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By European Space Agency
A groundbreaking study, funded by ESA, reveals that fire emissions in the Amazon and Cerrado are largely driven by the smouldering combustion of woody debris. This crucial discovery highlights the significant influence of fuel characteristics on fire emissions, with wide-ranging implications for global carbon cycles, air quality and biodiversity.
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By NASA
On Jan. 24, 1985, space shuttle Discovery took off from NASA’s Kennedy Space Center (KSC) in Florida on STS-51C, the first space shuttle mission entirely dedicated to the Department of Defense (DOD). As such, many of the details of the flight remain classified. Discovery’s crew of Commander Thomas “T.K.” Mattingly, Pilot Loren Shriver, Mission Specialists Ellison Onizuka and James Buchli, and Payload Specialist Gary Payton deployed a classified satellite that used an Inertial Upper Stage (IUS) to reach its final geostationary orbit. The three-day mission ended with a landing at KSC. Postflight inspection of the Solid Rocket Boosters (SRBs) revealed the most significant erosion of O-ring seals seen in the shuttle program up to that time, attributed to unusually cold weather before and during launch.
The STS-51C crew of Pilot Loren Shriver, seated left, and Commander Thomas “T.K.” Mattingly; Payload Specialist Gary Payton, standing left, and Mission Specialists James Buchli and Ellison Onizuka. The STS-51C crew patch. In October 1982, NASA assigned astronauts Mattingly, Shriver, Onizuka, and Buchli as the STS-10 crew for a dedicated DOD flight aboard Challenger then scheduled for September 1983. Payton joined the crew as a payload specialist in the summer of 1983 with Keith Wright assigned as his backup. The failure of the IUS on STS-6 in April 1983 delayed the STS-10 mission, that also used the IUS, until engineers could identify and fix the cause of the problem. By September 1983, NASA had remanifested the crew and the payload on STS-41F with a July 1984 launch, that changed to STS-41E by November 1983. Additional delays in fixing the IUS delayed the mission yet again, by June 1984 redesignated as STS-51C and slated for December 1984 aboard Challenger.
STS-51C marked the third spaceflight for Mattingly, selected in 1966 as part of NASA’s fifth group of astronauts. He served on the prime crew for Apollo 13 until exposure to German measles forced his last-minute replacement by his backup. He then flew on Apollo 16 and STS-4. For Shriver, Onizuka, and Buchli, all three selected as astronauts in the class of 1978, STS-51C marked their first trip into space. The U.S. Air Force selected Payton and Wright in August 1979 in its first class of Manned Spaceflight Engineers, and STS-51C marked Payton’s first and only space mission.
In November 1984, NASA decided to delay STS-51C from December 1984 to January 1985 and swap orbiters from Challenger to Discovery. Postflight inspections following Challenger’s STS-41G mission in October 1984 revealed degradation of the bonding materials holding thermal protection system tiles onto the orbiter, requiring the replacement of 4,000 tiles. The time required to complete the work precluded a December launch. Tests conducted on Discovery prior to its November STS-51A mission revealed the bonding material to be sound.
Space shuttle Discovery rolls out to Launch Pad 39A. The STS-51C crew poses during launch pad evacuation drills associated with the Terminal Countdown Demonstration Test. The STS-51C crew exits crew quarters for the ride to Launch Pad 39A. On Jan. 5, 1985, Discovery rolled out from KSC’s Vehicle Assembly Building, where workers mated it with its External Tank (ET) and SRBs, to Launch Pad 39A. There, engineers conducted the Terminal Countdown Demonstration Test, essentially a dress rehearsal for the actual countdown, on Jan. 6-7, with the crew participating in the final few hours much as they would on launch day. The astronauts returned to KSC on Jan. 20 to prepare for the planned launch on Jan. 23. The day before, NASA managers decided to delay the launch by one day due to unseasonably cold weather, with concern about sub-freezing temperatures causing ice to form on the ET and possibly coming loose during ascent and damaging the vehicle. The DOD had requested that NASA keep the actual launch time secret until T minus nine minutes, with most of the countdown taking place hidden from public view.
