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On a third and final tour of duty in the Jovian system, NASA's dauntless Galileo spacecraft makes its closest pass yet to Jupiter's outermost large moon.
Friday, May 25, 2001, the orbiter should skim over Callisto, at an altitude of about 123 kilometers, or 76 miles, at 7:24 a.m. EDT. If Callisto were the size of a baseball, that would be just a nickel's thickness away.
Mission managers expect the pull of the moon's gravity to alter Galileo's orbit around Jupiter. "The main reason we're flying so close to Callisto is to set up flybys of Io," said Dr. Eilene Theilig, Galileo project manager at NASA's Jet Propulsion Laboratory (JPL), Pasadena, CA. Io is an intensely volcanic moon closer to Jupiter that continually resurfaces itself with fiery eruptions.
Galileo will pass over polar regions of Io in August and October to help scientists determine if the seething and violent moon generates its own magnetic field. "Since we have to go close to Callisto anyway to get to Io, we'll take advantage of the opportunity for studying Callisto," said JPL's Dr. Torrence Johnson, Galileo project scientist.
Unlike the planet's other large moons, Callisto, which is about as big as the planet Mercury, appears to be inactive and still bears craters billions of years old.
Although earlier magnetic studies by Galileo indicated that Callisto may have a liquid saltwater layer deep beneath its surface, Callisto hasn't drawn the excitement generated by Io or its sister moon Europa, which appears to have liquid water closer to its surface, or two-toned Ganymede.
"Callisto is sort of the ugly duckling of the moons, but it's the one we need to look at to get the bombardment history of the Jovian system," Johnson added. "The craters on Callisto are the visible record of what sizes of comets and other objects have pelted Jupiter and its moons with what frequency over the past four billion years."
Data from the flyby will be transmitted to Earth over the next two months. Scheduled observations include high-resolution imaging to study the density of small craters and the details of how some features appear to be degraded or eroded, said Dr. Duane Bindschadler, leader of Galileo's science planning team. "Some earlier imaging of Callisto has shown fewer small craters than expected."
Scientists also plan to snap new pictures of Io, though from a much greater distance than Callisto, and hope to see if a volcanic plume detected near Io's North Pole five months ago is still active. On Aug. 5, Galileo will pass directly over the plume's source area at an altitude of less than 350 kilometers, or about 220 miles.
Another set of planned observations this week will point at Jupiter. Galileo will make a map of Jupiter's clouds in infrared wavelengths. "One goal is to see if fresh clouds are still being made at the same types of locations they were during similar mapping more than five years ago," said Dr. Kevin Baines, JPL atmospheric scientist. Another is to check for "brown barges," a type of dark cloud that was prominent on Jupiter when NASA's two Voyager spacecraft flew by in 1979, but has not been seen during the years since Galileo began orbiting Jupiter in 1995. Baines believes recent observations from Earth-based telescopes hint at a return of brown barges.
Galileo's mission was originally scheduled to end in 1997, but has been extended repeatedly as the spacecraft continues to return scientific discoveries. The orbiter has survived more than three times the cumulative radiation exposure it was designed to withstand. Some electronic components have been affected by the radiation, and each swing near Jupiter increases the odds of more serious damage from exposure to the radiation belts around the planet.
Galileo has made 30 previous flybys of Jupiter's large moons, including seven of Callisto. Before reaching Jupiter, it made close passes of Venus, Earth and two asteroids. After three more encounters with Io and one with the small inner moon Amalthea, Galileo's mission will end in 2003 with a final plunge into the crushing pressure of Jupiter's atmosphere.
For more information:
http://galileo.jpl.nasa.gov
A striking color picture showing mottled cloud patterns near Jupiter's north pole begins a sequence of more frequent release of Jupiter images from NASA's Cassini spacecraft as the craft gets nearer to the planet over the next two weeks.
The Cassini Imaging Team made the true-color, contrast-enhanced, sharpened composite picture released today from frames taken by Cassini's narrow angle camera as the spacecraft flew within 19 million kilometers (11.4 million miles) on Dec. 13, 2000. The details in Cassini's images of Jupiter surpass those seen in the highest resolution Hubble Space Telescope Planetary Camera images, notes Carolyn C. Porco of the University of Arizona, Cassini Imaging Team leader.
The picture of how cloud patterns at high latitude differ from the familiar horizontal bands around Jupiter's middle is available from the web site of the Cassini Imaging Science team at the University of Arizona, Tucson, at http://ciclops.lpl.arizona.edu/ciclops/ and from the website of NASA's Jet Propulsion Laboratory, Pasadena, Calif., at http://www.jpl.nasa.gov/pictures/jupiter
The imaging team and JPL plan to release pictures almost daily from now through Cassini's closest approach to Jupiter, on Dec. 30. The images will likely include shots of Jupiter's moons and rings, as well as its clouds.
