September 22

 Face to Face with a Comet 

2001 — Deep Space 1 Flies Past Comet Borrelly 

22:29:33 UTC 

On September 22, 2001, NASA's Deep Space 1 swept past the nucleus of Comet 19P/Borrelly, completing an encounter that its designers had never originally required the spacecraft to make. 

At 22:29:33 UTC, Deep Space 1 made its closest approach, passing approximately 2,171 kilometers (1,349 miles) from the comet's nucleus while traveling about 16.6 kilometers per second relative to it. 

The spacecraft entered Borrelly's coma—the cloud of gas and dust surrounding its nucleus—and returned what were then the highest-resolution images ever obtained of a cometary nucleus. 

That accomplishment was remarkable because Deep Space 1 had not primarily been built as a comet mission. 

Launched in 1998 as part of NASA's New Millennium Program, the spacecraft was designed to test advanced technologies that could make future planetary missions more capable and autonomous. Among them was a form of solar-electric ion propulsion, in which electrically charged xenon atoms were accelerated to extremely high speeds to provide a small but continuous thrust. 

Unlike a conventional chemical rocket, an ion engine produces very little thrust at any given moment. But because it can operate efficiently for extraordinarily long periods, it can gradually accelerate a spacecraft to substantial velocities while using relatively little propellant. 

Deep Space 1 also tested autonomous navigation, advanced spacecraft electronics, a compact camera and spectrometer, and software intended to allow spacecraft to make more decisions without waiting for instructions from Earth. 

By July 1999, the spacecraft had successfully demonstrated all of its primary technologies. It also flew past asteroid 9969 Braille, although navigational difficulties prevented the close encounter originally planned. 

Its primary mission was essentially complete. 

Then NASA gave Deep Space 1 another assignment: fly past Comet Borrelly. 

The extended mission nearly ended before the spacecraft could get there. In November 1999, Deep Space 1's star tracker failed. Without it, the spacecraft could not reliably determine its orientation in space, threatening both communications with Earth and operation of its ion engine. 

Rather than abandon the spacecraft, engineers spent months developing a new attitude-control system. They reprogrammed Deep Space 1 to use its science camera in place of the failed star tracker. 

The improvised system worked. 

Deep Space 1 resumed its journey and reached Borrelly on September 22, 2001. 

The images it returned revealed an elongated, irregular nucleus roughly 8 kilometers (5 miles) long, covered by an extremely dark surface. The observations also showed that jets of material streaming from the comet were associated with particular regions of the nucleus rather than being emitted uniformly across its surface. 

Instruments aboard the spacecraft measured gases, plasma, infrared radiation, and the interaction between the comet's escaping material and the solar wind. 

Deep Space 1 had been sent into space to demonstrate technologies for future explorers. By surviving long enough to reach Borrelly, it became an important scientific explorer itself. 

Why It Matters: Deep Space 1 demonstrated technologies—including ion propulsion and autonomous navigation—that would influence later planetary missions. Its encounter with Borrelly also produced the most detailed views of a cometary nucleus obtained to that time. Perhaps just as importantly, the mission demonstrated the value of ingenuity on Earth: engineers rescued a spacecraft hundreds of millions of kilometers away and enabled it to accomplish a mission that once appeared lost. 

 

Also on This Day 

1931 — Planetary Astronomer Bradford A. Smith Is Born 

Time unknown 

On September 22, 1931, Bradford A. Smith was born in Cambridge, Massachusetts. 

Smith would become one of the important figures in the development of modern planetary imaging, helping transform distant planets from blurry telescopic disks into detailed worlds. 

His career became particularly associated with NASA's great robotic missions to the outer solar system. 

Smith participated in the imaging teams for the Mariner 6 and 7 missions to Mars, later becoming involved with Mariner 9 and the Viking missions. But his most influential work came as leader of the imaging science team for the Voyager missions. 

Voyager 1 and Voyager 2 carried television camera systems that returned tens of thousands of photographs during their journeys through the outer solar system. Smith and the international team of scientists working with those images helped interpret a succession of extraordinary discoveries. 

The Voyager cameras revealed active volcanoes erupting on Io, intricate structures within Saturn's rings, previously unknown moons, the fractured surfaces of icy satellites, Uranus's unusual system of rings and moons, and Neptune's turbulent atmosphere. 

The images were scientifically important, but they also had an enormous cultural effect. 

Before Voyager, the giant planets and their moons were primarily telescopic objects. After Voyager, people could see them as places—worlds with mountains, craters, clouds, rings, volcanoes, fractures, and changing weather. 

Smith also participated in the discovery of several planetary satellites and contributed extensively to the scientific interpretation of spacecraft imagery. 

Why It Matters: Bradford Smith belonged to the generation of astronomers who transformed planetary science through spacecraft imaging. Under his leadership, Voyager's cameras revealed the outer solar system with unprecedented detail and helped change both scientific and public perceptions of the planets and moons beyond Mars. 

1968 — The Soviet Union Announces Zond 5's Historic Lunar Voyage 

Announcement time not established 

On September 22, 1968, the Soviet news agency TASS publicly announced the successful completion of Zond 5's journey around the Moon and return to Earth. 

The spacecraft had actually splashed down in the Indian Ocean the previous day, September 21. Soviet authorities, however, did not immediately announce the mission's successful conclusion. 

When the announcement came on September 22, it described an extraordinary accomplishment. 

