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NASA’s Global Precipitation Measurement Mission: 10 years, 10 stories
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By European Space Agency
Hera asteroid mission launch kit
Everything you'd ever want to know about ESA's first planetary defence mission
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By NASA
4 min read
Preparations for Next Moonwalk Simulations Underway (and Underwater)
NASA astronaut Tracy C. Dyson smiles for a portrait in the vestibule between the Kibo laboratory module and the Harmony module aboard space station.NASA NASA astronaut Tracy C. Dyson is returning home after a six-month mission aboard the International Space Station. While on orbit, Dyson conducted an array of experiments and technology demonstrations that contribute to advancements for humanity on Earth and the agency’s trajectory to the Moon and Mars.
Here is a look at some of the science Dyson conducted during her mission:
Heart-Shaped Bioprints
NASA NASA astronaut Tracy C. Dyson operates the BioFabrication Facility for the Redwire Cardiac Bioprinting Investigation, which 3D prints cardiovascular tissue samples. In microgravity, bio inks used for 3D printing are less likely to settle and retain their shape better than on Earth. Cardiovascular disease is currently the number one cause of death in the United States, and findings from this space station investigation could one day lead to 3D-printed organs such as hearts for patients awaiting transplants.
Wicking in Weightlessness
NASA NASA astronaut Tracy C. Dyson handles hardware for the Wicking in Gel-Coated Tubes (Gaucho Lung) experiment. This study uses a tube lined with various gel thicknesses to simulate the human respiratory system. A fluid mass known as a liquid plug is then observed as it either blocks or flows through the tube. Data regarding the movement and trailing of the liquid plug allows researchers to design better drug delivery methods to address respiratory ailments.
Programming for Future Missions
NASA NASA NASA astronaut Tracy C. Dyson runs student-designed software on the free-flying Astrobee robot. This technology demonstration is part of Zero Robotics, a worldwide competition that engages middle school students in writing computer code to address unique specifications. Winning participants get to run their software on an actual Astrobee aboard the space station. This educational opportunity helps inspire the next generation of technology innovators.
Robo-Extensions
NASA As we venture to the Moon and Mars, astronauts may rely more on robots to ensure safety and preserve resources. Through the Surface Avatar study, NASA astronaut Tracy C. Dyson controls a robot on Earth’s surface from a computer aboard station. This technology demonstration aims to toggle between manipulating multiple robots and “diving inside” a specific bot to control as an avatar. This two-way demonstration also evaluates how robot operators respond their robotic counterparts’ efficiency and general output. Applications for Earth use include exploration of inhospitable zones and search and rescue missions after disasters.
Capturing Earth’s Essence
NASA For Crew Earth Observations, astronauts take pictures of Earth from space for research purposes. NASA astronauts Suni Williams (left) and Tracy C. Dyson (right) contribute by aiming handheld cameras from the space station’s cupola to photograph our planet. Images help inform climate and environmental trends worldwide and provide real-time natural disaster assessments. More than four million photographs have been taken of Earth by astronauts from space.
Multi-faceted Crystallization Processor
NASA NASA astronaut Tracy C. Dyson holds a cassette for Pharmaceutical In-Space Laboratory – 04 (ADSEP-PIL-04), an experiment to crystallize the model proteins lysozyme and insulin. Up to three cassettes with samples can be processed simultaneously in the Advanced Space Experiment Processor (ADSEP), each at an independent temperature. Because lysozyme and insulin have well-documented crystal structures, they can be used to evaluate the hardware’s performance in space. Successful crystallization with ADSEP could lead to production and manufacturing of versatile crystals with pharmaceutical applications.
Cryo Care
NASA NASA astronauts Tracy C. Dyson and Matthew Dominick preserve research samples in freezers aboard the space station. Cryopreservation is essential for maintaining the integrity of samples for a variety of experiments, especially within the field of biology. The orbiting laboratory has multiple freezer options with varying subzero temperatures. Upon return, frozen samples are delivered back to their research teams for further analysis.
Welcoming New Science
NASA NASA astronaut Tracy C. Dyson is pictured between the Unity module and Northrop Grumman’s Cygnus spacecraft in preparation for depressurization and departure from the International Space Station. On long-duration missions, visiting vehicles provide necessities for crew daily living as well as new science experiments and supplies for ongoing research. This vehicle brought experiments to test water recovery technology, produce stem cells in microgravity, study the effects of spaceflight on microorganism DNA, and conduct science demonstrations for students.
