NASA Headquarters, Washington
Jet Propulsion Laboratory, Pasadena, Calif.
Sept. 25, 2001
AGING NASA SPACECRAFT CAPTURES BEST-EVER VIEW OF COMET'S CORE
In a risky flyby, NASA's ailing Deep Space 1 spacecraft
successfully navigated past a comet, giving researchers the
best look ever inside the glowing core of icy dust and gas.
The space probe's close encounter with comet Borrelly provided the best-resolution pictures of the comet to date. The already-successful Deep Space 1, without protection from the little-known comet environment, whizzed by just 2,200 kilometers (1,400 miles) from the rocky, icy nucleus of the 10-kilometer-long (more than 6-mile-long) comet.
Exceeding the team's expectations of how this elderly spacecraft would perform, the intrepid spacefarer sent back black-and-white photos of the inner core of the comet. It also measured the types of gases and infrared waves around the comet, and how the gases interacted with the solar wind.
"Deep Space 1 plunged into the heart of comet Borrelly and has lived to tell every detail of its spine-tingling adventure!" said Dr. Marc Rayman, the project manager of Deep Space 1 at the Jet Propulsion Laboratory (JPL), Pasadena, Calif. "The images are even better than the impressive images of comet Halley taken by Europe's Giotto spacecraft in 1986."
Rayman added, "After years of nursing this aged and wounded bird along -- a spacecraft not structured to explore comets, a probe that exceeded its objectives more than two years ago -- to see it perform its remarkably complex and risky assignment so well was nothing short of incredible."
"It's mind-boggling and stupendous," said Dr. Laurence Soderblom, the leader of Deep Space 1's imaging team, and a geologist with the U.S. Geological Survey, Flagstaff, Ariz. "These pictures have told us that comet nuclei are far more complex than we ever imagined. They have rugged terrain, smooth rolling plains, deep fractures and very, very dark material."
Scientists also realized that Borrelly was different than they expected as Deep Space 1 flew through the coma, the cloud of dust and gas surrounding the nucleus. They had expected that the solar wind would flow symmetrically around the cloud, with the nucleus in the center.
Instead, they found that though the solar wind was flowing symmetrically around the cloud, the nucleus was off to one side shooting out a great jet of material forming the cloud that makes the comet visible from Earth. "The formation of the coma is not the simple process we once thought it was," said Dr. David Young of the University of Michigan, Ann Arbor, leader of the team that made the measurements. "Most of the charged particles are formed to one side, which is not what we expected."
Deep Space 1 completed its primary mission testing ion propulsion and 11 other advanced, high-risk technologies in September 1999. NASA extended the mission, taking advantage of the ion propulsion and other systems to undertake this chancy but exciting encounter with the comet.
Deep Space 1, launched in October 1998 as part of NASA's New Millennium Program, is managed by JPL for NASA's Office of Space Science in Washington. The California Institute of Technology manages JPL for NASA.
More information can be found on the Deep Space 1 Internet home page.
NEWSALERT: Monday, September 24, 2001 @ 0418 GMT
The latest news from Astronomy Now and Spaceflight Now
Deep Space 1 Mission Status
September 22, 2001
Deep Space 1's risky encounter with comet Borrelly has gone extremely well as the aging spacecraft successfully passed within 2,200 kilometers (about 1,400 miles) of the comet at 22:30 Universal Time (3:30 p.m. PDT) today.
"The images and other data we collected from comet Borrelly so far will help scientists learn a great deal about these intriguing members of the solar system family," said Dr. Marc Rayman, project manager of Deep Space 1 at NASA's Jet Propulsion Laboratory. "It's very exciting to be among the first humans to glimpse the secrets that this comet has held since before the planets were formed."
Signals confirming the successful encounter were received on Earth at 3:43 p.m. PDT, and data containing the first clues to the composition of the comet came a few hours after the close brush with the comet.
Mission managers confirmed that the spacecraft was able to use all four of its instruments at Borrelly. Data will be returned over the next few days as the spacecraft sends to Earth black-and-white pictures, infrared spectrometer measurements, ion and electron data, and measurements of the magnetic field and plasma waves around the comet. Pictures of the comet will be released after they are all sent to Earth in the next few days.
Several hours before the encounter, the ion and electron monitors began observing the comet's environment. The action increased about an hour and a half before the closest approach, when for two minutes the infrared spectrometer collected data that will help scientists understand the overall composition of the surface of the comet's nucleus. Deep Space 1 began taking its black-and-white images of the comet 32 minutes before the spacecraft's closest pass to the comet, and the best picture of comet Borrelly was taken just a few minutes before closest approach, as the team had planned. Two minutes before the spacecraft whizzed by the comet, its camera was turned away so that the ion and electron monitors could make a careful examination of the comet's inner coma the cloud of dust and gas that envelops the comet.
Scientists on Deep Space 1 hope to find out the nature of the comet's surface, measure and identify the gases coming from the comet, and measure the interaction of solar wind with the comet.
Deep Space 1 completed its primary mission testing ion propulsion and 11 other advanced, high-risk technologies in September 1999. NASA extended the mission, taking advantage of the ion propulsion and other systems to undertake this chancy but exciting encounter with the comet. More information can be found on the Deep Space 1 home page at nmp.jpl.nasa.gov/ds1/.
Deep Space 1 was launched in October 1998 as part of NASA's New Millennium Program, which is managed by JPL for NASA's Office of Space Science, Washington, D.C. The California Institute of Technology manages JPL for NASA.
============================================================== SKY & TELESCOPE'S NEWS BULLETIN - SEPTEMBER 21, 2001 ============================================================== For images and Web links for these items, visit www.skypub.com ==============================================================
But a comet-chaser it has become. On September 22nd at about 22:30 Universal Time (3:30 p.m. PDT), Deep Space 1 is programmed to slip past the nucleus of Comet Borrelly at a range of roughly 2,000 kilometers (1,250 miles). Racing through the comet's gas-and-dust coma at 16.5 km (10 miles) per second, the spacecraft will attempt to pivot toward the bright nucleus in order to capture details of its surface. Meanwhile, a plasma spectrometer will "taste" the coma's ionized gases to determine their composition, and sensors that ordinarily monitor the ion engine's performance will record the electromagnetic environment inside the coma.
All this presumes that the spacecraft can spot the comet early enough to have time to maneuver close to it. Deep Space 1's tracking camera failed in November 1999, just a few months after a mixed-success flyby of asteroid 9969 Braille. So now the "science" camera, known formally as MICAS, must perform the tracking duties. A pointing error of little more than 1/4 deg means that scientists waiting on Earth will see blank computer screens. Yet they will be powerless to correct it from 220 million km away, because at that distance a round-trip radio exchange takes more than 24 minutes to complete. Flight controllers are also concerned that the aging spacecraft will run out of hydrazine fuel for its thrusters before the flyby occurs.
Still, the potential for scientific reward is great. Comet Borrelly (designated 19P) circles the Sun every 6.9 years and has a reputation for predictable behavior - though in 1994-95 its coma became very elongated. The comet's nucleus, which usually looks intense and starlike through telescopes, is probably no bigger than 10 km across. Deep Space 1's flyby will take place just a week after Borrelly's closest approach to the Sun, so the coma should be large and active. Amateur astronomers report that the comet, currently near the Cancer-Gemini border, is about 10th magnitude.
Today on SPACE.com -- Thursday, September 20, 2001
Universe Today
Space News for September 19, 2001
NEWSALERT: Wednesday, September 19, 2001 @ 0432 GMT
The latest news from Astronomy Now and Spaceflight Now
Jet Propulsion Laboratory
September 18, 2001
Deep Space 1, which has already completed a highly successful mission testing a number of advanced spacecraft technologies, will attempt to pass inside the mostly unknown environment just 2,000 kilometers (about 1,200 miles) from the nucleus of comet Borrelly at 2230 Universal time (3:30 p.m. PDT) on Sept. 22.
