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STS-51
IMAX photography of Discovery in orbit, viewed from the free-flying SPAS-ORFEUS astronomy platform
NamesSpace Transportation System-51
Mission typeAdvanced Communications Technology Satellite (ACTS) satellite deployment
Astronomy
OperatorNASA
COSPAR ID1993-058A Edit this at Wikidata
SATCAT no.22795Edit this on Wikidata
Mission duration9 days, 20 hours, 11 minutes, 6 seconds (achieved)
Distance travelled6,608,628 km (4,106,411 mi)
Orbits completed157
Spacecraft properties
SpacecraftSpace Shuttle Discovery
Landing mass92,371 kg (203,643 lb)
Payload mass18,947 kg (41,771 lb)
Crew
Crew size5
Members
Start of mission
Launch dateSeptember 12, 1993, 11:45:00 UTC
Launch siteKennedy, LC-39B
ContractorRockwell International
End of mission
Landing dateSeptember 22, 1993, 07:56:06 UTC
Landing siteKennedy, SLF Runway 15
Orbital parameters
Reference systemGeocentric orbit
RegimeLow Earth orbit
Perigee altitude300 km (190 mi)
Apogee altitude308 km (191 mi)
Inclination28.45°
Period90.60 minutes
Instruments
  • Air Force Maui Optical Site (AMOS)
  • Airborne Support Equipment (ASE)
  • Auroral Photography Experiment (APE-B)
  • Chromosome and Plant Cell Division in Space (CHROMEX)
  • Commercial Protein Crystal Growth (CPCG)
  • High Resolution Shuttle Glow Spectroscopy (HRSGS-A)
  • Interstellar Medium Absorption Profile Spectrograph (IMAPS)
  • Investigation into Polymer Membrane Processing (IPMP)
  • Limited Duration space environment Candidate materials Exposure (LDCE)
  • Radiation Monitoring Equipment (RME-III)

STS-51 mission patch

From left: Culbertson, Bursch, Walz, Readdy and Newman
← STS-57 (56)
STS-58 (58) →

STS-51 was a NASA Space Shuttle Discovery mission that launched the Advanced Communications Technology Satellite (ACTS) in September 1993. Discovery's 17th flight also featured the deployment and retrieval of the SPAS-ORFEUS satellite and its IMAX camera, which captured spectacular footage of Discovery in space. A spacewalk was also performed during the mission to evaluate tools and techniques for the STS-61 Hubble Space Telescope (HST) servicing mission later that year. STS-51 was the first shuttle mission to fly a Global Positioning System (GPS) receiver, a Trimble TANS Quadrex. It was mounted in an overhead window where limited field of view (FoV) and signal attenuation from the glass severely impacted receiver performance.[1] Full triple-redundant 3-string GPS would not happen until 14 years later with STS-118 in 2007.

Crew

[edit]
Position Astronaut
Commander Frank L. Culbertson Jr.
Second spaceflight
Pilot William F. Readdy
Second spaceflight
Mission Specialist 1 James H. Newman
First spaceflight
Mission Specialist 2
Flight Engineer 		Daniel W. Bursch
First spaceflight
Mission Specialist 3 Carl E. Walz
First spaceflight

Crew seat assignments

[edit]
Seat[2] Launch Landing
Seats 1–4 are on the flight deck.
Seats 5–7 are on the mid-deck.
1 Culbertson
2 Readdy
3 Newman Walz
4 Bursch
5 Walz Newman
6 Unused
7 Unused

Launch Preparations

[edit]
Launch as seen from the RSS.

STS-51 was notable for having been scrubbed three times on the launchpad, each time after the crew had boarded the spacecraft:[3][4]

Attempt Planned Result Turnaround Reason Decision point Weather go (%) Notes
1 17 Jul 1993, 9:22:00 am Scrubbed — Technical 17 Jul 1993, 8:55 am ​(T−00:20:00 hold) The launch was scrubbed on the pad due to a flaw in the pyrotechnic initiator controller that triggers the release of the solid rocket boosters from the mobile launcher platform.[5]: 2 [6]
2 24 Jul 1993, 9:27:00 am Scrubbed 7 days 0 hours 5 minutes Technical 24 Jul 1993, 9:26 am ​(T−00:00:19) Problems with a hydraulic power unit in one of the solid rocket boosters caused another scrub on the pad. Because of the Perseids meteor shower, the next launch window did not open until the second week of August 1993.[5]: 2 
3 12 Aug 1993, 9:12:35 am Scrubbed 18 days 23 hours 46 minutes Technical 12 Aug 1993, 9:12 am ​(T−00:00:03) Countdown clock was held at T−5 minutes due to a communication problem.[5]: 2  The count reached the T−3 second mark, at which point the Space Shuttle Main Engines (SSMEs) had ignited. A shutdown was then triggered by faulty fuel flow sensors in one of the SSMEs.[7]
4 12 Sep 1993, 7:45:00 am Success 30 days 22 hours 32 minutes

Advanced Communications Technology Satellite (ACTS)

[edit]
ACTS deployment
ACTS heads for geostationary orbit

The Advanced Communications Technology Satellite (ACTS) was built by Lockheed Martin Astro Space for NASA in East Windsor, NJ.[8] The satellite was deployed on flight day 1 and served as a test bed for advanced experimental communications satellite concepts and technology. Its Transfer Orbit Stage (TOS) upper stage fired on time 45 minutes after deployment and boosted the satellite to geosynchronous orbit on the first day of the mission.

The first attempt to deploy ACTS was delayed by the crew when two-way communications were lost with Mission Control Center (MCC) about 30 minutes before the deploy time. Flight controllers could receive telemetry and voice communications from Discovery, however the crew could not receive communications from the ground. The crew waived the 2:43 p.m. CDT deploy when they did not receive a "go" from MCC as called for in preflight plans made for just such an occurrence. After the waive off of deploy, the crew changed the shuttle's S-Band communications system to a lower frequency and restored two-way communications with the ground. The two-way communications had been lost for a total of about 45 minutes. After consulting the crew, flight controllers began immediately planning for the second, and ultimately successful deploy.

