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STS-41-C
Mission Specialists George Nelson and James van Hoften repair the captured Solar Maximum Mission satellite on April 11, 1984
NamesSpace Transportation System-41C
STS-13
Mission typeSatellite deployment
Satellite repair
OperatorNASA
COSPAR ID1984-034A Edit this at Wikidata
SATCAT no.14897Edit this on Wikidata
Mission duration6 days, 23 hours, 40 minutes, 7 seconds
Distance travelled4,620,000 km (2,870,000 mi)
Orbits completed108
Spacecraft properties
SpacecraftSpace Shuttle Challenger
Launch mass115,328 kg (254,255 lb)
Landing mass89,346 kg (196,974 lb)
Payload mass15,345 kg (33,830 lb)[1]
Crew
Crew size5
Members
EVAs2
EVA duration
  • 10 hours, 6 minutes
  • 1st EVA: 2 hours, 59 minutes
  • 2nd EVA: 7 hours, 7 minutes
Start of mission
Launch dateApril 6, 1984, 13:58:00 (1984-04-06UTC13:58Z) UTC (8:58 am EST)
Launch siteKennedy, LC-39A
ContractorRockwell International
End of mission
Landing dateApril 13, 1984, 13:38:07 (1984-04-13UTC13:38:08Z) UTC (5:38:07 am PST)
Landing siteEdwards, Runway 17
Orbital parameters
Reference systemGeocentric orbit[2]
RegimeLow Earth orbit
Perigee altitude222 km (138 mi)
Apogee altitude428 km (266 mi)
Inclination28.50°
Period91.40 minutes

STS-41-C mission patch

From left: Crippen, Hart, van Hoften, Nelson and Scobee
← STS-41-B (10)
STS-41-D (12) →

STS-41-C (formerly STS-13) was NASA's eleventh Space Shuttle mission, and the fifth mission of Space Shuttle Challenger. The launch, which took place on April 6, 1984, marked the first direct ascent trajectory for a Space Shuttle mission. During the mission, Challenger's crew captured and repaired the malfunctioning Solar Maximum Mission ("Solar Max") satellite, and deployed the Long Duration Exposure Facility (LDEF) experimental apparatus. STS-41-C was extended one day due to problems capturing the Solar Max satellite, and the landing on April 13, 1984, took place at Edwards Air Force Base, instead of at Kennedy Space Center as had been planned. The flight was originally numbered STS-13.[3][4]

Crew

[edit]
Position Astronaut
Commander Robert Crippen
Third spaceflight
Pilot Francis R. 'Dick' Scobee
Only spaceflight
Mission Specialist 1 Terry Hart
Only spaceflight
Mission Specialist 2
Flight Engineer 		James van Hoften
First spaceflight
Mission Specialist 3 George Nelson
First spaceflight

Spacewalks

[edit]
EVA 1
  • Personnel: Nelson and van Hoften
  • Date: April 8, 1984 (14:18–17:17 UTC)
  • Duration: 2 hours, 59 minutes[5]
EVA 2
  • Personnel: Nelson and van Hoften
  • Date: April 11, 1984 (08:58–16:05 UTC)
  • Duration: 7 hours, 7 minutes[5]

Crew seat assignments

[edit]
Seat[6] Launch Landing
Seats 1–4 are on the flight deck.
Seats 5–7 are on the mid-deck.
1 Crippen
2 Scobee
3 Hart Nelson
4 van Hoften
5 Nelson Hart
6 Unused
7 Unused

Mission summary

[edit]
STS-41-C post flight presentation, narrated by the astronauts (19 minutes).

STS-41-C launched successfully at 8:58 a.m. EST on April 6, 1984. The mission marked the first direct ascent trajectory for the Space Shuttle; Challenger reached its 533 km-high (331 mi) orbit using its Orbiter Maneuvering System (OMS) engines only once, to circularize its orbit. During the ascent phase, the main computer in Mission control center (MCC) failed, as did the backup computer. For about an hour, the controllers had no data on the orbiter.[7]

The flight had two primary objectives. The first was to deploy the Long Duration Exposure Facility (LDEF), a passive, retrievable, 12-sided experimental cylinder. The 9,700 kg (21,400 lb) LDEF was 4.3 m (14 ft) in diameter and 9.1 m (30 ft) long, and carried 57 scientific experiments. The second objective of STS-41-C was to capture, repair and redeploy the malfunctioning Solar Maximum Mission satellite ("Solar Max"), which had been launched in 1980.