Liftoff of space shuttle Discovery on STS-51C. Liftoff of Discovery on its third mission, STS-51C, came at 2:50 p.m. EST on Jan. 24, beginning the 15th space shuttle flight. Eight and a half minutes later, Discovery and its five-man crew had reached orbit. And, at the DOD customer’s request, all public coverage of the mission ended. Although NASA could not reveal the spacecraft’s orbital parameters, trade publications calculated that Discovery first entered an elliptical orbit, circularized over the next few revolutions, prior to Onizuka deploying the IUS and payload combination on the seventh orbit. Neither NASA nor the DOD have released any imagery of the deployment or even of the payload bay, with only a limited number of in-cabin and Earth observation photographs made public.
STS-51C Commander Thomas “T.K.” Mattingly films the Earth from Discovery’s overhead flight deck window. STS-51C crew members Loren Shriver, left, Ellison Onizuka, and James Buchli on Discovery’s flight deck. STS-51C Payload Specialist Gary Payton on Discovery’s flight deck. Sunlight streams through Earth’s upper atmosphere, with Discovery’s tail and Orbital Maneuvering Engine pods outlined by sunlight. The Pacific coast of Guatemala and southern Mexico. New Orleans and the Mississippi River delta. Discovery touches down at NASA’s Kennedy Space Center in Florida. The STS-51C astronauts are greeted by NASA officials as they exit Discovery. To maintain the mission’s secrecy, NASA could reveal the touchdown time only 16 hours prior to the event. On Jan. 27, Mattingly and Shriver brought Discovery to a smooth landing at KSC’s Shuttle Landing Facility after a flight of three days one hour 33 minutes, the shortest space shuttle mission except for the first two orbital test flights. The astronauts orbited the Earth 49 times. About an hour after touchdown, the astronaut crew exited Discovery and boarded the Astrovan for the ride back to crew quarters. Neither NASA management nor the astronauts held a post mission press conference. The U.S. Air Force announced only that the “IUS aboard STS-51C was deployed from the shuttle Discovery and successfully met its mission objectives.” Later in the day, ground crews towed Discovery to the Orbiter Processing Facility to begin preparing it for its next planned mission, STS-51D in March.
Postscript
Following the recovery of SRBs after each shuttle mission, engineers conducted detailed inspections before clearing them for reuse. After STS-51C, inspections of the critical O-ring seals that prevented hot gases from escaping from the SRB field joints revealed significant erosion and “blow-by” between the primary and secondary O-rings. Both left and right hand SRBs showed this erosion, the most significant of the program up to that time. Importantly, these O-rings experienced weather colder than any previous shuttle mission, with overnight ambient temperatures in the teens and twenties. Even at launch time, the O-rings had reached only 60 degrees. Engineers believed that these cold temperatures made the O-rings brittle and more susceptible to erosion. One year later, space shuttle Challenger launched after similarly cold overnight temperatures, with O-rings at 57 degrees at launch time. The Rogers Commission report laid the blame of the STS-51L accident on the failure of O-rings that allowed super-hot gases to escape from the SRB and impinge on the hydrogen tank in the ET, resulting in the explosion that destroyed the orbiter and claimed the lives of seven astronauts. The commission also faulted NASA’s safety culture for not adequately addressing the issue of O-ring erosion, a phenomenon first observed on STS-2 and to varying degrees on several subsequent missions.
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By NASA
3 min read
Preparations for Next Moonwalk Simulations Underway (and Underwater)
Equipped with state-of-the-art technology to test and evaluate communication, navigation, and surveillance systems NASA’s Pilatus PC-12 performs touch-and-go maneuvers over a runway at NASA’s Armstrong Flight Research Center in Edwards, California on Sept. 23, 2024. Researchers will use the data to understand Automatic Dependent Surveillance-Broadcast (ADS-B) signal loss scenarios for air taxi flights in urban areas. To prepare for ADS-B test flights pilots and crew from NASA Armstrong and NASA’s Glenn Research Center in Cleveland, ran a series of familiarization flights. These flights included several approach and landings, with an emphasis on avionics, medium altitude air-work with steep turns, slow flight and stall demonstrations.NASA/Steve Freeman As air taxis, drones, and other innovative aircraft enter U.S. airspace, systems that communicate an aircraft’s location will be critical to ensure air traffic safety.