During the deployment on September 12, 1993, two Super*Zip explosive cords in the Airborne Support Equipment cradle (ASE) designed to release the spacecraft, one primary and the other a backup, simultaneously detonated. This caused minor tears in two dozen insulation blankets mounted on the bulkhead between the payload bay and the AFT near the #3 APU. The ASE ring holding the TOS was damaged as well, and ejected debris was visible as the stack moved away from the orbiter.

The Advanced Communications Technology Satellite (ACTS), a significant activity of the NASA Space Communications Program, provided for the development and flight test of high-risk advanced communications satellite technology. Using multiple spot beam antennas and advanced on-board switching and processing systems, ACTS pioneered new initiatives in communications satellite technology. NASA Glenn Research Center was responsible for the development, management, and operation of ACTS as part of a long legacy of experimental communications satellites.

After fulfilling its original mission as a key part of the ACTS Gigabit Satellite Network, the spacecraft continued operations through a partnership between the space agency and a nonprofit consortium. It was shut down April 28, 2004, after funding dried up. The satellite was put into a flat spin with its solar array edges facing the Sun, which should theoretically prevent it from ever being restarted. The spacecraft was moved to its final graveyard orbit at 105.2° west longitude – where it poses minimal risk to other satellites – after NASA concluded in 2000 that it probably lacked the fuel to move to a higher graveyard orbit. Nevertheless, ACTS should not re-enter the atmosphere for thousands of years, according to Richard Krawczyk, the ACTS operations manager at Glenn Research Center.[9]

SPAS-ORFEUS

[edit]
The ORFEUS/SPAS platform is captured by the Canadarm.

Another payload on this mission was the Orbiting Retrievable Far and Extreme Ultraviolet Spectrometer (ORFEUS) telescope mounted on the Shuttle Pallet Satellite (SPAS) payload carrier. ORFEUS was designed to provide information on how stars are born and how they die, while studying gaseous interstellar clouds. Also in the cargo bay was the Limited Duration space environment Candidate materials Exposure (LDCE).

Messerschmitt-Bölkow-Blohm (MBB) began development of the SPAS carrier (flown previously on STS-7, STS-41-B, and STS-39) in 1986 into a free-flying astronomical platform. The DARA/NASA agreement called for four co-operative science missions, with Deutsche Agentur für Raumfahrtangelegenheiten (DARA) providing the satellite, NASA the Shuttle launch and deployment/retrieval services, and the two parties sharing the science instruments. NASA provided the Shuttle free of charge, in return for access to data and the inclusion of U.S. experiments. ORFEUS, the Orbiting Retrievable Far and Extreme Ultraviolet Spectrometer, designed to measure radiation between 400 and 1280 angstroms, was released at 14:06 UTC, on September 13, 1993, and was retrieved at 11:50 UTC, on September 19, 1993. Science contributions came from the University of Tübingen, Sternwarte Heidelberg, University of California, Berkeley and Princeton University (IMPAS). ORFEUS' telescope was fabricated by Kayser-Threde in Germany; France's REOSC provided the 1 m (3 ft 3 in) f/2.5 mirror. The separate 950–1150 Å Interstellar Medium Absorption Profile Spectrograph (IMAPS) added to the observations of hot galactic objects and the interstellar medium at high spectral resolution (240,000). Other payloads were Deutsches Zentrum für Luft- und Raumfahrt (DLR's) Surface Effective Sample Monitor and Canada's IMAX Cargo Bay Camera, which was used to film Discovery in orbit for the IMAX film Destiny in Space. A portion of this footage was also included in Space Station 3D. This was the fourth flight of the SPAS platform, of a total of seven during the space shuttle program. The SPAS-ORFEUS version was reflown on mission STS-80 in 1996.

Extravehicular activity (EVA)

[edit]
Walz during the EVA.

On September 16, 1993, spacewalkers James H. Newman and Carl E. Walz performed an extravehicular activity (EVA) designed to evaluate tools, tethers and a foot restraint platform. Their findings reassured the designers and planners of the Hubble Space Telescope (HST) servicing flight that their preparations were sound. This was the third and final shuttle mission to include a preparatory EVA in response to the weaknesses in EVA training exposed by the STS-49 mission. The new equipment tested during the extensive spacewalk would later be required for the December 1993 Hubble Space Telescope servicing mission, and was only part of the objectives of the spacewalk, with Newman and Walz fulfilling the other goals as they explained at length to Mission Control Center the differences they perceived between work in orbit and ground training. The two EVA crewmen were ahead of schedule much of the day, and completed more tasks than originally planned. As the two astronauts were cleaning up, a balky tool box lid slowed them down when they had to pry it free and close it for Discovery's trip home. The toolbox lid stretched the spacewalk by about 45 minutes over what had been planned, with Newman and Walz logging a total seven hours, five minutes, and twenty-eight seconds of time outside the vehicle. This was the 112th EVA performed in the history of human spaceflight.

Spacewalk

[edit]
  • Newman and Walz – EVA 1
  • EVA 1 Start: September 16, 1993 – 08:40 UTC
  • EVA 1 End: September 16, 1993 – 15:45 UTC
  • Duration: 7 hours 5 minutes

Secondary experiments

[edit]

In-cabin payloads included the Air Force Maui Optical Site (AMOS), the Auroral Photography Experiment (APE-B), the Commercial Protein Crystal Growth (CPCG), Chromosome and Plant Cell Division in Space (CHROMEX), High Resolution Shuttle Glow Spectroscopy (HRSGS-A), IMAX, Investigations into Polymer Membrane Processing (IPMP) and the Radiation Monitoring Equipment (RME-III) experiment. The Investigation into Polymer Membrane Processing (IPMP), is designed to research the mixing of various solvent systems in the absence of convection found on Earth in hopes of controlling the porosity of various polymer membranes. RME measures gamma ray, electron, neutron and proton radiation levels in the crew cabin throughout the flight.