They will be available at the web sites given above. Cassini is already close enough to Jupiter to return higher-resolution images than possible with the planetary camera of NASA's Earth-orbiting Hubble Space Telescope.
Cassini will use a boost from Jupiter's gravity to reach its ultimate destination, Saturn. While near Jupiter, it is studying that planet in collaboration with NASA's Galileo spacecraft, which has been orbiting Jupiter since Dec. 7, 1995. More information on the joint Cassini-Galileo observations is available at http://www.jpl.nasa.gov/jupiterflyby
The very first asteroids to be discovered were named after the major heroes of the Trojan War without regard for Greek vs Trojan (Achilles, Patroclus, Hector, Nestor). At this early point, 1906-7, presumably, astronomers didn't know that many, many more asteroids would be discovered, and so weren't thinking about a large-scale naming scheme that would have the leading group of asteroids as the 'Greek army' and the trailing group as the 'Trojan army'. Asteroids named after the first four do appear consistent with this naming scheme.
For more information, see http://cfa-www.harvard.edu/cfa/ps/lists/JupiterTrojans.html
For images, go to the Planetary Imaging Research Laboratory -
Galileo web page:
http://pirlwww.lpl.arizona.edu/~turtle/Releases/Releases.19_May_2000.htm
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When the Galileo spacecraft flew close by Jupiter's moon, Io, late last year and early this year, it took sharpest-ever pictures of the best volcanic show in the solar system.
Galileo took more than 100 high-resolution images during Io flybys on Oct. 11, Nov. 26, 1999, and Feb. 22, 2000. Results include pictures of an active lava flow as long as the Grand Canyon, a mile-high curtain of burning lava, a unique long-lived "wandering" volcanic plume, and a 6-mile-diameter lava lake that shines steady as a beacon. The Galileo imaging team reports the results in the May 19 issue of Science.
"Io is absolutely fascinating because every single thing we see is completely new and completely unexpected," said Jani Radebaugh, a graduate student at the University of Arizona who helps analyze the photographs. "You can take what you know about volcanology and about planetary processes, but in every picture we see, there's something new going on that we don't understand. There's something brand new, every time."
"Io is like a laboratory for large-scale volcanic experiments," said Alfred S. McEwen of the Galileo imaging team. McEwen directs the Planetary Imaging Research Laboratory (PIRL) at the UA Lunar and Planetary Lab (LPL). "We don't have controlled laboratories big enough to study these processes. And large-scale volcanic fields on Earth are very modified. So here's a place we can watch the changes and really understand how this activity might happen at this scale. With that insight, we can go back and reconsider what happened in Earth's past."
"I like Io as a model of what might be going on under the crust of Europa," said Paul Geissler, senior research associate at LPL and member of the Galileo imaging team. "The whole (jovian moon) system is a great exercise in comparative planetology," Geissler said. "You have four separate moons, separated at birth, and they've grown up completely differently. So it's very important to study them from that point of view."
The Galileo imaging scientists are trying to understand how Io's extraordinary volcanism fits within the big geologic picture of the moon and the jovian system. They'd like to discover the composition of Io's crust. They'd like to know if Io's interior holds a magma ocean - a question images alone won't answer. They use Galileo to explore how volcanoes erupt and modify the landscape, what the lavas are made of, and how Io's strange terrain forms and evolves.
Results discussed in the Science article include -
*Pele - Pele is a very unusual volcano, even for Io, in that it consistently shines brightly. The new images show it to be an active lava lake about 10 km (6 miles) across. Galileo imaging and spectral data show it must be at least 1,030 degrees Celsius (1,890 Fahrenheit). Nighttime pictures of Pele taken in October show a hot, glowing line at the margin of the Pele caldera. The researchers interpret this line to be where molten lava pushes against the caldera walls and is exposed, breaking through the edges of the crust that covers the lava lake. (A caldera is a depression that forms from collapse over a magma chamber.)
*Pillan - New high-resolution images of Pillan Patera, show a complex mix of pits, domes, channels and possibly rafted plates near a 70-km lava flow that erupted in June 1997. Such channels and rafted plates form when lava erupts at flow rates violent enough to destroy stable crust -- a kind of volcanism also seen on Mars and Earth. But pits and domes, which range in size from a few tens of meters to many hundreds of meters in diameter, are harder to explain. Possibly, They are vents of plumes, analogous to volcanic "rootless cones" on Earth.
The new images also reveal color properties of the dark diffuse deposits around Pillan that provide the first evidence that silicate particles are spewed more than 100 kilometers high in Io's plumes.
*Zamama - The new images show the primary vent at the westernmost end of the 100-km-long dark flow (roughly the length of Arizona's Grand Canyon) with lava flows forming a radial pattern around the vent. The 75-km Zamama plume comes not from the primary vent, but from the center of a lava field extending to the east.