The Federal Aviation Administration (FAA) requires aircraft to communicate their locations to other aircraft and air traffic control in real time using an Automatic Dependent Surveillance-Broadcast (ADS-B) system. NASA is currently evaluating an ADS-B system’s ability to prevent collisions in a simulated urban environment. Using NASA’s Pilatus PC-12 aircraft, researchers are investigating how these systems could handle the demands of air taxis flying at low altitudes through cities.
When operating in urban areas, one particular challenge for ADS-B systems is consistent signal coverage. Like losing cell-phone signal, air taxis flying through densely populated areas may have trouble maintaining ADS-B signals due to distance or interference. If that happens, those vehicles become less visible to air traffic control and other aircraft in the area, increasing the likelihood of collisions.
NASA pilot Kurt Blankenship maps out flight plans during a pre-flight brief. Pilots, crew, and researchers from NASA’s Armstrong Flight Research Center in Edwards, California and NASA’s Glenn Research Center in Cleveland are briefed on the flight plan to gather Automatic Dependent Surveillance-Broadcast signal data between the aircraft and ping-Stations on the ground at NASA Armstrong. These flights are the first cross-center research activity with the Pilatus-PC-12 at NASA Armstrong.NASA/Steve Freeman To simulate the conditions of an urban flight area and better understand signal loss patterns, NASA researchers established a test zone at NASA’s Armstrong Flight Research Center in Edwards, California, on Sept. 23 and 24, 2024.
Flying in the agency’s Pilatus PC-12 in a grid pattern over four ADS-B stations, researchers collected data on signal coverage from multiple ground locations and equipment configurations. Researchers were able to pinpoint where signal dropouts occurred from the strategically placed ground stations in connection to the plane’s altitude and distance from the stations. This data will inform future placement of additional ground stations to enhance signal boosting coverage.
“Like all antennas, those used for ADS-B signal reception do not have a constant pattern,” said Brad Snelling, vehicle test team chief engineer for NASA’s Air Mobility Pathfinders project. “There are certain areas where the terrain will block ADS-B signals and depending on the type of antenna and location characteristics, there are also flight elevation angles where reception can cause signal dropouts,” Snelling said. “This would mean we need to place additional ground stations at multiple locations to boost the signal for future test flights. We can use the test results to help us configure the equipment to reduce signal loss when we conduct future air taxi flight tests.”
Working in the Mobile Operations Facility at NASA’s Armstrong Flight Research Center in Edwards, California, NASA Advanced Air Mobility researcher Dennis Iannicca adjusts a control board to capture Automatic Dependent Surveillance-Broadcast (ADS-B) data during test flights. The data will be used to understand ADS-B signal loss scenarios for air taxi flights in urban areas.NASA/Steve Freeman The September flights at NASA Armstrong built upon earlier tests of ADS-B in different environments. In June, researchers at NASA’s Glenn Research Center in Cleveland flew the Pilatus PC-12 and found a consistent ADS-B signal between the aircraft and communications antennas mounted on the roof of the center’s Aerospace Communications Facility. Data from these flights helped researchers plan out the recent tests at NASA Armstrong. In December 2020, test flights performed under NASA’s Advanced Air Mobility National Campaign used an OH-58C Kiowa helicopter and ground-based ADS-B stations at NASA Armstrong to collect baseline signal information.
NASA’s research in ADS-B signals and other communication, navigation, and surveillance systems will help revolutionize U.S. air transportation. Air Mobility Pathfinders researchers will evaluate the data from the three separate flight tests to understand the different signal transmission conditions and equipment needed for air taxis and drones to safely operate in the National Air Space. NASA will use the results of this research to design infrastructure to support future air taxi communication, navigation, and surveillance research and to develop new ADS-B-like concepts for uncrewed aircraft systems.
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Last Updated Jan 23, 2025 EditorDede DiniusContactLaura Mitchelllaura.a.mitchell@nasa.govLocationArmstrong Flight Research Center Related Terms
Armstrong Flight Research Center Advanced Air Mobility Aeronautics Air Mobility Pathfinders project Airspace Operations and Safety Program Ames Research Center Glenn Research Center Langley Research Center Explore More
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The inclusion of these C2 centers was a deliberate effort to add a layer of realism and enhance the exercise's effectiveness in preparing joint space forces for the challenges of the Great Power Competition.
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