On the second day of the flight, the LDEF was grappled by the Remote Manipulator System (Canadarm) and successfully released into orbit. Its 57 experiments, mounted in 86 removable trays, were contributed by 200 researchers from eight countries. Retrieval of the passive LDEF was initially scheduled for 1985, but schedule delays and the Challenger disaster of 1986 postponed the retrieval until January 12, 1990, when Columbia retrieved the LDEF during STS-32.

On the third day of the mission, Challenger's orbit was raised to about 560 km (350 mi), and it maneuvered to within 61 m (200 ft) of the stricken Solar Max satellite. Astronauts Nelson and van Hoften, wearing space suits, entered the payload bay. Nelson, using the Manned Maneuvering Unit (MMU), flew out to the satellite and attempted to grasp it with a special capture tool, called the Trunnion Pin Acquisition Device (TPAD). Three attempts to clamp the TPAD onto the satellite failed. Solar Max began tumbling on multiple axes when Nelson attempted to grab one of the satellite's solar arrays by hand, and the effort was called off. Crippen had to perform multiple maneuvers of the orbiter to keep up with Nelson and Solar Max, and nearly ran out of RCS fuel.[7]

During the night of the third day, the Solar Max Payload Operations Control Center (POCC), located at Goddard Space Flight Center (GSFC), Greenbelt, Maryland, was able to establish control over the satellite by sending commands ordering the satellite's magnetorquers to stabilize its tumbling. This was successful, and Solar Max went into a slow, regular spin. The next day, Crippen maneuvered Challenger back to Solar Max, and Hart was able to grapple the satellite with the RMS. They placed Solar Max on a special cradle in the payload bay using the RMS. Nelson and van Hoften then began the repair operation, replacing the satellite's attitude control mechanism and the main electronics system of the coronagraph instrument. The ultimately successful repair effort took two separate spacewalks. Solar Max was deployed back into orbit the next day. After a 30-day checkout by the Goddard POCC, the satellite resumed full operation.

Other STS-41-C mission activities included a student experiment located in a middeck locker which found that honeybees can successfully make honeycomb cells in a microgravity environment. Highlights of the mission, including the LDEF deployment and the Solar Max repair, were filmed using an IMAX movie camera, and the results appeared in the 1985 IMAX movie The Dream is Alive.

The 6 days, 23 hours, 40 minutes, and 7 seconds mission ended on April 13, 1984, at 5:38 a.m. PST, when Challenger landed safely on Runway 17, at Edwards Air Force Base, having completed 108 orbits. Challenger was returned to KSC on April 18, 1984.

  • The launch of STS-41-C on 6 April 1984
    The launch of STS-41-C on 6 April 1984
  • The deployed Long Duration Exposure Facility (LDEF), which became an important source of information on the small-particle space debris environment.
    The deployed Long Duration Exposure Facility (LDEF), which became an important source of information on the small-particle space debris environment.
  • George Nelson attempts to capture the Solar Maximum Mission satellite.
    George Nelson attempts to capture the Solar Maximum Mission satellite.
  • STS-41-C touches down at Runway 17, Edwards Air Force Base, on 13 April 1984.
    STS-41-C touches down at Runway 17, Edwards Air Force Base, on 13 April 1984.

Wake-up calls

[edit]
Alternate mission patch, referencing the mission's original designation, STS-13; and landing under a black cat, given that April 13, 1984, was a Friday the 13th.[8]

NASA began a tradition of playing music to astronauts during the Project Gemini, and first used music to wake up a flight crew during Apollo 15. Each track is specially chosen, often by the astronauts' families, and usually has a special meaning to an individual member of the crew, or is applicable to their daily activities.[9]

Flight Day Song Artist/Composer
Day 2 "A Boy Named Sue" Johnny Cash
Day 3 "Fight for California" UC Berkeley Fight Song
Day 4 Unidentified
Day 5 "Theme from Rocky" Bill Conti
Day 6 Unidentified
Day 7 None
Day 8 "University of Texas Fight Song"

See also

[edit]

