Дата: 19 января 1998 (1998-01-19)
От: Alexander Bondugin
Тема: 1997 - The Year Of Mars Pathfinder
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From The "JPL Universe"
Special issue: 1997 in review
January 9, 1998
1997 - The year of Mars Pathfinder
Mission captivates the world while setting new standards in
planetary exploration
By DIANE AINSWORTH
Of all the headline news in 1997, Mars Pathfinder's
remarkable landing and performance on the surface of frozen,
nearly airless Mars stole the show. Pathfinder became a landmark
mission and a catalyst for new and affordable ways of exploring
other worlds.
Pathfinder's landing marked America's return to the red
planet after more than 20 years. In addition to a swift, seven-
month cruise to the planet, Pathfinder dived directly into the
Martian atmosphere and landed with the aid of a parachute and
giant cocoon of airbags. This novel entry technique had never
been demonstrated before.
Nor had any spacecraft before Pathfinder carried a roving
vehicle the size of a small microwave oven to the surface of
another planet. Pathfinder's companion rover, named "Sojourner"
after Sojourner Truth, a female abolitionist who lived during
the American Civil War, was the first robotic vehicle ever to
make direct measurements of rocks and soil on Mars.
Over the course of three months -- which was three times the
design lifetime of the spacecraft -- Mars Pathfinder returned
about 2.6 gigabits of data, which included more than 16,000
images of the Martian landscape from the lander camera, 550
images from the rover and about 8.5 million temperature,
pressure and wind measurements. All science objectives had been
fulfilled when the mission ended, 83 days after a nearly perfect
landing on July 4. The only remaining objective was to complete
a high-resolution 360-degree image of the landing site called
the "Super Pan," of which 83 percent had been received. The last
successful data transmission cycle from Pathfinder was completed
at 3:23 a.m. Pacific Daylight Time on Sept. 27, 1997.
Sojourner, built to last seven days, wound up roaming the
floor of an ancient flood basin and exploring about 250 square
meters (820 square feet) of the Martian surface. In all, the
rover traveled a total of about 100 meters (328 feet) in 230
commanded maneuvers, performed more than 16 in-situ chemical
analyses of rocks and soil, and carried out numerous soil
mechanics and technology experiments.
"The mission demonstrated a reliable and low-cost system for
placing science payloads on the surface of Mars," said Project
Manager Brian Muirhead. "We've validated NASA's commitment to
low-cost planetary exploration, shown the usefulness of sending
microrovers to explore Mars, and obtained significant science
data to help understand the structure and meteorology of the
Martian atmosphere and to understand the composition of the
Martian rocks and soil."
"Pathfinder was an unequivocal success and has given us
phenomenal insights into how to operate future landers and
rovers on the surface of Mars," added Dr. Wesley Huntress,
associate administrator for science at NASA Headquarters, when
the mission was officially declared over. "I congratulate the
entire Pathfinder team on their accomplishment, which is a lofty
but wonderful standard for future missions to attempt to
exceed."
Part of NASA's Discovery program of low-cost planetary
missions with highly focused science goals, the spacecraft used
an innovative method of directly entering the Martian
atmosphere. Assisted by an 11-meter (36-foot) diameter
parachute, the spacecraft descended to the surface of Mars and
landed, using airbags to cushion the impact.
This innovative method of diving into the Martian atmosphere
worked like a charm. "Every event during the entry, descent and
landing (EDL) went almost perfectly," said Mission Manager
Richard Cook. "The sequences were executed right on time and
well within our margins."
Pathfinder's descent through the Martian atmosphere was
nearly flawless. After being suspended from a 20-meter (65-foot)
bridle and firing its retro rockets, the spacecraft released a
5.8-meter (19-foot) diameter cluster of airbags intended to
soften the landing. The entry, descent and landing sequence
marked the first time this airbag technique had been used.
