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65 Years Ago: First Powered Flight of the X-15 Hypersonic Rocket Plane
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By NASA
In September 1969, celebrations continued to mark the successful first human Moon landing two months earlier, and NASA prepared for the next visit to the Moon. The hometowns of the Apollo 11 astronauts held parades in their honor, the postal service recognized their accomplishment with a stamp, and the Smithsonian put a Moon rock on display. They addressed Congress and embarked on a 38-day presidential round the world goodwill tour. Eager scientists received the first samples of lunar material to study in their laboratories. Meanwhile, NASA prepared Apollo 12 for November launch as the astronauts trained for the mission with an increased emphasis on lunar science. Plans called for additional Moon landings in 1970, with spacecraft under construction and astronauts in training.
Apollo 11
For Apollo 11 astronauts Neil A. Armstrong, Michael Collins, and Edwin E. “Buzz” Aldrin, their busy August 1969 postflight schedule continued into September with events throughout the United States and beyond. These included attending hometown parades, dedicating a stamp to commemorate their historic mission, unveiling a display of a Moon rock they collected, addressing a Joint Meeting of Congress, and visiting contractor facilities that built parts of their rocket and spacecraft. They capped off the hectic month with their departure, accompanied by their wives, on a presidential round-the-world goodwill tour that lasted into early November.
Left: Neil A. Armstrong at his hometown parade in Wapakoneta, Ohio. Image credit: Ohio Historical Society. Middle: Edwin E. “Buzz” Aldrin at his hometown parade in Montclair, New Jersey. Image credit: Star-Register. Right: Michael Collins at his adopted hometown parade in New Orleans, Louisiana. Image credit: AP Photo.
On Sep. 6, each astronaut appeared at hometown events held in their honor. Apollo 11 Commander Armstrong’s hometown of Wapakoneta, Ohio, welcomed him with a parade and other events. Montclair, New Jersey, held a parade to honor hometown hero Lunar Module Pilot (LMP) Aldrin. And New Orleans, Louisiana, the adopted hometown of Command Module Pilot (CMP) Michael Collins, honored him with a parade.
Left: Apollo 11 astronauts Michael Collins, left, Neil A. Armstrong, and Edwin E. “Buzz” Aldrin with Postmaster General Winton M. Blount display an enlargement of the stamp commemorating the first Moon landing. Right: Aldrin, left, Collins, and Armstrong examine a Moon rock with Smithsonian Institution Director General of Museums Frank A. Taylor.
Three days later, the astronauts reunited in Washington, D.C., where they appeared at the dedication ceremony of a new postage stamp that honored their mission. The U.S. Postal Service had commissioned artist Paul Calle in 1968 to design the stamp. The Apollo 11 astronauts had carried the stamp’s master die to the Moon aboard the Lunar Module (LM) Eagle and after its return to Earth the Postal Service used it to make the printing pages for the 10¢ postage stamp. At the National Postal Forum, Armstrong, Collins, and Aldrin unveiled the stamp together with Postmaster General Winton M. Blount, and each astronaut received an album with 30 of the “First Man on the Moon” stamps. On Sep. 15, the crew returned to Washington to present a two-pound rock they collected in the Sea of Tranquility during their historic Moon walk to Frank A. Taylor, the Director General of Museums at the Smithsonian Institution in Washington, D.C. The rock went on public display two days later at the Smithsonian’s Arts and Industries Building, the first time the public could view a Moon rock.
Left: Apollo 11 astronauts Michael Collins, left, Edwin E. “Buzz Aldrin, and Neil A. Armstrong each addressed a Joint Meeting of Congress, with Vice President Spiro T. Agnew and Speaker of the House John W. McCormack seated behind them. Middle: Apollo 11 astronauts’ wives Joan Aldrin, left, Patricia Collins, and Janet Armstrong receive recognition in the Visitors Gallery of the House Chamber. Right: The Apollo 11 astronauts and their wives cut at a cake at a reception at the Capitol.