"It has been a tremendously rewarding effort for the small Deep Space 1 team to keep this aged and wounded bird aloft," said Dr. Marc Rayman, project manager of Deep Space 1 at NASA's Jet Propulsion Laboratory, Pasadena, Calif. "Its mission to test new technologies is already highly successful and any science we get at the comet will be a terrific bonus."
By the time of the flyby Deep Space 1 will have completed three times its intended lifetime in space and its primary mission to test ion propulsion and 11 other high-risk, advanced technologies in September 1999. NASA extended the mission, taking advantage of the ion propulsion and other systems to target a chancy but exciting encounter with Borrelly.
The spacecraft may tell us more about comets and their place in the solar system. The robotic explorer will attempt to investigate the comet's environment when it tries to fly through the cloud of gas and dust surrounding the comet's nucleus, known as the coma.
The risks involved in gathering science data are very high, so results of this latest venture are unpredictable. The spacecraft will be traveling through a cloud of gas, dust and comet pieces to collect its data. Since Deep Space 1 wasn't built to go to a comet, it does not carry a protective shield. "We expect to be hit by debris from the comet, and at 16.5 kilometers per second (about 36,900 mph), even a tiny particle might prove fatal," said Rayman. "But this is an adventure too exciting to pass up."
If all goes well, scientists will use the comet chaser's measurements to find out the nature of Borrelly's surface and to measure and identify the gases coming from the comet. The spacecraft will also attempt to measure the interaction of solar wind with the comet, a process that leads to formation of the beautiful tail.
Borrelly makes a good target for study now, as it is just 1.34 astronomical units (about 200 million kilometers or 125 million miles) from the Sun -- the closest it will get for another seven years. The Sun's heat will make the gases escaping from the nucleus flow faster and more thickly, so they will be easier to study. The icy nucleus and the spacecraft will flash past each other at 16.5 kilometers per second (more than 36,900 miles per hour).
The flight team is also hoping that Deep Space 1 will have enough gas to get to the comet. The long-lived spacecraft keeps itself pointed correctly by firing small thrusters fueled by hydrazine gas. When the hydrazine runs out, Deep Space 1 will be unable to keep itself pointed correctly, and the spacecraft will die. The flight team has an estimate of how much gas is left, but a few hours' worth of gas could make all the difference in the comet encounter.
As it approaches the center of the coma, the spacecraft will face its greatest challenge: to obtain pictures and infrared measurements of the nucleus. Deep Space 1 can't tell exactly where the nucleus is or what it will look like. The craft will have to locate the nucleus on its own and try to point the camera toward it as it streaks by.
In late 1999, Deep Space 1 lost its star tracker, which helps determine the spacecraft's orientation. Faced with what could have been a mission-terminating injury, the controllers performed a spectacular ultra-long-distance rescue. They reconfigured the spacecraft to use the photographic camera to orient itself by the stars around it.
The camera cannot align the spacecraft and snap photos of Borrelly at the same time. Instead, Deep Space 1 will have to rely on its fiber-optic gyroscopes to help maintain its orientation. But the gyros are not accurate enough by themselves, so engineers designed complex new software to help the camera stay pointed at the comet's nucleus during the critical few minutes that the probe will be close enough to try to get a view of it.
More information can be found online at http://nmp.jpl.nasa.gov/ds1/.
Deep Space 1 was launched in October 1998 as part of NASA's New Millennium Program, which is managed by JPL for NASA's Office of Space Science, Washington. The California Institute of Technology in Pasadena manages JPL for NASA.
JET PROPULSION LABORATORY
CALIFORNIA INSTITUTE OF TECHNOLOGY
NATIONAL AERONAUTICS AND SPACE ADMINISTRATION
July 27, 2000
Deep Space 1 met or exceeded all of its primary mission objectives of testing 12 advanced, high-risk technologies in September 1999, providing important data for future users. However, engineers and scientists at NASA's Jet Propulsion Laboratory, Pasadena, CA, believed that even further challenges could be met. NASA approved an extended mission in order to gain more scientific knowledge of comets.
"NASA decided that it could afford to go ahead with a risky extended mission," said Paul Hertz, NASA Headquarters program executive for Deep Space 1. "The talented Deep Space 1 folks at JPL are working hard to squeeze a bonus science mission, an encounter with Comet Borrelly, out of this already successful mission. Although there is no guarantee of success, trying for the comet makes much more sense than just turning the spacecraft off."
Shortly after it began traveling to meet the comet, Deep Space 1 lost a critical sensor -- its star tracker -- to determine and control its orientation system.
"We had to rebuild a significant part of the spacecraft from hundreds of millions of kilometers away and complete it to begin ion-powered flight in time to keep our date with Comet Borrelly," said Project Manager Dr. Marc Rayman. "This was crucial, because the star tracker that had been used previously to determine the spacecraft's orientation in space failed in November 1999."
The star tracker determined orientation by tracking the positions of stars. Without the star tracker, Deep Space 1 did not know in which direction it was pointed. It couldn't thrust in the direction of the comet, since it didn't know which way to go. Use of the newly developed camera method allowed the spacecraft to regain full three-dimensional control.
Engineers at JPL radioed software to the spacecraft to reprogram the camera on board to serve as a replacement for the lost star tracker. This boost is helping Deep Space 1 go on to perform a mission that is above and beyond the plans at launch.
"In a very short time, the spacecraft operations team developed a very complex and innovative new system that gives Deep Space 1 a new chance to try to reach the comet," said Rayman. "The new system is working beautifully. I think this is one of the most impressive in-space rescues ever completed."
With Deep Space 1 knowing its orientation in space, controllers instructed the ion propulsion system to resume thrusting. Return data showed that the system was operating successfully and the spacecraft is on its way to Comet Borrelly.
Now that the software enables the spacecraft to point its antenna toward Earth on its own, more software will be transmitted to the spacecraft in February 2001.
Among the differences between the star tracker and the camera is the amount of sky that each views. The camera sees an area only a bit larger than the full moon as viewed from Earth, but the star tracker covers well over 100 times as much area. Both can see stars that are fainter than the unaided human eye can detect. The star tracker would update the spacecraft computer four times per second, while the camera produces a computer file containing a picture. It then takes 20 seconds to transfer the picture to the computer for analysis. The navigation system processes the picture and delivers the result to the attitude control system.
Scientists plan to image the comet's nucleus and the environment around it as well as collect infrared measurements to determine its composition. They will also measure charged particles in the vicinity of Borrelly, including the interaction of the comet with the solar wind.
Deep Space 1 was launched in October 1998 as part of NASA's New Millennium Program and served as a technology demonstrator during its prime mission.
This program is managed by JPL for NASA's Office of Space Science. JPL is managed for NASA by the California Institute of Technology in Pasadena.
17 May 2000
PASADENA, Calif. - Reaching across 179 million miles (288 million kilometers) of space, engineers will shortly begin beaming new software to a NASA spacecraft in a last-ditch effort to ready the idle probe for a 2001 rendezvous with a distant comet.
The innovative software, hastily written and tested over the past five months, will allow NASA's Deep Space 1 to recast the role of its science camera into that of navigational instrument. The original instrument, called a star tracker, ceased functioning in November 1999.
That loss, still unexplained, left the spacecraft without a way to use the stars to orient itself in space. Since then, the spacecraft has remained in a near slumber.
But that slumber must end soon if Deep Space 1 is to resume its course so it can pull off a bonus September 2001 flyby of the comet Borrelly.
NASA Headquarters, Washington, DC
Jet Propulsion Laboratory, Pasadena, CA
July 28, 1999
Deep Space 1 will rely on its experimental autonomous navigation system, called AutoNav, to guide the spacecraft past the mysterious space rock at 12:46 a.m. EDT at a relative speed of nearly 35,000 mph (56,000 kilometers per hour).