*Prometheus - Prometheus is Io's most faithful, persistent plume. It has been seen in every image of the area taken by Voyager, Galileo and Hubble Space Telescope. Remarkably constant in size, shape and brightness throughout its observed history, Prometheus had "wandered" between 75 to 95 km west in the 20 years between the 1979 Voyager flyby and the 1996 Galileo flyby. In 1996, Galileo also saw a new dark flow extending between the Voyager-era and the Galileo-era plume sources.
McEwen and others on the Galileo imaging team had suggested that Prometheus comes not from the primary vent, but from the end of a lava flow - an argument that some of their peers questioned. The new Galileo evidence strengthens the UA researchers' case.
The latest Galileo images and spectra show two main hot spots. One is 15 km south of the caldera and marks where lava spews from a fissure to the surface. The other hot spot, 80 km to the west, is where the 100-km-high Prometheus plume rises above active lava beds.
"The new Io images pretty strongly confirm the view that the plume comes from the lava flow, not the volcano," McEwen said. "But that doesn't mean we understand it." Although Prometheus erupts at 10 times the rate of Kilauea, Earth's most active volcano, it in many ways resembles Kilauea, only on a larger scale, McEwen said. However, he added, "Prometheus' plume and its behavior is totally alien from anything seen on Earth."
*Emakong Patera - Emakong is one of the largest calderas on Io without an observed "hot spot." It features a brightly colored surface that may be sulfur lava flows. The images show that at some point lava filled the entire 40-km diameter caldera and overflowed. This has happened at a much smaller scale at Kilauea in Hawaii..
Emakong and many other calderas on Io are irregular in shape, rather than circular, as are Earth's calderas, Radebaugh said."That tells us there are interesting things going on underneath the surface of the crust. There's probably fractures and some stresses that make those irregular shapes when the surface collapses.
*Tvashtar Catena - A lava "curtain", or line of lava fountains, rises to 1.5 km above a linear fissure within one of the calderas. On Io, as on Earth, lava erupting from a fissure can create a curtain of fire along the fissure. But because Io's atmospheric pressure is a billion times less than the Earth's, because Io's gravity is lower and its lava is hotter, Io's lava fountains can reach 100 times higher than those on Earth.
* Mountains and related landforms - Researchers know of about 100 mountains on Io that do not appear to be volcanoes. Io's mountains resemble tilted blocks bounded by steep scarps, said LPL research associate Elizabeth Turtle of the Galileo imaging team. The highest mountain known on Io is 16 km high, Turtle said. The new photos suggest an intriguing association between mountains and calderas, which may help explain how both form, she added.
The sharp new Galileo photos show that several mountains have calderas cut into their sides. The photos also suggest that mountains and calderas are geologically related in other ways. For example, Turtle said, rising plumes of new material in Io's mantle may concentrate stresses acting in Io's crust, causing it to fail, forming mountains by thrust faulting. As the mountains are tilted up, layers of weak, sulfur-rich material deposited by Io's plumes may fail, resulting in tremendous landslides.
From a mosaic of new pictures of the lava-filled depression called Hi'iaka Patera and its two bordering mountains, UA graduate student Windy Jaeger speculates that Io's crust there might have been laterally pulled apart. It may be only coincidence that the north and south parts, if pushed together, would fit together like pieces of a puzzle, Jaeger said. At this point, evidence is only circumstantial.
But if Hi'iaka Patera was once pulled apart, McEwen said, "that would be very surprising, because on Earth a movement on that scale is associated with plate tectonics. But we see no evidence for plate tectonics on Io. There again might be some unique Ionian process involved."
Jupiter's fiery moon Io is providing scientists with a window on volcanic activity and colossal lava flows similar to those that raged on Earth eons ago, thanks to new pictures and data gathered by NASA's Galileo spacecraft.
The sharp images of Io were taken on Oct. 11 during the closest-ever spacecraft flyby of the moon, when Galileo dipped to just 380 miles (611 kilometers) above Io's surface. The new data reveal that Io, the most volcanic body in the solar system, is even more active than previously suspected, with more than 100 erupting volcanoes.
"The latest flyby has shown us gigantic lava flows and lava lakes, and towering, collapsing mountains," said Dr. Alfred McEwen of the University of Arizona, Tucson, a member of the Galileo imaging team. "Io makes Dante's Inferno seem like another day in paradise."
Ancient rocks on Earth and other rocky planets show evidence of immense volcanic eruptions. The last comparable lava eruption on Earth occurred 15 million years ago, and itUs been over 2 billion years since lava as hot as that found on Io (reaching 2,700 degrees Fahrenheit) flowed on Earth.
