At 11:59 a.m. Eastern Standard Time, the orbiter Atlantis rose from Launch Pad 39B at Kennedy Space Center. Its primary payload was the Atmospheric Laboratory for Applications and Science-3, a reusable platform of instruments housed in the shuttle's cargo bay. The mission, designated STS-66, aimed to measure the middle atmosphere's chemical composition and energy input from the sun. It was the third flight of the ATLAS series, timed for a period of minimal solar flares and sunspots.
This mission mattered because it provided a baseline. Scientists needed data from the solar minimum to compare with readings taken during the more active solar maximum captured by the prior ATLAS flights. The crew of six astronauts operated instruments that scrutinized ozone levels, measured solar irradiance, and cataloged atmospheric gases. Their work contributed directly to the growing body of evidence on human-caused ozone depletion and the complex physics of climate change.
A common assumption is that space shuttle missions were either about deploying satellites or building the International Space Station. STS-66 performed neither. It was a dedicated laboratory mission, a ten-day orbital science expedition focused purely on Earth itself. The shuttle served as a stable, power-supplying platform for instruments that required retrieval and recalibration.
The data collected during the 175 orbits of Earth filled a specific gap in the solar cycle record. Findings from this and the other ATLAS missions helped refine atmospheric models. These models remain critical for predicting upper atmospheric behavior, which affects satellite drag and long-term climate projections. Atlantis landed at Edwards Air Force Base on November 14, concluding the final shuttle mission of 1994.