On board, Mission specialist James Newman donned a special visor to perform a medical experiment testing vision in weightlessness as part of investigations into how vision compensates for the inner ear's lack of balance in space. Newman also successfully tested a Global Positioning System receiver flying aboard Discovery as an evaluation of using such equipment to supplement the shuttle's navigation. Also, in a precursor of space station operations, one of Discovery's fuel cells was turned off and restarted.

In another medical evaluation, Commander Frank Culbertson and Mission specialist Daniel Bursch rode a stationary bike on Discovery's lower deck as part of a continuing study of using exercise to counteract the effects of weightlessness on the body. The crew also powered up an experiment that looks at improving membrane filters in weightlessness and checked on another experiment that has been running well studying the effects of microgravity on plant cells.

Astronauts Carl Walz and Jim Newman operated the experiments designed to study the glowing effect, one a spectrometer that records the effect on film in fine detail and another that records the effect on still photographs. The experiments are hoped to provide information about just what types of gases – in addition to atomic oxygen – create the glow. The information on kinds of gases in the extreme reaches of the atmosphere may be coupled with the materials exposure experiment in the cargo bay to assist with the design and construction of future spacecraft.

Mission insignia

[edit]

The five white stars and one yellow star of the insignia symbolize the flight's numerical designation in the Space Transportation System's mission sequence. The insignia also depicts the triangular SPAS-ORFEUS on the right.

Documentary

[edit]

The crew of STS-51 were followed by a camera crew from Channel 4 from the United Kingdom from the day they were assigned to the flight and then through their training and, finally, the mission itself. The documentary of this crew is called "Space Shuttle Discovery" and it was narrated by Heather Couper. It was released in 1993.

See also

[edit]

References

[edit]
[edit]
Revisions and contributorsEdit on WikipediaRead on Wikipedia

STS-51

View on Grokipedia
from Grokipedia
STS-51 was the 57th flight of NASA's and the 17th mission for , which launched from on September 12, 1993, at 7:45 a.m. EDT, to deploy the experimental Advanced Communications Technology Satellite (ACTS) and the Orbiting and Retrievable Far and Extreme Ultraviolet Spectrograph - Shuttle Pallet Satellite (ORFEUS-SPAS) for ultraviolet astronomical observations. The five-person crew consisted of Commander Frank L. Culbertson Jr., Pilot William F. Readdy, and Mission Specialists James H. Newman, Daniel W. Bursch, and Carl E. Walz, all astronauts. The primary objectives focused on deploying ACTS, a -developed satellite designed to test high-speed Ka-band communications technologies including onboard and spot-beam antennas for future broadband applications, and releasing ORFEUS-SPAS, a free-flying platform equipped with spectrographs to study far-ultraviolet and extreme-ultraviolet emissions from celestial sources such as white dwarfs and hot stars during a six-day detached mission. The mission experienced multiple launch delays, including concerns over a hydrogen leak in the orbiter's propulsion system and the timing of the Perseid meteor shower, pushing the liftoff from an original target in August to September. ACTS was successfully deployed on flight day one using the Payload Assist Module (PAM-D) upper stage to reach geosynchronous orbit, while ORFEUS-SPAS was released on flight day two, operated remotely for six days of data collection, and retrieved on flight day eight via the shuttle's Remote Manipulator System (RMS) arm operated by Bursch. A key highlight was the September 16 extravehicular activity (EVA) conducted by Newman and Walz, lasting 7 hours, 5 minutes, and 28 seconds—the longest shuttle spacewalk to date at that time—which tested hardware and procedures for the upcoming Hubble Space Telescope servicing mission, including the use of the RMS to simulate satellite capture and evaluation of foot restraint and tether systems. Discovery orbited at an altitude of 160 nautical miles with a 28.45-degree inclination, completing 157 orbits before landing at on September 22, 1993, at 3:56 a.m. EDT, marking the first night landing at the Florida site and concluding a mission duration of 9 days, 20 hours, 11 minutes, and 11 seconds. The flight achieved all major objectives, advancing technology and while providing valuable EVA experience that informed subsequent shuttle operations and repairs.

Mission Background

Objectives

The primary objectives of STS-51 centered on the deployment of the Advanced Communications Technology Satellite (ACTS), which utilized a Transfer Orbit Stage (TOS) booster to reach geosynchronous transfer orbit, enabling tests of advanced satellite communications technologies including high-data-rate transmission and Ka-band frequencies. Another key goal was the release and subsequent retrieval of the Orbiting and Retrievable Far and Spectrograph-Shuttle Pallet Satellite (SPAS-ORFEUS), a free-flying platform designed for observations of stellar atmospheres, interstellar gas, and galactic phenomena over a six-day period. Secondary objectives included conducting the first Space Shuttle extravehicular activity (EVA) dedicated to evaluating tools, procedures, and hardware for future servicing of the , such as portable foot restraints and tether systems, during a 7-hour, 5-minute spacewalk. The mission also encompassed a range of in-orbit experiments in (e.g., plant growth under microgravity), (e.g., and metal processing), and , highlighting the shuttle's versatility as a platform for multidisciplinary research. Mission parameters were planned for an 8-day duration but extended to 9 days, 20 hours, 11 minutes, and 11 seconds, encompassing 157 orbits at a 28.45° inclination and an altitude of approximately 160 nautical miles, with the orbiter traveling a total distance of 6,608,628 kilometers. Unique aspects included the inaugural operational use of the (GPS) for shuttle navigation, demonstrating real-time positioning accuracy to support rendezvous and , as well as refined techniques for retrieving free-flying payloads like SPAS-ORFEUS to minimize collision risks.

