IMP-8 was a weather satellite launched on this day, October 26, 1973. It was one of the longest operational satellites launched, fulfilling its mission in 2001, 28 years after launch. After a brief intermission, the satellite was re-purposed and recommissioned and remained active for an additional five years, finally stopping in 2006. Although the batteries stopped functioning years ago, the solar panels allow the IMP-8 to continue transmitting data. With a planned lifespan of 10 years, the IMP-8, like both Voyager probes and many spacecraft, far outperformed its original mission parameters!
IMP-8 was the last of a series of satellites commissioned for studying weather and interplanetary solar winds. IMP stands for Interplanetary Monitoring Platform. Over 1,000 scientific papers reference the data sets collected by IMP-8. The spacecraft takes 12.5 days to orbit around the Earth—seven to eight days are spent in the solar wind, with the rest of the time in the magnetosheath and magnetosphere.
Image of IMP-8 pre-launch courtesy of NASA.