"Deep Space 1's main purpose is to test advanced technologies for the benefit of future missions, so we view the flyby and its science return as a bonus," said Dr. Marc Rayman, Deep Space 1's chief mission engineer and deputy mission manager. "This ambitious encounter is a high-risk endeavor and its success is by no means guaranteed. But should there be significant data return, the findings will be of great interest to the science community."
Asteroid Braille was previously known as 1992 KD. The new name was announced today by the Planetary Society, Pasadena, CA, as the result of a contest that focused on inventor themes and drew more than 500 entries from around the world. The name honors Louis Braille (1809-1852), the blind French educator who developed the system of printing and writing named for him and used extensively by the blind.
The winning entry was submitted by Kerry Babcock of Port Orange, FL. Eleanor Helin, who co-discovered the asteroid with fellow astronomer Kenneth Lawrence, made the final decision on the name. Helin and Lawrence are astronomers at NASA's Jet Propulsion Laboratory (JPL), Pasadena, CA, which also manages Deep Space 1.
During the encounter, Deep Space 1 will be in the ecliptic plane (the plane in which Earth and most other planets orbit the Sun), moving more slowly than the asteroid, which will be progressing up through the ecliptic plane from below. It may well be more appropriate to say that the asteroid will zoom by Deep Space 1 than the reverse.
The flyby will allow final testing of AutoNav, which enables the spacecraft to use images of distant stars and asteroids within our Solar System to keep track of its location in space and to guide trajectory changes. Deep Space 1 has successfully completed tests of its 11 other new technologies.
The asteroid and the space environment surrounding it make scientifically interesting targets for two advanced science instruments aboard Deep Space 1. During the flyby, a spectrometer and imaging instrument will send back black-and-white photographs and images taken in infrared light, while a second instrument observes the three-dimensional distribution of ions and electrons, or plasma, in the area.
In addition to their value for designing future missions, the images and other data returned from this encounter will greatly assist scientists in understanding the fundamental properties of asteroids. Although scientists believe Braille's diameter is approximately 0.6 to 3 miles (1 to 5 kilometers), they know little else about it. With this flyby, they can learn more about its shape, size, surface composition, mineralogy and terrain.
Launched on Oct. 24, 1998, from Cape Canaveral Air Station, FL, Deep Space 1 marked the first launch of NASA's New Millennium Program, which tests and validates new technologies for future space and Earth-observing missions. The technologies that have been tested on Deep Space 1 will help make future science spacecraft smaller, less expensive and capable of more independent decision-making so that they rely less on ground controllers.
The mission has exceeded almost all of its technology validation requirements by conducting more extensive tests than had been planned. As one dramatic example, the spacecraft's experimental xenon ion engine, which was required to thrust for a minimum of 200 hours, has been operated for nearly 1,800 hours.
Deep Space 1 is budgeted at $152 million, including design, development, launch and operations. The mission is managed for NASA's Office of Space Science by JPL, a division of the California Institute of Technology.
http://www.jpl.nasa.gov/files/misc/ds1asteroid.pdf
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Ron Baalke
From The "JPL Universe"
July 23, 1999
Deep Space 1 has been remarkably successful with a complicated mission. Now the 44- member operations team, busy working out of mission control facilities on the second floor of historic Building 230, is preparing to undertake a still more challenging assignment: the spacecraft is poised to encounter asteroid 1992 KD on Wednesday, July 28, at 9:46 p.m. Pacific time, marking the closest flyby of an asteroid ever attempted.
"Busy" may be an understatement. Unlike missions of yore, when flyby activities were solidified long in advance, at press time the small team continued to test and make modifications to the flyby sequence. With an overall compression of the development timeline, the encounter has proven to be challenging indeed in more ways than one.
The spacecraft's new autonomous navigation system, or AutoNav, will attempt to guide Deep Space 1 to just under 15 kilometers (9.3 miles) of the asteroid's surface. During the encounter, the spacecraft will fly past the asteroid at a relative velocity of about 56,000 kilometers per hour (35,000 miles per hour). The encounter will provide an opportunity to complete the final 5 percent of testing of AutoNav, through which the spacecraft keeps track of its location in space and makes trajectory changes to remain on course.
Deep Space 1 has completed validation of its 11 other new technologies. Since testing of these technologies is at the heart of the mission, the flyby and its science return is a bonus. The ambitious encounter is a high-risk endeavor whose success is by no means guaranteed but whose findings, should there be significant data return, will be of great interest to the science community.
The asteroid and the space environment surrounding it make scientifically interesting targets for two advanced, highly integrated science instruments. During the flyby, an integrated spectrometer and imaging instrument is scheduled to send back images taken in infrared and visible light while an instrument that studies the three-dimensional distribution of ions and electrons, or plasma, will conduct several investigations.
Asteroid 1992 KD, which was discovered in May 1992, by astronomers Eleanor Helin and Kenneth Lawrence of JPL, was chosen from more than 100 flyby possibilities.
In addition to their value for engineering future space missions, images and other data returned from this encounter will greatly assist scientists in their understanding of the fundamental properties of asteroids. Asteroid 1992 KD was chosen from more than 100 flyby possibilities. Its elliptical orbit curves within and outside Mars' orbit of the Sun, at its most distant extending more than three times farther from the Sun than Earth. Although scientists believe its diameter is approximately 1 to 5 kilometers (0.6 to 3 miles), they know little else about the object. With this flyby, they can learn more about its shape, size, surface composition, mineralogy and terrain.
The diminutive Deep Space 1 spacecraft, reaching just 2.5 meters (8.2 feet) in height, was launched on October 24, 1998, onboard a Delta II rocket from Cape Canaveral Air Station, Fla. It marked the first launch of NASA's New Millennium Program, testing and validating new technologies in a series of deep space and Earth-observing missions. This is one of the first-ever deep space NASA missions to have technology, rather than science, as its key focus.
The technologies that have been tested on Deep Space 1 generally fall into two categories: those concerned with making future spacecraft smaller and less expensive, and those concerned with making spacecraft more autonomous. Many of the technologies are designed to make spacecraft smaller, less expensive and capable of more independent decision-making so that they rely less on tracking and intervention by ground controllers.
The mission has exceeded almost all of its technology validation requirements by conducting more extensive tests than had been planned. As one dramatic example, the ion engine, which was required to thrust for a minimum of 200 hours, has in fact been operated for nearly 1,800 hours to date.
Deep Space 1 has also tested the feasibility of compressing mission preparation periods to as short as 39 months from initial concept through launch and of reducing mission budgets to substantially less than that of other recent NASA missions. Deep Space 1 is budgeted at $152 million, including design, development, launch and operations.
Xenon, the same gas that fills photo flash tubes and glows brightly in many lighthouse bulbs, is the propellant for the ion propulsion system. Although this type of engine has been tested in labs and on Earth-orbiting satellites, only now has it been flight-tested as the primary propulsion source on a deep space mission. Having been proven in flight, ion drives are likely to be used on many future deep space and Earth-orbiting missions that would otherwise be impractical or unaffordable with conventional propulsion systems. The mission also features three key experiments that give the spacecraft more autonomy in navigating and general decision-making. Autonomous navigation, when combined with ion propulsion, "is like having one's car find its own way from Los Angeles to Washington, D.C., arrive in a designated parking space, and do it all while getting 300 miles to the gallon," said Dr. Marc Rayman, Deep Space 1's chief mission engineer and deputy mission manager.
JPL manages the Deep Space 1 mission for NASA's Office of Space Science.
The Planetary Society
July 26, 1999
Spacecraft Target Asteroid Named in Planetary Society Contest
The target of NASA's Deep Space 1 mission now
has a name: 9969 Braille, after Louis Braille,
the inventor of the language system that enables
sightless people to read. Astronomer Eleanor
Helin, lead discoverer of the asteroid formerly
known as 1992 KD, selected Braille from hundreds of suggestions
submitted to The Planetary Society in a worldwide contest to name the
object.