"No people were around to observe and document these past events," said Dr. Torrence Johnson, Galileo project scientist at NASA's Jet Propulsion Laboratory (JPL), Pasadena, CA. "Io is the next best thing to traveling back in time to Earth's earlier years. It gives us an opportunity to watch, in action, phenomena long dead in the rest of the solar system."
The new data focus on three of Io's most active volcanoes -- Pele, Loki and Prometheus. The vent region of Pele has an intense high-temperature hot spot that is remarkably steady, unlike lava flows that erupt in pulses, spread out over large areas, and then cool over time. This leads scientists to hypothesize that there must be an extremely active lava lake at Pele that constantly exposes fresh lava. Galileo's camera snapped a close-up picture showing part of the volcano glowing in the dark. Hot lava, at most a few minutes old, forms a thin, curving line more than six miles (10 kilometers) long and up to 150 feet (50 meters) wide. Scientists believe this line is glowing liquid lava exposed as the solidifying crust breaks up along the caldera's walls. This is similar to the behavior of active lava lakes in Hawaii, although Pele's lava lake is a hundred times larger.
Loki, the most powerful volcano in the solar system, consistently puts out more heat than all of Earth's active volcanoes combined. Two of Galileo's instruments -- the photopolarimeter radiometer and near-infrared mapping spectrometer - -- have provided detailed temperature maps of Loki. "Unlike the active lava lake at Pele, Loki has an enormous caldera that is repeatedly flooded by lava, over an area larger than the state of Maryland," said Dr. Rosaly Lopes-Gautier of JPL, a member of the spectrometer team.
Observations of Prometheus made early in the Galileo mission showed a new lava flow and a plume erupting from a location about 60 miles (100 kilometers) west of the area where the plume was observed in 1979 by NASA's Voyager spacecraft. New Galileo data clarify where lava is erupting, advancing, and producing plumes. The most unexpected result is that the 50-mile (75 kilometer) tall plume erupts from under a lava flow, far from the main volcano. The plume is fed by vaporized sulfur dioxide-rich snow under the lava flow.
Mountains on Io are much taller than Earth's largest mountains, towering up to 52,000 feet (16 kilometers) high. Paradoxically, they do not appear to be volcanoes. Scientists are not sure how the mountains form, but new Galileo images provide a fascinating picture of how they die. Concentric ridges covering the mountains and surrounding plateaus offer evidence that the mountains generate huge landslides as they collapse under the force of gravity. The ridges bear a striking resemblance to the rugged terrain surrounding giant Olympus Mons on Mars.
Scientists hope to learn more about dynamic Io when Galileo swoops down for an even closer look on Nov. 25 from an altitude of only 186 miles (300 kilometers). Because Io's orbit is bathed in intense radiation from Jupiter's radiation belts, there is a risk of radiation damage to spacecraft components. In fact, several spacecraft systems sustained damage during the October flyby. Given these radiation risks, the Io flybys were scheduled near the end of the spacecraft's two-year extended mission.
New Io images taken by the spacecraft are available at:
http://www.jpl.nasa.gov/pictures/io
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-the newsletter of NASA's Radio JOVE Project "Planetary Radio Astronomy for Schools"
JUNE 1999 ISSUE Visit our Web Site:
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http://radiojove.gsfc.nasa.gov
Email Radio JOVE at: thieman@nssdc.gsfc.nasa.gov
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CONTENTS
1. Radio JOVE Project Leader's Welcome
2. Editor's Welcome
3. RJ News
4. Feedback - RJ schools in action.
5. On the Horizon - Upcoming events.
6. Radio JOVE at a Glance
7. Acknowledgments
8. Subscription Information
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RADIO JOVE PROJECT LEADER'S WELCOME
by Jim Thieman, NASA GSFC
Hello to all present and future Radio JOVE project participants! My name is Jim Thieman and I am the person who is listed as the "principal investigator" for the two grants we have received for Radio JOVE, a Goddard Space Flight Center Director's Discretionary Fund grant and an Initiative to Develop Education through Astronomy and Space Science (IDEAS) grant administered by the Space Telescope Science Institute. I am a scientist at NASA's Goddard Space Flight Center, a manager of the National Space Science Data Center information systems, and also a manager of the NASA Sun-Earth Connection Education Forum. These tasks keep me busy, but, aside from the ever-present government paperwork, most of what I do for NASA is very enjoyable, especially projects like Radio JOVE.
The Radio JOVE project team is made up of many dedicated people, however, and I hope that with time we will be able to introduce you to all of them. We are all tied together by an interest in radio astronomy and education and hope that you too will enjoy sharing in the excitement of studying the strange and unique radio phenomena of the solar system.