Spacecraft and Launch Site

The Space Shuttle Discovery, designated Orbiter Vehicle-103 (OV-103), served as the primary spacecraft for STS-51, marking its 17th spaceflight since entering service in 1984. Discovery was a reusable orbiter designed for low Earth orbit operations, featuring a crew compartment for up to eight astronauts, a 60-foot-long payload bay capable of accommodating large satellites and experiments, and three Space Shuttle Main Engines (SSMEs) mounted in the aft fuselage. For this mission, the orbiter was outfitted with the Canadarm Remote Manipulator System (RMS), a 50-foot articulated robotic arm manufactured by Spar Aerospace, essential for deploying and retrieving payloads such as the ORFEUS-SPAS satellite. The payload bay was specifically configured to house the primary payloads: the Advanced Communications Technology Satellite (ACTS) integrated with its Transfer Orbit Stage (TOS) upper stage in the forward section for geostationary transfer, and the Orbiting Retrievable Far and Extreme Ultraviolet Spectrometer - Shuttle Pallet Satellite (ORFEUS-SPAS) in the aft section, secured on an adapter for free-flyer operations. The launch vehicle stack for STS-51 consisted of Discovery mated to two reusable Solid Rocket Boosters (SRBs), designated as Booster Pair BI-060 with Reusable Solid Rocket Motors (RSRMs) serial 33, and a External Tank (ET) designated ET-59. The SRBs, each 149 feet tall and providing initial thrust exceeding 3 million pounds, were attached to the ET's sides to propel the stack off the pad, while the ET, measuring 154 feet in length and holding over 1.5 million pounds of cryogenic propellants, fueled the orbiter's SSMEs during ascent. ET-59 was the 52nd ET flown, featuring aluminum-lithium alloy construction to reduce mass by approximately 7,500 pounds compared to earlier steel models. STS-51 launched from Launch Complex 39B (LC-39B) at in , a facility originally developed for Apollo launches and adapted for the with a fixed launch platform, flame trench, and sound suppression water system. The mission concluded with a landing at KSC's on 15, a 15,000-foot-long concrete runway oriented 15 degrees from north, equipped with microwave landing systems and drag chutes for orbiter deceleration. Vehicle preparations began in the (OPF) at KSC, where Discovery arrived on April 17, 1993, for post-flight maintenance, system checks, and payload integration; technicians installed the ACTS/TOS and ORFEUS-SPAS elements into the payload bay during this phase. On June 18, 1993, the orbiter was towed to the (VAB), a 525-foot-high structure where it was stacked atop ET-59 and the SRBs on Mobile Launcher Platform 3, followed by final closeout and transport to LC-39B on June 26, 1993.

Crew

Members

The STS-51 crew consisted of five astronauts, all male, with backgrounds in the U.S. Navy, , and civilian research, bringing a combined total of two prior space missions among them. This experienced team was selected for their technical expertise in piloting, payload management, and extravehicular activities, aligning with the mission's focus on deployments and spacewalk evaluations. Frank L. Culbertson Jr. served as commander at age 44. A U.S. Navy captain and graduate of the U.S. Naval Academy in 1971, Culbertson earned his wings as a naval aviator in 1973 and later became a distinguished , logging over 4,500 flight hours in more than 30 aircraft types. Selected as an astronaut by in June 1984, this was his second , following his role as pilot on STS-38 in 1990, where he supported Department of Defense objectives. His prior command training and leadership in naval operations qualified him to oversee the complex satellite deployments and EVAs central to STS-51. William F. Readdy was the pilot at age 41. A U.S. Navy captain who graduated from the U.S. Naval Academy in 1974, Readdy qualified as a naval aviator in 1976, flying A-6 Intruders during deployments and later serving as a with over 5,000 hours in more than 50 aircraft. selected him as an astronaut in June 1987; STS-51 marked his second spaceflight, after serving as pilot on in 1992, which involved International Microgravity Laboratory operations. His extensive test piloting experience prepared him for shuttle ascent, rendezvous, and Remote Manipulator System tasks during the mission. James H. Newman was a at age 36 and served as an EVA crewmember. Holding a Ph.D. in physics from (1984), Newman worked as a research scientist before joining in 1984 as a research scientist in the Man-Systems Division; he was selected as a full in 1990. This was his first , but his expertise in space physics and , combined with rigorous EVA training, positioned him to conduct untethered spacewalks evaluating tools and procedures for future servicing. Daniel W. Bursch was a at age 36, focusing on payload operations. A U.S. Navy captain and 1979 graduate of the U.S. Naval Academy, Bursch became a naval aviator in 1981, accumulating over 3,500 hours in aircraft like the A-7 Corsair II and later the F/A-18 Hornet as a . Selected by in 1990, STS-51 was his first , with his naval operational experience in carrier-based and systems testing making him ideal for managing the mission's and free-flyer deployments. Carl E. Walz was a at age 38 and served as an EVA crewmember. A U.S. who earned a in from (1979), Walz flew F-16 fighters and served as a with over 3,500 flight hours. selected him as an in 1990; this was his first spaceflight, but his engineering background and EVA certification enabled him to partner with Newman on spacewalks testing Hubble repair techniques and filming procedures.