Diana Garcia
International Space Station Research Communications Team
NASA’s Johnson Space Center
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Expedition 71
Expedition 71 began on April 5, 2024 and ends in September 2024. This crew will explore neuro-degenerative diseases and therapies,…
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By NASA
6 min read
Preparations for Next Moonwalk Simulations Underway (and Underwater)
This artist’s concept depicts NASA’s Europa Clipper spacecraft in orbit around Jupiter. The mission is targeting an Oct. 10, 2024, launch.NASA/JPL-Caltech The first NASA spacecraft dedicated to studying an ocean world beyond Earth, Europa Clipper aims to find out if the ice-encased moon Europa could be habitable.
NASA’s Europa Clipper spacecraft, the largest the agency has ever built for a planetary mission, will travel 1.8 billion miles (2.9 billion kilometers) from the agency’s Kennedy Space Center in Florida to Europa, an intriguing icy moon of Jupiter. The spacecraft’s launch period opens Thursday, Oct. 10.
Learn more about how NASA’s Europa Clipper came together – and how it will explore an ocean moon of Jupiter. Credit: NASA/JPL-Caltech Data from previous NASA missions has provided scientists with strong evidence that an enormous salty ocean lies underneath the frozen surface of the moon. Europa Clipper will orbit Jupiter and conduct 49 close flybys of the moon to gather data needed to determine whether there are places below its thick frozen crust that could support life.
Here are eight things to know about the mission:
1. Europa is one of the most promising places to look for currently habitable conditions beyond Earth.
There’s scientific evidence that the ingredients for life — water, the right chemistry, and energy — may exist at Europa right now. This mission will gather the information scientists need to find out for sure. The moon may hold an internal ocean with twice the water of Earth’s oceans combined, and it may also host organic compounds and energy sources under its surface. If the mission determines that Europa is habitable, it would mean there may be more habitable worlds in our solar system and beyond than we have imagined.
2. The spacecraft will fly through one of the most punishing radiation environments in our solar system — second only to the Sun’s.
Jupiter is surrounded by a gigantic magnetic field 20,000 times stronger than Earth’s. As the field spins, it captures and accelerates charged particles, creating radiation that can damage spacecraft. Mission engineers designed a spacecraft vault to shield sensitive electronics from radiation, and they plotted orbits that will limit the time Europa Clipper spends in most radiation-heavy areas around Jupiter.
3. Europa Clipper will orbit Jupiter, studying Europa while flying by the moon dozens of times.
The spacecraft will make looping orbits around Jupiter that bring it close to Europa for 49 science-dedicated flybys. On each orbit, the spacecraft will spend less than a day in Jupiter’s dangerous radiation zone near Europa before zipping back out. Two to three weeks later, it will repeat the process, making another flyby.
4. Europa Clipper features NASA’s most sophisticated suite of science instruments yet.
To determine if Europa is habitable, Europa Clipper must assess the moon’s interior, composition, and geology. The spacecraft carries nine science instruments and a gravity experiment that uses the telecommunications system. In order to obtain the best science during each flyby, all the science instruments will operate simultaneously on every pass. Scientists will then layer the data together to paint a full picture of the moon.
5. With antennas and solar arrays fully deployed, Europa Clipper is the largest spacecraft NASA has ever developed for a planetary mission.
The spacecraft extends 100 feet (30.5 meters) from one end to the other and about 58 feet (17.6 meters) across. That’s bigger than a basketball court, thanks in large part to the solar arrays, which need to be huge so they can collect enough sunlight while near Jupiter to power the instruments, electronics, and other subsystems.
6. It’s a long journey to Jupiter.
Jupiter is on average some 480 million miles (about 770 million kilometers) from Earth; both planets are in motion, and a spacecraft can carry only a limited amount of fuel. Mission planners are sending Europa Clipper past Mars and then Earth, using the planets’ gravity as a slingshot to add speed to the spacecraft’s trek. After journeying about 1.8 billion miles (2.9 billion kilometers) over 5½ years, the spacecraft will fire its engines to enter orbit around Jupiter in 2030.
7. Institutions across the U.S. and Europe have contributed to Europa Clipper.
Currently, about a thousand people work on the mission, including more than 220 scientists from both the U.S. and Europe. Since the mission was officially approved in 2015, more than 4,000 people have contributed to Europa Clipper, including teams who work for contractors and subcontractors.
8. More than 2.6 million of us are riding along with the spacecraft, bringing greetings from one water world to another.
As part of a mission campaign called “Message in a Bottle,” the spacecraft is carrying a poem by U.S. Poet Laureate Ada Limón, cosigned by millions of people from nearly every country in the world. Their names have been stenciled onto a microchip attached to a tantalum metal plate that seals the spacecraft’s electronics vault. The plate also features waveforms of people saying the word “water” in over 100 spoken languages.