With their wives observing from the Visitors Gallery of the House of Representatives, on Sep. 16 Armstrong, Aldrin, and Collins addressed a Joint Meeting of Congress. In this same chamber in May 1961, President John F. Kennedy committed the nation to land a man on the Moon and return him safely to the Earth before the end of decade. In a sense, the astronauts reported on the safe and successful completion of that challenge. Speaker of the House John W. McCormack introduced the astronauts to the gathering, as Vice President Spiro T. Agnew looked on. Each astronaut reflected on the significance of the historic mission.
Armstrong noted that their journey truly began in the halls of Congress when the Space Act of 1958 established NASA. Aldrin commented that “the Apollo lesson is that national goals can be met when there is a strong enough will to do so.” Collins shared a favorite quotation of his father’s to describe the value of the Apollo 11 mission: “He who would bring back the wealth of the Indies must take the wealth of the Indies with him.” Armstrong closed with, “We thank you, on behalf of all the men of Apollo, for giving us the privilege of joining you in serving – for all mankind.” After their speeches, the astronauts presented one American flag each to Vice President Agnew in his role as President of the Senate and to Speaker McCormack. The flags, that had flown over the Senate and House of Representatives, had traveled to the Moon and back with the astronauts. Speaker McCormack recognized the astronauts’ wives Jan Armstrong, Joan Aldrin, and Pat Collins for their contributions to the success of the Apollo 11 mission.
Left: Neil A. Armstrong and Michael Collins address North American Rockwell employees in Downey, California. Right: Presidential Boeing VC-137B jet at Ellington Air Force Base in Houston to take the Apollo 11 astronauts and their wives on the Giantstep goodwill world tour.
On Sep. 26, Armstrong and Collins visited two facilities in California of North American Rockwell (NAR) Space Division, the company that built parts of the Saturn V rocket and Apollo 11 spacecraft. First, they stopped at the Seal Beach plant that built the S-II second stage of the rocket, where 3,000 employees turned out to welcome them. Armstrong commented to the assembled crowd that during the July 16, 1969, liftoff, “the S-II gave us the smoothest ride ever.” Collins added that despite earlier misgivings about using liquid hydrogen as a rocket fuel, “after the ride you people gave us, I sure don’t have doubts any longer.” About 7,000 employees greeted the two astronauts and showered them with confetti at their next stop, the facility in Downey that built the Apollo Command and Service Modules. Both Armstrong and Collins thanked the team for building an outstanding spacecraft that took them to the Moon and returned them safely to Earth. The astronauts inspected the Command Module (CM) for Apollo 14, then under construction at the plant.
On the morning of Sep. 29, a blue and white Boeing VC-137B presidential jet touched down at Ellington Air Force Base in Houston. Neil and Jan Armstrong, Buzz and Joan Aldrin, and Mike and Pat Collins boarded the plane and joined their entourage of State Department and NASA support personnel. They departed Houston for Mexico City, the first stop on the Apollo 11 Giantstep goodwill world tour. They didn’t return to the United States until Nov. 5, having visited 29 cities in 24 countries, just nine days before Apollo 12 took off on humanity’s second journey to land on the Moon.
Distribution of Apollo 11 lunar samples to scientists at the Lunar Receiving Laboratory at the Manned Spacecraft Center, now NASA’s Johnson Space Center in Houston.
Back in Houston, distribution to scientists of samples of the lunar material returned by the Apollo 11 astronauts began on Sep. 17 at the Lunar Receiving Laboratory (LRL) at the Manned Spacecraft Center (MSC), now NASA’s Johnson Space Center in Houston. Daniel H. Anderson, curator of lunar samples at the LRL, supervised the distribution of approximately 18 pounds – about one-third of the total Apollo 11 lunar material – to 142 principal investigators from the United States and eight other countries according to prior agreements. The scientists examined the samples at their home institutions and reported their results at a conference in Houston in January 1970. They returned to the LRL any of the samples not destroyed during the examination process.