We are a very new project since we did not receive our first grant until last November. Much of the foundation had already been laid, however, since a number of our group had been thinking of doing something like this for years. Thus, it came together very quickly. Dick Flagg of RF Associates in Honolulu, Hawaii had already put together a design for a radio receiver especially for observing Jupiter based on his past experience at the University of Florida Radio Observatory.
The antenna design and testing have involved many of the team. We also appreciate the quick feedback we have been getting from our group of beta testers. As mentioned in our literature, the kit is intended for receiving signals from either Jupiter or the Sun. Jupiter is a relatively predictable radio source, but it is very difficult to receive Jupiter radio emissions when it is close to the Sun. For the past few months, almost since the inception of the project, Jupiter has been near the Sun and we have not been able to test Jupiter radio reception under good observing conditions. Now Jupiter is moving away from the Sun and the coming months will bring prime observing conditions. We hope our participants will share with us the excitement of seeing how well the kit works in observing Jupiter. Our Radio JOVE website will indicate the best time for observing the coming Jovian radio storms.
Solar observations are, of course, also possible but not as predictable. Nonetheless, the Sun is approaching the maximum of its eleven-year activity cycle and the number of solar storms observable through radio emission should increase as well in the months ahead.
This summer we will have several teachers and students helping us to build our Radio JOVE website. We expect to have radio astronomy background information, training in what to expect, educational activities, news items, bulletin boards, and hopefully data contributions, feedback, and interactions among you, the participants. So, don't be shy, let us know how you are doing and share with us what you and hopefully all of us are discovering about our solar system.
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EDITOR'S WELCOME
by Leonard Garcia, NASA GSFC
Welcome to the first issue of The JOVE Bulletin, the newsletter of Radio JOVE. We will present here the latest updates to the Radio JOVE program. Here you may find announcements of updates to our website, new software that is available, and other web sites to check out. This is your newsletter; a forum where you, both teachers and students, can announce your successes. Whether it is letting us know how building your RJ receiver and antenna proceeded, announcing your first detection of Solar or Jovian radio bursts or ways that you have incorporated Radio JOVE in the classroom, we want to hear from you! We also want to hear about ways we can improve our manuals, websites, software (and newletters!) We want to know what problems you've encountered in building and/or operating your Radio JOVE equipment. We also would like to know if you've come up with novel solutions to problems you may have faced in operating/building the RJ equipment. Your tips and suggestions may help some other schools that are facing the same problem. Good luck and I hope you enjoy being members of Radio JOVE!
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RADIO JOVE NEWS
*Members of the Radio JOVE Core Team are presenting information on the Radio JOVE program at two scientific conferences this month. Chuck Higgins went to Boston, MA, to present a poster at a meeting of the American Geophysical Union. Leonard Garcia is presenting a Radio JOVE poster in Chicago, IL, at a meeting of the American Astronomical Society.
*Application forms to participate in Radio JOVE will be available soon from the Radio JOVE Web site http://radiojove.gsfc.nasa.gov
*Francisco Reyes, Core Team member at the University of Florida, gave a talk to students at the P.K. Yonge school about Radio JOVE.
*The Radio JOVE CDs have gone out recently. These CDs contain software to analyze the Radio JOVE receiver output, the instruction manuals and photos of the equipment as well as copies of several of our web pages. Please let us know your thoughts on the CD.
*Radio JOVE Online observatory has officially begun construction as the University of Florida crew begins software development. A student-programmer has been hired to assist in the software and webpage development. The radio link for the observatory will begin as soon as the contractor is hired.
*Dean Knight of Sonoma Valley High School in Sonoma, CA writes that he has 9 students (mostly 9th graders) working in teams of two after school on the Radio JOVE RJ 1.1 receiver and antenna. Thank you for your findings in building and testing the equipment. Please keep us informed on your progress.
*Linden Lundback and Brian Cowan, INSPIRE team members from Watrous, SK, Canada, provided us with very thorough descriptions of their findings in building the Radio JOVE receiver. Their suggestions for improvements to the manual are greatly appreciated.
*Nancy Rocheleau of the Sacred Heart Academy in Honolulu, Hawaii writes us with news that eight students from her class successfully completed their RJ 1.1 receiver. Congratulations to Sandy Liang, Elna Oshiro, Ahreum Kang, Dawoon Kang, Akiko Furutani, Peggy Lau, Tracy Wang and Carolyn Kawamoto. We are looking forward to more reports from you and appreciate your thoughtful input on improvements to the receiver and antenna manuals.
*We will provide more details of the results of the beta testers in upcoming issues of The JOVE Bulletin. We will also be posting more information on our website.
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FEEDBACK - RJ SCHOOLS IN ACTION
- -We've had great response from our beta testers. Included in this section are two letters written by students at Chaffey High School in Ontario, California.
