September 29

Return to Flight

1988 — Discovery Returns the Space Shuttle to Flight

15:37:00 UTC

On September 29, 1988, the three main engines of Space Shuttle Discovery ignited at Kennedy Space Center. Seconds later, its two solid rocket boosters came alive. At 15:37:00 UTC, Discovery lifted away from Launch Pad 39B carrying five astronauts into orbit. The moment was unlike any previous Shuttle launch. For 32 months, no Space Shuttle had flown. On January 28, 1986, Space Shuttle Challenger had broken apart 73 seconds after liftoff, killing all seven members of the STS-51L crew: Francis “Dick” Scobee, Michael Smith, Ellison Onizuka, Judith Resnik, Ronald McNair, Gregory Jarvis, and Christa McAuliffe. The accident brought Shuttle operations to an immediate halt. Investigators traced the physical cause of the disaster to the failure of seals in a joint of the right solid rocket booster. Hot gases escaped through the joint, eventually contributing to the catastrophic destruction of the vehicle. But the investigation went beyond hardware. The Presidential Commission examining the accident also identified serious problems in decision-making, communication, and NASA's organizational culture. Returning to flight therefore required more than replacing a defective component. NASA redesigned the solid rocket booster field joints, made numerous modifications to Shuttle hardware and procedures, strengthened safety oversight, and reconsidered how risks were evaluated and communicated. Discovery itself underwent more than 200 modifications before STS-26. The crew chosen to make the return was deliberately experienced. Commander Frederick “Rick” Hauck, pilot Richard Covey, and mission specialists John Lounge, George “Pinky” Nelson, and David Hilmers had all flown in space before. They became the first all-veteran American spaceflight crew since Apollo 11. Their spacecraft also reflected lessons learned from Challenger. During launch and landing, the astronauts wore newly introduced Launch and Entry Suits, providing greater protection than the clothing worn by Shuttle crews immediately before the accident. Discovery also carried equipment for a new emergency escape system that could allow astronauts, under certain circumstances, to leave a disabled orbiter during controlled gliding flight. But first the spacecraft had to launch. More than a million spectators reportedly gathered along Florida's Space Coast. After weather caused a delay of approximately an hour and a half, the countdown resumed. Discovery rose from the pad. About two minutes later came one of the flight's most closely watched moments. The redesigned solid rocket boosters completed their burns normally and separated. Discovery continued toward orbit. NASA's flight controllers, engineers, astronauts, and spectators had just watched the Shuttle safely pass the point at which Challenger had been lost. Approximately eight and a half minutes after liftoff, Discovery's main engines shut down normally. About 40 minutes into the mission, the astronauts fired the Orbital Maneuvering System engines to circularize their orbit. Hauck radioed Mission Control: “It's nice to be in orbit.” STS-26 was intentionally conservative. Its principal objective was to demonstrate that the redesigned Shuttle system could operate safely. But the mission also had important work to do. Approximately six hours after launch, the crew deployed TDRS-3, a Tracking and Data Relay Satellite. A similar satellite had been lost aboard Challenger. The TDRS network allowed spacecraft in low Earth orbit to communicate with Earth through satellites in much higher geosynchronous orbits, greatly increasing the amount of each orbit during which astronauts and spacecraft could remain in contact with ground controllers. Discovery remained in space for four days. On October 3, it landed safely at Edwards Air Force Base in California. The Shuttle program had returned.

Why It Matters: STS-26 restored American human spaceflight after the Challenger disaster, but its significance was greater than simply resuming launches. The mission tested redesigned hardware and new safety procedures developed after one of NASA's darkest moments. It demonstrated that returning from catastrophe requires understanding not only what hardware failed, but also the human and organizational systems that allowed failure to occur.

 

Also on This Day

1962 — Alouette I Places Canada Among the Spacefaring Nations

UTC launch time uncertain; approximately 05:30–07:06 UTC in surviving official accounts

On September 29, 1962 UTC, a Thor-Agena rocket lifted off from California carrying a small Canadian spacecraft named Alouette I. The satellite marked Canada's arrival in the Space Age. Only the Soviet Union and the United States had previously designed and built their own artificial Earth satellites. Canada became the third nation to do so. Alouette I emerged from an invitation NASA issued in 1958 for international participation in its new satellite program. Canadian scientists John Chapman and Eldin Warren, working at the Defence Research Telecommunications Establishment, proposed building a satellite that could investigate the ionosphere from above. The ionosphere is a region of Earth's upper atmosphere containing electrically charged particles. It has enormous practical importance because it affects the propagation of radio waves and therefore long-distance communications. Scientists had studied the ionosphere from the ground by transmitting radio signals upward and examining their reflections. Alouette would reverse the geometry. Orbiting above much of the ionosphere, it could transmit radio signals downward and investigate the structure of the region from the top. The challenge was formidable. Canada had never built a satellite. Engineers incorporated technologies that were still relatively new, including transistors, solar cells, and ingenious deployable antennas. The spacecraft's long antennas were designed to unroll after reaching orbit. Alouette I weighed approximately 145 kilograms and entered an orbit roughly 1,000 kilometers above Earth. It worked extraordinarily well. The spacecraft had been designed for a lifetime of about one year. Instead, it returned useful scientific data for more than ten years and produced more than one million ionospheric images. Its success led to further Canadian-American cooperation through the International Satellites for Ionospheric Studies program, including Alouette II, ISIS I, and ISIS II. It also helped establish Canadian expertise in spacecraft engineering that would later contribute to communications satellites, robotic systems such as the Canadarm, and Canada's continuing role in international space exploration. The name itself was distinctly Canadian. “Alouette”—French for meadowlark—evoked flight while also acknowledging Canada's French-language heritage.