References

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

STS-41-C

View on Grokipedia
from Grokipedia
STS-41-C was the eleventh mission of NASA's , launched on April 6, 1984, at 8:58 a.m. EST from Kennedy Space Center's Launch Complex 39A aboard the orbiter Challenger. The primary objectives included deploying the (LDEF), a 21,400-pound designed to study the effects of long-term exposure to the , and retrieving, repairing, and redeploying the malfunctioning Solar Maximum Mission (SMM) , known as "Solar Max." This mission marked several historic firsts, including the first in-space repair and the first direct-to-orbit ascent using only the shuttle's main engines. The crew consisted of five astronauts: Commander Robert L. "Crip" Crippen, who had previously commanded ; Pilot Francis R. "Dick" Scobee; and Mission Specialists Terry J. "T.J." Hart, James D. "Ox" Van Hoften, and George D. "Pinky" Nelson. Originally designated STS-13 and announced in February 1983, the mission was renamed STS-41-C in September 1983 as part of NASA's updated numbering system for operational flights. During the flight, which lasted 6 days, 23 hours, and 40 minutes and completed 108 orbits of , the successfully deployed LDEF on April 7, the largest and heaviest payload carried by the shuttle at that time. The highlight was the repair of Solar Max, which had failed in 1980 due to a fault in its attitude ; on April 11, Nelson and Hoften conducted two extravehicular activities (EVAs), including a record-setting 6-hour, 44-minute spacewalk to manually capture and berth the in Challenger's payload bay for repairs. After replacing a failed motor and other components, the was redeployed on April 12 and operated successfully until 1989, far exceeding its original design life. The mission concluded with a on April 13, 1984, at 9:38 a.m. PDT on runway 17 at , , after an extension of one day to accommodate the repair efforts. STS-41-C demonstrated the shuttle's versatility for on-orbit servicing, paving the way for future satellite maintenance missions and advancing techniques for in space.

Mission Background

Designation History

STS-41-C was originally designated as STS-13 under NASA's initial sequential numbering system for Space Shuttle missions, which simply incremented from through before the program's expansion necessitated changes. In early 1983, announced the crew for this mission while it still carried the STS-13 label, reflecting its position as the planned eleventh flight in the overall program. To accommodate the increasing complexity of the launch manifest and provide more flexibility in scheduling, transitioned to a new alphanumeric designation system beginning with flights in 1984. This system used the last digit of the (4 for 1984), followed by the launch site code (1 for ), and a letter indicating the sequence of missions from that site in that year (A, B, C, etc.). Accordingly, STS-13 was renamed STS-41-C in September 1983, positioning it as the third mission planned under the new scheme for 1984 from . The mission launched on April 6, 1984, following the February 3 liftoff of and amid ongoing adjustments to the shuttle program's accelerated pace after in November 1983. As the eleventh Space Shuttle mission overall and the fifth flight of Orbiter Vehicle Challenger (OV-099), STS-41-C introduced the program's ascent trajectory, achieving an initial altitude of 288 nautical miles (533 km) without the intermediate orbital adjustments used in prior missions.

Primary Objectives

The primary objectives of STS-41-C centered on advancing satellite deployment and in-orbit servicing capabilities, with a focus on deploying the (LDEF) and repairing the Mission (Solar Max) satellite. The LDEF, a 21,400-pound cylindrical structure measuring 14 by 30 feet, was designed to carry 57 experiments across 86 trays to investigate the effects of the —including atomic oxygen, ultraviolet radiation, micrometeoroids, and thermal extremes—on materials, , , and systems over an intended exposure period of up to one year. Managed by NASA's and involving 194 investigators from the U.S. and international partners, the LDEF aimed to provide critical data for future spacecraft design by simulating long-term orbital conditions in a passive, retrievable configuration. A second core objective was the retrieval, repair, and redeployment of the Solar Max satellite, which had been launched on February 14, 1980, by a Delta rocket from and subsequently suffered malfunctions in its attitude control system due to an electronics failure shortly after reaching orbit. This mission represented the first attempt to service and repair an operational satellite in space, demonstrating the feasibility of on-orbit maintenance using the Space Shuttle's Remote Manipulator System (RMS) and extravehicular activities to replace faulty components on the Multi-Mission Modular Spacecraft bus managed by NASA's . By restoring Solar Max's functionality, the effort sought to extend the satellite's ability to observe solar activity, including flares and coronal mass ejections, thereby supporting ongoing research. Secondary objectives encompassed a range of scientific and technological investigations to leverage the mission's orbital platform. These included Earth observations using the IMAX camera system to document terrestrial features and atmospheric phenomena from the shuttle's high-altitude orbit, achieved via a direct ascent trajectory. Biomedical experiments featured a student-led study on the effects of microgravity on 3,300 honeybees, examining their behavior and physiology in weightlessness. Additional technology tests involved RMS operations to support payload handling and the Radiation Monitoring Experiment (RME) along with the Student-Sponsored Microgravity Payload (SSIP) to assess radiation exposure and material behaviors in space.

