having a successful mission under their belt, the Pioneer 11 team chose to direct the craft through Saturn´s inner rings. The Voyager team disagreed with this call and wanted to see Pioneer 11 pass through the outer rings on the same trajectory Voyager 1 would soon follow.
NASA headquarters finally sided with the Voyager team and told the Pioneer crew to pass their craft through the outer “E” ring of Saturn.
“It was a controversial decision at the time,” remembers Pioneer´s last project manager, Larry Lasher in the tribute to the spacecraft on NASA.
“But with the brave path it forged, Pioneer 11 was proud to contribute to the success of Voyager 2 in its completion of the “Grand Tour,” and the exploration of two of the outermost planets in our Solar System.”
Pioneer 11 had only been projected to be in service for 21 months. Yet, NASA was able to continue receiving data from the spacecraft long after its retirement. In fact, it didn´t reach Saturn until eight months after its original deadline. By this time, the Voyager 2 had already surpassed it.
The Pioneer mission finally ended in 1995 when NASA received their last transmission from the spacecraft.