Apollo 12
In September 1969, NASA continued preparations for the second Moon landing mission, Apollo 12, scheduled for launch on Nov. 14. The Apollo 12 mission called for a pinpoint landing in Oceanus Procellarum (Ocean of Storms) near where the robotic spacecraft Surveyor 3 had touched down in April 1967. They planned to stay on the lunar surface for about 32 hours, compared to Apollo 11’s 21 hours, and conduct two surface spacewalks totaling more than 5 hours. During the first of their two excursions, the astronauts planned to deploy the Apollo Lunar Surface Experiments Package (ALSEP) and collect lunar samples. During the second spacewalk, they planned to visit Surveyor 3 and remove some of its equipment for return to Earth and collect additional lunar samples. The Apollo 12 prime crew of Commander Charles “Pete” Conrad, CMP Richard F. Gordon, and LMP Alan L. Bean and their backups David R. Scott, Alfred M. Worden, and James B. Irwin continued intensive training for the mission.
Left: The Apollo 12 Saturn V exits the Vehicle Assembly Building on its way to Launch Pad 39A. Middle: The Apollo 12 Saturn V rolling up the incline as it approaches Launch Pad 39A. Right: Apollo 12 astronauts Alan L. Bean, left, Richard F. Gordon, and Charles “Pete” Conrad pose in front of their Saturn V during the rollout to the pad.
On Sep. 8, the Saturn V rocket with the Apollo 12 spacecraft on top rolled out from Kennedy Space Center’s (KSC) Vehicle Assembly Building to Launch Pad 39A. The rocket made the 3.5-mile trip to the pad in about 6 hours, with Conrad, Gordon, and Bean on hand to observe the rollout. Workers at the pad spent the next two months thoroughly checking out the rocket and spacecraft to prepare it for its mission to the Moon. The two-day Flight Readiness Test at the end of September ensured that the launch vehicle and spacecraft systems were in a state of flight readiness. In addition to spending many hours in the spacecraft simulators, Conrad and Bean as well as their backups Scott and Irwin rehearsed their lunar surface spacewalks including the visit to Surveyor 3. Workers at NASA’s Jet Propulsion Laboratory in Pasadena, California, shipped an engineering model of the robotic spacecraft to KSC, and for added realism, engineers there mounted the model on a slope to match its relative position on the interior of the crater in which it stood on the Moon. Conrad and Scott used the Lunar Landing Training Vehicle (LLTV) at Ellington Air Force Base (AFB) near MSC to train for the final 200 feet of the descent to the lunar surface.
Left: Apollo 12 astronauts Alan L. Bean, left, and Charles “Pete” Conrad rehearse their lunar surface spacewalks at NASA’s Kennedy Space Center in Florida. Middle: Conrad trains in the use of the Hasselblad camera he and Bean will use on the Moon. Right: Bean, left, and Conrad train with an engineering model of a Surveyor spacecraft.
With regard to lunar geology training, the Apollo 12 astronauts had one advantage over their predecessors – they could inspect actual Moon rocks and soil returned by the Apollo 11 crew. On Sep. 19, Conrad and Bean arrived at the LRL, where Lunar Sample Curator Anderson met them. Anderson brought out a few lunar rocks and some lunar soil that scientists had already tested and didn’t require to be stored under vacuum or other special conditions, allowing Conrad and Bean to examine them closely and compare them with terrestrial rocks and soil they had seen during geology training field trips. This first-hand exposure to actual lunar samples significantly augmented Conrad and Bean’s geology training. To highlight the greater emphasis placed on lunar surface science, the Apollo 12 crews (prime and backup) went on six geology field trips compared to just one for the Apollo 11 crews.
Left: Apollo 12 astronauts Charles “Pete” Conrad, left, Richard F. Gordon, and Alan L. Bean prepare for water egress training aboard the MV Retriever in the Gulf of Mexico. Middle: Wearing Biological Isolation Garments and assisted by a decontamination officer, standing in the open hatch, Apollo 12 astronauts await retrieval in the life raft. Right: The recovery helicopter hoists the third crew member using a Billy Pugh net.