Crew and Training

Commander and Pilot

The commander of STS-41-C was Robert L. Crippen, a veteran U.S. selected as a in September 1969. Born on September 11, 1937, in , Crippen earned a in from the University of in 1960 and was commissioned through the U.S. 's Aviation Officer Program. He served as a Navy pilot from June 1962 to November 1964 aboard the , later attended the U.S. Air Force Aerospace Research Pilot School at , and became an instructor there while being selected for the U.S. Air Force Program in October 1966. By the time of STS-41-C, Crippen had already commanded in June 1983 and served as pilot on the historic mission in April 1981, accumulating significant experience in Space Shuttle operations. As commander, Crippen was responsible for overall mission command, including critical piloting duties during reentry and landing on April 13, 1984, at . The pilot was Francis R. "Dick" Scobee, a U.S. Air Force officer on his first flight. Born on May 19, 1939, in , Scobee enlisted in the U.S. Air Force in 1957, graduated from Auburn Senior High School that year, and earned a B.S. in from the in 1965. He completed U.S. Air Force pilot training, received his wings in 1966, and logged over 6,500 hours in more than 45 types of aircraft, including a combat tour in . Selected as a astronaut candidate in January 1978 and completing training in August 1979, Scobee handled ascent maneuvers, orbital insertion adjustments, and flight deck operations during STS-41-C. Crew seating on the followed standard configuration, with Crippen in the left-hand commander's seat (Seat 1) and Scobee in the right-hand pilot's seat (Seat 2) for both launch and reentry. Their joint training emphasized the mission's unique profile—the first for the Shuttle program—which propelled Challenger directly to a high 288-nautical-mile (533 km) without intermediate orbital adjustments, requiring precise handling of the steeper and higher insertion. This preparation ensured seamless coordination during ascent on April 6, 1984, while allowing brief oversight of mission specialists' activities in orbital phases.

Mission Specialists

The mission specialists for STS-41-C were Terry J. Hart, George D. Nelson, and James D. A. van Hoften, all selected as part of NASA's eighth class in January 1978 and qualifying as full by August 1979 after intensive training at the . This class emphasized scientists and engineers to support the program's growing payload and servicing demands, with each specialist undergoing rigorous preparation in , spacecraft systems, and mission-specific simulations. For STS-41-C, their training focused on satellite rendezvous techniques, Remote Manipulator System (RMS) operations via high-fidelity simulators, and (EVA) procedures tailored to the Solar Maximum Mission (Solar Max) satellite repair, including neutral buoyancy simulations for zero-gravity handling of satellite components. These preparations enabled the crew to execute complex proximity operations, marking a milestone in on-orbit satellite servicing. Terry J. Hart, 1, was a U.S. and mechanical engineer born on October 27, 1946, in , . He earned a in from in 1968, a from the in 1970, and a Ph.D. from the in 1977, with prior service as an F-106 Delta Dart pilot accumulating over 2,500 flight hours. Selected for his engineering expertise and aviation background, Hart's first role on STS-41-C centered on payload operations, where he served as the primary operator of the shuttle's 50-foot RMS robotic arm to deploy the (LDEF) and capture the malfunctioning Solar Max satellite during rendezvous maneuvers. His RMS proficiency, honed through extensive simulator sessions modeling satellite grappling under varying orbital conditions, was critical to securing the satellite in the payload bay without damage, facilitating subsequent repairs. George D. Nelson, Mission Specialist 2, was a physicist and astronomer born on July 13, 1950, in Charles City, Iowa, with a Bachelor of Science in physics from Harvey Mudd College in 1972, a Master of Science in astronomy from the University of Washington in 1974, and a Ph.D. in astronomy from the same institution in 1978. Prior to astronaut selection, he conducted solar physics research and flew as a scientific operator on NASA's WB-57F high-altitude aircraft for earth resources missions. On his debut flight, Nelson led efforts for the Solar Max retrieval, leveraging his astrophysics knowledge to support satellite diagnostics and serving as the primary EVA crewmember for the initial capture attempt using the Manned Maneuvering Unit (MMU). His training included specialized EVA simulations for untethered spacewalks and rendezvous proximity operations, enabling him to approach and stabilize the spinning Solar Max satellite at close range before RMS capture. James D. A. van Hoften, Mission Specialist 3, was a civil and hydraulic engineer born on June 11, 1944, in , holding a in from the , in 1966, a in from in 1968, and a Ph.D. in fluids and mathematics from Colorado State in 1976. With experience as a structural design at Lockheed Missiles and Space Company, van Hoften was chosen for his technical acumen in fluid dynamics and large-scale structures. During STS-41-C, his first mission, he acted as backup RMS operator for payload integration and primary EVA crewmember for Solar Max repairs, performing intricate component replacements outside the orbiter. Van Hoften's preparation emphasized EVA procedures in the neutral buoyancy lab for handling satellite electronics and coronagraph modules, as well as RMS backup simulations to ensure seamless transitions during dynamic orbital phases.