Pathfinder hit the ground at a speed of about 18 meters per
second (40 mph) and bounced about 16 times across the landscape
before coming to a halt, Dr. Tim Parker of JPL later reported.
The airbag sustained little damage. To top it off, the
spacecraft landed on its base petal, consequently allowing a
thumb-sized auxiliary antenna to communicate the successful
landing just three minutes after impact.
Once safely on the surface, Pathfinder opened its solar-
powered petals and unveiled the small, 10.5-kilogram (23-pound)
rover and science instruments to their new home. Science
operations got under way within a day of landing, after the
rover had exited the lander using one of two exit ramps.
As the rover ventured out into unexplored territory, the
lander's camera began to image the surroundings, often taking
shots of the rover so that scientists and engineers could
monitor the vehicle's progress. A new portrait of the Martian
environment began to emerge as the spacecraft started to record
weather patterns, atmospheric opacity, winds and a variety of
other Martian conditions. The rover's alpha proton X-ray
spectrometer began studying rocks and making direct measurements
of their chemical compositions, another first in this mission.
Some of the rocks near the landing site were rich in silica,
or quartz, and some were identified as possible conglomerates,
reported Project Scientist Dr. Matthew Golombek and his
colleagues. Conglomerates are usually formed by running water,
which smoothes and rounds pebbles and cobbles found in the
conglomerate. Running water would also be the agent necessary to
deposit these rocks in a sand or clay matrix.
"If you consider all of the evidence we have at Ares Vallis -
- the rounded pebbles and cobbles and the possible conglomerate,
the abundant sand- and dust-sized particles and models for their
origins, in addition to the high silica rocks," Golombek said,
"it suggests a water-rich planet that may have been more Earth-
like than previously recognized, with a warmer and wetter past
in which liquid water was stable and the atmosphere was
thicker."
A panoramic view of Pathfinder's Ares Vallis landing site was
featured on the cover of the Dec. 5, 1997 issue of Science,
showing traces of this warmer, wetter past. The Ares Vallis
flood plain was covered with a variety of rock types, boulders,
rounded and semi-rounded cobbles and pebbles, deposited by
floods which occurred early in Mars' evolution.
"Before the Pathfinder mission, knowledge of the kinds of
rocks present on Mars was based mostly on the Martian meteorites
found on Earth, which are all igneous rocks rich in magnesium
and iron and relatively low in silica," Golombek and his
colleagues reported in Science. Chemical analyses of more than
16 rocks and studies of different regions of soil--along with
spectral imaging of rock colors, textures and structures--
confirmed that these rocks had compositions distinct from those
of the Martian meteorites found on Earth.
"The rocks that were analyzed by the rover's alpha proton X-
ray spectrometer were basaltic or volcanic rocks, with granite-
like origins, known as andesitic rocks," Golombek said. "The
high silica or quartz content of some rocks suggests that they
were formed as the crust of Mars was being recycled, or cooled
and heated up, by the underlying mantle. Analyses of rocks with
lower silica content appear to be rich in sulfur, implying that
they are covered with dust or weathered. Rover images show that
some rocks appear to have small air sacks or cavities, which
would indicate that they may be volcanic. In addition, the soils
are chemically distinct from the rocks measured at the landing
site."
Golombek noted that the rocky surface and rock types found in
Ares Vallis matched the characteristics of a flood plain on
Earth, created when a catastrophic flood washed rocks and
surface materials from another region into the basin. Ares
Vallis was formed in the same way that the 40-kilometer-long
(25-mile) Ephrata Fan of the Channeled Scabland in Washington
state was formed, and the Pathfinder scientists traveled to that
area a year before the landing to study the geology and
experiment with rover prototype hardware.
Additional data from the Pathfinder landing site revealed
that magnetic dust in the Martian atmosphere had been gradually
blanketing most of the magnetic targets on the lander over time.