Roles and Assignments

The of STS-51 was assigned specific seats to facilitate operations during launch and reentry, with Commander in seat 2 (left forward), Pilot William F. Readdy in seat 3 (right forward), Carl E. Walz in seat 4 (right middeck), Daniel W. Bursch in seat 6 (middeck forward), and James H. Newman in seat 5 (middeck aft). Culbertson, on his second , oversaw all mission phases, including deployments, rendezvous operations, and overall coordination. Readdy, also on his second flight, was responsible for managing ascent and entry profiles, as well as supporting remote manipulator system (RMS) operations for deployments. Newman and Walz, both on their first spaceflights, conducted the mission's (EVA) to evaluate tools and procedures in preparation for future servicing missions. Bursch, likewise on his first flight, handled primary operations for the SPAS-ORFEUS satellite, including RMS deployment and retrieval, along with supporting secondary experiments. No dedicated backup crew was assigned for STS-51, consistent with practices for later Shuttle missions; instead, the primary crew underwent to provide redundancy in payload handling, RMS operations, and EVA tasks.

Preparation and Launch

Delays and Preparations

Following the completion of STS-56, was towed to the on April 17, 1993, where post-flight maintenance and preparations for STS-51 commenced. Payload integration, including the Advanced Communications (ACTS) with its Transfer Orbit Stage and the Orbiting and Retrievable Far and Extreme Ultraviolet Spectrograph-Shuttle Pallet (SPAS-ORFEUS), began in May 1993 at the . was then rolled over to the on June 18, 1993, for mating with the external tank and solid rocket boosters, after which the fully stacked vehicle was rolled out to 39B on June 26, 1993. The mission faced multiple technical setbacks that postponed the launch from its original July target. On July 17, 1993, the first attempt was scrubbed at T-minus 20 minutes due to a failure in which controllers for the external tank vent arm system armed prematurely, traced to a faulty circuit card that was subsequently replaced and retested. The second attempt on July 24, 1993, reached T-minus 20 seconds before scrubbing owing to an underspeed condition (65,000 rpm versus the required 66,200-77,800 rpm) in the right solid rocket booster's thrust vector control hydraulic power unit; the unit was replaced, hot-fired for verification, and the launch rescheduled initially for August 2 but slipped to August 12 to avoid risks from the peak of the Perseid meteor shower on August 11. A third attempt on August 12, 1993, aborted at T-minus 3 seconds when a fuel flow meter on the No. 2 main engine registered a miscompare due to a failed speed pickup coil sensor in channel A2; all three main engines were replaced with a qualified set from , cryogenic testing was completed, and the launch was reset for September 10 before a further two-day delay to September 12 for an independent engineering review of the ACTS in light of recent anomalies on Mars Observer and NOAA-13. In parallel with these technical resolutions, pre-launch preparations emphasized crew and payload readiness. The five-member crew entered standard quarantine protocols approximately one week prior to the final launch window to minimize health risks, with adjustments made after each scrub. Comprehensive checks confirmed the operational integrity of ACTS and SPAS-ORFEUS systems, including deployment mechanisms and scientific instruments, while ongoing weather assessments monitored conditions at both the and backup sites like . Although planned for nine days with up to three contingency days, the mission was extended by one day post-launch due to forecasts of unacceptable weather at the primary landing site, resulting in a touchdown at on September 22, 1993.

Liftoff Sequence

The launch countdown for STS-51 proceeded to T-0 on September 12, 1993, at 11:45:00 UTC from Launch Complex 39B at in . Solid rocket boosters ignited at T-0, propelling off the pad after the three main engines had started approximately seven seconds earlier. The solid rocket boosters separated nominally at T+2:05 (124.6 seconds mission elapsed time). During ascent, the main engines operated at 104% throttle to optimize performance through the atmosphere, reaching main engine cutoff at about T+8:30. This flight marked the first operational use of Global Positioning System (GPS) navigation on a Space Shuttle mission, through Development Test Objective 700-6, which provided real-time state vector data despite a minor floating-point error that required a receiver restart. The vehicle achieved initial orbital insertion at a 28.45° inclination and approximately 306 km altitude following external tank separation. The engines executed the OMS-2 burn beginning at 00:39:54 mission elapsed time, lasting 145.2 seconds to circularize the orbit at 296 km (160 nautical miles). Crew members reported feeling well post-insertion, with Commander Frank Culbertson noting a smooth ride. Initial systems checks confirmed nominal performance of the Orbiter's subsystems, including the opening of the payload bay doors shortly after reaching orbit.

Primary Payloads

Advanced Communications Technology Satellite (ACTS)

The Advanced Communications Technology (ACTS) served as the primary communications for STS-51, designed to demonstrate next-generation technologies for high-capacity transmission. Launched aboard , ACTS aimed to validate Ka-band operations at 30/20 GHz frequencies, onboard baseband switching for efficient signal routing, and beam-forming antennas capable of hopping spot beams to optimize coverage and capacity. These features targeted applications for and Department of Defense (DoD) missions, including high-rate voice, video, and services that could support future commercial systems. On flight day 1, September 12, 1993, the crew used the Remote Manipulator System (RMS) to grapple and lift ACTS from Discovery's payload bay, releasing it at 14:40 UTC. Approximately 45 minutes later, the attached Payload Assist Module-D (PAM-D) upper stage fired successfully, propelling ACTS into a geosynchronous transfer en route to its operational geostationary position at 99° W . Unlike retrievable payloads on the mission, ACTS was not recovered, marking its transition to independent operations managed from . Post-deployment confirmation showed stable separation and nominal performance of the satellite's systems, with full operations commencing in December 1993. Over its lifetime, ACTS conducted more than 100 experiments, demonstrating technologies such as (ATM) protocols for data rates up to 622 Mbit/s and mitigation techniques essential for Ka-band reliability. The satellite remained active until its deactivation and deorbit on April 28, 2004, after exceeding its planned operational duration by over a decade and providing critical data that influenced subsequent satellite designs.

