Short answers, pulled from the story.
The Pegasus Project was a NASA initiative to measure the frequency, size, direction, and penetration of micrometeoroid impacts on spacecraft in orbit. The data was gathered in support of the Apollo Program, which needed to understand whether micrometeoroids posed a puncture hazard to crewed lunar spacecraft.
All three Pegasus satellites were launched in 1965. Pegasus 1 launched on the 16th of February 1965, Pegasus 2 on the 25th of May 1965, and Pegasus 3 on the 30th of July 1965.
Each Pegasus satellite extended a pair of winglike arrays to a span of 96 feet. The arrays consisted of 104 sensor panels and exposed more than 2,300 square feet of instrumented surface to the space environment.
All three Pegasus satellites were launched by Saturn I rockets. Pegasus 1 flew on vehicle A-103, Pegasus 2 on A-104, and Pegasus 3 on A-105, which were Saturn I test flights.
Beyond micrometeoroid data, the Pegasus missions provided information on gyroscopic motion of rigid bodies in orbit, lifetimes of electronic components in space, thermal control system performance, and radiation environments including the Van Allen radiation belts.
Pegasus 3 had the shortest orbital life, decaying on the 4th of August 1969. Pegasus 1 remained in orbit until the 17th of September 1978, and Pegasus 2 stayed aloft until the 3rd of November 1979.