More About Europa Clipper
Europa Clipper’s three main science objectives are to determine the thickness of the moon’s icy shell and its interactions with the ocean below, to investigate its composition, and to characterize its geology. The mission’s detailed exploration of Europa will help scientists better understand the astrobiological potential for habitable worlds beyond our planet.
Managed by Caltech in Pasadena, California, NASA’s Jet Propulsion Laboratory leads the development of the Europa Clipper mission in partnership with the Johns Hopkins Applied Physics Laboratory in Laurel, Maryland, for NASA’s Science Mission Directorate in Washington. The main spacecraft body was designed by APL in collaboration with JPL and NASA’s Goddard Space Flight Center in Greenbelt, Maryland, NASA’s Marshall Space Flight Center in Huntsville, Alabama, and NASA’s Langley Research Center in Hampton, Virginia. The Planetary Missions Program Office at Marshall executes program management of the Europa Clipper mission.
NASA’s Launch Services Program, based at Kennedy, manages the launch service for the Europa Clipper spacecraft, which will launch on a SpaceX Falcon Heavy rocket from Launch Complex 39A at Kennedy.
Find more information about Europa here:
https://europa.nasa.gov
Europa Clipper Teachable Moment See Europa’s Chaos Terrain in Crisp Detail Europa Clipper Gets Its Super-Size Solar Arrays News Media Contacts
Gretchen McCartney
Jet Propulsion Laboratory, Pasadena, Calif.
818-393-6215
gretchen.p.mccartney@jpl.nasa.gov
Karen Fox / Molly Wasser
NASA Headquarters, Washington
202-358-1600
karen.c.fox@nasa.gov / molly.l.wasser@nasa.gov
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By NASA
The X-15 hypersonic rocket-powered aircraft, built by North American Aviation (NAA), greatly expanded our knowledge of flight at speeds exceeding Mach 6 and altitudes above 250,000 feet. A joint project among NASA, the U.S. Air Force, and the U.S. Navy, the X-15’s first powered flight took place on Sept. 17, 1959, at the Flight Research Center, now the Armstrong Flight Research Center, at Edwards Air Force Base (AFB) in California. NAA chief test pilot A. Scott Crossfield piloted this flight and other early test flights before NASA and the Air Force took ownership of the aircraft. Between 1959 and 1968, 12 pilots completed 199 missions and achieved ever higher speeds and altitudes, knowledge and experience that later influenced the development of future programs such as the space shuttle.
Left: During its October 1958 rollout ceremony at the North American Aviation (NAA) facility in Los Angeles, NAA pilot A. Scott Crossfield poses in front of the X-15-1. Right: Rollout of X-15-2 at the NAA facility in February 1959.
The origins of the X-15 date to 1952, when the Committee on Aerodynamics of the National Advisory Committee for Aeronautics (NACA) adopted a resolution to expand their research portfolio to study flight at altitudes between 12 and 50 miles and Mach numbers between 4 and 10. The Air Force and Navy agreed and conducted joint feasibility studies at NACA’s field centers. In 1955, the Air Force selected North American Aviation (NAA), Los Angeles, to build three X-15 hypersonic aircraft.
On Oct. 1, 1958, the new National Aeronautics and Space Administration (NASA) incorporated the NACA centers and inherited the X-15 project. Two weeks later, on Oct. 15, 1958, the rollout of the first of the three aircraft took place at NAA’s Los Angeles facility where several of the early X-15 pilots, including Crossfield, attended. After the ceremony, workers wrapped the aircraft, placed it on a flatbed truck, and drove it overnight to the High Speed Flight Station, renamed by NASA the Flight Research Center in September 1959, where all the X-15 flights took place. Before this first aircraft took to the skies, NAA rolled out X-15-2 on Feb. 27, 1959. The X-15-3 rounded out the small fleet in early 1960.
Aerial view of the Flight Research Center, now NASA’s Armstrong Flight Research Center, at Edwards Air Force Base, California, with one of the B-52 carrier aircraft at left and an X-15 at right. Image credit: courtesy JD Barnes Collection.
Left: Diagram showing the two main profiles used by the X-15, either for altitude or speed. Right: The twin XLR-11 engines, left, and the more powerful XLR-99 engine used to power the X-15.