Although the Apollo 11 astronauts returned from the Moon in excellent health and scientists found no evidence of any harmful lunar microorganisms, NASA managers still planned to continue the postflight quarantine program for the Apollo 12 crew members, their spacecraft, and the lunar samples they brought back. The first of these measures involved the astronauts donning Biological Isolation Garments (BIG) prior to exiting the spacecraft after splashdown. Since they didn’t carry the BIGs with them to the Moon and back, one of the recovery personnel, also clad in a BIG, opened the hatch to the capsule after splashdown and handed the suits to the astronauts inside, who donned them before exiting onto a life raft.
On Sep. 20, the Apollo 12 astronauts rehearsed these procedures, identical to the ones used after the first Moon landing mission, in the Gulf of Mexico near Galveston, Texas, using a boilerplate Apollo CM and supported by the Motorized Vessel (MV) Retriever. As it turned out, NASA later removed the requirement for the crew to wear BIGs, and after their splashdown the Apollo 12 crew wore overalls and respirators.
Apollo 13
Left: Apollo 13 prime crew members James A. Lovell and Thomas K. “Ken” Mattingly in the Command Module (CM) for an altitude chamber test – Fred W. Haise is out of the picture at right – at NASA’s Kennedy Space Center in Florida. Middle: Apollo 13 backup astronaut John L. “Jack” Swigert prepares to enter the CM for an altitude chamber test. Right: Apollo 13 backup crew members John W. Young, left, and Swigert in the CM for an altitude chamber test – Charles M. Duke is out of the picture at right.
Preparations for Apollo 13 continued in parallel. In KSC’s Manned Spacecraft Operations Building (MSOB), Apollo 13 astronauts completed altitude chamber tests of their mission’s CM and LM. Prime crew members Commander James A. Lovell, CMP Thomas K. “Ken” Mattingly, and LMP Fred W. Haise completed the CM altitude test on Sep. 10, followed by their backups John W. Young, Jack L. Swigert, and Charles M. Duke on Sep. 17. The next day, Lovell and Haise completed the altitude test of the LM, followed by Young and Duke on Sep. 22. At the time of these tests, Apollo 13 planned to launch on March 12, 1970, on a 10-day mission to visit the Fra Mauro highlands region of the Moon. To prepare for their lunar surface excursions, Lovell, Haise, Young, and Duke, accompanied by geologist-astronaut Harrison H. “Jack” Schmitt and Caltech geologist Leon T. “Lee” Silver, spent the last week of September in Southern California’s Orocopia Mountains immersed in a geology boot camp.
Apollo 14 and 15
Left: At North American Rockwell’s (NAR) Downey, California, facility, workers assemble the Apollo 14 Command Module (CM), left, and Service Module. Right: NAR engineers work on the CM originally intended for Apollo 15.
Looking beyond Apollo 13, the Apollo 14 crew of Commander Alan B. Shepard, CMP Stuart A. Roosa, and LMP Edgar D. Mitchell and their backups Eugene A. Cernan, Ronald E. Evans, and Joe H. Engle had started training for their mission planned for mid-year 1970. At the NAR facility in Downey, engineers prepared the CM and SM and shipped them to KSC in November 1969. Also at Downey, workers continued assembling the CM and SM planned for the Apollo 15 mission in late 1970. As events transpired throughout 1970, plans for those two missions changed significantly.
NASA management changes
Left: Portrait of NASA astronaut James A. McDivitt. Right: NASA Administrator Thomas O. Paine, right, swears in George M. Low as NASA deputy administrator.
On Sept. 25, NASA appointed veteran astronaut James A. McDivitt as the Manager of the Apollo Spacecraft Program Office at MSC. McDivitt, selected as an astronaut in 1962, commanded two spaceflights, Gemini IV in June 1965 that included the first American spacewalk and Apollo 9 in March 1969, the first test of the LM in Earth orbit. He succeeded George M. Low who, in that position since April 1967, led the agency’s efforts to recover from the Apollo 1 fire and originated the idea to send Apollo 8 on a lunar orbital mission. Under his tenure, NASA successfully completed five crewed Apollo missions including the first human Moon landing. MSC Director Robert R. Gilruth initially assigned Low to plan future programs until Nov. 13, when President Richard M. Nixon nominated him as NASA deputy administrator. The Senate confirmed Low’s nomination on Nov. 25, and NASA Administrator Thomas O. Paine swore him in on Dec. 3. Low filled the position vacant since March 20, 1969.