On July 28, Deep Space 1 (DS1) will encounter asteroid Braille. This is the first of NASA's New Millennium missions, which are testing revolutionary technologies that could take humanity farther and faster into our solar system. Validating ion drive and an autonomous navigation system are among the primary goals of this mission; investigating the nature of asteroid Braille is frosting on the cake.
Kerry Babcock of Port Orange, Florida submitted the winning name. His citation reads: "Louis Braille invented the Braille language so those who could not see could obtain knowledge and explore through the `written' word. Likewise, asteroid Braille provides knowledge about our universe and its origin to the people of Earth, who thorugh Deep Space 1, are also able to explore and discover what previously they could not `see.'"
Mr. Babcock is a software engineer at the Kennedy Space Center. A few years ago, he began to learn to transcribe the braille system and was very impressed with Louis Braille's achievement. Mr. Babcock gave his daughter the name "Braille," so in a sense it is her namesake as well that is now traveling through the solar system.
Dr. Helin and The Planetary Society chose the theme "Inventors" for the naming contest to recognize the nature of the Deep Space 1 mission: It is a technology demonstration mission, not primarily a mission of scientific discovery. Its purpose is to test new technologies that will make future scientific missions easier, more efficient and less costly and thus enable NASA to fly more missions of exploration in the future.
"Inventions are the products of the human mind," said Dr. Helin, "It is particularly appropriate to honor Braille for his invention of a means of communication with the minds of humans who are otherwise limited in their ability to `see' the outside world. Spacecraft such has DS1, in their own way, also provide a means for humans to `see' other worlds."
Louis Braille (1809-1852) invented the raised-dot alphabet that enables sightless people to read by sense of touch. Blinded by a childhood accident, Braille was sent to a special school where he was introduced to early, but unwieldy, raised-dot methods of translating printed words into symbols readable with fingertips. The braille alphabet, using more efficient combinations of six dots, revolutionized reading for those without sight.
The Planetary Society asked people to suggest names through its Web site. The Society's staff made a preliminary selection of candidates, and Dr. Helin and team member Ken Lawrence made the final selection. It is the discoverers' privilege to name the object, subject to the approval of the Small Bodies Naming Committee of the International Astronomical Union. The committee has given its official approval to the name Braille.
Dr. Louis D. Friedman, Executive Director of The Planetary Society, said, "To have the winning entry in our contest be such an interesting and thoughtful choice is rewarding. It captures the spirit of discovery."
Dr. Friedman added, "At The Planetary Society, we believe it is very important to involve members of the public in space missions. Giving them the opportunity to name a target of exploration is an exciting and concrete way to get the public involved."
When it reaches asteroid Braille, DS1 will try to determine the asteroid's size, shape, mass, volume, and density. Its elemental and mineralogical composition will greatly interest scientists, who will also be hoping to learn whether this asteroid is a large solid rock floating in space or a conglomeration of smaller rocks traveling as a group, bound together by gravity.
The asteroid formerly known as 1992 KD was discovered May 27, 1992 by Dr. Helin and Ken Lawrence from the Palomar Observatory during the NASA-funded Planet-Crossing Asteroid Survey. Asteroid Braille orbits the Sun in the neighborhoods of Mars and Earth. It is not a large world, having an estimated diameter of two to five kilometers.
Dr. Helin eagerly awaits the first close look at one of her 25-year-old program's discoveries.
For more information, visit the Jet Propulsion Laboratory's Deep Space 1 website.
Dr. Marc Rayman's Deep Space 1 Mission Log
Mission Update:
Thank you for visiting the Deep Space 1 mission status information site, now beginning its tenth month on the list of most popular sites on any habitable planet in or near the plane of the Milky Way galaxy for information on this technology validation mission. This message was logged in at 4:00 pm Pacific Time on Sunday, July 25.
With its mission of testing high risk, important new technologies having exceeded expectations, Deep Space 1 is now nearly ready to attempt a very very challenging encounter with the asteroid formerly known as 1992 KD. This asteroid was discovered 7 years ago by JPL astronomers Eleanor Helin and Kenneth Lawrence as part of an extensive and productive effort to locate and study asteroids. Faithful listeners know that a contest organized by The Planetary Society and JPL was conducted to select a new name for 1992 KD. As hard as it is to believe, a better name was found. Kerry Babcock of Port Orange, Florida won with his terrific proposal to name the asteroid Braille, after Louis Braille who invented the raised-dot alphabet for blind readers. The Planetary Society will be issuing a press release with more details about the newly selected name.
DS1 got some help from the operations team this past week. Previous logs have described the impressive performance of AutoNav in determining its location and course. But because of shortcomings in the camera, it is not quite accurate enough for the job of guiding DS1 to its extraordinarily close encounter with Braille. So engineers borrowed the navigation pictures AutoNav took and performed more analyses with them than AutoNav is designed to do, so they were able to improve upon AutoNav's results. (The work performed by humans in this case could have been done easily by AutoNav if the necessary instructions had been on board.) For the first time in nearly 5 months, an update to its location was transmitted to DS1. AutoNav now combines that information with its own navigation estimates as it progresses toward the asteroid.
To keep DS1 on course, AutoNav designed a course correction and executed it on Friday. But it turned out that in order to point the ion engine in the desired direction, the orientation of the spacecraft would have allowed the Sun to point at the camera and the device that tracks stars, imaginatively known as the star tracker. So the on-board system did what the operations team refers to as "vectorizing the burn": it computed two different orientations that were acceptable for ion engine firings that combined to produce the desired effect. Then AutoNav turned the spacecraft, used the ion propulsion system for 3 hours, and then turned DS1 again and fired it again for another 3 hours before turning back to point the main antenna at Earth. The course correction went well and changed the spacecraft speed by about 2.5 miles/hour.
Very little is known about asteroid Braille. Even estimates of its size are quite uncertain, but it is probably just a few kilometers in diameter (perhaps a mile or so). This is the smallest solar system body ever targeted for a spacecraft encounter. In fact, the asteroid is so small that it has been difficult for astronomers to determine its exact location, and it is still too far away for the spacecraft to see it. Beginning today however, whenever AutoNav takes pictures of larger, more distant asteroids for its navigational fixes, it also will try to find asteroid Braille. As expected, the tiny asteroid did not show up in this morning's pictures, even though it is only a little over 3 days before the spacecraft arrives. One of the greatest uncertainties right now is where the asteroid really is, and the sooner AutoNav can spot its target, the better job it can do zeroing in on it. Braille apparently rotates very slowly, taking nearly 10 Earth days to complete one turn. Although DS1 was designed to test technologies, it will attempt to make scientific measurements when it flies past the asteroid. Black and white pictures may reveal Braille's size and shape and show craters, hills, valleys, and other topography. Infrared measurements may help scientists determine the minerals that make up the surface. By searching for changes in the solar wind, the stream of charged particles flowing from the Sun, in the vicinity of the asteroid, it may be possible to determine if it has a magnetic field. Perhaps the solar wind or sunlight even cause surface material to be slowly eroded from the asteroid and flung into space, in which case the spacecraft may directly measure the resulting free atoms.
To get close enough to make all these measurements, AutoNav will attempt to bring DS1 closer to Braille than any spacecraft has ever come to a solar system body without actually landing on it. Speeding by at 15.5 km/s, or nearly 35,000 miles/hour, the spacecraft will pass by more than 50 times faster than a commercial jet and more than twice as fast as the space shuttle. But it will come a mere 15 kilometers from the center of the asteroid, or less than 9 miles from the surface. This is a great challenge to AutoNav and to the operations team, but if it works this high risk encounter should be exciting indeed.