Like earlier X-planes, a carrier aircraft, in this case a modified B-52 Stratofortress, released the 34,000-pound X-15 at an altitude of 45,000 feet to conserve its fuel for the research mission. Flights took place within the High Range, a flight corridor extending from Wendover AFB in Utah to the Rogers Dry Lake landing zone adjacent to Edwards AFB, with emergency landing zones along the way. Typical research missions lasted eight to 12 minutes and followed either a high-altitude or a high-speed profile following launch from the B-52 and ignition of the X-15’s rocket engine. After burnout of the engine, the pilot guided the aircraft to an unpowered landing on the lakebed runway. To withstand the high temperatures during hypersonic flight and reentry, the X-15’s outer skin consisted of a then-new nickel-chrome alloy called Inconel-X. Because traditional aerodynamic surfaces used for flight control while in the atmosphere do not work in the near vacuum of space, the X-15 used its Ballistic Control System thrusters for attitude control while flying outside the atmosphere. NAA substituted eight smaller XLR-11 engines that produced only 16,000 pounds of thrust because of delays in the development of the 57,000-pound thrust XLR-99 rocket engine, built specifically for the X-15, For the first 17 months of test flights, the X-15 remained significantly underpowered. NAA chief pilot Crossfield had the primary responsibility for carrying out the initial test flights of the X-15 before handover of the aircraft to NASA and the Air Force.
Left: Flight profile of the first unpowered glide test flight of the X-15. Right: A. Scott Crossfield pilots the X-15 during its first unpowered glide test flight in June 1959.
With Crossfield at the controls of X-15-1, the first captive flight during which the X-15 remained attached to the B-52’s wing, took place on March 10, 1959. Crossfield completed the first unpowered glide flight of X-15-1 on June 8, the flight lasting just five minutes.
Left: The B-52 carrier aircraft taxis on the runway at Edwards Air Force Base in California, with the X-15 and pilot A. Scott Crossfield ready to perform the first powered flight of the hypersonic research aircraft. Right: The B-52 carries the X-15 and Crossfield to the drop altitude.
Left: Pilot A. Scott Crossfield is visible in the cockpit of the X-15 shortly before the release from the B-52 carrier aircraft. Image credit: courtesy North American Aviation. Right: The X-15 dumps excess fuel just prior to the drop.
Left: The X-15 drops from the B-52 carrier aircraft to begin its first powered flight. Middle: The view from the B-52 as the X-15 drops away. Right: Pilot A. Scott Crossfield has ignited all eight of the X-15’s engines to begin the powered flight.
Left: View taken from a chase plane of the X-15 during its glide to the lakebed following its first powered flight. Middle: Pilot A. Scott Crossfield brings the X-15 to a smooth touchdown on the lakebed runway at Edwards Air Force Base in California. Image credit: courtesy North American Aviation. Right: Crossfield hops out of the cockpit at the conclusion of the X-15’s first successful powered flight.
On Sept. 17, at the controls of X-15-2, Crossfield completed the first powered flight of an X-15. Firing all eight of the XLR-11 engines for 224 seconds, he reached a speed of Mach 2.11, or 1,393 miles per hour, and an altitude of 52,341 feet. Overcoming a few hardware problems, he brought the aircraft to a successful landing after a flight lasting just over nine minutes and traveling 88 miles. During 12 more flights, Crossfield expanded the aircraft’s flight envelope to Mach 2.97 and 88,116 feet while gathering important data on its flying characteristics. His last three flights used the higher thrust XLR-99 engine, the one designed for the aircraft. Crossfield’s 14th flight on Dec. 6, 1960, marked the end of the contracted testing program, and North American turned the X-15 over to the Air Force and NASA.
Standing between the first two aircraft, North American Aviation chief test pilot A. Scott Crossfield, left, symbolically hands over the keys to the X-15 to U.S. Air Force pilot Robert M. White and NASA pilot Neil A. Armstrong at the conclusion of the contracted flight test program. Image credit: courtesy North American Aviation.
Left: Chief NASA X-15 pilot Joseph “Joe” A. Walker following his altitude record-setting flight in August 1963. Middle left: Air Force pilot William J. “Pete” Knight following his speed record-setting flight in October 1967. Middle right: NASA pilot Neil A. Armstrong stands next to an X-15. Right: Air Force pilot Joe H. Engle following a flight aboard X-15A-2 in December 1965.
Over nine years, Crossfield and 11 other pilots – five NASA, five U.S. Air Force, and one U.S. Navy – completed a total of 199 flights of the X-15, gathering data on the aerodynamic and thermal performance of the aircraft flying to the edge of space and returning to Earth. The pilots also conducted a series of experiments, taking advantage of the plane’s unique characteristics and flight environment. NASA chief pilot Joseph “Joe” A. Walker flew the first of his 25 flights in March 1960. On his final flight on Aug. 22, 1963, he took X-15-3 to an altitude of 354,200 feet, or 67.1 miles, the highest achieved in the X-15 program, and a record for piloted aircraft that stood until surpassed during the final flight of SpaceShipOne on Oct. 4, 2004.