"The dust is bright red, with magnetic properties that are
similar to that of composite particles," Golombek said. "A small
amount of the mineral maghemite has been deposited almost like a
stain or cement. These results could be interpreted to mean that
the iron was dissolved out of crustal materials in water,
suggesting an active hydrologic cycle on Mars. The maghemite
stain could be a freeze-dried precipitate."
Another team of scientists used daily radio Doppler tracking
and less frequent two-way radio ranging techniques during
communications sessions with the spacecraft to pinpoint the
location of the Pathfinder lander in inertial space and the
direction of Mars' rotational axis.
Dr. William Folkner, an interdisciplinary scientist at JPL,
and co-investigators were able to estimate the Martian polar
moment of inertia, which showed that Mars had a dense metallic
core surrounded by a lighter mantle. The results implied that
the radius of Mars' core was larger than about 1,300 kilometers
(807 miles) and less than about 2,400 kilometers (1,490 miles).
Mars' core and mantle were probably warmer than Earth's at
comparable depths.
"Variations in Mars' rotation around its own spin axis are
thought to be dominated by mass exchange between the polar caps
and the atmosphere," Folkner said. "During winter, part of the
atmosphere condenses at the poles. If the southern cap increased
symmetrically as the northern cap decreased, then there would
not be any change in moment of inertia or rotation rate.
However, because of Mars' orbital eccentricity, differences in
elevation and albedo, the polar caps are not formed
symmetrically.
"The unbalanced waxing and waning of the Martian polar ice
caps results in seasonal changes in air pressure at the
Pathfinder and Viking landing sites," he added. "These changes
in air pressure are correlated with changes in Mars' rotation
rate, which have been observed in our radio tracking
measurements."
The season and time of arrival of Mars Pathfinder in the late
northern summer resulted in some variations in the temperature
of the upper atmosphere compared to Viking data, Dr. Tim
Schofield, JPL team leader of the atmospheric structure and
meteorology instrument, and colleagues reported.
High in the atmosphere, at altitudes of 80 kilometers (50
miles) above the surface, temperatures were cold enough to make
carbon dioxide condense and form carbon dioxide clouds. At
altitudes of between 60 and 120 kilometers (37 and 75 miles),
the Martian atmosphere was an average of 20 degrees colder than
Viking measurements, Schofield said. Seasonal variations and
Pathfinder's entry at 3 a.m. local solar time, compared with
Viking's entry at 4 p.m. local solar time, may account for these
variations. On the surface, however, daytime temperatures were
typically 10 to 12 degrees warmer than Viking surface
temperatures.
Pathfinder measured regular pressure fluctuations twice a
day, which suggested that a moderate amount of dust was being
uniformly mixed in a warm lower atmosphere, as was the case with
Viking data. The daily average pressure reached a minimum on the
20th day of the mission (Sol 20), indicating the winter south
polar cap had reached its maximum size.
Schofield said that surface temperatures followed a regular
daily cycle, with a maximum of 15 degrees Fahrenheit during the
day and a minimum of minus 105 degrees Fahrenheit at night. The
science team also observed rapid daytime temperature
fluctuations of up to 30 degrees Fahrenheit in as little as 25
to 30 seconds. These observations suggested that cold air was
warmed by the surface and convected upward in small eddies.
Among a variety of other science findings, Pathfinder also
observed winds that were light and variable compared to the
winds encountered by the Viking landers. The winds blew steadily
from the south during the Martian nights, but during the day
they rotated in a clockwise direction from south to west to
north to east. Whirlwinds or dust devils were detected
repeatedly from mid-morning through the late afternoons.
Additional scientific findings are likely to result in the
months ahead as researchers continue to analyze data from this
mission. Meanwhile, another mission--Mars Global Surveyor--will be
observing the planet from space, while other missions gear up
for launches in the near term. As part of a sustained program of
exploration, Mars is likely to become a familiar place to
everyone over the next decade.