To be continued …
News from around the world in September 1969:
September 2 – The first automated teller machine is installed at a Chemical Bank branch in Rockville Center, New York.
September 13 – Hannah-Barbera’s “Scooby Doo, Where Are You?” debuts on CBS.
September 20 – John Lennon announces in a private meeting his intention to leave The Beatles.
September 22 – San Francisco Giant Willie Mays becomes the second player, after Babe Ruth, to hit 600 career home runs.
September 23 – “Butch Cassidy and the Sundance Kid,” starring Paul Newman and Robert Redford, premieres.
September 24 – Tokyo’s daily newspaper Asahi Shimbun announced that it would be the first to deliver an edition electronically, using a FAX machine that could print a page in five minutes.
September 26 – Apple Records releases “Abbey Road,” The Beatles’ 11th studio album.
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Celebrating the First Earth Day Event at NASA Headquarters
Photo. Young attendees pose in front of the NASA Worm at the Earth Day celebration at NASA HQ. Photo credit: NASA Introduction
Organized by the Science Mission Directorate’s Science Support Office (SSO), NASA hosted its 12th annual Earth Day Celebration event from April 18–19, 2024. For the first time ever, the two-day event was held at NASA Headquarters (HQ) in Washington, DC.
The in-person event, which was free and open to the public, featured the newly installed Earth Information Center (EIC) exhibit – see Photos 1–4. The event featured 17 hands-on activities offered in NASA HQ’s East Lobby as well as two adjacent outdoor tents. Event participants were given an activity passport called the “Passport to Fun” listing all the activities and encouraging attendees to visit the stations and interact with NASA staff – see Figure 1. After completing six or more activities, attendees were able to claim giveaway items, e.g., lenticulars, NASA bags, posters, and calendars.
Photos 1–3. Student attendees at the Earth Information Center (EIC) interactive exhibit. Photo credits: NASA Photos 1–3. Student attendees at the Earth Information Center (EIC) interactive exhibit. Photo credits: NASA Photos 1–3. Student attendees at the Earth Information Center (EIC) interactive exhibit. Photo credits: NASA
Photo 4. Mark Subbarao [GSFC—Scientific Visualization Studio Lead] engages attendees with NASA science in front of the EIC Hyperwall. Photo credit: NASA Figure 1. Earth Day Activity Passport. Figure credit: NASA Prior to the event, Trena Ferrell [GSFC—Earth Science Education and Public Outreach Lead] arranged for groups of students from several local schools to visit the NASA Earth Day event. This included over 300 students from DuVal High School, Morgan State University, Howard University, Prince George’s County Environmental Academy, Prince George’s County Virtual Academy, International Hispanic School, and homeschoolers. On April 19, all of the students who were present at that time gathered for a plenary in the Webb Auditorium. Ferrell welcomed the attendees and provided introductions to prepare them for a virtual presentation by former NASA astronaut Paul Richards, who interacted with attendees and answered questions for roughly 20 minutes.
After Richard’s presentation, the attendees heard from Karen St. Germain [NASA HQ—Director of NASA’s Earth Science Division], whose in-person remarks emphasized to the students the crucial albeit less publicized studies that NASA does of our home planet. Related to this year’s Earth Day theme, “Water Touches Everything,” she discussed the ability of NASA’s Earth observing satellites to track water in all its forms as it circulates throughout the Earth system. St. Germain then answered questions from the audience for 15 minutes – see Photos 5–8.
Photo 5.Trena Ferrell [GSFC—Earth Science Education and Public Outreach Lead] welcomed student attendees to the Earth Day event. Photo credit: NASA Photos 6–7. Former NASA astronaut Paul Richards takes audience questions at the NASA Earth Day event. Photo credit: NASA Photos 6–7. Former NASA astronaut Paul Richards takes audience questions at the NASA Earth Day event. Photo credit: NASA Photo 8. Karen St. Germain [NASA Headquarters—Director of NASA’s Earth Science Division] provided remarks and answered student questions in the Webb Auditorium. Photo credit: NASA
NASA Administrator Bill Nelson visited the event on April 19, accompanied by Karen St. Germain and several NASA staff members who guided him as he explored the activities offered – see Photos 9–10.