Preparation and Launch

Vehicle Assembly and Payload Integration

Following its return from STS-7 on June 29, 1983, (OV-099) underwent post-flight maintenance and refurbishment in the at NASA's , including inspections of thermal protection systems, avionics, and structural components. Closeout activities in the facility were completed on February 11, 1984, after which the orbiter was towed to the for stacking with a new External Tank and pair of Solid Rocket Boosters. The complete flight vehicle was then rolled out along the crawlerway to Launch Complex 39A on March 29, 1984, where pad-side processing began. Payload integration in Challenger's cargo bay focused on accommodating the mission's dual objectives of satellite deployment and on-orbit repair. The (LDEF), a 4.3-meter-diameter by 9.1-meter-long cylindrical platform weighing approximately 9,700 kilograms, was installed as the primary payload. This structure hosted 57 experiments spanning , effects, and technology demonstrations, developed by more than 200 investigators from seven centers, 21 universities, 33 private companies, and international partners including the (ESA). LDEF was secured to the bay's trusses via the Remote Manipulator System (RMS) berthing mechanism, positioned for deployment on flight day two using the orbiter's robotic arm. To support the rendezvous, retrieval, and repair of the Solar Maximum Mission (Solar Max) satellite, the payload bay was outfitted with specialized fixtures for proximity operations and (EVA) support. This included the integration of two Manned Maneuvering Units (MMUs), self-contained nitrogen-jet propulsion backpacks each weighing 136 kilograms, stowed in dedicated lockers in the aft section of the bay. The MMUs, qualified on the prior mission, enabled untethered astronaut mobility up to 100 meters from the orbiter, critical for grappling the 2,300-kilogram Solar Max satellite and maneuvering it into the payload bay for repairs. Additional equipment, such as the Orbiter Docking System and trunnion pins for satellite securing, was installed to facilitate the complex choreography of capture and redeployment. Pre-launch verification at the pad involved rigorous testing of integrated systems, including a demonstration test (CDDT) conducted as a full-duration of launch operations to validate procedures, , and vehicle interfaces. This dry-run , completed in late March 1984, confirmed the functionality of , hydraulic, and flight control systems without major anomalies, paving the way for arrival and final preparations.

Countdown and Liftoff

The countdown for STS-41-C proceeded flawlessly without any holds, culminating in liftoff on April 6, 1984, at 13:58 UTC from Launch Complex 39A at . Clear skies and favorable weather conditions at the launch site supported the on-schedule departure of , powered by its three main engines and two solid rocket boosters (SRBs) in a mode that eliminated the need for initial (OMS) burns to reach orbit. The crew monitored the ascent from the flight deck, with Commander Robert L. Crippen and Pilot Francis R. Scobee overseeing vehicle performance and systems status during the dynamic phase. Challenger's ascent followed a direct profile, the first of its kind for the , designed to insert the orbiter into a high initial orbit without intermediate OMS firings for circularization until later. Key events unfolded nominally: the SRBs separated at T+2:06, jettisoning the expended boosters into the Atlantic Ocean, followed by main engine cutoff (MECO) at T+8:31 after throttling down, and external tank (ET) separation at T+8:49. This achieved orbital insertion into an initial elliptical orbit with a perigee of approximately 120 nautical miles and an apogee of 231 nautical miles. This efficient profile marked a significant operational advancement, reducing consumption for the ascent while meeting the mission's high-orbit requirements for payload deployment.