###
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Дата: 19 января 1998 (1998-01-19)
От: Alexander Bondugin
Тема: Reconfigured Mars Global Surveyor Ready For Mission Based On New Orbit
Subject: Reconfigured Mars Global Surveyor Ready For Mission Based On New Orbit
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From The "JPL Universe"
Special issue: 1997 in review
January 9, 1998
Reconfigured MGS ready for mission based on new orbit
By DIANE AINSWORTH
1997 saw the arrival of two spacecraft at Mars and the
beginning of an extended program of Mars exploration. Two months
after Pathfinder's landing, NASA's Mars Global Surveyor was
captured in orbit on Sept. 12, after a 10-month journey through
deep space.
Global Surveyor was designed to replace Mars Observer, which
was lost in August 1993. Ingenuity, teamwork and an
exceptionally dedicated group of engineers and scientists
quickly went to work to develop and launch the spacecraft within
a short amount of time and on a tight budget. The time and cost
of the mission broke all the records--26 months to build the
spacecraft at a cost of only $148 million, which was well under
the cost cap and a fraction of what it cost to build previous
spacecraft destined for Mars.
Mars Global Surveyor carried six scientific instruments to
study Mars' climate, surface topography and subsurface
resources. Its primary scientific objective, though, was to map
the entire surface of the red planet.
The journey to Mars wasn't as smooth as the team had hoped
for, but each problem that cropped up was remedied in a creative
and swift manner. In mid-November, as the spacecraft began to
aerobrake into the upper fringes of the Martian atmosphere,
structural damage to the yoke hinge of one of the solar panels,
incurred during initial deployment of the panels shortly after
launch, caused the unlatched panel to begin flexing during each
dip lower into the Martian atmosphere.
Mechanical stress analysis tests suggested that the solar
panel yoke--a triangular, aluminum honeycomb material sandwiched
between two sheets of graphite epoxy--had probably fractured on
one surface during initial deployment. The analysis further
suggested that the fractured surface, with increased pressure on
the panel during aerobraking, began to pull away from the
aluminum honeycomb beneath it.
The flight team at Lockheed Martin Astronautics in Denver, in
collaboration with atmospheric specialists at JPL, decided upon
a more gradual aerobraking strategy in which to lower the
spacecraft. Aerobraking was reinitiated at 0.2 newtons per
square meter (3/100,000 of 1 pound per square inch), about one-
third of the original aerobraking level. That level was thought
to be safe, but could be adjusted in the event of additional
trouble with the panel.
Science teams then came up with a new aerobraking strategy
and a new mapping orbit.
The new mapping orbit would be a mirror image of the original
mapping orbit, but it would take an additional year to set up.
The spacecraft would have to take a six-month hiatus in the
spring of 1998 to allow Mars to move into the proper alignment
for mapping. The spacecraft's orbit would take Global Surveyor
across Mars' equator at 2 a.m. rather than at 2 p.m., and the
side of Mars that would have been dark would now be illuminated
by the Sun.
"From the perspective of the science instruments, the orbit
will look just like the original orbit, except that instead of
taking data from north to south on the sunny side of Mars,
Global Surveyor will be making its observations in a south to
north direction in the sunlight," said Glenn E. Cunningham, Mars
Global Surveyor project manager, at a mid-November press
briefing at JPL. Rather than reaching its final mapping orbit in
mid-January 1998, and beginning the science mission in mid-March
1998, Mars Global Surveyor would achieve its final orbital
position in mid-January 1999, and mapping was to begin in mid-
March 1999. Apart from the year's delay in beginning mapping,
the new mapping orbit would preserve all of the science
objectives of the mission.
During this year's hiatus, Global Surveyor will remain in a
fixed, elliptical orbit in which it will pass much closer to the
surface of Mars during each periapsis--or closest part of its
orbit around Mars--than it will in the final mapping orbit. These
close-range bonus passes will provide superb opportunities for
data acquisition. The spacecraft's full suite of instruments,
including the laser altimeter, will be turned on during this
time to study the planet close up.