Why It Matters: Alouette I made Canada the first country after the Soviet Union and United States to design and build its own satellite. Its extraordinary ten-year scientific lifetime demonstrated that important space science need not be confined to the two Cold War superpowers and helped establish Canada as a significant participant in space research.

1977 — Salyut 6 Begins a New Era of Space-Station Operations

Launch time not established

On September 29, 1977, the Soviet Union launched Salyut 6, a space station whose design would fundamentally change how humans lived and worked in orbit. Earlier Salyut stations had already demonstrated that crews could occupy orbital laboratories for extended periods. But they had an important limitation. A station with only one docking port could accommodate only one Soyuz spacecraft at a time. Because the crew needed its Soyuz to return home, another spacecraft could not easily dock while the resident crew was aboard. Salyut 6 had two docking ports. That seemingly straightforward change transformed space-station operations. A resident crew could remain aboard with its Soyuz docked at one end while another vehicle arrived at the other. Visiting crews could come aboard. Replacement spacecraft could be delivered. Most importantly, uncrewed Progress cargo spacecraft could bring food, water, equipment, scientific supplies, and propellant. For the first time, an inhabited space station could be resupplied routinely while its crew remained aboard. That capability made progressively longer missions practical. Salyut 6 would host numerous Soviet and international crews. Its cosmonauts repeatedly broke human-spaceflight endurance records, eventually remaining aboard for missions lasting roughly six months. The station also became an important venue for the Soviet Intercosmos program, through which cosmonauts from several allied countries flew in space. The operational model established aboard Salyut 6—resident crews, visiting crews, multiple docking ports, cargo deliveries, orbital refueling, repairs, and long-duration habitation—would be developed further aboard Salyut 7 and Mir. Today those practices are routine aboard modern space stations.

Why It Matters: Salyut 6 helped transform a space station from a laboratory visited for a single expedition into an orbital facility capable of sustained operations. Its second docking port and Progress resupply system established an operational model that ultimately led toward continuously inhabited stations such as Mir and the International Space Station.

2011 — China Launches Tiangong-1

13:16 UTC

On September 29, 2011, China launched Tiangong-1, an experimental orbital laboratory that represented another major step in the development of the country's human-spaceflight program. Its name meant “Heavenly Palace.” Tiangong-1 was not a large permanently inhabited space station comparable with Mir or the International Space Station. It was something more transitional: a laboratory in which China could learn and demonstrate technologies required to build such a station. One capability was particularly important: rendezvous and docking. Reaching orbit is one challenge. Bringing two spacecraft traveling thousands of meters per second around Earth into the same orbit, guiding them toward one another, and joining them safely is another. Without dependable rendezvous and docking, constructing a modular space station is effectively impossible. Tiangong-1 provided the target. In November 2011, the uncrewed Shenzhou 8 spacecraft successfully rendezvoused and docked with it, demonstrating China's first orbital docking. Human crews followed. Shenzhou 9 docked with Tiangong-1 in 2012, carrying China's first woman in space, Liu Yang. Shenzhou 10 visited in 2013 for another crewed mission. The small laboratory thus served as a technological bridge between China's early Shenzhou missions and its much more ambitious plans for long-term human habitation in orbit. Those plans eventually produced the modular Tiangong space station, assembled in orbit beginning with the Tianhe core module in 2021.

Why It Matters: Tiangong-1 gave China practical experience in rendezvous, docking, orbital habitation, and station operations. It was an essential stepping-stone from independent crewed spaceflight toward China's construction and operation of a permanently crewed modular space station.

 

The Bigger Picture

September 29 tells a story about how spaceflight grows from an extraordinary achievement into a sustainable capability. Alouette I demonstrates that progression at the national level. In 1962, the ability to build a satellite was still associated overwhelmingly with the two Cold War superpowers. Canada demonstrated that another nation could design a sophisticated scientific spacecraft, place it in orbit through international cooperation, and produce important research for more than a decade. Salyut 6 addressed sustainability differently. Putting people aboard a space station was no longer enough. If humans were truly going to remain in orbit, they needed a way to receive supplies, replace equipment, welcome other crews, and keep the station operating. Two docking ports helped make that possible. Tiangong-1 represents another nation climbing a similar technological ladder. China had learned to launch astronauts. Then it learned to conduct a spacewalk. With Tiangong-1, it began mastering rendezvous, docking, and orbital habitation—the capabilities required to construct a larger station. And Discovery's return to flight reminds us that maintaining a capability also means confronting what happens when the system fails catastrophically. The Challenger disaster demonstrated that technological maturity can never be assumed. Spaceflight remains unforgiving. The lesson of STS-26 was therefore not simply: We can fly again. The deeper question was: What have we changed because of what happened? That question belongs not only to NASA but to the entire history of exploration. Alouette I required Canada to develop capabilities it had never possessed. Salyut 6 required engineers to rethink how a station could be supported. Tiangong-1 required China to master techniques needed for a future station. STS-26 required NASA to examine a system that had failed and determine how—and whether—it could safely return to flight. September 29 therefore illustrates that exploration does not advance through achievement alone. It advances when institutions learn. Build → operate → discover weaknesses → adapt → build something better. That cycle has carried spaceflight from small experimental satellites to spacecraft that can operate for decades and stations that can remain inhabited year after year.