Dear Creator(s) of JOVE,
Constructing the JOVE receiver was a thrill. I haven't been involved in such an innovative area of study since the INSPIRE project, and my experience working on the JOVE receiver was quite interesting. I endorse projects such as INSPIRE and JOVE because they elaborate the ever expanding curiosity of high school students nation wide. Over the duration of a few weeks, my physics professor, fellow student and I accepted the challenge of building the JOVE receiver. We were issued a kit, told that it was a trial kit, and that we should attempt to assemble the receiver and critique the clarity of the instructions according to how we perceived them to be. Over all the soldering procedure was a success reassured by the bright LED. I had never soldered prior to this my entire life and am now comfortable with my ability to do so. Our only confusion in this area dwelled in the interpretation of the resistor color scheme. Double gold bands were interesting to translate from the provided information on the subject of multipliers and other resistor specifications. Had our teacher not resolved our dilemma with his electronic cognizance, we would have been on our way to Radio Shack's customer service desk for enlightenment. In all polite constructive criticism, definite problems occurred when we reached Testing and Alignment section of the project. We had difficulty with the oscillator tuning and oscilloscope reading. I am aware that this section is by far the most difficult to execute and there is purpose behind the inclusion of four different methods and trouble shooting procedures. We were not even receiving steady tone through our speaker/amplifier and were quite bilked by the oscilloscope's opinion of what was going on. During the receiver's assembly only minor setbacks occurred due to slightly vague instructions and ignorance on our part. A guide book that could anticipate every possible confusion that could arise with the exclusive JOVE line of receivers written in layman's with an elaborate glossary from Ampere to Zeta would be ideal. Concluding on a more practical note, perhaps a hotline-telephone # and/or computer site- where the fascinated and interested, yet the easily confused and partially perplexed individuals like my self could seek refuge in a time of mild frustration. I want to thank you again for the opportunity to broaden my horizons - this time all the way to Jupiter's inner moon from the comfort of my own backyard. My interaction with the project was indubitably a positive experience.
Sincerely,
Andre' Ouellette
Class of 1999
Chaffey High School
Ontario, California, U.S.A.
Putting together the JOVE receiver was a great learning experience. My partner and I had never done something like this before. The instructions were well written. The only trouble we had was a small part in the organization; we didn't know where to put in the ends of the Resistor r28 through r31 and we had trouble installing the volume control to the right place. We quickly caught on to that, though, and the rest was just as the instructions read.
Our teacher gave us brief instructions in soldering the components. Being the first time doing this we were amazed that is worked. We followed the steps accurately and of course we expected it to work, but to see it happen was just amazing. This was fun in the making and we all learned many things and this makes me want to further my experience in electronics.
Daniel Chaffey
High School
Ontario, California, U.S.A.
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ON THE HORIZON
- UPCOMING EVENTS by Chuck Higgins, NASA GSFC
* A Radio JOVE summer student, Albert Davison, a junior in astronomy from the University of Maryland, begins working at Goddard Space Flight Center. He will help the JOVE team with hardware and software checkout, revisions, and testing. He will also assist with the education development as needed. A second student, Autumn Thayer, a high school student from Maryland, will be joining us on June 28th to help with the Radio JOVE summer activities.
June 1999
* Radio JOVE kits are finalized and ready to be shipped to interested schools and persons. The first 100 kits ordered by schools (Schools ONLY) will receive a subsidized kit at approximately one-half of the regular price of the kit. All kits ordered by schools after the first 100 will be sold at the regular price (approx. $100.00). Any individual may order a kit at any time at the regular price (approx. $100.00).
* Two summer teacher interns, Bill Pine from Chaffey High School in Ontario, California and Tom Smith from Briggs-Chaney Middle School in Maryland, arrive at Goddard Space Flight Center to begin working on the educational curricula for Radio JOVE. This will include lesson plan development, lab exercise development, and more.
Upcoming Predicted Jovian Radio Noise Storms The position of Jupiter in the sky for northern hemisphere observers is not favorable for the months of May, June, and the first part of July. Jupiter is visible in the pre-dawn sky at low elevation at the end of May through June. It rises earlier and earlier (about 2 hours earlier each month) until it rises about midnight in the latter half of July. (Source: The Observer's Handbook). Due to the unfavorable position of Jupiter the predicted storms for May, June and early July will not be detectable by the RJ antenna. Please see our website for the list of predicted storms for late July, August, and September.
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Radio JOVE at a Glance
(from the RJ Web Site)
* Teaches planetary and solar radio astronomy, space physics, and the scientific method
* Target audience - Teachers and students of high school / college science courses
* Provides teachers and students with a hands-on radio astronomy experience
* Gain experience in electronics construction and testing
* Interact with other Radio JOVE schools to exchange data, ideas, and experiences
* Radio JOVE kits available for $100, additional equipment is required, including antenna supports, a tape recorder, and a PC with a sound card
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ACKNOWLEDGMENTS
The Radio JOVE project is an educational/public outreach program involving scientists and educators from NASA, Raytheon ITSS, the University of Florida, the Florida Space Grant Consortium, RF Associates and The INSPIRE Project, Inc.
