Spybirds: POPPY 8 and the dawn of satellite ocean surveillanceby Dwayne A. Day Monday, May 10, 2021
Artist impression of the September 1969 launch of multiple satellites. The four yellow objects at the front represent the POPPY 8 signals intelligence satellites that for the first time had a mission of locating Soviet ships at sea by detecting their radar emissions. POPPY scanned large portions of the electromagnetic spectrum searching for new and unusual signals, and the use of four satellites in a constellation enabled precise location of detected radars. (credit: NRO)At the end of September 1969, a Thor-Agena rocket roared off its launch pad in California and climbed high over the Pacific Ocean, heading south. The rocket dropped its stubby pencil-like solid booster motors not very long after lifting off and continued its arc. A few minutes later, its first stage, burning a mixture of kerosene and liquid oxygen, ran low on fuel and its engine shut down. The Agena upper stage separated and small motors fired, pushing it away and forcing the fuel in its tanks to settle to the rear, and in moments its Bell rocket engine ignited, pushing it faster and higher. Its bulbous nose cone separated and flew away, revealing a cluster of four shiny, egg-shaped satellites surrounding a small pointy object. Upon reaching orbital velocity the Agena’s engine shut down and the shiny satellites began to pop off, pushed away by springs. Each satellite was about the size of a toddler, and collectively they were known as POPPY 8. They were followed by several other satellites that also separated from the front of the Agena. Moments later, various small satellites were pushed off the rear of the Agena. Then came the finale: at the rear of the Agena, a box-shaped satellite the size of a fat suitcase and named WESTON rotated back on a hinge and was shoved away on springs before firing its solid rocket motor and heading to a higher orbit.
https://www.thespacereview.com/article/4174/1