At a Glance

1962 — Approximately 05:30–07:06 UTC; exact time uncertain — Alouette I launches from California, making Canada the third nation to design and build its own artificial Earth satellite.

1977 — Launch time not established — The Soviet Union launches Salyut 6, whose two docking ports and ability to receive Progress resupply spacecraft transform long-duration space-station operations.

1988 — 15:37:00 UTC — Space Shuttle Discovery launches on STS-26, returning the Shuttle program to flight 32 months after the Challenger disaster.

2011 — 13:16 UTC — China launches Tiangong-1, an experimental orbital laboratory that will help establish rendezvous, docking, and habitation capabilities needed for a future modular space station.

September 28

A New Road to Orbit

2008 — Falcon 1 Becomes the First Privately Developed Liquid-Fueled Rocket to Reach Orbit

23:15 UTC

On September 28, 2008, a slender two-stage rocket rose from Omelek Island, part of Kwajalein Atoll in the Pacific Ocean. It was called Falcon 1. The rocket had flown three times before. All three attempts had failed. The fourth would change the history of commercial spaceflight. At 23:15 UTC, Falcon 1 lifted off carrying a 165-kilogram inert payload known as RatSat, or Demosat. Minutes later, the rocket's second stage successfully reached Earth orbit. Falcon 1 had become the first privately developed and funded liquid-fueled rocket to reach orbit. Its builder was Space Exploration Technologies Corporation—SpaceX—a company founded only six years earlier. The achievement had been anything but inevitable. Falcon 1's first flight, in March 2006, ended less than a minute after launch when a fuel leak led to an engine fire. The second attempt, in March 2007, traveled much farther but failed to achieve orbit after problems during the second-stage portion of the flight. The third attempt came on August 3, 2008. This time the first stage performed well, but residual thrust caused it to recontact the second stage after separation. The rocket was lost along with several payloads. The failure was particularly painful because Falcon 1 was no longer simply an experimental vehicle. It was carrying real spacecraft. SpaceX engineers identified the problem and prepared another rocket with remarkable speed. Only 55 days later, Falcon 1 stood ready again. Flight 4 carried no operational satellite. Instead, RatSat served as a payload simulator. The first stage's Merlin engine carried the vehicle through the lower atmosphere. After stage separation, the second-stage Kestrel engine continued the climb. This time, the stages separated cleanly. The second stage reached an initial orbit of approximately 622 by 643 kilometers above Earth. Falcon 1 had succeeded. The payload itself remained attached to the second stage, but that did not change the central achievement: the launch vehicle had reached orbit. NASA's contemporary chronology described Falcon 1 as the first privately developed and funded rocket to do so. The importance of that accomplishment became clearer with time. Falcon 1 flew only once more, successfully, in July 2009. SpaceX then shifted its attention to the much larger Falcon 9 and the Dragon spacecraft.

In 2010, Falcon 9 reached orbit on its first flight.

In 2012, Dragon became the first commercial spacecraft to deliver cargo to the International Space Station.

In 2015, a Falcon 9 first stage returned from an orbital-class mission and landed vertically on land.

In 2016, another landed on a ship at sea.

In 2020, SpaceX's Crew Dragon carried NASA astronauts to the International Space Station, restoring crewed orbital launch capability from the United States.

Falcon 1 therefore occupies a pivotal place in that progression. It was small. Its operational life was brief. But on September 28, 2008, it demonstrated that a privately developed liquid-fueled launch vehicle could reach orbit.

Why It Matters: Falcon 1's fourth flight marked a turning point in commercial spaceflight. The achievement demonstrated that a comparatively young private company could develop and operate an orbital launch vehicle, helping open a path toward the commercial launch, cargo, and human-spaceflight systems that would become increasingly important during the following decades.

 

Also on This Day

1951 — Seth Nicholson Discovers Ananke, a Moon of Jupiter

Observation time not established

On September 28, 1951, American astronomer Seth Barnes Nicholson discovered another member of Jupiter's growing family of moons. The discovery was made photographically using the 100-inch Hooker Telescope at Mount Wilson Observatory in California. The object would eventually receive the name Ananke. By the middle of the twentieth century, astronomers had learned that Jupiter possessed two very different kinds of satellites. The four large moons discovered by Galileo in 1610—Io, Europa, Ganymede, and Callisto—travel in relatively regular orbits close to the planet's equatorial plane. Farther away are much smaller irregular satellites. Ananke belongs to this second population. It travels around Jupiter in a distant, eccentric, highly inclined retrograde orbit, meaning that it moves in the direction opposite Jupiter's rotation. Those characteristics provide clues to its origin. Rather than forming alongside Jupiter in the disk of material surrounding the young planet, Ananke was probably associated with an object captured by Jupiter's gravity. Today astronomers recognize an entire Ananke group of small retrograde moons with similar orbital characteristics. One leading explanation is that they are fragments produced when a larger captured body was broken apart by a collision. Ananke itself has a mean radius of only about 14 kilometers. Nicholson was particularly skilled at discovering faint planetary satellites. During his career at Mount Wilson, he discovered several moons of Jupiter, greatly expanding the known architecture of the Jovian system. The contrast with modern planetary exploration is striking. Nicholson discovered Ananke as a tiny point recorded on a photographic plate. Decades later, spacecraft would transform other Jovian moons from points of light into complex worlds containing volcanoes, oceans, magnetic fields, mountains, craters, and icy terrain. Yet distant irregular moons such as Ananke remain reminders that even the planetary systems closest to us still contain populations whose histories must be reconstructed largely through careful astronomical observation.