"We expect to gain some spectacular new data during this
time," Cunningham said. "The spacecraft's orbit will still be
elliptical during this period, with a duration of between eight
to 12 hours, but at periapsis, the surface resolution will be
much greater and the lighting angles will be spectacular."
If additional problems arise with the aerobraking process,
the new mission plan will offer the Surveyor team other
opportunities to reach an elliptical orbit that will satisfy
many of the mission's science objectives. These so-called "off-
ramps" from the aerobraking process will be detailed in a new
mission plan to be reviewed by NASA officials in February 1998.
With renewed vigor that the science mission had not been
compromised, the flight team resumed aerobraking on Nov. 7.
Since then, the spacecraft's scientific instruments have
performed flawlessly, continuing to return new information about
Martian magnetic properties, its atmosphere, surface features,
temperatures and mineralogy.
Among the most intriguing science discoveries was
confirmation that Mars had a weak, non-uniform, planet-wide
magnetic field. The discovery continues to baffle scientists,
but it was the first time that Mars' magnetic field had, in
fact, been studied.
The spacecraft's magnetometer, which began making
measurements of Mars' magnetic field after its capture in orbit
on Sept. 11, detected the magnetic field just four days after
the beginning of its orbit around Mars. The existence of a
planetary magnetic field has important implications for the
geological history of Mars and for the possible development and
continued existence of life on Mars.
"Preliminary evidence of a stronger than expected magnetic
field of planetary origin was collected and is now under
detailed study," said Dr. Mario Acuna, principal investigator of
the magnetometer/electron reflectometer instrument at NASA's
Goddard Space Flight Center, Greenbelt, Md. "This was the first
opportunity in the mission to collect close-in magnetic field
data. Much additional data will be collected in upcoming orbits
during the aerobraking phase of the mission to further
characterize the strength and geometry of the field.
"The current observations suggest a field with a polarity
similar to that of Earth's and opposite that of Jupiter, with a
maximum strength not exceeding 1/800 of the magnetic field at
the Earth's surface.
"This result is the first conclusive evidence of a magnetic
field at Mars," Acuna continued. "More distant observations
obtained previously by the Russian missions Mars 2,3 and 5 and
Phobos 1 and 2 were inconclusive regarding the presence or
absence of a magnetic field of internal origin."
The magnetic field holds important clues to the evolution of
Mars. Planets like Earth, Jupiter and Saturn generate their
magnetic fields by means of a dynamo made up of moving molten
metal at the core. This metal is a very good conductor of
electricity, and the rotation of the planet creates electrical
currents deep within the planet, which give rise to the magnetic
field. A molten interior suggests the existence of internal heat
sources that could give rise to volcanoes and a flowing crust
responsible for moving continents over geologic time periods.
The latter phenomenon is called plate tectonics.
"A magnetic field shields a planet from fast-moving,
electrically charged particles from the Sun, which may affect
its atmosphere, as well as cosmic rays, which are an impediment
to life," Acuna said. "If Mars had a more active dynamo in its
past, as we suspected from the existence of ancient volcanoes
there, then it may have had a thicker atmosphere and liquid
water on its surface."
It is not known whether the current weaker field now results
from a less active dynamo, or if the dynamo is now extinct and
what the scientists are observing is really a remnant of an
ancient magnetic field still detectable in the Martian crust.
"Whether this weak magnetic field implies that we are
observing a fossil crustal magnetic field associated with a now
extinct dynamo -- or merely a weak but active dynamo similar to
that of Earth, Jupiter, Saturn, Uranus and Neptune -- remains to
be seen," Acuna said.
Mars Global Surveyor is the first in a sustained program of
robotic exploration of Mars. In December 1998, a second pair of
spacecraft will be launched toward the red planet, carrying
instruments that will augment this new global portrait of Mars.
As those spacecraft arrive at Mars, Global Surveyor will be
generating a global map of the planet that will aid in the
selection of future landing sites.