Orbital Phase

LDEF Deployment

On flight day 2 of the STS-41-C mission, the crew deployed the Long Duration Exposure Facility (LDEF) using the orbiter's Remote Manipulator System (RMS). Mission Specialist Terry J. Hart operated the 15-meter RMS arm to unberth the 9.1-meter-long, 4.3-meter-diameter cylindrical satellite from Challenger's payload bay over the Pacific Ocean near Wake Island. The deployment sequence, which began approximately 24 hours after launch, involved lifting LDEF clear of the bay, rotating it to a stable gravity-gradient orientation with its long axis vertical, and releasing it after a controlled separation using orbiter thrusters to achieve an initial rate of 0.15 m/s, increasing to 1.5 m/s. LDEF was released at 17:26 UTC on April 7, 1984, entering a nearly circular of approximately 475 km altitude at a 28.5-degree inclination. This orbit was selected to expose the facility to the full range of environmental conditions, including varying solar activity and thermal cycling, while remaining accessible for future retrieval. The , weighing 9,700 kg and containing 57 experiments across 86 trays with over 10,000 material specimens, was designed for a nominal 1- to 2-year exposure to study the effects of atomic oxygen erosion, and , and and impacts on a variety of materials and components. Post-deployment, ground-based radar tracking from confirmed LDEF's stable and separation from Challenger, with no observable rotation rates exceeding 0.025 degrees per second as verified by onboard observations and preliminary film analysis. Initial signals from the indicated successful activation of its experiment electrical systems and attitude control mechanisms, ensuring proper orientation for . The RMS played a key role in this precise maneuver, demonstrating the shuttle's capability for deployment in early orbital operations.

Solar Max Retrieval and Repair

On April 8, 1984, during flight day three of the STS-41-C mission, the , orbiting at an altitude of approximately 290 miles (467 km), executed a rendezvous with the Solar Maximum Mission (SMM) satellite, commonly known as Solar Max, whose orbit had decayed to a similar altitude due to atmospheric drag. The crew used Challenger's (OMS) thrusters and (RCS) jets to perform a series of burns that closed the initial separation distance from over 300 miles to within visual range, station-keeping at about 140 feet (43 meters) from the satellite without physical contact. This rendezvous demonstrated the shuttle's precision navigation capabilities, matching the satellite's slowly decaying orbit of approximately 490 km that threatened its premature reentry. The initial capture attempt later that day failed due to issues with the satellite's Trunnion Pin Acquisition Device (TPAD), where a thermal button interfered with secure attachment after three tries using the Manned Maneuvering Unit (MMU), causing the satellite to begin an unintended tumble. Ground controllers at NASA's Goddard Space Flight Center temporarily stabilized Solar Max using its onboard magnetic torque bars overnight. On April 10, mission specialist Terry J. Hart successfully captured the satellite from the shuttle's flight deck using the Remote Manipulator System (RMS) arm in a rolling grapple maneuver, securing it without further incident after approaching to within 40 feet (12 meters). This marked the first in-orbit capture of an operational satellite by a robotic arm, enabling its transfer to a cradle in Challenger's payload bay for repairs. The repair process involved extravehicular activities (EVAs) to address the satellite's primary malfunctions: a failed attitude control system that had rendered most instruments inoperable since 1980 and a degraded coronagraph/polarimeter instrument. Mission specialists George D. Nelson and James D. A. van Hoften, who had undergone extensive neutral buoyancy training for these tasks, replaced the main attitude control electronics module and the coronagraph/polarimeter's Main Electronics Box (MEB), restoring the satellite's pointing accuracy and full scientific functionality. These modular replacements, prepared as spares on the ground, took several hours and confirmed the satellite's viability through post-repair checkouts. On April 12, after verifying operations, Hart used the RMS to redeploy Solar Max into a higher of approximately 550 kilometers (342 miles), boosting its altitude to mitigate further decay and extend its mission life. Challenger maintained a safe distance of 200 to 300 feet (61 to 91 meters) during the release and monitored the satellite for two orbits as it autonomously deployed its antennas and resumed solar observations. This successful intervention prolonged Solar Max's operations until its planned decommissioning in 1989, yielding five additional years of data on solar flares and activity during the peak of 21.

