Unidentified flying object

An unidentified flying object, or UFO, in its most general definition, is any apparent anomaly in the sky that is not identifiable as a known object or phenomenon. Culturally, UFOs are associated with claims of visitation by extraterrestrial life or government-related conspiracy theories, and have become popular subjects in fiction. While UFOs are often later identified, sometimes identification may not be possible owing to the usually low quality of evidence related to UFO sightings (generally anecdotal evidence and eyewitness accounts).

Stories of fantastical celestial apparitions have been told since antiquity, but the term "UFO" (or "UFOB") was officially created in 1953 by the United States Air Force (USAF) to serve as a catch-all for all such reports. In its initial definition, the USAF stated that a "UFOB" was "any airborne object which by performance, aerodynamic characteristics, or unusual features, does not conform to any presently known aircraft or missile type, or which cannot be positively identified as a familiar object." Accordingly, the term was initially restricted to that fraction of cases which remained unidentified after investigation, as the USAF was interested in potential national security reasons and/or "technical aspects" (see Air Force Regulation 200-2).

STS-48

STS-48 was a Space Shuttle mission that launched on 12 September 1991, from Kennedy Space Center, Florida. The orbiter was Space Shuttle Discovery. The primary payload was the Upper Atmosphere Research Satellite. The mission landed on 18 September at 12:38 am at Edwards Air Force Base on runway 22. The mission was completed in 81 revolutions of the Earth and traveled 2.2 million miles. The 5 astronauts carried out a number of experiments and deployed several satellites. The total launch mass was 240,062 pounds (108,890 kg) and the landing mass was 192,780 pounds (87,440 kg).

Crew

Crew seating arrangements

Mission highlights

Space Shuttle Discovery was launched into a 57-degree inclination orbit from the Kennedy Space Center (KSC) Launch Complex 39A at 7:11 p.m. Eastern Daylight Time (EDT) on 12 September 1991. Launch was delayed for 14 minutes at the T-5 minute mark due to a noise problem in the air-to-ground link. The noise cleared itself, and the countdown proceeded normally to launch.

Space Shuttle

The Space Shuttle was a partially reusable low Earth orbital spacecraft system operated by the U.S. National Aeronautics and Space Administration (NASA), as part of the Space Shuttle program. Its official program name was Space Transportation System (STS), taken from a 1969 plan for a system of reusable spacecraft of which it was the only item funded for development. The first of four orbital test flights occurred in 1981, leading to operational flights beginning in 1982. They were used on a total of 135 missions from 1981 to 2011, launched from the Kennedy Space Center (KSC) in Florida. Operational missions launched numerous satellites, interplanetary probes, and the Hubble Space Telescope (HST); conducted science experiments in orbit; and participated in construction and servicing of the International Space Station. The Shuttle fleet's total mission time was 1322 days, 19 hours, 21 minutes and 23 seconds.

Shuttle components included the Orbiter Vehicle (OV), a pair of recoverable solid rocket boosters (SRBs), and the expendable external tank (ET) containing liquid hydrogen and liquid oxygen. The Shuttle was launched vertically, like a conventional rocket, with the two SRBs operating in parallel with the OV's three main engines, which were fueled from the ET. The SRBs were jettisoned before the vehicle reached orbit, and the ET was jettisoned just before orbit insertion, which used the orbiter's two Orbital Maneuvering System (OMS) engines. At the conclusion of the mission, the orbiter fired its OMS to de-orbit and re-enter the atmosphere. The orbiter then glided as a spaceplane to a runway landing, usually at the Shuttle Landing Facility of KSC or Rogers Dry Lake in Edwards Air Force Base, California. After landing at Edwards, the orbiter was flown back to the KSC on the Shuttle Carrier Aircraft, a specially modified Boeing 747.