The small operations team has been continuing to refine the complex set of instructions that will govern the spacecraft, including the ones that give AutoNav the opportunity to design and execute more maneuvers to keep the spacecraft on course, the commands to the new technology science instruments to collect data, directions to the attitude control system on how to turn the spacecraft as it nears the asteroid, and instructions on how to transfer, manipulate, and store the large volume of data to be collected. Completing this unusually complex choreography, in which all the spacecraft systems including AutoNav need to work together, is the focus of the team's work right now. A group of instructions is known as a sequence, and each day, the sequences covering the final 6 hours before the closest approach to Braille are run through the Deep Space 1 test facility at JPL. This is a simulation of the spacecraft, created using some hardware similar to what is on the real spacecraft and some computer programs that emulate the behavior of other parts of the spacecraft. The test facility is certainly not identical to the spacecraft, so a successful test does not guarantee success on the spacecraft, but it has allowed many of the bugs to be worked out.
The final sequences will be radioed to DS1 on Monday. In the meantime, AutoNav will continue to check its course and, if necessary, make course corrections as it closes in on the asteroid. DS1's closest approach to the asteroid will occur at approximately 9:46 pm PDT on Wednesday, and it will be several hours after that before it can begin reporting its results to Earth. Returning all the data may require several days; this page will be updated on Thursday or Friday with a report on the outcome of this exciting adventure.
Deep Space 1 is still about 4.3 million kilometers, or 2.7 million miles, from Braille. The spacecraft is now almost 25% farther away from Earth than the Sun is and over 480 times as far as the moon. At this distance of over 185 million kilometers, or more than 115 million miles, radio signals, traveling at the universal limit of the speed of light, take almost 21 minutes to make the round trip.
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NASA Headquarters, Washington, DC
Jet Propulsion Laboratory, Pasadena, CA
April 6, 1999
Of the 12 advanced technologies onboard the spacecraft, seven have completed testing, including the ion propulsion system, solar array and new technologies in communications, microelectronics and spacecraft structures.
"We've taken these technologies around the test track, and now they're ready for the production line," said Dr. Marc Rayman, deputy mission manager and chief mission engineer for Deep Space 1 at NASA's Jet Propulsion Laboratory (JPL), Pasadena, CA.
Launched October 24, Deep Space 1 is the first mission under NASA's New Millennium Program, which features flight testing of new technology, rather than science, as its main focus. These new technologies will make spacecraft of the future smaller, cheaper, more reliable and more independent of human control.
By summer, engineers expect to have finished testing all 12 advanced technologies aboard the spacecraft.
Testing of two technologies that make the Deep Space 1 less reliant on humans is 75 percent complete, while testing of a third is scheduled to begin in May. These technologies include a robotic navigator, called AutoNav, that will guide the spacecraft to a rendezvous with asteroid 1992 KD on July 29 without active human control from the Earth.
In addition, Deep Space 1's two advanced science instruments -- a combination camera/spectrometer and an instrument that studies electrically charged particles emitted by the Sun and other sources -- are on schedule, having finished 75-percent of their tests.
"What has pleased us more than anything is how well the technologies have been working in general," Rayman said, noting that their performance is remarkably close to engineers' estimates developed before launch.
"Of course, everything hasn't worked perfectly on the first try," Rayman added. "If it had, it would mean that we had not been sufficiently aggressive in selecting the technologies. Diagnosing the behavior of the various technologies is a fundamental part of Deep Space 1's objective of enabling future space science missions."
When the ion propulsion system was first activated November 10, the engine shut itself off after 4-1/2 minutes, and engineers were unable to restart it later that day. During the next attempt two weeks later, however, the engine started up easily and has performed flawlessly since then, logging more than 1,300 hours of operation.
Engineers believe the problem was caused by a piece of grit stuck to high-voltage grids within the ion engine. The grit was later dislodged, they believe, when parts expanded and contracted as the ion engine was exposed alternately to sunlight and shade.
Engineers also discovered after launch that stray light enters the camera/spectrometer, resulting in streaks of light when pictures are taken with a long exposure. The streaks are a result of how the instrument was mounted on the spacecraft, Rayman said.
The camera should be able to take acceptable pictures when Deep Space 1 flies by asteroid 1992 KD this summer, because it will use short exposures.
Despite such glitches, the great majority of the advanced technologies have worked extremely well, according to Rayman. "Mission designers and scientists can now confidently use them on future missions," he said.
Deep Space 1 will continue testing technologies until its prime mission concludes on September 18. NASA is considering a possible extended mission that would take the spacecraft on flybys of two comets in 2001.
The Deep Space 1 mission is managed for NASA's Office of Space Science, Washington, DC, by JPL, a division of the California Institute of Technology, Pasadena, CA. Spectrum Astro Inc., Gilbert, AZ, was JPL's primary industrial partner in spacecraft development.
JET PROPULSION LABORATORY
CALIFORNIA INSTITUTE OF TECHNOLOGY
NATIONAL AERONAUTICS AND SPACE ADMINISTRATION
Deep Space 1 is currently operating its ion engine after a series of successful technology tests involving its two advanced science instruments and ion propulsion system.
Following the activation of the Plasma Experiment for Planetary Exploration (PEPE) on Tuesday and Wednesday, December 8-9, the instrument demonstrated the ability to measure both electrons and ions in the solar wind. PEPE combines several functions into a unit of lower mass and lower power consumption than on traditional science missions.
On Thursday, December 10, benefiting from the success of PEPE's activation, a more streamlined activation procedure was successfully tested, assuring that PEPE can be turned on easily in the future. PEPE was developed by the Southwest Research Institute in San Antonio and the Los Alamos National Laboratory.
On Friday, December 11, Deep Space 1 collected data on another of its 12 advanced technologies, the Miniature Integrated Camera Spectrometer (MICAS). This device is designed both to collect black-and-white pictures and to make measurements in the infrared and ultraviolet. Data will aid in characterizing the device and in refining software to allow Deep Space 1's autonomous navigation system to use the pictures. MICAS was developed by the U.S. Geological Survey, Flagstaff, AZ; SSG Inc., Waltham, MA; the University of Arizona Lunar and Planetary Laboratory, Tucson, AZ; Boston University Center of Space Physics, Boston, MA; Rockwell International Science Center, Thousand Oaks, CA; and the Jet Propulsion Laboratory.
Also on Friday, the ion propulsion system was turned back on after having been commanded off the previous Tuesday, December 8. The team then attempted to find the highest throttle level at which the spacecraft could operate. At level 85, it became necessary for the spacecraft's batteries to supplement solar array power. When those batteries reached a predefined level, onboard fault protection software turned off the ion propulsion system later in the day Friday and placed the spacecraft in a safe state. Through this activity, the team has determined that the highest throttle level that can currently be supported is approximately 83; this will decrease as the spacecraft recedes from the Sun.
The operations team commanded the thruster back on at a lower level Monday, December 14. The ion propulsion system will be turned off at the end of this week and again next week for other activities.
Deep Space 1 is now more than 22 times as far away from Earth as the Moon is.
December 10, 1998
Deep Space 1 is currently operating its ion engine after a series of successful technology tests involving its two advanced science instruments and ion propulsion system.
Following the activation of the Plasma Experiment for Planetary Exploration (PEPE) on Tuesday and Wednesday, December 8-9, the instrument demonstrated the ability to measure both electrons and ions in the solar wind. PEPE combines several functions into a unit of lower mass and lower power consumption than on traditional science missions.
On Thursday, December 10, benefiting from the success of PEPE's activation, a more streamlined activation procedure was successfully tested, assuring that PEPE can be turned on easily in the future. PEPE was developed by the Southwest Research Institute in San Antonio and the Los Alamos National Laboratory.