SPAS-ORFEUS

The SPAS-ORFEUS (Shuttle Pallet Satellite - Orbiting Retrievable Far and Extreme Ultraviolet Spectrometer) pallet was deployed from Space Shuttle Discovery's payload bay on flight day 2, September 13, 1993, using the Remote Manipulator System (RMS), with operations similar to the earlier deployment of the ACTS satellite. Mission specialist Daniel Bursch maneuvered the RMS to release the pallet approximately 27 hours after launch, at around 14:45 UTC, separating it to an initial distance of 100-200 meters before the orbiter fired steering jets to move farther away, enabling a 6-day free flight for independent operations. During free flight, the ORFEUS instruments—including far-ultraviolet (FUV, 90-125 nm) and extreme-ultraviolet (EUV, 40-90 nm) spectrometers such as the Echelle, Berkeley, and IMAPS (Imaging Multiple Alignment Photon Spectrometer), along with supporting cameras—performed astronomical observations focused on white dwarfs and remnants to investigate , cooling mechanisms, and interstellar gas dynamics. Data from these observations was relayed to ground stations via the (TDRS) communications network, with real-time control provided by the SPAS Payload Operations Control Center at and collaborating facilities at the . The payload achieved approximately 30 hours of effective observation time across 20 orbits, exceeding initial objectives despite minor instrument issues like a mirror misalignment affecting the Echelle spectrometer. Retrieval occurred on flight day 8, September 19, 1993, following rendezvous maneuvers that brought Discovery within grappling range of the , which had drifted to a maximum separation of about 115 km. Bursch used the RMS to recapture SPAS-ORFEUS at approximately 11:50 UTC, successfully berthing it back into the payload bay for secure stowage and preparation for reentry. The mission produced high-resolution spectra of 22 stellar and interstellar targets, providing key insights into hot and cold astrophysical phenomena with velocity resolutions down to 1.6 km/s.

Extravehicular Activity

Spacewalk Objectives

The primary objectives of the STS-51 extravehicular activity (EVA) centered on evaluating tools, restraints, and procedures critical for the Hubble Space Telescope (HST) repair mission, designated STS-61. Specifically, the spacewalk tested the portable foot restraint (PFR) for astronaut positioning during intricate tasks, safety tether systems to prevent uncontrolled drift, and worksite interfaces compatible with the Remote Manipulator System (RMS) arm for enhanced mobility and stability. These evaluations, part of Development Test Objective (DTO) 1210 and DTO 671, focused on operational efficiency in microgravity, including translation aids and high-torque tool performance like the Goddard power ratchet tool (PRT). Preparation for the EVA included intensive neutral buoyancy simulations in the Weightless Environment Training Facility (WETF) at NASA's , where Mission Specialists James H. Newman and Carl J. Walz practiced procedures under water to mimic orbital conditions. Additional training occurred in vacuum chambers to assess suit performance and tool functionality. The Extravehicular Mobility Units (EMUs) were outfitted for a nominal seven-hour duration, with prebreathing protocols to mitigate decompression risks; cabin pressure was reduced to 10.2 psia prior to the event. This marked the first Space Shuttle EVA since in May 1992, resuming untried capabilities after a 16-month hiatus. The significance of the STS-51 EVA lay in its validation of hardware and techniques that directly supported the HST servicing efforts on , including refined tether configurations—such as a preference for radial-hook over swivel-hook tethers—and restraint egress methods that proved less challenging than simulated, with training being more difficult overall. By successfully completing all tasks within the allotted time, the spacewalk generated operational data on thermal management, lighting, and tool stowage, enhancing procedures for subsequent shuttle missions and early assembly. The crew also conducted a glove warming exercise and inspected pyrotechnic from the ACTS deployment, confirming payload bay stability.

EVA Timeline and Procedures

The (EVA) of STS-51 commenced on , September 16, 1993, with egress at 08:39 UTC by mission specialists James H. Newman (EV1) and Carl J. Walz (EV2). Pre-EVA preparations included cabin depressurization to 10.2 psia on flight day 2, (EMU) checkout on flight day 4 lasting 1 hour 17 minutes, and prebreathing initiation at 07:38 UTC on , followed by depressurization starting at 08:18 UTC and completing in 11 minutes. The spacewalk concluded with ingress at 15:45 UTC, achieving a total duration of 7 hours, 5 minutes, and 28 seconds. Newman and Walz began procedures by performing unencumbered and encumbered translation exercises along the remote manipulator system (RMS), evaluating mobility without and with full equipment loads to simulate Hubble Space Telescope (HST) servicing tasks. The RMS, operated by pilot William F. Readdy, assisted in maneuvering the crew clear of the airlock during initial egress. Key evaluations included testing the portable foot restraint (PFR) in the payload bay for HST operations, where egress and heel motion proved less challenging than in water immersion training at the Johnson Space Center's Weightless Environment Training Facility (WETF). The crew conducted untethered maneuvers as part of translation tests and executed a contingency drill for a stuck tool, addressing a low battery power warning by replacing the tool battery mid-EVA. Additional procedures involved a 45-minute delay to resolve a jammed port side portable safety airlock (PSA) sliding door using pry bars, as well as payload bay cleanup and investigation of pyrotechnic fastener damage. All primary objectives were met, including development test objectives (DTO) 1210 for EVA translation and DTO 671 for HST tool and procedure evaluations, with the crew completing more tasks than planned despite minor anomalies such as a disconnected left waist tether and a momentary master warning system end effector disconnect. No significant operational issues arose, and the EVA provided valuable video documentation via closed-circuit television (CCTV) for future training, emphasizing the need for enhanced thermal vacuum simulations in post-mission debriefs.