Spacewalks

First EVA

The first extravehicular activity (EVA-1) of STS-41-C took place on April 8, 1984, lasting 2 hours and 38 minutes, and was conducted by mission specialists George D. Nelson and James D. Van Hoften to facilitate the retrieval of the malfunctioning Solar Maximum Mission (SMM) satellite, known as Solar Max, for on-orbit repair. The overall repair objectives aimed to replace the satellite's faulty attitude control system and / modules to restore its ability to study solar flares and activity. Nelson, serving as the lead spacewalker, donned the (MMU) and translated from the payload bay of Challenger toward the free-flying Solar Max, which was positioned approximately 200 feet away after rendezvous maneuvers by commanders Robert L. Crippen and pilot Francis R. Scobee. Van Hoften remained tethered and supported operations from the and payload bay, coordinating with mission specialist Terry J. Hart, who operated the Remote Manipulator System (RMS) as a backup capture option. Key pre-grapple activities included a visual survey of the satellite's exterior to assess damage from its three years in , such as degraded blankets and structural , along with preparation and checkout of tools like the Trunnion Pin Acquisition Device (TPAD) mounted on Nelson's MMU. Approaching to within 15 feet, Nelson executed three docking attempts with the TPAD aimed at Solar Max's trunnion pins, but each failed due to a small button () interfering with the mechanism's jaws, preventing them from closing and securing the . The unsuccessful grapples induced an unanticipated wobble in the 's attitude, causing it to spin uncontrollably at up to 5 degrees per second; Nelson manually intervened by grasping one of the 's solar arrays in an effort to stabilize it, but this only exacerbated the rotation. With MMU propellant levels critically low after 42 minutes of free-flight operations, Nelson released the array and returned to Challenger, where the crew secured the and deferred further retrieval to ground-controlled stabilization and a revised RMS-based plan. These mid-EVA adjustments highlighted the complexities of untethered servicing, including the need for precise attitude control and redundant capture methods.

Second EVA

The second extravehicular activity (EVA-2) of the STS-41-C mission took place on April 11, 1984, lasting 6 hours and 44 minutes, and was conducted by mission specialists George D. Nelson and James D. Van Hoften. Following rendezvous with the Solar Maximum Mission (SMM) satellite, the EVA began with an RMS-assisted capture, during which Van Hoften, secured in a foot restraint at the end of the Remote Manipulator System (RMS) operated by Terry J. Hart, successfully grappled the satellite for berthing in Challenger's payload bay. Once berthed, Nelson and Van Hoften, using foot restraints and tethers for stability, replaced the satellite's faulty attitude control system module in approximately 45 minutes and installed a new main electronics box for the coronagraph/polarimeter instrument, a task that required about 1 hour and involved cutting thermal blankets and securing connections with specialized tools. They also added a protective manifold over the X-ray polychromator to safeguard it from debris. With repairs complete, the astronauts performed final inspections to verify the satellite's integrity before preparing it for release from the payload bay. The extended duration of this EVA, combined with the complexity of the procedures, necessitated a one-day extension of the overall mission timeline. This spacewalk marked the first successful on-orbit servicing of a free-flying satellite, showcasing innovations such as untethered mobility tests with the (MMU) by Van Hoften in the payload bay and the use of the RMS for precise capture and repair support.

Reentry and Landing

Deorbit Preparation

Following the successful redeployment of the repaired Solar Maximum Mission (Solar Max) satellite on flight day 6, the STS-41-C extended the mission by one day to seven days total due to delays during the extravehicular activities (EVAs) for satellite retrieval and repair. This extension allowed additional time for systems checks and ensured optimal conditions for reentry preparations. The deorbit burn was executed on April 13, 1984, initiating the vehicle's return to Earth. In preparation for deorbit, the crew focused on securing the payload bay to prevent any loose items from interfering with reentry dynamics. The Remote Manipulator System (RMS) was used to stow tools and equipment from the EVAs, while ground controllers and onboard systems confirmed clear separation between Challenger and both the (LDEF) and the Solar Max satellite, which had been released into their respective orbits days earlier. Payload bay doors were closed approximately one hour prior to the deorbit burn, with thermal and structural integrity verified through telemetry data. The flight crew then reconfigured the orbiter's flight deck for reentry. Commander Robert L. Crippen and Pilot Francis R. (Dick) Scobee adjusted their acceleration couches to the upright position for optimal g-force distribution, while mission specialists Terry J. Hart, James D. van Hoften, and George D. Nelson conducted diagnostics on critical systems including the (OMS), (RCS), and guidance computers. These checks confirmed nominal performance across avionics, hydraulics, and environmental control subsystems, ensuring readiness for the atmospheric descent. To set up the proper reentry trajectory, two OMS burns were performed to lower the from its operational altitude of approximately 288 nautical miles (533 km). The first burn reduced perigee, transitioning the to an elliptical profile suitable for reentry interface, while the second fine-tuned inclination and velocity for the targeted landing at . These maneuvers consumed a controlled amount of , with post-burn assessments verifying the orbit decay path aligned with mission parameters.