Why It Matters: Ananke's discovery expanded the known Jovian satellite system and contributed to recognition that giant planets possess families of small irregular moons very different from their large regular satellites. Their unusual orbits preserve clues to capture, collision, and the violent early history of the solar system.

1953 — Edwin Hubble Dies

Time unknown

On September 28, 1953, American astronomer Edwin Powell Hubble died in San Marino, California. Few astronomers had done more to enlarge humanity's conception of the universe. When Hubble began his most important work, astronomers were still debating the nature of the faint spiral objects visible through telescopes. Were they relatively small clouds located within the Milky Way? Or were they enormous systems of stars lying far beyond it? Using the 100-inch Hooker Telescope at Mount Wilson—the same instrument Seth Nicholson used in discovering Ananke—Hubble identified Cepheid variable stars in the Andromeda Nebula. Cepheids were enormously valuable because their pulsation periods could be used to estimate their intrinsic luminosities. By comparing their actual luminosities with how faint they appeared from Earth, astronomers could calculate their distances. Hubble's measurements demonstrated that Andromeda was far too distant to lie within the Milky Way. The universe was suddenly much larger. The Milky Way was not the universe. It was one galaxy among many. Hubble then helped develop a system for classifying galaxies according to their appearance—spirals, barred spirals, ellipticals, and irregular systems. His work soon contributed to an even more profound discovery. Astronomers had measured the spectra of galaxies and found that many were redshifted, indicating recession. Combining galaxy-distance measurements with recession velocities, Hubble published in 1929 the relationship between distance and recession velocity that became fundamental to observational cosmology. The interpretation developed into one of the central pieces of evidence that the universe is expanding. The history deserves an important qualification. Hubble did not accomplish this alone. Vesto Slipher had already performed the difficult spectroscopic work that established the large radial velocities of spiral nebulae. Belgian astronomer and physicist Georges Lemaître had derived an expanding-universe solution from general relativity and, in 1927, published a relationship between distance and recession velocity before Hubble's famous 1929 paper. Modern historical treatments therefore place Hubble's achievements within a larger community of theoretical and observational work. His importance nevertheless remains immense. The Hubble Space Telescope, launched in 1990, was named in his honor. Its observations would extend the kind of extragalactic astronomy Hubble helped establish into realms he could scarcely have imagined.

Why It Matters: Edwin Hubble helped demonstrate that the Milky Way is only one galaxy among an enormous population of galaxies and provided crucial observational evidence associated with the expansion of the universe. His work was central to the transformation of astronomy into modern observational cosmology.

1971 — Luna 19 Launches to Map the Moon

Launch time not established

On September 28, 1971, the Soviet Union launched Luna 19, continuing an increasingly sophisticated program of robotic lunar exploration. By this point, Soviet spacecraft had already accomplished several historic lunar firsts. Luna 2 had become the first human-made object to reach another celestial body. Luna 3 had photographed the Moon's far side. Luna 9 had achieved the first successful soft landing. Luna 10 had become the first artificial satellite of the Moon. Luna 16 had returned lunar material robotically to Earth. And Lunokhod 1 was operating as the first successful remotely controlled rover on another world. Luna 19 represented another kind of investigation. Rather than landing, the spacecraft entered lunar orbit in early October and began systematically studying the Moon from above. Its scientific program included investigations of the Moon's gravitational field, surface environment, radiation conditions, and other properties. Orbital tracking was particularly useful for improving knowledge of variations in lunar gravity. Those variations were not merely academic. Earlier lunar spacecraft had revealed gravitational concentrations known as **mascons—mass concentrations—**beneath some of the Moon's great impact basins. Their gravitational pull could perturb the orbit of a spacecraft. Understanding the lunar gravity field was therefore important both scientifically and operationally. Luna 19 continued returning information from lunar orbit into 1972.

Why It Matters: Luna 19 formed part of the Soviet Union's broad robotic investigation of the Moon. Its orbital observations helped refine understanding of the lunar environment and gravity field, demonstrating that exploration required not merely reaching or landing on the Moon but systematically mapping and measuring it.

 

The Bigger Picture

September 28 gives us two very different telescopic views of the universe—and then shows what happened when humanity began building machines capable of leaving Earth altogether. In 1951, Seth Nicholson used Mount Wilson's 100-inch Hooker Telescope to identify a tiny new moon orbiting Jupiter. Two years later, Edwin Hubble died, leaving behind a scientific legacy built in large part with that very same telescope. That coincidence is particularly evocative. Nicholson used the Hooker Telescope to enlarge our knowledge of a planetary system. Hubble used it to enlarge our conception of the universe. One instrument could reveal a faint moon accompanying a nearby planet and help demonstrate that apparently faint patches of light were actually enormous galaxies far beyond our own. Then came the Space Age. Luna 19 no longer needed to examine the Moon from Earth. Humanity could send an observatory into orbit around the Moon itself.

And Falcon 1 represents another transformation. For most of the Space Age, the ability to place substantial objects into orbit had belonged principally to national governments and the large industrial organizations working for them. Falcon 1 suggested another model. Private companies might develop their own orbital launch systems and sell transportation to governments, scientists, businesses, and other customers. The consequences became increasingly visible during the following decades. The progression across September 28 is therefore remarkable: look through a telescope → discover new worlds → discover a universe of galaxies → send machines to another world → broaden who can build the machines that reach space. There is another lesson in Falcon 1's story. The rocket that reached orbit on September 28 was Flight 4. Flights 1, 2, and 3 had failed. Had the history ended with any one of those attempts, Falcon 1 might have been remembered as an unsuccessful experiment. Instead, engineers examined what had gone wrong, changed the vehicle, and tried again. Fifty-five days after the third failure, Falcon 1 reached orbit. September 28 therefore illustrates something we have encountered repeatedly in the history of astronomy and space exploration: progress is not the absence of failure. Very often, progress is what happens when people understand a failure well enough to make the next attempt different.