The Radio JOVE project wishes to acknowledge support from the NASA/Goddard Space Flight Center Director's Discretionary Fund and the Initiative to Develop Education through Astronomy and Space Science (IDEAS) grant program administered by the Space Telescope Science Institute.
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THE JOVE BULLETIN SUBSCRIPTION INFORMATION
The JOVE Bulletin is published several times a year. It is a free service of the Radio JOVE Project. We hope you will find it of value. If any of your friends would like to subscribe, they may do so by sending
E-mail to Leonard.Garcia@gsfc.nasa.gov
If you do not want to receive any more issues, send E-mail to
Leonard.Garcia@gsfc.nasa.gov
Back issues are available on the Radio JOVE Project Web site,
http://radiojove.gsfc.nasa.gov/
For assistance or information send inquiries to:
Radio JOVE Project
Code 633
NASA Goddard Space Flight Center
Greenbelt, Maryland 20771 USA
or
Email: thieman@nssdc.gsfc.nasa.gov
FAX: 1-301-286-1771
NASA's Galileo spacecraft has detected a thin carbon dioxide atmosphere on Jupiter's moon Callisto, and has confirmed the existence of carbon dioxide on Callisto's surface. The findings appear in the February 5 issue of the journal Science.
This latest discovery means that all four of Jupiter's large Galilean moons -- Callisto, Europa, Io and Ganymede -- have some form of atmosphere.
"Callisto's atmosphere is so tenuous that the carbon dioxide particles are literally drifting around without bumping into one another," said Dr. Robert Carlson of NASA's Jet Propulsion Laboratory, Pasadena, CA, principal investigator for Galileo's near-infrared mapping spectrometer instrument. "An atmosphere this thin is known as an exosphere."
The instrument detected the carbon dioxide atmosphere during observations of Callisto made during the 10th orbit around Jupiter in September 1997. Carlson says he and other scientists were following up on discoveries made by Galileo upon its arrival at Jupiter's system in 1995. The spacecraft detected what appeared to be carbon dioxide on Callisto's surface. This latest finding confirms that the surface chemical was, in fact, carbon dioxide, and that the chemical also appears in the atmosphere above Callisto.
"An atmosphere this thin is easily lost due to ultraviolet radiation from the Sun, which breaks the molecules into ions and electrons which are swept away by Jupiter's magnetic field," said Carlson. "For us to find such an atmosphere implies that there is a steady flux of carbon dioxide into the atmosphere. Venting of gas from the interior is one possibility, and Galileo images show surface erosion that suggests carbon dioxide outgassing."
Previous findings indicated that two of Jupiter's moons, Europa and Ganymede, have a thin oxygen atmosphere, while Io's atmosphere contains sulfur dioxide.
"We're anxious to look for other gases that may be contained in Callisto's atmosphere," said Carlson. Scientists will have that opportunity when Galileo observes Callisto during two of four flybys planned during the remainder of the current extended mission. Galileo will make observations of Callisto during encounters in May and June; it will be observing other targets during flybys of Callisto in August and September.
Those encounters will take place before the two Io flybys that will wrap up the spacecraft's extended mission, known as Galileo Europa Mission. During the extended mission, Galileo has flown by Europa eight times. The spacecraft has been orbiting Jupiter and its four largest moons for more than three years.
spacecraft are available on the Internet at http://www.jpl.nasa.gov/galileo . Images are also available at http://www.photojournal.jpl.nasa.gov .
New data from NASA's Galileo spacecraft have prompted scientists to modify their concept of the interior structure of Jupiter's moon, Callisto, and suggest that Callisto has evolved differently than the other largest Jovian moons -- Io, Ganymede and Europa. The new findings, to be published in the journal Science on Friday, June 5, will be presented Monday, June 8 at the American Astronomical Society meeting in San Diego, CA.
"Previous Galileo data had indicated that Callisto's interior was totally undifferentiated," said Dr. John Anderson, planetary scientist at NASA's Jet Propulsion Laboratory, Pasadena, CA. "But new information suggests Callisto has a strange interior--it's not completely uniform nor does it vary dramatically. There are signs that interior materials, most likely compressed ice and rock, have settled partially, with the percentage of rock increasing toward the center of Callisto."
The new information was collected during Galileo's third Callisto encounter in September 1997. Anderson reported on the findings, along with UCLA geophysics and planetary physics professor Gerald Schubert, a Galileo gravity investigator, and Dr. William B. Moore, also of UCLA; and Dr. Robert A. Jacobson, Eunice L. Lau, and William L. Sjogren of JPL.