Descent and Touchdown

The deorbit for STS-41-C commenced at approximately 6 days, 21 hours GET on April 13, 1984, utilizing both (OMS) engines for a duration of approximately 4 minutes 57 seconds. This maneuver reduced the orbiter Challenger's orbital velocity sufficiently to commit it to atmospheric reentry from its 290-nautical-mile altitude, marking the transition from orbital operations to . The was nominal, with the crew monitoring propulsion performance closely as part of final preparations. Atmospheric entry interface occurred at 400,000 feet (122 km) altitude at approximately 6 days, 21 hours, 45 minutes GET, with Challenger traveling at approximately Mach 25, where peak heating rates were experienced along the underside thermal protection system. The orbiter then executed a controlled glide, descending through the sensible atmosphere while the crew employed the (RCS) thrusters for roll modulation to maintain the desired trajectory and energy management profile. This phase produced a visible plasma sheath and light show observable through the forward windows, characteristic of hypersonic reentry conditions. Pilot Francis R. Scobee and Commander Robert L. Crippen shared primary flight control duties during this segment, ensuring precise attitude adjustments. Challenger touched down on lakebed Runway 17 at Edwards Air Force Base, California, at 13:38:07 UTC (05:38:07 PST), concluding the mission after 108 orbits and a total duration of 6 days, 23 hours, 40 minutes, and 7 seconds. The main landing gear contacted the surface first, followed by nose gear touchdown, resulting in a rollout of 8,716 feet over 49 seconds at a landing weight of 196,975 pounds. Weather conditions at Edwards were favorable, featuring scattered clouds at 20,000 feet, visibility exceeding 7 miles, and light variable winds of 5 knots; Scobee adeptly handled the approach and minor crosswind components to achieve a smooth wheels-stop at 13:51:16 UTC. The alternate landing site was selected due to deteriorating weather at Kennedy Space Center, including thickening cloud decks and a stalling frontal system.

Post-Mission Analysis

Mission Achievements

The STS-41-C mission achieved the first successful on-orbit repair of a satellite, when astronauts retrieved the malfunctioning Solar Maximum Mission (Solar Max) , replaced its faulty attitude control system and / instrument, and redeployed it into . This pioneering effort demonstrated the feasibility of in-space servicing operations, paving the way for subsequent missions such as the repairs by establishing techniques for rendezvous, capture, and component replacement in microgravity. The repaired Solar Max satellite continued scientific observations of solar activity for an additional five years, until its reentry in December 1989, far exceeding its original post-launch lifespan. Another key accomplishment was the successful deployment of the (LDEF), a 12-sided cylindrical structure carrying 57 experiments to study the effects of the low-Earth orbit environment on materials, components, and biological samples. LDEF operated autonomously for nearly six years until its retrieval by the crew in January 1990, yielding extensive data on , atomic oxygen erosion, impacts, and other space weather phenomena that informed the design of future spacecraft and components. The mission set several operational records, including the first direct ascent for a launch, where Challenger's main engines propelled the orbiter directly to its 313-nautical-mile operational altitude without an initial lower . It also marked the first (EVA) dedicated to satellite repair, with astronauts using the to perform untethered spacewalks that facilitated the Solar Max operations. Overall, STS-41-C lasted 6 days, 23 hours, 40 minutes, and 7 seconds, covering a total distance of 2.9 million miles across 108 orbits.

Technical Outcomes and Legacy

The repair of the Solar Maximum Mission (SMM) satellite during STS-41-C fully restored its scientific instruments, enabling continued operations and the collection of data until its reentry in December 1989. Following a 30-day post-redeployment checkout, the satellite achieved nominal performance, providing key insights into solar flares and coronal mass ejections that advanced understanding of solar activity despite having missed the peak of the 1980 . The in-orbit repair techniques, including (EVA) component replacement and the use of the Remote Manipulator System (RMS) for berthing, were directly adopted for later missions, such as the servicing operations, demonstrating the viability of extending satellite lifespans through human intervention. The (LDEF), deployed from Challenger during the mission, orbited for 5.7 years before retrieval by in January 1990, yielding a comprehensive dataset on atomic oxygen erosion, ultraviolet radiation effects, and impacts on over 200 materials samples. This information established a benchmark for environmental degradation models, informing spacecraft design standards and verifying material selections, including solar arrays, for the . LDEF results contributed to more accurate predictions of long-term material durability, reducing risks in future orbital platforms. Overall, the mission encountered no major safety concerns, with all primary objectives achieved within the 6 days, 23 hours, 40 minutes, and 7 seconds duration across 108 orbits. STS-41-C's advancements in EVA procedures and tools, such as the for untethered operations and specialized ratchet wrenches for precise repairs, laid foundational precedents for on-orbit satellite servicing. These innovations influenced subsequent efforts, including robotic-human synergies for the assembly and emerging commercial satellite repair architectures, by proving the feasibility of complex interventions on non-cooperative targets.

References

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