On Oct. 3, 1967, Air Force pilot William J. “Pete” Knight flew X-15A-2, with fully fueled external tanks, to an unofficial speed record for a piloted winged vehicle of Mach 6.70, or 4,520 miles per hour. The mark stood until surpassed during the reentry of space shuttle Columbia on April 14, 1981. NASA pilot Neil A. Armstrong and Air Force pilot Joe H. Engle flew the X-15 before joining NASA’s astronaut corps. Armstrong took to the skies seven times in the X-15 prior to becoming an astronaut, where he flew the Gemini VIII mission in 1966 and took humanity’s first steps on the Moon in July 1969. Engle has the unique distinction as the only person to have flown both the X-15 (16 times) and the space shuttle (twice in the atmosphere and twice in space). Of the first powered X-15 flight, Engle said, it “was a real milestone in a program that we still benefit from today.”
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By NASA
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Aura at 20 Years
Introduction
In the 1990s and early 2000s, an international team of engineers and scientists designed an integrated observatory for atmospheric composition – a bold endeavor to provide unprecedented detail that was essential to understanding how Earth’s ozone (O3) layer and air quality respond to changes in atmospheric composition caused by human activities and natural phenomena. This work addressed a key NASA Earth science objective. Originally referred to as Earth Observing System (EOS)–CHEM (later renamed Aura,) the mission would become the third EOS Flagship mission, joining EOS-AM 1 (Terra) launched in 1999 and EOS-PM 1 (Aqua), launched in 2002. The Aura spacecraft – see Figure 1 – is similar in design to Terra and identical to Aqua. Aura and its four instruments were launched on July 15, 2004 from Vandenberg Air Force Base (now Space Force Base) in California – see Photo.
Figure 1. An artist’s representation of the Aura satellite in orbit around the Earth. Image credit: NASA Photo. A photo of the nighttime launch of Aura on July 15, 2004. Image credit: NASA In 2014 The Earth Observer published an article called “Aura Celebrates Ten Years in Orbit,” [Nov–Dec 2014, 26:6, pp. 4–18] which details the history of Aura and the first decade of science resulting from its data. Therefore, the current article will focus on the science and applications enabled by Aura data in the last decade. It also examines Aura’s future and the legacies of the spacecraft’s instruments. Readers interested in more information on Aura and the scientific research and applications enabled by its data can visit the Aura website.
Recent Science Achievements from Aura’s Instrument (in alphabetical order)
High Resolution Dynamics Limb Sounder
The capabilities of the High Resolution Dynamics Limb Sounder (HIRDLS) were compromised at launch and operations ceased in March 2008 due to an image chopper stall. Nevertheless, the HIRDLS team was able to produce a three-year dataset notable for high vertical resolution profiles of greater than 1 km (0.62 mi) for temperature and O3 in the upper troposphere to the mesosphere. Though limited, the HIRDLS dataset demonstrated the incredible potential of the instrument for atmospheric research. So much so, that scientists are now in the study phase for a new instrument, part of the proposed Stratosphere Troposphere Response using Infrared Vertically-Resolved Light Explorer (STRIVE) mission, which would have similar capabilities as HIRDLS with advancements in spectral and spatial imaging. (STRIVE is one of four missions currently undergoing one-year concept studies, as part of NASA’s Earth System Explorer Program, which was established in the 2017 Earth Science Decadal Survey. Two winning proposals will be chosen in 2025 for full development and launch in 2030 or 2032.)
Microwave Limb Sounder
The Microwave Limb Sounder (MLS) was developed to study: 1) the evolution and recovery of the stratospheric O3 layer; 2) the role of the stratosphere, notably stratospheric humidity, in climate feedback processes; and 3) the behavior of air pollutants in the upper troposphere. MLS measures vertical profiles from the upper troposphere at ~10 km altitude (6.2 mi) to the mesosphere at ~90 km (56 mi) of 16 trace gases, temperature, geopotential height, and cloud ice. Its unique measurement suite has made it the “go-to” instrument for most data-driven studies of middle atmosphere composition over the last two decades.