Zond 5 had traveled from Earth around the Moon and back, tested spacecraft systems needed for future lunar missions, investigated the environment near the Moon, survived high-speed atmospheric reentry, descended by parachute, and been recovered from the Indian Ocean. 

Its biological passengers included two Russian steppe tortoises along with flies, worms, plants, seeds, bacteria, and other organisms. 

The tortoises survived. 

Although Zond 5 carried no people, the spacecraft was closely related to hardware intended for a Soviet crewed circumlunar mission. Its successful return therefore carried implications far beyond the biological experiment. 

The United States was preparing Apollo 7 for its first crewed flight, but no human being had yet traveled beyond low Earth orbit. Zond 5 demonstrated that Soviet hardware could travel around the Moon and return safely. 

American officials had additional reason for concern. U.S. reconnaissance satellites had observed the enormous Soviet N1 lunar rocket, suggesting that the Soviet Union remained actively engaged in the race to send people toward the Moon. 

Zond 5's success became part of the environment in which NASA made one of the boldest decisions in its history: sending Apollo 8 around the Moon in December 1968. 

Why It Matters: The September 22 announcement made clear to the world that the Soviet Union had successfully completed a circumlunar flight and recovery. It demonstrated significant progress toward crewed lunar travel and contributed to the urgency surrounding America's decision to send Apollo 8 to the Moon before the end of 1968. 

1993 — Discovery Completes STS-51 with a Historic Night Landing 

07:56:11 UTC 

On September 22, 1993, Space Shuttle Discovery touched down at Kennedy Space Center at 07:56:11 UTC, completing the nearly ten-day STS-51 mission. 

The landing itself established an unusual Shuttle milestone: it was the first end-of-mission nighttime landing at Kennedy Space Center. 

Discovery's five-person crew—Frank Culbertson, William Readdy, James Newman, Daniel Bursch, and Carl Walz—had launched on September 12. 

During the mission, the crew deployed the Advanced Communications Technology Satellite, or ACTS. The satellite tested technologies intended to increase the capacity and efficiency of satellite communications, including advanced switching and high-frequency Ka-band communications. 

The mission also deployed and later retrieved ORFEUS-SPAS, the Orbiting and Retrievable Far and Extreme Ultraviolet Spectrometer-Shuttle Pallet Satellite. 

After being released from Discovery's robotic arm, ORFEUS-SPAS flew independently near the Shuttle while its instruments studied astronomical objects in ultraviolet wavelengths largely blocked by Earth's atmosphere. Near the end of the mission, the crew retrieved the satellite and returned it to the payload bay for the journey home. 

Astronauts Newman and Walz also conducted a seven-hour spacewalk intended in part to evaluate tools and procedures that could be used in the construction and maintenance of the future International Space Station. 

After 9 days, 20 hours, 11 minutes, and 11 seconds in space, Discovery landed on Runway 15 at Kennedy. 

Why It Matters: STS-51 combined communications technology, ultraviolet astronomy, satellite deployment and retrieval, and preparation for future space-station assembly. Its nighttime return also demonstrated the Shuttle program's increasing operational flexibility as missions became more complex. 

 

The Bigger Picture 

September 22 offers an interesting lesson about the relationship between technology and discovery. 

Bradford Smith's career reminds us that exploration requires people capable of interpreting what new instruments reveal. A spacecraft camera is an engineering achievement, but the images become scientific knowledge through the work of astronomers and planetary scientists. 

Zond 5 demonstrates technology as a source of possibility. Its successful circumlunar voyage showed that hardware intended ultimately to carry people around the Moon was approaching readiness. 

STS-51 demonstrates technology as a platform. The Space Shuttle could deploy one spacecraft, release another to conduct astronomical observations, retrieve it, support a spacewalk, and return everything to Earth. 

But Deep Space 1 may illustrate the principle most clearly. 

Its primary purpose was to test technologies for spacecraft that had not yet been built. Its ion engine, autonomous navigation, miniature instruments, and advanced electronics were intended to make later missions possible. 

Then the technology demonstrator became an explorer. 

And when part of that technology failed, human ingenuity created another solution. 

There is a useful pattern here: 

invent the instrument → test the technology → learn to operate it → use it to discover something no one has seen before. 

Astronomy and space exploration have always advanced this way. Galileo's telescope, Herschel's great reflectors, photographic plates, spectroscopy, radio antennas, spacecraft cameras, ion engines, and autonomous navigation systems are separated by centuries, but they share the same underlying purpose. 

Each gives humanity a new way to ask the universe a question. 

And sometimes—as Deep Space 1 demonstrated on September 22, 2001—the experimental machine built to test the future survives long enough to make a discovery of its own. 

At a Glance 

1931 — Time unknown — Planetary astronomer Bradford A. Smith, later leader of the Voyager imaging science team, is born in Cambridge, Massachusetts. 

1968 — Announcement time not established — The Soviet Union publicly announces the successful circumlunar flight and recovery of Zond 5. 

1993 — 07:56:11 UTC — Space Shuttle Discovery lands at Kennedy Space Center following STS-51, completing the first end-of-mission nighttime Shuttle landing at Kennedy. 

2001 — 22:29:33 UTC — Deep Space 1 makes its closest approach to Comet 19P/Borrelly at approximately 2,171 kilometers, returning the most detailed images of a cometary nucleus obtained to that time. 

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