On Friday, December 11, Deep Space 1 collected data on another of its 12 advanced technologies, the Miniature Integrated Camera Spectrometer (MICAS). This device is designed both to collect black-and-white pictures and to make measurements in the infrared and ultraviolet. Data will aid in characterizing the device and in refining software to allow Deep Space 1's autonomous navigation system to use the pictures. MICAS was developed by the U.S. Geological Survey, Flagstaff, AZ; SSG Inc., Waltham, MA; the University of Arizona Lunar and Planetary Laboratory, Tucson, AZ; Boston University Center of Space Physics, Boston, MA; Rockwell International Science Center, Thousand Oaks, CA; and the Jet Propulsion Laboratory.
Also on Friday, the ion propulsion system was turned back on after having been commanded off the previous Tuesday, December 8. The team then attempted to find the highest throttle level at which the spacecraft could operate. At level 85, it became necessary for the spacecraft's batteries to supplement solar array power. When those batteries reached a predefined level, onboard fault protection software turned off the ion propulsion system later in the day Friday and placed the spacecraft in a safe state. Through this activity, the team has determined that the highest throttle level that can currently be supported is approximately 83; this will decrease as the spacecraft recedes from the Sun.
The operations team commanded the thruster back on at a lower level Monday, December 14. The ion propulsion system will be turned off at the end of this week and again next week for other activities.
Deep Space 1 is now more than 22 times as far away from Earth as the Moon is.
December 10, 1998
Ground controllers commanded Deep Space 1 to turn off thrusting of its ion engine this week, allowing them to perform critical tests of two of the mission's advanced technologies.
The ion engine was turned off Tuesday, December 8, after a marathon period of two weeks of thrusting. While operating, the ion engine ran more than twice as long as it was originally planned to thrust without interruption at any time during the mission. By running the ion engine for more than 200 hours and successfully conducting technology validation of the spacecraft's solar array and transponder (radio transmitter/receiver), the team achieved the minimum criteria that NASA established for overall mission success.
With the ion engine off, the team was able to activate one of the mission's two advanced science instruments, the Plasma Experiment for Planetary Exploration (PEPE). This involved a complex series of activities Tuesday and Wednesday. The advanced instrument, which has no moving parts, is now fully powered up and will be left on indefinitely.
The team was also able to test another of the mission's advanced technologies, the Ka-band solid-state power amplifier. On Tuesday and Wednesday nights, Deep Space 1 sent data to Earth in the Ka band at a frequency four times higher than that used for most communications with solar system exploration spacecraft today, transmitting to a ground station of the Deep Space Network at Goldstone, California. Deep Space 1 also sent data in the lower-frequency X band using its high-gain antenna for the first time. During the tests, the spacecraft's transponder sent telemetry at 14 different data rates.
On Friday, the team will command Deep Space 1 to resume ion engine thrusting. Plans call for the ion engine to operate nearly continuously until January. The spacecraft will suspend thrusting from January to March in order to conduct other technology validation activities and to help shape its flight path for its flyby of asteroid 1992 KD in July 1999.
Deep Space 1 is now 7.6 million kilometers (4.7 million miles) from Earth, or more than 19 times as far away from Earth as the Moon is. Radio signals traveling at the speed of light take about 50 seconds to make the round trip.
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The engine started up at 5:53 p.m. EST, in response to commands sent to the spacecraft. After running overnight in low- thrust mode, engineers commanded the engine to switch to higher- thrust modes today. The mission team plans to leave the engine running over the four-day Thanksgiving weekend.
The team originally powered up the engine Nov. 10, but the system shut itself off after running for 4-1/2 minutes. When controllers sent commands to the engine to turn itself on Tuesday, they planned to collect more data on the status of the system but believed it was unlikely the engine would keep running.
"We are very pleased that the engine started and continued to thrust," said Dr. Marc Rayman, Deep Space 1's chief mission engineer and deputy mission manager at NASA's Jet Propulsion Laboratory, Pasadena, CA. "In fact, it has been running very smoothly over the first day of its operation."
Engineers believe that the engine probably shut itself off when it was started two weeks ago because of metallic grit or other contamination between the two high-voltage grids at the rear of the advanced engine. It is likely that changes in temperature as the spacecraft conducted other technology validation activities affected the flakes, and powering-up the thruster may have vaporized the remains.
"It's common for new ion engines on the ground or on Earth- orbiting spacecraft to shut themselves off a few times when they are first exercised," said Rayman. "We would not be surprised if the engine shut itself off again over the first few days or weeks that it runs.
"Deep Space 1's charter is to test new, advanced technologies," Rayman added. "If everything worked perfectly on the first try, it would be an indication we had not been sufficiently aggressive in selecting the technologies. Diagnosing the behavior we have seen is a very valuable part of Deep Space 1's objective of enabling future space science missions."
The fuel used in Deep Space 1's ion engine is xenon, a colorless, odorless and tasteless gas more than 4-1/2 times heavier than air. When the ion engine is running, electrons are emitted from a hollow bar called a cathode into a chamber ringed by magnets, much like the cathode in a TV picture tube or computer monitor. The electrons strike atoms of xenon, knocking away one of the 54 electrons orbiting each atom's nucleus. This leaves each atom one electron short, giving it a net positive charge -- making the atom what is known as an ion.
At the rear of the chamber is a pair of metal grids which are charged positive and negative, respectively, with up to 1,280 volts of electric potential. The force of this electric charge exerts a strong "electrostatic" pull on the xenon ions - much like the way that bits of lint are pulled to a pocket comb that has been given a static electricity charge by rubbing it on wool on a dry day. The electrostatic force in the ion engine's chamber, however, is much more powerful, causing the xenon ions to shoot past at a speed of more than 60,000 miles per hour (100,000 kilometers per hour), continuing right on out the back of the engine and into space.
At full throttle, the ion engine would consume about 2,500 watts of electrical power and puts out 1/50th of a pound (90 millinewtons) of thrust. This is comparable to the force exerted by a single sheet of paper resting on the palm of a hand.
When the engine was started Tuesday, it ran overnight, thrusting at a power level of 500 watts. This morning engineers commanded it to thrust at a level of 885 watts, then at 1,300 watts. Engineers may decide to have the engine thrust at a lower level while it runs over the next few days.
The ion propulsion system flight hardware was built for Deep Space 1 by Hughes Electron Dynamics Division, Torrance, CA; Spectrum Astro Inc., Gilbert, AZ; Moog Inc., East Aurora, NY; and Physical Science Inc., Andover, MA. Development of the ion propulsion system was supported by NASA's Office of Space Science and Office of Aeronautics and Space Transportation Technology, Washington, DC. JPL is managed for NASA by the California Institute of Technology.
NASA Headquarters, Washington, DC
Jet Propulsion Laboratory, Pasadena, CA
November 25, 1998
The engine started up at 5:53 p.m. EST, in response to commands sent to the spacecraft. After running overnight in low- thrust mode, engineers commanded the engine to switch to higher- thrust modes today. The mission team plans to leave the engine running over the four-day Thanksgiving weekend.
The team originally powered up the engine Nov. 10, but the system shut itself off after running for 4-1/2 minutes. When controllers sent commands to the engine to turn itself on Tuesday, they planned to collect more data on the status of the system but believed it was unlikely the engine would keep running.
"We are very pleased that the engine started and continued to thrust," said Dr. Marc Rayman, Deep Space 1's chief mission engineer and deputy mission manager at NASA's Jet Propulsion Laboratory, Pasadena, CA. "In fact, it has been running very smoothly over the first day of its operation."
Engineers believe that the engine probably shut itself off when it was started two weeks ago because of metallic grit or other contamination between the two high-voltage grids at the rear of the advanced engine. It is likely that changes in temperature as the spacecraft conducted other technology validation activities affected the flakes, and powering-up the thruster may have vaporized the remains.