Data collection during the past decade has highlighted the ability of the stratosphere to exhibit surprising and/or envelope-redefining behavior, (Envelope-redefining is a term that is used to refer to an event that greatly exceeded previous observed ranges of this event.) MLS observations have been crucial for the discovery and diagnoses of these extreme events. For example, in 2019, a stratospheric sudden warming over the southern polar cap in September – rare in the Antarctic – curtailed chemical processing, leading to an anomalously weak O3 hole. As another example, prolonged hot and dry conditions in Australia during the subsequent 2019–2020 southern summer promoted the catastrophic “Australian New Year” (ANY) fires. MLS observations showed that fire-driven pyrocumulonimbus convection lofted plumes of polluted air into the stratosphere to a degree never seen during the Aura mission.
Apart from those individual plumes, smoke pervaded the southern lower stratosphere, leading to unprecedented perturbations in southern midlatitude lower stratospheric composition, with chlorine (Cl) shifting from its main reservoir species, hydrochloric acid (HCl), into the O3-destroying form, hypochlorite (ClO). Peak anomalies in chlorine species occurred in mid-2020 – months after the fires. State-of-the-art atmospheric chemistry models in which wildfire smoke has properties similar to those of sulfate (SO4) aerosols were unable to reproduce the observed chemical redistribution. New model simulations assuming that HCl dissolves more readily in smoke than in SO4 particles under typical midlatitude stratospheric conditions better match the MLS observations.
As extraordinary as these events were, their impacts on the stratosphere were spectacularly eclipsed by the impact of the January 2022 eruption of the Hunga Tonga-Hunga Ha’apai (Hunga) volcano in the Pacific Ocean. The Hunga eruption lofted about 150 Tg of water vapor into the stratosphere – with initial injections reaching into the mesosphere. The eruption almost instantaneously increased total stratospheric water vapor by about 10%. MLS was the only sensor able to track the plume in the first weeks following the eruption. The Hunga humidity enhancement resulted in an envelope-redefining, low-temperature anomaly in the stratosphere, in turn inducing changes in stratospheric circulation. Repartitioning of southern midlatitude Cl also occurred, though to a lesser degree than following the ANY fires and in a manner broadly consistent with known chemical mechanisms. The Hunga water vapor enhancement has not substantially declined in the 2.5 years since the eruption, and studies indicate that it will likely endure for several more years.
Impacts of the Hunga humidity on polar O3 loss have also been investigated. The timing and location of the eruption were such that the plume reached high southern latitudes only after the 2022 Antarctic winter vortex had developed. Since the strong winds at the vortex edge present a transport barrier, polar stratospheric cloud (PSC) formation and O3 hole evolution were largely unaffected. When the vortex broke down at the end of the 2022 Antarctic winter, moist air flooded the southern polar region, increasing humidity in the region. Cold, moist conditions led to unusually early and vertically extensive PSC formation and Cl activation, but chemical processing ran to completion by mid-July, as typically occurs in southern winter. The cumulative chemical O3 losses ended up being unremarkable throughout the lower stratosphere. The Hunga plume was also largely excluded from the 2022–2023 Arctic vortex. The 2023–2024 Arctic O3 loss season was characterized by conditions that were dynamically disturbed and not persistently cold, and springtime O3 was near or above average. The extraordinary stratospheric hydration from Hunga has so far had minimal impact on chemical processing and O3 loss in the polar vortices in either hemisphere – see Figure 2.
Figure 2. The evolution of MLS water vapor anomalies (deviations from the baseline 2005–2021 climatology) from January 2019 through December 2023 as a function of equivalent latitude at 700 K potential temperature in the middle stratosphere at ~27 km altitude (17 mi). Black contours mark the approximate edge of the polar vortex. The green triangle marks the time of the main Hunga eruption at latitude 20.54°S on January 15, 2022. Figure credit: Updated and adapted from a 2023 paper in Geophysical Research Letters With the end of Aura and MLS, the future for stratospheric limb sounding observations is unclear. While stratospheric O3 and aerosol will continue to be measured on a daily, near-global basis by the Ozone Mapping and Profiler Suite (OMPS) Limb Profiler (OMPS-LP) instruments on the Suomi National Polar-orbiting Partnership (Suomi NPP) and Joint Polar Satellite System (JPSS-2, -3, and -4) satellites, there are no confirmed plans for daily, near-global observations of either long-lived trace gases or halogenated species – both of which are needed to diagnose observed changes in O3. The only other sensor making such measurements, the Canadian Atmospheric Chemistry Experiment Fourier Transform Spectrometer (ACE–FTS), is itself older than MLS and, as a solar occultation instrument, measures only 30 profiles-per-day, taking around a month to cover all latitudes. Similarly, no other sensor is set to provide daily, near-global measurements of stratospheric water vapor until the launch of the Canadian High-altitude Aerosols, Water vapour and Clouds (HAWC) mission in the early 2030s. Some potential new mission concepts are under consideration by both NASA and ESA, but they are subject to competition. Even if both instruments are ultimately selected, gaps in the records of many species measured by MLS are inevitable. The MLS PI is leading an effort to develop new technologies that would allow an instrument that could restart MLS measurements to be built in a far smaller mass/power footprint (e.g., 60 kg, 90 W vs. 500 kg, 500 W for Aura MLS), and technologies exist for yet-smaller MLS-like instruments that could assume the legacy of the highly impactful MLS record at low cost in future decades.
