STS-39

STS-39 was a dedicated United States Department of Defense research mission of the NASA Space Shuttle program. Launched aboard the Space Shuttle ''Discovery'' in late April 1991, its primary objective was to conduct a wide array of experiments focused on Earth's atmosphere and the space environment. The flight deployed and retrieved the CIRRIS instrument and carried the IBSS pallet, contributing significantly to the understanding of celestial backgrounds and spacecraft signatures.

Mission overview

STS-39 launched from Launch Complex 39A at the Kennedy Space Center on April 28, 1991. The mission was an unclassified DoD flight, allowing for greater public disclosure of its activities compared to earlier dedicated military shuttle missions. It operated in a high-inclination orbit, which was ideal for its atmospheric and celestial observation tasks. The flight concluded with a landing on Runway 15 at the Kennedy Space Center on May 6, 1991, after over eight days in space.

Crew

The seven-person crew was commanded by Michael L. Coats, a veteran of STS-41-D. The pilot was L. Blaine Hammond, on his first spaceflight. The mission specialists were Guion Bluford, a veteran of STS-8; Gregory J. Harbaugh; Richard J. Hieb; and Donald R. McMonagle. The flight also included a payload specialist, Charles Lacy Veach, who was responsible for operating specific experiments. This crew represented a mix of experienced NASA astronauts and specialists focused on the complex research objectives.

Mission highlights

A key highlight was the successful deployment and later retrieval of the Cryogenic Infrared Radiance Instrument for Shuttle (CIRRIS) using the shuttle's Canadarm robotic arm. The crew operated in two shifts around the clock to maximize data collection from the numerous experiments. Significant maneuvers were performed, including flying in formation with a deployed satellite and conducting observations of the shuttle's own engine plumes against the backdrop of space. The mission faced a minor issue with a fuel cell, but it was managed without impacting the overall schedule or success of the flight.

Payloads and experiments

The primary payloads were housed on the Infrared Background Signature Survey (IBSS) pallet in the shuttle's payload bay. Key experiments included the Air Force Program-675 (AFP-675), which studied celestial infrared backgrounds, and the Space Test Program (STP) payload. The Cryogenic Infrared Radiance Instrument for Shuttle (CIRRIS) collected high-resolution atmospheric data. Other instruments, such as the Cloud Logic to Optimize Use of Defense Systems (CLOUDS) experiment, gathered data on natural and man-made phenomena in the thermosphere and ionosphere.

Mission insignia

The mission patch, designed by the crew, features the Space Shuttle Discovery in orbit against a stylized representation of Earth. A prominent rainbow spectrum arcs from the planet to the orbiter, symbolizing the broad range of infrared and optical measurements being made. The names of the seven crew members encircle the design, with the NASA "worm" logo and the mission designation at the top. The patch's colors and elements directly reflect the scientific nature of the flight's research objectives.

Wake Shield Facility

Although not flown on this mission, the Wake Shield Facility (WSF) was an experimental science platform initially manifested for STS-39 but later reassigned. The WSF was designed to create an ultra-high vacuum in its wake to grow thin films in space, a process critical for advanced semiconductor development. Its removal from STS-39 allowed for a greater focus on the atmospheric and signature research experiments that defined the flight's legacy in space science. The facility would later fly on subsequent shuttle missions, including STS-60 and STS-69.