At a Glance

1951 — Observation time not established — Seth Barnes Nicholson discovers Ananke, an irregular moon of Jupiter, on a photograph obtained with Mount Wilson's 100-inch Hooker Telescope.

1953 — Time unknown — Edwin Hubble dies in California, leaving a legacy that helped establish extragalactic astronomy and modern observational cosmology.

1971 — Launch time not established — The Soviet Union launches Luna 19, beginning a mission to study the Moon from orbit.

2008 — 23:15 UTC — Falcon 1 lifts off from Omelek Island and becomes the first privately developed and funded liquid-fueled rocket to reach Earth orbit.

September 27

 A Journey to Two Worlds

2007 — Dawn Begins Its Journey to Vesta and Ceres

11:34 UTC

On September 27, 2007, NASA's Dawn spacecraft lifted off from Cape Canaveral aboard a Delta II Heavy rocket and began an extraordinary journey into the asteroid belt. Its destination was not one world. It was two. Dawn had been designed to investigate Vesta and Ceres, two of the largest bodies in the main asteroid belt between Mars and Jupiter. They had formed in the same general region of the early solar system, yet they evolved into remarkably different worlds. Vesta is dry, rocky, and heavily cratered—a protoplanet, or surviving planetary building block, whose interior differentiated into layers much as the terrestrial planets did. Ceres is larger, richer in water-bearing minerals and volatile materials, and massive enough for gravity to have pulled it into a nearly spherical shape. Today it is classified as a dwarf planet. By studying both with the same spacecraft and instruments, scientists hoped to understand why two bodies formed relatively close to one another could follow such different evolutionary paths. Dawn's journey depended upon a technology that had already proved itself on another remarkable spacecraft: ion propulsion. Instead of burning large quantities of chemical propellant to produce enormous thrust for a short time, Dawn electrically accelerated ions of xenon gas to extremely high speeds. The resulting thrust was extraordinarily gentle. At maximum thrust, Dawn would require about four days to accelerate from zero to 60 miles per hour. But an ion engine can continue operating for weeks or months. The result is cumulative. A tiny push maintained for a very long time can eventually change a spacecraft's velocity by an amount difficult to achieve with conventional chemical propulsion. Dawn carried three ion thrusters and approximately 425 kilograms of xenon propellant. Its enormous solar arrays—each about 8.3 meters long—generated the electrical power necessary to operate them. That propulsion system made Dawn's unprecedented itinerary possible. After launch, Dawn spent years gradually reshaping its orbit around the Sun. It flew past Mars in February 2009, using the planet's gravity to assist its journey toward Vesta. In July 2011, Dawn entered orbit around Vesta. For more than a year, it mapped and studied the protoplanet. Its observations revealed an enormous impact basin near Vesta's south pole, complex geological structures, and evidence confirming connections between Vesta and a class of meteorites found on Earth. Then Dawn did something no spacecraft had ever done. It left orbit around one extraterrestrial body and traveled to another. In September 2012, Dawn departed Vesta. Its ion engines gradually carried it farther through the asteroid belt. On March 6, 2015, Dawn entered orbit around Ceres, becoming the first spacecraft to orbit a dwarf planet. There it discovered a world far more geologically interesting than many scientists had anticipated. The famous bright deposits in Occator Crater proved to contain salts, evidence of briny material that had reached the surface. Dawn also found widespread evidence for water-related minerals and helped reveal Ceres as a chemically and geologically complex world. The spacecraft remained in orbit around Ceres until 2018, when it exhausted the hydrazine needed to control its orientation. NASA deliberately left Dawn in a stable orbit rather than allowing it to crash onto Ceres, partly because of planetary-protection considerations. The spacecraft may remain there for decades.

Why It Matters: Dawn was the first spacecraft to orbit two extraterrestrial destinations and the first to orbit a dwarf planet. Its long-duration ion propulsion system turned what would otherwise have required separate missions into a single voyage of comparative planetary exploration, revealing Vesta and Ceres as two very different survivors from the formation of the solar system.

 

Also on This Day

2003 — SMART-1 Begins Europe's First Mission to the Moon

23:14:46 UTC

On September 27, 2003, the European Space Agency's SMART-1 spacecraft lifted off aboard an Ariane 5 rocket from Europe's spaceport in Kourou, French Guiana. Its name stood for Small Missions for Advanced Research in Technology. Like NASA's Deep Space 1 before it—and Dawn after it—SMART-1 was both an explorer and a technology experiment. Its destination was the Moon, but getting there was part of the experiment. SMART-1 became ESA's first lunar mission and its first mission to use solar-electric propulsion as its primary means of traveling through space. The spacecraft carried only about 82.5 kilograms of xenon propellant for its electric propulsion system. Instead of following the relatively rapid trajectories used by Apollo spacecraft, SMART-1 began in an elongated Earth orbit and used its low-thrust electric engine to gradually enlarge that orbit. The process took months. SMART-1 fired its engine repeatedly, slowly spiraling farther from Earth while also exploiting the gravitational influence of the Moon. It was an extraordinarily fuel-efficient way to travel. The journey took more than a year, but SMART-1 was eventually captured by lunar gravity and entered orbit around the Moon. Once there, the spacecraft conducted scientific observations with a suite of miniaturized instruments. It mapped the lunar surface, investigated its mineral composition, studied the chemical elements present in lunar rocks, and searched for evidence related to water near the lunar poles. SMART-1 also tested technologies in communications, spacecraft autonomy, and compact scientific instrumentation that could be useful on future European deep-space missions. After completing its work, controllers deliberately lowered SMART-1's orbit. On September 3, 2006, the spacecraft struck the Moon in a controlled impact, allowing astronomers on Earth to observe the resulting flash and ejecta.

