STS039-367-006 - STS-39 Critical Ionization Velocity (CIV) gas release from OV-103 payload bay.jpg
The Critical ionization velocity (CIV) experiment in Discovery's payload bay
NamesSpace Transportation System-40
Mission typeU.S. Department of Defense (DoD) Research
COSPAR ID1991-031A Edit this at Wikidata
SATCAT no.21242
Mission duration8 days, 7 hours, 22 minutes, 23 seconds
Distance travelled5,584,423 km (3,470,000 mi)
Orbits completed134
Spacecraft properties
SpacecraftSpace Shuttle Discovery
Launch mass112,207 kg (247,374 lb)
Landing mass102,755 kg (226,536 lb)
Payload mass5,663 kg (12,485 lb)
Crew size7
Start of mission
Launch dateApril 28, 1991, 11:33:14 UTC
RocketSpace Shuttle Discovery
Launch siteKennedy Space Center, LC-39A
ContractorRockwell International
End of mission
Landing dateMay 6, 1991, 18:55:37 UTC
Landing siteKennedy Space Center,
SLF Runway 15
Orbital parameters
Reference systemGeocentric orbit
RegimeLow Earth orbit
Perigee altitude248 km (154 mi)
Apogee altitude263 km (163 mi)
Period89.60 minutes
  • Air Force Program-675 (AFP-675)
  • Chemical Release Observation (CRO)
  • Cryogenic Infrared Radiance Instrumentation for Shuttle (CIRRIS)
  • Cloud Logic to Optimize Use of Defense Systems (CLOUDS-1A)
  • Infrared Background Signature Survey (IBSS)
  • Multi-Purpose Release Canister (MPEC)
  • Shuttle pallet satellite (SPAS-II)
  • Space Test Program (STP-01)
  • Radiation Monitoring Equipment (RME-III)
STS-39 patch.svg

STS-39 mission patch
Sts-39 crew.jpg

Charles L. Veach, Michael Coats, Gregory J. Harbaugh, Donald R. McMonagle, L. Blaine Hammond, Richard Hieb, Guion Bluford
← STS-37 (39)
STS-40 (41) →

STS-39 was the twelfth mission of the NASA Space Shuttle Discovery, and the 40th orbital shuttle mission overall. The primary purpose of the mission was to conduct a variety of payload experiments for the U.S. Department of Defense (DoD).


Position Astronaut
Commander Michael Coats
Third and last spaceflight
Pilot L. Blaine Hammond
First spaceflight
Mission Specialist 1 Gregory J. Harbaugh
First spaceflight
Mission Specialist 2 Donald R. McMonagle
First spaceflight
Mission Specialist 3 Guion Bluford
Third spaceflight
Mission Specialist 4 Charles L. Veach
First spaceflight
Mission Specialist 5 Richard Hieb
First spaceflight

Crew seating arrangements

Seat[1] Launch Landing
Space Shuttle seating plan.svg

Seats 1–4 are on the Flight Deck. Seats 5–7 are on the Middeck.
S1 Coats Coats
S2 Hammond Hammond
S3 Harbaugh Bluford
S4 McMonagle McMonagle
S5 Bluford Harbaugh
S6 Veach Veach
S7 Hieb Hieb

Mission highlights

STS-39 observing Aurora australis.
STS-39 observing Aurora australis.

Launch was originally scheduled for March 9, 1991, but during processing work at Pad LC-39A, significant cracks were found on all four lug hinges on the two external tank umbilical door drive mechanisms. NASA managers opted to roll back the vehicle to the Vehicle Assembly Building (VAB) on March 7, 1991, and then to Orbiter Processing Facility (OPF) for repair. The faulty hinges were replaced with units taken from orbiter Columbia, and reinforced. Discovery was returned to the pad on April 1, 1991, and the launch was rescheduled for April 23. The mission was again postponed when, during prelaunch external tank loading, a transducer on high-pressure oxidizer turbopump for main engine number three showed readings out of specification. The transducer and its cable harness were replaced and tested. The launch was rescheduled for April 28. Actual launch occurred at April 28, 1991, 7:33:14 a.m. EDT. Launch weight: 112,207 kg (247,374 lb).