###
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Дата: 19 января 1998 (1998-01-19)
От: Alexander Bondugin
Тема: 97's Challenges Brings Changes To The Deep Space Network
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From The "JPL Universe"
Special issue: 1997 in review
January 9, 1998
'97's challenges bring changes to DSN
By SHIRLEY WOLFF, TMOD outreach coordinator
1997 brought many changes to the Deep Space Network (DSN). It
was the first full year in which the DSN operated under the
management of NASA's Space Operations Management Office. Major
organizational changes were introduced within the
Telecommunications and Mission Operations Directorate (TMOD)
that will result in a truly integrated, end-to-end, multi-
mission ground system derived from the DSN and the Advanced
Multi-Mission Operations System (AMMOS). It was also a very busy
year for tracking activities.
The DSN provided communications support for 46 NASA and other
missions, including international customers. Cassini was one of
14 launches, and the Mars Global Surveyor orbit insertion one of
12 critical mission events supported during 1997. The DSN
continues to track the twin Voyager spacecraft--in space for more
than 20 years--and now more than 6 billion miles from Earth.
The unique demands of the Mars Pathfinder mission created
some special communications challenges. To accommodate the
difficulties of communicating with the relatively low-powered
lander, a rapid paced, quick-response time was essential,
requiring the DSN to be exceptionally flexible with schedules.
An unusual request from Pathfinder was the requirement to
receive semaphore signals sent during the descent and landing.
The Galileo telemetry subsystem was modified to process and
display the semaphores in real-time. This allowed project
personnel to see that events were happening as planned and even
that the spacecraft had landed right side up.
For the Galileo mission, the DSN continued to implement the
complex arraying function for the return of science data
following Jovian moon encounters. Arraying the 70-meter antenna
at Goldstone with a 70-meter and two 34-meter antennas in
Canberra, Australia, plus the addition of a 64-meter antenna
leased from the Parkes Observatory, increased by 10 times the
quantity of raw data that could be received from Galileo.
During 1997 two new 34-meter beam waveguide antennas, one
each in Canberra and Madrid, Spain, began operational support
for the many flight projects that use the DSN. The Canberra
antenna played a role in the arraying support during the Galileo
prime mission, while the Madrid antenna was operational in time
for the October launch of the Cassini mission. Both of the new
antennas provided the additional X-band uplink capability
required by such missions as Mars Pathfinder, Mars Global
Surveyor and Cassini.
Recognizing that the Space Flight Operations Facility (SFOF)
has the potential for being a single point of failure for
missions, TMOD developed a new Emergency Control Center, which
began operations in early October in time for the Cassini
launch. Located at the Echo Site of the Goldstone complex, the
center provides a backup site from which JPL can sustain
emergency mission operations.
TMOD is also preparing for a future where smaller, faster,
cheaper spacecraft mean more missions flying concurrently, with
greater tracking and data acquisition demands. New technologies
will be required to meet this obligation and those under
development during the past year include improved error
correcting codes, called turbo codes, which will become the
standard codes for future missions. Also in the experimental
stage is the Spacecraft Transponding Modem (STM), the miniature
spacecraft peripheral of the future. The STM combines the
functionality of a spacecraft transponder, command unit,
telemetry encoding, timing services, and frame interface in a
package with far less mass, power and cost than today's
transponders.
The DSN Science Team has been supporting the development of
an educational program made possible by the decommissioning of
DSS 12, a 34-meter antenna at Goldstone. The antenna has been
converted into a dedicated radio telescope, remotely controlled
by trained volunteers at the Apple Valley Science and Technology
Center. A pilot program that enables middle- and high-school
teachers to conduct radio astronomy observations from their
classrooms was begun in April. Students from nine schools in
Alabama, California, Idaho, Kentucky and Michigan successfully
conducted observations of Jupiter and participated in data
analysis. The program will be expanded during 1998 to include
schools nationwide.