Ozone Monitoring Instrument
The Ozone Monitoring Instrument (OMI) continues the Total Ozone Mapping Spectrometer (TOMS) record for total O3 and other atmospheric parameters related to O3 chemistry and climate. It employs hyperspectral imaging in a push-broom mode to observe solar backscatter radiation in the visible and ultraviolet.
OMI is a Dutch–Finnish contribution to the Aura mission, and its remarkable stability and revolutionary two-dimensional (2D) detector (spatial in one dimension and spectral in the other) has produced a two-decade record of science- and trend-quality datasets of atmospheric column observations. OMI continues the long-term record of total column O3 measurements begun in 1979, and its observations of nitrogen dioxide (NO2), sulfur dioxide (SO2), formaldehyde (CH2O), and absorbing aerosols provided exceptional spatial resolution for study of anthropogenic and natural trends and variations of these pollutants around the world. Its radiometric and spectral stability has made it a valuable contributor for solar spectral irradiance measurements to complement dedicated solar instruments on other satellites. The many achievements made possible with OMI are documented in a review article.
OMI’s multidecade data records have revolutionized the ability to monitor air quality changes around the world, even at the sub-urban level. In particular, OMI NO2 data have been transformative. Recently, these data were used to track changes in air pollution associated with efforts to control the spread of SARS-CoV-2. OMI’s long, stable data record allowed for changes in pollution levels in 2020 – at the height of global lockdowns – to be put into historical perspective, especially within the envelope of typical year-to-year variations associated with meteorological variability. Many research studies assessed the impact of the pandemic lockdowns on air pollution, supporting novel uses of OMI data for socioeconomic-related research. For example, OMI NO2 data were shown to serve as an environmental indicator to evaluate the effectiveness of lockdown measures and as a significant predictor for the deceleration of COVID-19 spread. OMI NO2 data were also used as a proxy for the economic impact of the pandemic as NO2 is emitted during fossil fuel combustion, which is another proxy for economic activity since most global economies are driven by fossil fuels – see Animation.
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Animation. OMI data show changes in average levels of NO2 from March 20 to May 20 for each year from 2015 to 2023 over the northeast U.S. Levels in 2020 were ~30% lower relative to previous years because of efforts to slow the spread of COVID-19. OMI data indicate similar reductions in NO2 in cities across the globe in early 2020 and a gradual recovery in pollutant emissions in late 2020 into 2023. Additional images for other world cities and regions are available through the NASA Science Visualization Studio website and the Air Quality Observations from Space website. Animation credit: NASA Science Visualization Studio OMI’s datasets are being continued by successor 2D detector array instruments, such as the previously mentioned Copernicus Sentinel-5P TROPOMI mission, the Republic of Korea’s Geostationary Environment Monitoring Spectrometer (GEMS), and NASA’s Tropospheric Emissions: Monitoring of Pollution (TEMPO). All of these missions have enhanced spatial resolution relative to OMI, but have benefited from the innovative retrieval algorithms pioneered by OMI’s retrieval teams.
Tropospheric Emission Spectrometer
The Tropospheric Emission Spectrometer (TES) provided vertically-resolved distributions of a number of tropospheric constituents, e.g., O3, methane (CH4), and various volatile organic compounds. The instrument was decommissioned in 2018 due to signs of aging associated with a failing Interferometer Control System motor encoder bearing. Nevertheless, TES measurements led to a number of key results regarding changes in atmospheric composition that were published over the past 10 years.