Why It Matters: SMART-1 was Europe's first lunar mission and demonstrated that solar-electric propulsion could be used for travel beyond Earth orbit. Its combination of technology demonstration and lunar science helped prepare ESA for more ambitious planetary exploration.

2008 — Zhai Zhigang Conducts China's First Spacewalk

Approximately 08:40–08:58 UTC

On September 27, 2008, Zhai Zhigang opened the hatch of China's Shenzhou 7 spacecraft and emerged into space. He became the first Chinese citizen to perform a spacewalk. Shenzhou 7 had launched two days earlier carrying Zhai, Liu Boming, and Jing Haipeng. China had already demonstrated that it could independently launch people into orbit. Yang Liwei had made China's first crewed orbital flight aboard Shenzhou 5 in 2003, and Shenzhou 6 had carried two crew members in 2005. Now China was attempting another essential capability: learning to work outside the spacecraft. Zhai wore the Chinese-developed Feitian spacesuit. The name, meaning roughly “flying in the heavens,” had deep roots in Chinese art and culture. Technically, however, the suit was a highly sophisticated personal spacecraft. It had to maintain pressure around Zhai's body, supply oxygen, remove carbon dioxide and heat, provide communications, and protect him from the vacuum and thermal extremes of space. Liu Boming assisted from the hatch wearing a Russian-derived Orlan spacesuit. At approximately 08:40 UTC, Zhai emerged from the orbital module. Television viewers in China and around the world watched live as he moved outside the spacecraft and waved a Chinese flag. During the excursion, he also retrieved a sample of solid lubricant that had been mounted outside Shenzhou 7 before launch. Scientists could examine the material after its exposure to the space environment. The spacewalk lasted only about 20 minutes. But its importance was much greater than its duration. Extravehicular activity is essential for many complex human-spaceflight operations. The United States and Soviet Union had used spacewalks to conduct experiments, repair spacecraft, service satellites, and ultimately construct large orbital complexes. China was developing the same capability. Years later, Chinese astronauts would perform increasingly complex spacewalks while assembling and maintaining the Tiangong space station.

Why It Matters: Zhai Zhigang's excursion made China the third nation, after the Soviet Union and United States, to independently conduct a spacewalk. It demonstrated spacesuit, airlock, life-support, and operational capabilities essential to China's later development of a permanently crewed space station.

 

The Bigger Picture

September 27 is a remarkable date because all three of its major stories concern something space exploration must eventually learn to do: move beyond the simplest way of getting somewhere.

The earliest planetary spacecraft generally used chemical rockets to receive most of the velocity they needed near the beginning of their journeys. Once released toward their destinations, they largely coasted along carefully calculated trajectories, occasionally making relatively small corrections. Ion propulsion introduced another possibility. A spacecraft could continue accelerating—not dramatically, but patiently. SMART-1 demonstrated how that approach could slowly carry a European spacecraft from Earth orbit to the Moon.

Four years later, Dawn began an even more ambitious application of the idea. Its engines allowed the spacecraft not merely to fly past Vesta and Ceres, but to enter orbit around Vesta, leave that orbit, cross the asteroid belt, and enter orbit around Ceres. That is a profound change in what a single planetary spacecraft can do. Shenzhou 7 tells the human version of a similar story. Reaching orbit is one capability. Living and working beyond the protective shell of a spacecraft is another. Zhai Zhigang's brief excursion outside Shenzhou was therefore not simply a spectacular demonstration. It was one step in China's progression: reach orbit → send multiple crew members → conduct a spacewalk → rendezvous and dock → build a space station.

September 27 consequently reminds us that exploration develops through capabilities. A new propulsion system changes the destinations a spacecraft can reach. A new spacesuit changes where an astronaut can work. A new navigation system changes what a spacecraft can attempt without constant guidance from Earth. And once a capability has been demonstrated, the next mission can build upon it. There is also a particularly satisfying historical connection between SMART-1 and Dawn. On September 27, 2003, Europe launched a spacecraft whose gentle electric engine would slowly carry it toward the Moon. Exactly four years later, on September 27, 2007, Dawn launched with ion propulsion that would eventually carry it into orbit around two separate worlds. The technology had progressed from experiment to extraordinary scientific tool.

At a Glance

2003 — 23:14:46 UTC — ESA's SMART-1 launches from French Guiana, beginning Europe's first lunar mission and a major demonstration of solar-electric propulsion.

2007 — 11:34 UTC — NASA's Dawn spacecraft launches from Cape Canaveral to explore Vesta and Ceres.

2008 — Approximately 08:40 UTC — Zhai Zhigang emerges from Shenzhou 7 and begins China's first spacewalk.

2008 — Approximately 08:58 UTC — Zhai completes the historic excursion and returns inside Shenzhou 7.

September 26

Moving a World 

2022 — DART Strikes Dimorphos 

23:14:24 UTC 

On September 26, 2022, a spacecraft weighing roughly 570 kilograms raced toward a small asteroid moon at approximately 6.1 kilometers per second—14,000 miles per hour. 