Secondary Experiments

Biological and Materials Science

The Biological and Materials Science experiments aboard STS-51 investigated the impacts of microgravity on cellular processes and material formation, utilizing middeck facilities to facilitate controlled environments for and biological observations. These payloads contributed to broader efforts in life sciences by providing data on how weightlessness affects protein structures and , with potential applications in pharmaceuticals and . The Commercial Protein Crystal Growth (CPCG) experiment, configured in Block II, was designed to produce larger and higher-quality protein crystals free from and effects inherent to ground-based growth. It utilized a commercial /incubator module in the middeck through vapor diffusion methods in four cylinder units containing chemical reagents. Activated on flight day 1 and operated continuously until landing, the experiment exceeded operational requirements and yielded crystals suitable for in pharmaceutical development, where improved resolution aids . CHROMEX-4 examined the effects of microgravity on early embryonic development by fertilizing eggs and monitoring larval progression. Conducted in middeck lockers, the experiment observed rates and morphological changes in Lytechinus pictus specimens, revealing alterations in cleavage patterns compared to ground controls that inform understanding of gravitational influences on . Hardware performance met expectations, with post-flight enabling detailed genetic and histological analysis. Radiation Monitoring Equipment-III (RME-III) employed badges and real-time detectors to quantify crew exposure to , including gamma rays, electrons, neutrons, and protons, during the low-Earth orbit trajectory. Worn by crew members and placed in middeck locations, the third iteration of the payload calculated tissue-equivalent doses, recording a total mission of approximately 0.4 mGy (equivalent to ~1.4 mSv), consistent with typical shuttle flight levels and aiding in risk assessments for future missions. The Limited Duration Space Environment Candidate Materials Exposure (LDCE) experiment exposed various materials to the space environment in the payload bay to assess degradation from atomic oxygen, ultraviolet radiation, and , providing data for improving shuttle thermal protection and future spacecraft designs. The STS-51 mission marked the first integration of a (GPS) receiver aboard a , specifically the Trimble TANS Quadrex unit mounted in an overhead window, enabling real-time during ascent and on-orbit operations. This experiment, designated Development Test Objective (DTO) 700-6, demonstrated both absolute and relative GPS positioning in conjunction with the ORFEUS-SPAS payload, successfully computing high-quality state vectors for the Orbiter. The system provided real-time positioning accuracy of approximately 100 meters at 95% confidence for horizontal measurements, outperforming ground-based tracking in smoothness and reliability despite challenges like a single floating-point error that required a program restart. Post-flight analysis confirmed the GPS data's alignment with independent trajectory estimates, validating its potential for future Shuttle enhancements. Another key technology test involved the experiment, which utilized the Optical Site to calibrate ground-based optical sensors by observing the Shuttle as a target, thereby verifying models of the vehicle's attitude control dynamics. Although star trackers on the Orbiter contributed to attitude determination during sleep periods under DTO 779, the primary AMOS effort focused on a Reaction Control Subsystem (RCS) thruster firing to support optical tracking. Unfortunately, no usable data were obtained due to high atmospheric humidity at the site, limiting the test's immediate outcomes but providing procedural insights for subsequent missions. The Investigation into Polymer Membrane Processing (IPMP) served as a technology demonstration for materials processing in microgravity, employing two middeck units to flash evaporate solvents from solutions and observe the resulting formation. Activated and deactivated according to the planned timeline, the experiment captured photometry to monitor thermal and structural changes during , contributing to understandings of microgravity effects on synthesis without the need for complex hardware. Post-mission analysis of the collected observations aimed to refine ground-based models for applications in space environments. Communications technology tests emphasized the Shuttle's (TDRS) interactions, focusing on S-band link performance amid payload operations. A forward link loss occurred early in orbit 6 due to frequency interference from a payload interrogator, but it was promptly resolved by switching to a lower frequency band, restoring nominal data relay. Brief signal drops were also noted during ORFEUS-SPAS maneuvers, attributed to from the (EMU) television transmitter, highlighting the need for improved shielding in integrated shuttle-payload systems. Overall, these tests confirmed the robustness of TDRS for Shuttle communications, with 17 RCS firings and six Orbital Maneuvering Subsystem maneuvers executed without attitude disruptions. The High Resolution Shuttle Glow (HRSGS) experiment used spectrometers in the payload bay to study the shuttle's glow phenomenon caused by atmospheric interactions, collecting spectral data to model vehicle-plasma interactions for improving future mission designs.

Reentry and Landing

Deorbit Preparation

As the STS-51 mission approached its conclusion, the completed final orbital activities on flight day 8, including the retrieval and berthing of the ORFEUS-SPAS satellite at 262:14:05:44 G.m.t., after which the payload bay was reconfigured for reentry preparations. Secondary experiments were wrapped up, with remaining data downlinked to ground stations. The also conducted a period of rest to ensure readiness for the upcoming deorbit phase. The original 9-day mission plan was extended by 24 hours on flight day 8 due to unacceptable weather conditions at the primary landing site, , as well as alternative sites including . This extension allowed additional time for systems verification while conserving resources for the extended duration. Final systems checks included inspections of the (OMS) pods, which had performed nominally throughout the mission with a total firing time of 307.8 seconds for the left engine and 317.9 seconds for the right. systems were verified through the completion of Development Test Objective 700-6, demonstrating the Global Positioning System's integration with good state vectors, despite a minor floating-point error. Additionally, a Remote Manipulator System survey of the orbiter's thermal protection system identified 154 damage sites, including 18 major ones greater than 1 inch in diameter, but none required repair prior to entry. Payload bay doors were closed at 265:04:23:12 G.m.t. to complete reconfiguration.