Photo 9. NASA Administrator Bill Nelson [center, rear] spent time circulating among the NASA Earth Day hands-on activities. Here, he visits the “Measuring Light the Landsat Way” activity station, where Mike Taylor [GSFC/Science Systems and Applications, Inc.—Landsat Outreach Team] [left] explains how Landsat utilizes the electromagnetic spectrum and spectral signatures to better understand Earth. Photo credit: NASA Photo 10. [Left to right] Faith McKie [Acting NASA Press Secretary], Bill Nelson, Karen St. Germain, and Tom Wagner [Associate Director for Earth Action in the Earth Science Division of NASA’s Science Mission Directorate] during the Earth Day media briefing. Photo credit: NASA
Throughout the two-day event, it is estimated that as many as 1500 public participants attended along with the 300 students already discussed. While SSO staff distributed 500 activity passports, many small groups and families shared a single passport. SSO staff estimates that the true number of participants may be close to 1500 – see Photos 11–19.
Photo 11. A young Earth Day participant interacts with Ellen Gray [NASA GSFC—Earth Science News Team]. Photo credit: NASA Photo 12. Jenny Mottar [NASA HQ—Art Director for the Science Mission Directorate] and Kevin Miller [GSFC—SSO Senior Graphic Designer] hand out “Water Touches Everything” NASA Earth Day posters to student attendees. Photo credit: NASA Photos 13. Ross Walter [GSFC—Data Visualizer and Animator, Landsat Outreach Team] engages with students at the “Viewing Earth From Above with Landsat” station. Photo credit: NASA Photos 14. Students explore the Chesapeake Bay as seen by Landsat 8 with a large, vinyl floor mat. Photo credit: NASA Photo 15. Students play a Global Ecosystem Dynamics Investigation (GEDI) Jeopardy game at the “GEDI Knights Measure Forests from Space” table. Photo credit: NASA Photo 16. Student attendees make ultraviolet-bead bracelets and Helio Big Year buttons at the Heliophysics station. Photo credit: NASA Photo 17. Young attendees engage with Valerie Casasanto [GSFC—Ice, Cloud, and land Elevation Satellite-2 (ICESat-2) Outreach Lead], who helps them work on a three-dimensional glacier puzzle at the “ICESat-2: Ice, Trees, and Earth Height, If You Please!” station. Photo credit: NASA Photo 18. Young attendees engage with the “Meteorite Map Challenge.” Photo credit: NASA Photo 19. Dorian Janney [GSFC—GPM Outreach Specialist] engages visitors at the “Connect the Drops” station, where visitors learn how and why measuring global precipitation helps us better understand our home planet. Photo credit: NASA
Conclusion
NASA’s first Earth Day Celebration at NASA Headquarters was quite successful. While attendance was lower than previous events held at the more heavily trafficked Union Station or the National Mall, there was a steady stream of people throughout the exhibit on both days. It was also a great opportunity to showcase the new EIC to the public. Earth Day is the largest event organized annually by the SSO. This event requires months of planning, cross-divisional coordination, and intensive design of the hands-on activities – all carried from conceptualization through numerous revisions to implementation by more than 100 individuals from across the agency. This combined effort of SSO staff and assisting organizations results in an event that brings together thousands of visitors from a broad spectrum of ages and backgrounds to enjoy NASA science. This event would not have been possible were it not for the incredible efforts and collaboration put forth by so many of NASA’s outreach professionals. The SSO is grateful for all who helped to make this year’s Earth Day event a success and looks forward to Earth Day 2025.
Dalia Kirshenblat
NASA’s Goddard Space Flight Center/Global Science & Technology, Inc. (GSFC/GST)
dalia.p.zelmankirshenblat@nasa.gov
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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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