Measurements from TES, OMI, and MLS showed that transport of O3 and its precursors from East Asia offset about 43% of the decline expected in O3 over the western U.S., based on emission reductions observed there over the period 2005–2010. TES megacity measurements revealed that the frequency of high-O3 days is particularly pronounced in South Asian megacities, which typically lack ground-based pollution monitoring networks. TES water vapor and semi-heavy water measurements indicated that water transpired from Amazonian vegetation becomes a significant moisture source for the atmosphere, during the transition from dry to wet season. The increasing water vapor provides the fuel needed to start the next rainy season. Measurements of CH4 from TES and carbon monoxide (CO) from Measurements of Pollution in the Troposphere (MOPITT) on Terra showed that CH4 emissions from fires declined at twice the rate expected from changes in burned area from 2004–2014. This finding helped to balance the CH4 budget for this period, because it offset some of the large increases in fossil fuel and wetland emissions. Through direct measurement of the O3 greenhouse gas effect, TES instantaneous radiative kernels revealed the impact of hydrological controls on the O3 radiative forcing and were used to show substantial radiative bias in Intergovernmental Panel on Climate Change (IPCC) chemistry–climate models. The TES team pioneered the retrieval of a number of species, such as peroxyacetyl nitrate, carbonyl sulfide, and ethylene.
The spirit of TES lives on through the NASA TRopospheric Ozone and its Precursors from Earth System Sounding (TROPESS) project, which generates data products of O3 and other atmospheric constituents by processing data from multiple satellites through a common retrieval algorithm and ground data system. TROPESS builds upon the success of TES and is considered a bridge to allow the development of a continuous record of O3 and other trace gas species as a follow-on to TES.
Future of Aura
In April 2023, Aura’s mission operations team performed the last series of maneuvers to maintain its position in the A-Train constellation of satellites. Since then, Aura has begun drifting. As of July 2024, Aura has descended ~5 km (3 mi) in altitude from ~700 km (435 mi) and its equator crossing time has increased by ~9 min from ~1:44 PM local time. This amount of drift is small, and the Aura MLS and OMI retrieval teams are ensuring the science- and trend-quality of the datasets.
As Aura continues to drift, the amount of sunlight reaching its solar panels will slowly decrease and will no longer be able to generate sufficient power to operate the spacecraft and instruments by mid-2026. At this point, the amount of local time drift will still be relatively small – less than one hour – so the retrieval teams will be able to ensure quality for most data products until this time.
In the remaining years, Aura’s aging but remarkably stable instruments will continue to add to the unprecedented two decades of science- and trend-quality data of numerous key tropospheric and stratospheric constituents. Aura data will be key for monitoring the evolution of the Hunga volcanic plume and understanding its continued impact on the chemistry and dynamics of the stratosphere. Observations from MLS and OMI will also be used to evaluate data from new and upcoming instruments (e.g., ESA’s Atmospheric Limb Tracker for Investigation of Upcoming Stratosphere (Altius); NASA’s TEMPO, Plankton, Aerosol, Cloud, ocean Ecosystem (PACE), and Total and Spectral Solar Irradiance Sensor-2 (TSIS-2) missions, or at least used to help minimize the gaps between data collections.
Aura’s Scientific Legacy
The Aura mission has been nothing short of transformative for atmospheric research and applied sciences. The multidecade, stable datasets have furthered process-based understanding of the chemistry and dynamics of atmospheric trace gases, especially those critical for understanding the causes of trends and variations in Earth’s protective ozone layer.
The two decades that Aura has flown have been marked by profound atmospheric changes and numerous serendipitous events, both natural and man-made. The data from Aura’s instruments have given scientists and applied scientists an unparalleled view – including at the sub-urban scale – of air pollution around the world, clearly showing the influence of rapid industrialization, environmental regulations designed to improve air quality, seasonal agricultural burning, catastrophic wildfires, and even a global pandemic, on the air we breathe. The Aura observational record spans the period that includes the decline of O3-destroying substances, and Aura data illustrate the beginnings of the recovery of the Antarctic O3 hole, a result of unparalleled international cooperation to reduce these substances.
Aura’s datasets have given a generation of scientists the most comprehensive global view to date of critical gases in Earth’s atmosphere and the chemical and dynamic processes that shape their concentrations. Many, but not all, of these datasets are being/will be continued by successor instruments that have benefited from the novel technologies incorporated into the design of Aura’s instruments as well as the innovative retrieval algorithms pioneered by Aura’s retrieval teams.
Acknowledgements
The author wishes to acknowledge the decades of hard work of the many hundreds of people who have contributed to the success of the international Aura mission. There are too many to acknowledge here and I’m sure that many names from the early days are lost to time. I would like to offer special thanks to those scientists who, back in the 1980s, first dreamed of the mission that would become Aura.
Bryan Duncan
NASA’s Goddard Space Flight Center (GSFC)
bryan.n.duncan@nasa.gov
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Last Updated Sep 16, 2024 Related Terms
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