Landing Sequence

The deorbit phase of STS-51 began on flight day 10 with the execution of the Orbital Maneuvering Subsystem (OMS)-2 burn at 06:55:30 UTC on September 22, 1993. Both OMS engines fired for 137.4 seconds, achieving a delta-V of 251.3 ft/sec and lowering the orbit's perigee from a nominal 160 nautical miles to approximately 50 km, setting the stage for atmospheric reentry. This maneuver was performed nominally, with no deviations in engine performance or trajectory parameters reported. Reentry commenced at Entry Interface (EI) at 07:24:40 UTC, when Discovery crossed 400,000 feet altitude at approximately Mach 25 relative to the atmosphere. Peak heating occurred during this hypersonic phase, with the Thermal Protection System withstanding the intense aero-thermal loads as designed. The vehicle then transitioned through the subsonic regime, reaching the Terminal Area Energy Management (TAEM) interface at 07:49:30 UTC, where guidance shifted to the precision approach and landing mode. Throughout reentry, aerodynamic stability and control were maintained without issues, supported by real-time data from onboard systems. Touchdown occurred at 07:56:11 UTC on Runway 15 of the , with main gear contact at 194.6 knots equivalent airspeed and a sink rate of -1.3 ft/sec, followed by nose gear touchdown 4.6 seconds later. The rollout distance measured 8,276 feet over 50.1 seconds, culminating in wheels stop at 07:56:56 UTC; the drag chute deployed at 07:56:15.6 UTC and was jettisoned at 07:56:42.5 UTC. The landing weight was 206,438 pounds. Post-landing safing included shutdowns—APU-1 and APU-2 at approximately 08:02 UTC and APU-3 at 08:04 UTC—with the crew egressing the orbiter by 09:19 UTC. Conditions were clear following a one-day mission extension due to weather, and no anomalies affected the sequence.

Post-Mission Elements

Mission Insignia

The STS-51 mission insignia is a circular patch set against a black background, featuring a silhouette of the Space Shuttle Discovery positioned against a view of Earth. The design incorporates depictions of the Advanced Communications Technology Satellite (ACTS) and the SPAS-ORFEUS telescope platform, highlighting the mission's primary payloads. Five white stars represent the five-member crew, while a central yellow star signifies the mission designation, STS-51. The served as the official emblem, embroidered on the astronauts' flight suits and incorporated into mission documentation, briefing materials, and commemorative items.

Documentaries

The IMAX documentary Destiny in Space, released in 1994, featured extensive in-flight footage captured during STS-51 using a 70mm camera mounted on . This included dynamic views of satellite deployments, the (EVA) performed by astronauts James H. Newman and Carl J. Walz, and sweeping orbital perspectives of Earth, highlighting the mission's operational highlights and the shuttle's maneuverability in space. Directed by and written by Toni Myers, the 41-minute film was narrated by and produced in collaboration with and Lockheed, emphasizing human exploration and technological achievements in orbit. In 1993, the broadcaster aired an episode of its science documentary series dedicated to the STS-51 mission, titled "Discovery," which provided behind-the-scenes insights into the pre-launch preparations at and key mission events such as the ACTS satellite deployment and the EVA. Produced by Uden Associates, the program explored the engineering challenges and crew dynamics involved in the flight, offering viewers a detailed look at the ground operations and real-time decision-making during the September 12–22 mission timeline. NASA's television coverage of STS-51, broadcast live via TV and public networks, documented the mission from launch through landing, capturing unedited footage of operations, interviews, and orbital activities to engage global audiences with the shuttle program's ongoing advancements. As part of the mission's daily routine, Mission Control uplinked wake-up calls featuring selected music to the , such as "Changes in Attitudes, Changes in Latitudes" by on September 14 and "Star Wars Theme" by on September 18, fostering morale and connecting the astronauts to Earth-based culture. These audio elements, chosen by family and mission planners, were integrated into the broadcast feeds to humanize the high-stakes environment of .

References

  1. https://www.nasa.gov/mission/sts-51/
  2. https://ntrs.nasa.gov/citations/19990062742
  3. https://ntrs.nasa.gov/citations/20010011176
  4. https://ntrs.nasa.gov/api/citations/19940030746/downloads/19940030746.pdf
  5. https://ntrs.nasa.gov/api/citations/20100039589/downloads/20100039589.pdf
  6. https://www.nasa.gov/wp-content/uploads/2023/04/discovery-final.pdf
  7. https://ntrs.nasa.gov/citations/19940030746
  8. https://www.nasa.gov/humans-in-space/astronauts/former-astronauts/
  9. https://www.nasa.gov/wp-content/uploads/2016/01/culbertson_frank.pdf
  10. https://www.nasa.gov/wp-content/uploads/2016/01/readdy_william.pdf
  11. https://www.nasa.gov/wp-content/uploads/2016/01/newman_james.pdf
  12. https://www.americaspace.com/2023/09/13/an-ambitiously-dramatic-mission-remembering-all-in-one-sts-51-thirty-years-on-part-2/
  13. https://www.nasa.gov/history/rogersrep/v2appj.htm
  14. https://www.spaceline.org/united-states-manned-space-flight/space-shuttle-mission-program-fact-sheets/sts-51/
  15. https://www.eoportal.org/satellite-missions/acts
  16. https://ntrs.nasa.gov/citations/19960001913
  17. https://ntrs.nasa.gov/citations/20010019782
  18. https://archive.stsci.edu/imaps/expastro/node11.html
  19. https://www.spacefacts.de/mission/english/sts-51.htm
  20. https://uni-tuebingen.de/en/faculties/faculty-of-science/departments/physics/institutes/astronomy-astrophysics/astronomy-hea/research/closed-projects/orfeus/orfeus-i/
  21. https://sma.nasa.gov/SignificantIncidentsEVA/assets/walking-to-olympus-an-eva-chronology.pdf
  22. https://nssdc.gsfc.nasa.gov/nmc/spacecraft/display.action?id=1993-058A
  23. https://www.nasa.gov/wp-content/uploads/2024/05/shuttle-payloads-and-experiments.pdf
  24. https://ntrs.nasa.gov/api/citations/20070010704/downloads/20070010704.pdf
  25. https://ntrs.nasa.gov/api/citations/19970001337/downloads/19970001337.pdf
  26. https://www.youtube.com/watch?v=jHPfuvmv9wE
  27. https://www.nasa.gov/wp-content/uploads/2023/07/wakeup-calls.pdf
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