RXTE

The Rossi X-ray Timing Explorer (RXTE) was a NASA satellite launched in 1995 to observe the extreme variability in X-ray emissions. It specifically targeted black holes, neutron stars, and active galactic nuclei. It was uniquely designed to track rapid changes in X-ray brightness over fractions of a second.

After a highly successful 16-year mission, NASA officially decommissioned the RXTE satellite in 2012. The spacecraft was ordered to power down its transmitters and systems after it could no longer maintain its precise pointing accuracy due to fuel depletion. It remains in low Earth orbit but is completely inactive.

RXTE is famous for discovering the "Quasi-Periodic Oscillations" (QPOs) in X-ray emissions swirling around black holes and neutron stars. It also discovered the first accreting millisecond X-ray pulsar, providing crucial proof for how ancient, rapidly spinning neutron stars are spun up by infalling matter. These discoveries fundamentally changed the field of astrophysics.

The satellite was named in honor of Bruno Rossi, an Italian-American experimental physicist and pioneer in the field of X-ray astronomy. He was an MIT professor who discovered the first extrasolar source of X-rays, Scorpius X-1. His foundational work in the 1960s paved the way for missions like RXTE.