STS-39 was a dedicated U.S. Department of Defense mission. Unclassified payload included Air Force Program-675 (AFP-675); Infrared Background Signature Survey (IBSS) with Critical ionization velocity (CIV), Chemical Release Observation (CRO) and Shuttle pallet satellite-II (SPAS-II) experiments; and Space Test Payload-1 (STP-1). Classified payload consisted of Multi-Purpose Release Canister (MPEC). Also on board was Radiation Monitoring Equipment-III (RME-III) and Cloud Logic to Optimize Use of Defense Systems-1A (CLOUDS-1A).

STS-39 was the first unclassified Department of Defense (DoD)-dedicated Space Shuttle mission. There had previously been seven Shuttle missions dedicated to the DoD, but those were considered classified and information about the operation or success of the payloads or experiments was not released. For STS-39, only the payload in the Multi-Purpose Experiment Canister (MPEC) was listed as classified. (Bluford reportedly launched the classified payload by himself while, according to another member of the crew, "the rest of us pretended not to notice".[2])

The crew was divided into two teams for around-the-clock operations. Among other activities, the crew made observations of the atmosphere and gas releases, Discovery's orbital environment, and firings of the orbiter's engines, in wavelengths ranging from infrared to far ultraviolet. As part of the sophisticated experiments, five spacecraft or satellites were deployed from the payload bay, and one was retrieved later during the mission.

Carried in the orbiter's cargo bay were: Air Force Program-675 (AFP-675); Infrared Background Signature Survey (IBSS); Space Test Program-01 (STP-01); and the MPEC. Inside the crew cabin were the Cloud Logic to Optimize the Use of Defense Systems-1A (CLOUDS-1A) experiment and the Radiation Monitoring Equipment-III (RME-III).

The Remote Manipulator System (Canadarm) in the payload bay was used to deploy the Shuttle Pallet Satellite-II (SPAS-II), on which the IBSS was mounted. Among other observations, the SPAS-II/IBSS watched Discovery as it performed some orbital maneuvers including the "Malarkey Milkshake".[3] The deployment of IBSS was delayed a day, until Flight Day Four, to give priority to the completion of the CIRRIS (Cryogenic Infrared Radiance Instrumentation for Shuttle) experiment which was depleting its liquid helium coolant supply faster than expected while making observations of auroral and airglow emissions.

As usual, crew members faced some unexpected challenges during the mission. After working only about four hours, two tape recorders could not be reactivated. The tape recorders were designed to record observations made by three instruments on AFP-675. In a complicated two-hour bypass repair operation, the astronauts had to route wires and attach a splice wire to a Ku-band antenna system so the data could be sent directly to a ground station.

The high orbital inclination of the mission, 57.01° with respect to the equator, allowed the crew to fly over most of Earth's large land masses and observe and record environmental resources and problem areas.

STS-39 landed on May 6, 1991, at 2:55:35 p.m. EDT, at Runway 15, Kennedy Space Center, Florida. Landing was diverted there because of unacceptably high winds at the planned landing site, Edwards Air Force Base, California. Landing weight: 102,755 kg (226,536 lb). Rollout distance: 2,877 m (9,439 ft), rollout time: 55 seconds.


See also


  1. ^ "STS-39". Spacefacts. Retrieved February 26, 2014.
  2. ^ Cassutt, Michael (August 2009). "Secret Space Shuttles". Air & Space magazine. Retrieved April 19, 2015.
  3. ^ The "Malarkey Milkshake" was an orbital maneuver wherein Discovery rotated out-of-plane, fired one Orbital Maneuvering System (SSOMS) engine to move to a different orbital track, rapidly turned around 180° using Reaction control system RCS thrusters and returned to its original orbital track. This rapid sequence of maneuvers was named after the leader of the Johnson Space Center (JSC) guidance team which developed it (see NASA Press Kit p. 26) Public Domain This article incorporates text from this source, which is in the public domain.