Scientists now believe Callisto is different from Io, Ganymede and Europa, which have differentiated structures with separated layers. There is strong evidence that Ganymede is separated into a metallic core, rock mantle, and ice-rich outer shell, while Io has a metallic core and a rock mantle but no ice.
"The fact that Callisto is the only one of the four large Jovian moons that is not completely differentiated raises an intriguing possibility," said Schubert. "Because Io, Ganymede and Europa are closer to Jupiter, they have been more affected by gravitational squeezing and subsequent heating. Over time, the forces exerted on the three inner moons have caused different constituents such as water ice, rock, and metal to separate into different layers. However, because Callisto is farther from Jupiter, it is "half-baked" compared to the other moons, with its ingredients somewhat separated but still largely mixed together," he said.
"Learning about the structure of these celestial bodies enhances our knowledge of how all planets and moons form and evolve, including our own Earth and Moon," Schubert added.
Scientists had previously reported a differentiated interior for Europa, consisting of a metallic core surrounded by a rock mantle and a water ice-liquid outer shell. They are now refining the model by studying the newest Galileo data, including that gathered during the closest-ever Europa flyby in December 1997, at an altitude of 205 kilometers (127 miles). Europa's metallic core could be up to half the size of the moon's radius, with the water ice-liquid shell estimated to be between 80 to 170 kilometers thick (50 to 106 miles), with 100 km (62 miles) considered the most likely thickness. As more data become available from additional flybys, scientists hope to learn more about Europa's structure. Europa is of particular interest because of the prospect that liquid oceans may lie beneath its icy crust.
Information about the interior structure of Jupiter's moons is obtained by studying radio Doppler data that is gathered when the Galileo spacecraft flies by the satellites. Each moon exerts a gravitational tug, and the strength of that tug is affected by the distribution of rock inside. The tug, in turn, changes the spacecraft's speed and the radio frequency of its signals. By studying those changes, scientists can characterize the rock content and structure of the body.
The Galileo spacecraft entered orbit around Jupiter on December 7, 1995, and spent two years studying Jupiter, its four largest moons and its magnetosphere during its primary mission. The spacecraft is now in the midst of a two-year extension, known as the Galileo Europa Mission. JPL manages the Galileo mission for NASA's Office of Space Science, Washington, D.C. JPL is a division of the California Institute of Technology, Pasadena, CA.
Additional information about the Galileo mission and images sent back by the spacecraft is available on the Internet at: http://www.jpl.nasa.gov/galileo/. Images are also available at: http://photojournal.jpl.nasa.gov .
In December 1997, the Galileo spacecraft completed its originally targeted mission. Because of the problem with the deployment of its main antenna, not all the hoped for data were gathered, but it is estimated that the success rate was 70%, much better than feared for a while. It has made four passes by Ganymede, three by Europa, and two by Callisto. It has not been able to make observations close to Io, though it has Io observations from farther off. Now, through the end of 1999, the spacecraft is in an "Extended Mission" phase. It will have 8 close encounters with Europa. Then it will use 4 close encounters with Callisto to change its orbit so that it can make 2 passes close to Io, which may be suicidal because the spacecraft will have to travel through Jupiter's radiation belts. Studying the gravitational tugs on the spacecraft are revealing the structure of the interiors of the moons. The two inner moons, Io and Europa, are smaller than the outer pair of Galilean satellites and are mainly made of rock and metal. The other two Galilean satellites, Ganymede and Callisto, which are close to the size of Mercury, are about half ice. Io, Europa, and Ganymede seem to have cores of iron and nickel surrounded by rocky shells. Callisto appears to be a uniform mixture of ice and rock through and through. The largest interest is in Europa's ocean, and whether there is really liquid water under an icy crust, as it seems.
The Galileo spacecraft has now spent more than two years in orbit around Jupiter, studying the giant planet and its moons Io, Ganymede, Europa and Callisto. Observations made by Galileo of the Jovian system have included:
- Jupiter: a dynamic climate of wet and dry regions and auroras
in its atmosphere.
- Io: massive volcanic eruptions and an ionosphere.
- Europa: a metallic core; ice rafts hinting at the possibility
of a liquid ocean lying underneath; an atmosphere.
- Callisto: no core but hints of an atmosphere.
- Ganymede: a magnetosphere, magnetic field and metallic core;
strong tectonic processes.
Galileo is now in the second phase of its mission, called the Galileo Europa Mission (GEM), the main objectives of which are to conduct a detailed study of Europa over 14 months, then plunge repeatedly through the Io plasma torus to reach the volcanic moon Io.
A Hubble NICMOS infrared set of images shows Jupiter's atmosphere, its ring, and its moon Metis.