"It's common for new ion engines on the ground or on Earth- orbiting spacecraft to shut themselves off a few times when they are first exercised," said Rayman. "We would not be surprised if the engine shut itself off again over the first few days or weeks that it runs.
"Deep Space 1's charter is to test new, advanced technologies," Rayman added. "If everything worked perfectly on the first try, it would be an indication we had not been sufficiently aggressive in selecting the technologies. Diagnosing the behavior we have seen is a very valuable part of Deep Space 1's objective of enabling future space science missions."
The fuel used in Deep Space 1's ion engine is xenon, a colorless, odorless and tasteless gas more than 4-1/2 times heavier than air. When the ion engine is running, electrons are emitted from a hollow bar called a cathode into a chamber ringed by magnets, much like the cathode in a TV picture tube or computer monitor. The electrons strike atoms of xenon, knocking away one of the 54 electrons orbiting each atom's nucleus. This leaves each atom one electron short, giving it a net positive charge -- making the atom what is known as an ion.
At the rear of the chamber is a pair of metal grids which are charged positive and negative, respectively, with up to 1,280 volts of electric potential. The force of this electric charge exerts a strong "electrostatic" pull on the xenon ions - much like the way that bits of lint are pulled to a pocket comb that has been given a static electricity charge by rubbing it on wool on a dry day. The electrostatic force in the ion engine's chamber, however, is much more powerful, causing the xenon ions to shoot past at a speed of more than 60,000 miles per hour (100,000 kilometers per hour), continuing right on out the back of the engine and into space.
At full throttle, the ion engine would consume about 2,500 watts of electrical power and puts out 1/50th of a pound (90 millinewtons) of thrust. This is comparable to the force exerted by a single sheet of paper resting on the palm of a hand.
When the engine was started Tuesday, it ran overnight, thrusting at a power level of 500 watts. This morning engineers commanded it to thrust at a level of 885 watts, then at 1,300 watts. Engineers may decide to have the engine thrust at a lower level while it runs over the next few days.
The ion propulsion system flight hardware was built for Deep Space 1 by Hughes Electron Dynamics Division, Torrance, CA; Spectrum Astro Inc., Gilbert, AZ; Moog Inc., East Aurora, NY; and Physical Science Inc., Andover, MA. Development of the ion propulsion system was supported by NASA's Office of Space Science and Office of Aeronautics and Space Transportation Technology, Washington, DC. JPL is managed for NASA by the California Institute of Technology.
JET PROPULSION LABORATORY
CALIFORNIA INSTITUTE OF TECHNOLOGY
NATIONAL AERONAUTICS AND SPACE ADMINISTRATION
November 21, 1998
The image was captured by Jet Propulsion Laboratory astronomers November 16, 1998, when the spacecraft was 3.7 million kilometers (2.3 million miles) from Earth.
Observers were Drs. Bonnie J. Buratti, Paul R. Weissman, Michael D. Hicks and Alain Doressoundiram. Jon Giorgini assisted with telescope-pointing predictions using JPL's Horizons online ephemeris system, an Internet-accessible computer program Giorgini developed that computes positions of objects in the solar system as seen from any location on Earth. These predictions were based on orbit determination performed by the Deep Space 1 navigation team.
Deep Space 1 is the first mission under NASA's New Millennium Program testing new technologies for use on future science missions. Among its 12 new technologies are a xenon ion propulsion system, autonomous navigation, a high-efficiency solar array and a miniature camera/spectrometer.
In het septembernummer van maandblad KIJK verscheen een uitgebreid artikel over Deep Space 1 en de overige missies van NASA's New Millennium Program.
JET PROPULSION LABORATORY
CALIFORNIA INSTITUTE OF TECHNOLOGY
NATIONAL AERONAUTICS AND SPACE ADMINISTRATION
A test of Deep Space 1's autonomous navigation system Tuesday afternoon, November 17, was interrupted when the spacecraft went into a safe mode at approximately 3:30 p.m. Pacific Standard Time.
After the system, called AutoNav, took 12 of an expected 20 images during a session of flight tests, the spacecraft turned to an orientation in which its onboard Sun detector was not able to retain its view of the Sun. Although this should have been an acceptable orientation, the onboard fault-protection software terminated the test activity and commanded the spacecraft to a safe configuration. Shortly thereafter, the flight team began returning the spacecraft to its normal configuration. The team expects to have the configuration returned to normal later today.
A firm date has not yet been set for the team to resume working with Deep Space 1's ion engine, although it will likely begin next week. The team plans to conduct further data analysis and simulation tests before attempting to restart the engine, which shut itself down 4-1/2 minutes after it was turned on for its first test Tuesday, November 10. The team is currently preparing to modify onboard software that controls the ion engine to give engineers greater resolution in studying currents and voltages when they attempt to start the ion engine. The new software will be tested for several days and transmitted to the spacecraft once a date is set for further work on the ion engine. Several different strategies for resuming thrusting are being evaluated, and a decision on which ones to pursue and in which order should be made soon.
Monday and Tuesday, November 16-17, were devoted to technology validation. On Monday, the mission operations team radioed new files to the spacecraft to permit the autonomous navigation system to start its work with up-to-date information.
On Tuesday, the first major test of AutoNav was conducted, and it was during this test that the spacecraft went into a safe configuration. Under AutoNav's control, the spacecraft turned to point the the spacecraft's camera to take pictures of various asteroids. The flight team watched as AutoNav took the spacecraft to several different orientations to collect its data. The preliminary view of AutoNav's performance is that it operated extremely well.
November 14, 1998
Ground controllers returned Deep Space 1 to normal cruise configuration Friday, November 13, two days after an event that put the spacecraft into safe mode. The spacecraft is in excellent condition, and the flight team will now resume testing the dozen advanced technologies that the mission is flying.
The process of restoring normal cruise configuration occupied about six hours Friday afternoon and early evening, beginning at 2 p.m. PST. The spacecraft fired its thrusters to turn it to regular cruise orientation, with one low-gain antenna pointing at Earth. Ground controllers also commanded the telecommunications system to return to sending data to Earth at a higher rate of 9,480 bits per second; during the time that the spacecraft was in safe mode, it switched to a slower rate of 2,100 bits per second. Several spacecraft devices that had been turned off during the safe mode were turned back on.
With the return of normal cruise mode, the flight team will resume validating the mission's advanced technologies. Early next week, they expect to focus on the spacecraft's autonomous navigation system and one of its advanced science instruments, the Miniature Integrated Camera Spectrometer (MICAS). Toward the end of next week, the team expects to work with the ion engine. At that time they will probably attempt to restart the engine, which shut itself down 4-1/2 minutes after it was turned on for its first test Tuesday, November 10.
Also on Friday, the team obtained important new evidence to help understand why devices used to deploy the spacecraft's solar arrays were unexpectedly activated Wednesday, November 11, about the same time that the safing event took place. The team was able to replicate the event activating the solar array deployment devices in a testbed version of the spacecraft on the ground. This makes it less likely that the problem was caused by a hardware failure or cosmic-ray hit; mission managers suspect the event may be easily preventable. They are still studying an apparent problem with the spacecraft's star tracker that was the cause of Deep Space 1 entering safe mode.
November 11, 1998
After operating as expected for approximately 4-1/2 minutes after startup Tuesday, November 10, Deep Space 1's xenon ion engine turned off for reasons that are still under investigation. After the startup at 11:30 a.m. PST and subsequent shutdown Tuesday, the operations team sent a number of commands to try to restart the ion propulsion system. Each time, the system went through its normal startup routine, but was unable to achieve thrusting. Valuable diagnostic data were collected, and the team observed that the rest of the spacecraft behaved exactly as planned during the brief interval of thrusting and during subsequent attempts to restart the thruster.
Engine turn-off behavior has been observed in the past in solar electric propulsion systems both in Earth-based test and on Earth-orbiting spacecraft. Deep Space 1 is designed to test and validate the use of such propulsion in deep space for the first time, so the ongoing diagnosis of Tuesday's behavior is in keeping with the mission's goals.