Its destruction was not a failure. 

It was the mission. 

At 23:14:24 UTC, NASA's Double Asteroid Redirection Test, or DART, slammed into Dimorphos, a small moon orbiting the larger near-Earth asteroid Didymos. The collision marked humanity's first full-scale experiment designed to determine whether deliberately striking an asteroid could measurably change its motion. Neither Didymos nor Dimorphos posed a threat to Earth. That was precisely why the system was useful. Dimorphos, approximately 160 meters (525 feet) across, orbited Didymos, which is about 780 meters (2,560 feet) across. Because astronomers could measure the smaller body's orbit around its companion, they could determine whether DART's impact changed that orbit without needing to alter the asteroid system's trajectory around the Sun enough to create a hazard. DART had launched on November 24, 2021. For most of its journey, controllers on Earth guided and monitored the spacecraft. But during the final approach, the mission faced an unavoidable problem: radio signals could not travel between Earth and the spacecraft quickly enough for humans to steer DART into such a small moving target in real time. The spacecraft therefore had to finish the job itself. Its autonomous navigation system, SMART Nav, used images from DART's DRACO camera to distinguish Didymos from Dimorphos and guide the spacecraft toward the smaller body. During the final minutes, images arriving on Earth showed Dimorphos growing from a tiny point into a recognizable world. Its surface was unexpectedly covered with rocks and boulders. Then the images stopped. DART had struck its target. But the impact itself was only the beginning of the experiment. Astronomers around the world used ground-based and space-based telescopes to observe the aftermath and measure Dimorphos's orbit. Before impact, the moonlet took approximately 11 hours 55 minutes to orbit Didymos. NASA initially reported that DART shortened that period by about 32 minutes, vastly exceeding the mission's minimum-success criterion of 73 seconds. Continued measurements subsequently refined the change to roughly 33 minutes. The collision also excavated enormous amounts of material from Dimorphos. That ejecta carried momentum of its own, enhancing the effect of the impact—rather like the recoil produced when material is thrown in the opposite direction. A small Italian Space Agency spacecraft named LICIACube, which DART had released before impact, flew past the asteroid system minutes later and photographed the expanding debris. Telescopes including Hubble and James Webb also observed the event and its aftermath. DART's experiment was not designed to destroy Dimorphos or knock it dramatically out of its solar orbit. Planetary defense generally does not require such an extreme intervention. If a hazardous asteroid were discovered sufficiently far in advance, even a very small change in its velocity could accumulate over years into a large change in position. The goal would be to make the asteroid arrive at the point where it would otherwise intersect Earth's orbit a little earlier or a little later—when Earth is somewhere else. 

Why It Matters: DART was the first mission to demonstrate a technique for changing the motion of a celestial body through kinetic impact. Humanity had spent centuries discovering asteroids and decades sending spacecraft to study them. On September 26, 2022, we demonstrated that—with sufficient warning—we may also be capable of changing an asteroid's trajectory to protect Earth. 

 

Also on This Day 

1960 — Pioneer 5 Becomes the Most Distant Human-Made Object in Communication with Earth 

Record date; precise time not established 

On September 26, 1960, NASA's Pioneer 5 reached a communications milestone as it traveled through interplanetary space. Launched on March 11, Pioneer 5 was designed primarily to investigate the environment between Earth and Venus. The small spacecraft carried instruments to measure magnetic fields, cosmic radiation, and solar particles. Unlike satellites confined to Earth orbit, Pioneer 5 entered a heliocentric orbit—an orbit around the Sun. As the spacecraft receded from Earth, engineers faced a challenge fundamental to deep-space exploration: could radio communication be maintained across increasingly enormous distances? On September 26, Pioneer 5 transmitted data from approximately 36.2 million kilometers—22.5 million miles—from Earth, establishing what was then a record for communications with a spacecraft. The accomplishment may appear modest beside the billions of kilometers across which later missions such as Voyager would communicate. But those later achievements depended upon the development of deep-space radio systems, tracking networks, sensitive antennas, and techniques first tested during missions like Pioneer. Pioneer 5 also returned valuable scientific measurements of the interplanetary magnetic field and solar energetic particles, helping scientists understand that the region between planets was not simply empty space. 

Why It Matters: Pioneer 5 helped demonstrate that spacecraft could remain scientifically useful and communicate with Earth far beyond the immediate neighborhood of our planet. Its work contributed to the communications and tracking techniques upon which later planetary exploration depended. 

1983 — Soyuz T-10-1 Crew Escapes a Launch-Pad Explosion 

19:37:49 UTC 

On September 26, 1983, cosmonauts Vladimir Titov and Gennady Strekalov sat atop a fully fueled Soyuz launch vehicle at Baikonur, preparing for a mission to the Salyut 7 space station. Then the rocket caught fire. Approximately 90 seconds before the planned launch, a valve problem caused fuel to spill near the base of the vehicle. Fire rapidly spread around the rocket. The crew was now sitting atop hundreds of tons of propellant in a launch vehicle that could explode at any moment. Ground controllers attempted to activate the spacecraft's launch escape system. The normal command path had been disrupted by the fire, requiring controllers at separate locations to send commands nearly simultaneously before the system would respond. It activated. Explosive bolts separated the Soyuz descent and orbital modules from the rest of the spacecraft, and powerful solid-fueled escape rockets pulled the crew capsule away from the burning booster. Only seconds later, the launch vehicle exploded. The escape system accelerated the capsule rapidly upward, subjecting Titov and Strekalov to forces estimated around 14 to 17 g for several seconds. The capsule climbed roughly a kilometer before separating from the escape tower and descending by parachute. Approximately five minutes after the emergency began, the cosmonauts landed a few kilometers from the launch pad. Both survived. The mission never received the normal Soyuz flight designation because it never reached orbit. It is commonly identified as Soyuz T-10-1, and in some Soviet records as Soyuz T-10A.  