Tuesday's planned activities had included stepping up the thruster through different throttle levels over more than 16 hours, taking the engine to its peak thrusting level. This would allow the team to assess the overall performance of the spacecraft and the ion propulsion system at increasingly powerful levels and to measure the power needed from the spacecraft's pair of solar arrays to achieve each thrust level. Concurrently, ground-based radio navigation was to take Doppler data to measure the amount of thrust imparted by the ion engine system at each throttle level. These activities will be conducted once the resolution of Tuesday's premature shutdown is found.
Today, other technology validation activities will continue while a portion of the team analyzes Tuesday's data and formulates a plan for subsequent ion propulsion system operations. Much of the key testing will be completed within the first eight weeks after launch; the technologies on which the spacecraft depends for its basic operation -- such as its solar arrays and the transponder or radio transmitter/receiver -- were proven to work within the first hours after launch.
To prepare for Tuesday's planned activities, the spacecraft successfully executed a large turn Friday, October 30, to point the ion engine toward the Sun. Sunlight heated portions of the xenon feed system and the ion thruster core (which reached about 110 C (230 F)), and baked off some contaminants that held the potential to interfere with the engine's operation. While the spacecraft remained in that orientation, a small amount of xenon from the ion propulsion system was allowed to flow through the system to assure there were no blockages. The spacecraft returned to its previous orientation the next day.
On Thursday, November 5, a heater inside the thruster's cathode was turned on and the xenon system was pressurized. As a final test before thrusting, xenon was ionized inside the thruster on Monday, November 9, but was not accelerated. Engineering data show that the test went as planned. The suite of diagnostic sensors onboard to measure the effects of the ion propulsion system on the local space environment worked as planned.
Once Tuesday's behavior is diagnosed and resolved, the engine is scheduled to be turned on intermittently for the remainder of the mission, which ends in late September 1999.
The ion engine is among 12 technologies being tested on Deep Space 1, the first mission of the New Millennium Program, designed to validate new technologies so that they may be used on space missions of the 21st century.
HUGHES SPACE AND TELECOMMUNICATIONS COMPANY
Electron Dynamics Division
Los Angeles, CA 90009
The NASA Solar Electric Power Technology Application Readiness (NSTAR) 30-centimeter system, consisting of an ion thruster, power processor, and digital control and interface units, was designed specifically to support NASA's future requirements. It is being validated by the New Millennium Deep Space 1 project. Unlike its commercial satellite counterpart that uses a xenon ion propulsion system, XIPS (pronounced "zips"), for north-south stationkeeping and for orbit raising, the NSTAR system will be the primary propulsion system for the Deep Space 1 spacecraft.
The Deep Space 1 spacecraft may be the first of several to use the NSTAR system. Under the $8.1 million contract that was awarded by NASA to Hughes Electron Dynamics Division in 1995, two flight thrusters, and associated power processor and digital control and interface units, were produced.
The advantage of ion propulsion is efficiency. Ion propulsion is 10 times more efficient than chemical thrusters. This translates into a reduction of propellant mass of up to 90%. For commercial communications satellites, the reduced propellant mass creates an option to reduce launch cost, increase payload, or increase satellite lifetime, or any combination of the above.
For Deep Space 1, the improved propellant efficiency of the NSTAR system results in a lighter spacecraft that will reach its destination in half the time. Deep Space 1 is currently scheduled to reach the near-Earth asteroid 1992 KD in July 1999. By Oct. 1999, Deep Space 1 will have completed its primary mission and will be on a trajectory that could result in an encounter with Comets Wilson-Harrington and Borelly in 2001.
"XIPS is the result of more than 40 years of research by Hughes and NASA. The NSTAR 30-centimeter system was designed to meet very specific operational parameters," said Tim Fong, manager of Hughes Electron Dynamics Division. "The NSTAR ion propulsion system on Deep Space 1 requires operation over a wide range of thrust and input power, since the solar power available drops significantly as the spacecraft goes further away from the sun. This NSTAR system is remotely programmable, allowing NASA to adjust its thrust to meet these changing conditions over the life of the mission."
In addition to the 30-centimeter NSTAR system designed for NASA, Hughes Electron Dynamics Division also produces two commercial XIPS systems: a 13-centimeter unit that is an option on the HS 601 spacecraft built by Hughes Space and Communications Company, and a 25-centimeter version that will debut on Hughes' first HS 702 in early 1999.
Hughes Electron Dynamics Division built the first commercial XIPS system, which was launched Aug. 28, 1997, on PAS-5, an HS 601HP satellite for PanAmSat Corporation.
Hughes Electron Dynamics Division is a world leader in the design and manufacture of microwave, traveling wave-tube amplifiers, and ion thrusters for commercial and military applications. The earnings of Hughes Electronics are used to calculate the earnings per share attributable to GMH (NYSE symbol) common stock.
NASA Kennedy Space Center
August 17, 1998
Among the experiments aboard Deep Space 1 is an ion propulsion engine strikingly similar to those described in futuristic science fiction works, and software that tracks celestial bodies so that the spacecraft can make its own navigation decisions without the intervention of ground controllers.
At launch, the diminutive Deep Space 1 weighs only 1,080 pounds fully fueled and is just 8.2 feet high, 6.9 feet deep and 5.6 feet wide, including such attached items as twin stowed solar arrays. However, when those arrays are deployed, the width will grow to 38.6 feet across. Deep Space 1 should complete most of its mission objectives during the first two months after launch. However, it will continue validating these instruments while doing a flyby of a near-Earth asteroid named 1992 KD in July 1999.
The spacecraft is being processed in NASA's Payload Hazardous Servicing Facility (PHSF) located in the KSC Industrial Area. Among the processing activities to be performed are the attachment to the spacecraft bus of the Plasma Experiment for Planetary Exploration (PEPE) instrument and the attachment of the solar arrays, each of which is among the dozen new technologies being tested on Deep Space 1.
There is to be a functional test of the advanced technology science instruments as well as of the basic spacecraft subsystems. Checks of Deep Space 1's communications system will be performed including a verification of the spacecraft's ability to send data to the Jet Propulsion Laboratory via the tracking stations of the Deep Space Network. Also, the last of the thermal blankets will be installed.
Finally, before the spacecraft leaves the Payload Hazardous Servicing Facility, it will be fueled with its hydrazine attitude control propellant. Then, on Sept. 22, it is to be transported to a spin test facility on Cape Canaveral Air Station. There it will be mated to a Star 37 solid propellant upper stage, and the combined elements will undergo a series of spin balance tests.
Meanwhile, at Complex 17, the Delta II rocket will be undergoing erection and prelaunch checkout by Boeing. The first stage is scheduled to be installed into the launcher on Sept. 10. Three solid rocket boosters will be attached around the base of the first stage the next day. The second stage will be mated atop the first stage on Sept. 15, and the dual-sector spacecraft fairing will be hoisted into the cleanroom of the pad's mobile service tower the following day.
Deep Space 1 will be transported to Complex 17 on Oct. 5 for hoisting aboard the Delta rocket on Pad A and mating to the second stage. After the spacecraft undergoes state of health checks, the fairing can be placed around it three days later. Launch, currently targeted for Thursday, Oct. 15 is at 8:42:44 a.m. EDT. The launch period ends Nov. 10.
If the spacecraft is healthy when the primary mission is completed on Sept. 18, 1999, NASA could choose to continue the spacecraft's voyage. Deep Space 1 may then be on a trajectory resulting in the flyby in January 2001 of the dormant comet Wilson-Harrington that is in the process of changing from a comet to an asteroid. Finally, in September 2001, as the spacecraft continues on this trajectory, it may also do a flyby of an active comet, Borrelly.
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