Why It Matters: The Soyuz T-10-1 accident provided a dramatic real-world demonstration of the value of a launch escape system. The rocket was destroyed, but its crew survived because engineers had designed for a catastrophe they hoped would never occur. Human spaceflight safety depends not only on preventing failures but also on providing a way to survive them. 

1996 — Shannon Lucid Returns After a Record 188 Days in Space 

12:13:20 UTC 

On September 26, 1996, Space Shuttle Atlantis touched down at Kennedy Space Center, bringing astronaut Shannon Lucid home after an extraordinary 188 days in space. Lucid had launched aboard Atlantis on STS-76 on March 22 and transferred to the Russian space station Mir. She had originally expected to remain aboard for approximately four months. But delays to the Shuttle mission scheduled to retrieve her—including hurricane-related launch-pad rollbacks—extended her stay considerably. Lucid adapted. For more than six months, she lived and worked aboard Mir alongside Russian cosmonauts. She conducted life-science, materials, biotechnology, and other experiments while becoming part of the station's daily operations. Her mission was scientifically valuable, but it also represented an important human experiment in international cooperation. Only a few years had passed since the end of the Cold War. Now an American astronaut was living for months aboard a Russian space station, working within a different language, culture, engineering system, and operational environment. Atlantis arrived at Mir on STS-79 in September carrying John Blaha, who replaced Lucid as NASA's resident astronaut. After the crew exchange, Lucid boarded Atlantis for the journey home. At 12:13:20 UTC on September 26, the Shuttle landed at Kennedy Space Center. Her 188 days, 4 hours in space established a new American single-flight endurance record and a world endurance record for a woman. The American record remained hers until 2002; her women's record stood until 2007. President Bill Clinton later awarded Lucid the Congressional Space Medal of Honor.  

Why It Matters: Shannon Lucid demonstrated that American astronauts could live and work productively for months aboard a foreign space station. Her mission provided valuable experience in long-duration spaceflight and international operations that helped prepare NASA and Russia for the International Space Station. 

2019 — Soyuz MS-15 Completes the Final Crewed Launch from Gagarin's Start 

13:57:43 UTC 

On September 25 UTC—rather than September 26—2019, Soyuz MS-15 launched from Baikonur's historic Site No. 1, known as Gagarin's Start. Because some anniversary lists associate the mission with September 26 through docking or local-calendar reporting, it can appear under this date. Under our project's UTC convention, however, its launch does not belong in the September 26 chronology. Its significance remains worth noting for editorial purposes: the launch carried Jessica Meir, Oleg Skripochka, and Hazzaa AlMansoori, the first Emirati in space, and became the final crewed launch from the same launch complex used by Yuri Gagarin in 1961. We should therefore reserve that story for September 25 if we choose to include it when assembling or revising that entry. 

 

The Bigger Picture 

September 26 tells an unusually coherent story about risk. Pioneer 5 confronted the risks of distance. The farther a spacecraft traveled from Earth, the weaker its radio signal became. Engineers had to learn how to maintain contact across interplanetary space before more ambitious planetary missions could succeed. Soyuz T-10-1 confronted the immediate physical danger of human spaceflight. Engineers could not guarantee that a rocket would never explode, so they built another system whose sole purpose was to save the crew when everything else failed. Shannon Lucid confronted a different kind of challenge: duration. Living in space for more than six months demanded physical adaptation, psychological resilience, dependable life-support systems, and cooperation between people and organizations from different nations. And DART confronted a risk on an entirely different scale. Asteroid impacts are natural events. Earth's surface—and the cratered surfaces of the Moon and other worlds—preserve abundant evidence that such collisions are part of the history of the solar system. For almost all of human existence, nothing could have been done about that danger. Astronomy changed the situation. Telescopes allow us to discover near-Earth objects. Mathematics allows us to calculate their future paths. Spacecraft allow us to reach them. DART added another possibility: perhaps we can move one. That is a remarkable progression. We learned to communicate across interplanetary distances. We learned to protect people when rockets fail. We learned to live in space for months. And eventually we began testing whether knowledge of the heavens could be used to protect the planet from which all of those journeys began. September 26 therefore represents one of the deepest purposes of astronomy. For thousands of years, people watched the sky partly because the heavens affected life on Earth. DART brought that ancient relationship into the Space Age. We study the sky not only to understand what is out there, but sometimes to protect what is here. 

At a Glance 

1960 — Precise time not established — Pioneer 5 communicates with Earth from approximately 36.2 million kilometers away, establishing a deep-space communications record. 

1983 — 19:37:49 UTC — The Soyuz T-10-1 launch escape system pulls Vladimir Titov and Gennady Strekalov away from their burning rocket seconds before it explodes. 

1996 — 12:13:20 UTC — Space Shuttle Atlantis lands at Kennedy Space Center, returning Shannon Lucid after 188 days in space. 

2022 — 23:14:24 UTC — NASA's DART spacecraft deliberately strikes Dimorphos at approximately 6.1 kilometers per second, conducting the first full-scale test of asteroid deflection by kinetic impact.