In the year ahead, TMOD will continue to upgrade and develop
new systems and technologies for the DSN and associated systems
to meet the growing demands of JPL's future missions.
###
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Дата: 19 января 1998 (1998-01-19)
От: Alexander Bondugin
Тема: Ice and Fire: 3 Missions Rolled Into 1
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From The "JPL Universe"
Special issue: 1997 in review
January 9, 1998
Ice and Fire: 3 missions rolled into 1
By JANE PLATT
1997 brought new names and greater budget certainty to the
three missions of the Ice and Fire Preprojects. Rob Staehle,
formerly preproject manager of Pluto Express, was appointed to
manage the preproject work for all three Ice and Fire missions--
Europa Orbiter, Solar Probe and the renamed Pluto-Kuiper
Express.
Pluto-Kuiper Express underwent a name change to reflect its
new designation as an extended mission after the Pluto flyby, to
visit one or more objects in the Kuiper disk.
Perhaps the most dramatic change for the Ice and Fire
Preprojects came with the budgetary separation of the technology
development from the missions. The technology budget received a
new start in FY '98 as the Advanced Flight Systems (X2000)
Program, under the leadership of JPL's Anthony Spear. The Ice
and Fire Preprojects are the primary users of X2000 technology.
The Outer Planets/Solar Probe Program, which is to carry out the
Ice and Fire missions, is slated for its new start in FY2000.
Although the preprojects' three missions are diverse, they
were combined because of the potential for using the same
electronics, software, mission operations systems and, perhaps,
even the same mission operations teams for all three. The
technology of X2000 may enable such a high level of efficiency
that the Ice and Fire spacecraft cost could be lower than that
of the Mars Pathfinder spacecraft.
Ice and Fire got a big boost in 1997 from various new and
intriguing science discoveries. Interest in the Europa Orbiter,
for instance, was heightened by the return of fascinating new
Galileo pictures showing more evidence that the icy moon may
have had liquid oceans at some point in its history, perhaps
even today. This premise was boosted by the images of volcanic
ice flows and chunky "rafting" features resembling icebergs on
Earth.
The science community watched with interest new images from
the Solar and Heliospheric Observatory, which showed newly
discovered polar plumes in the Sun's corona. The Solar Probe
mission, which is now a serious candidate for a 2004 launch,
will fly through those plumes and make in-situ measurements.
The discovery of more objects in the Kuiper disk inspired the
broadening of the Pluto-Kuiper Express mission scope, as more
questions arise about the farthest reaches of the solar system.
###
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Дата: 19 января 1998 (1998-01-19)
От: Alexander Bondugin
Тема: JPL Make Big Splash With El Nino Observations
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From The "JPL Universe"
Special issue: 1997 in review
January 9, 1998
JPL makes big splash with El Nino observations
By MARY HARDIN
JPL has been riding the wave of early El Nino forecasting in
1997 as three Lab-managed instruments where used by
meteorologists to confirm that the ocean warming phenomenon is
back in the Pacific.
And while the El Nino predictions have resulted in stories of
panicked sandbagging and TV weather forecaster hyperbole, JPL
scientists say their data show this El Nino is the real thing.
JPL's TOPEX/Poseidon radar altimeter, the NASA Scatterometer
(NSCAT) and the Microwave Limb Sounder (MLS) have all
contributed to tracking the current El Nino condition in the
Pacific.
"The sea surface height data that we have collected all year
confirm what the National Oceanographic and Atmospheric
Administration has predicted_a full-blown El Nino condition is
established in the Pacific," said Dr. Lee-Lueng Fu, project
scientist for the U.S./French TOPEX/Poseidon satellite at JPL.
The five years of global ocean topography observations made by
TOPEX/ Poseidon have been a boon for El Nino researchers, who
have been able to track three El Nino events since the
satellite's launch in August 1992.
NOAA issued its first advisory regarding the presence of El
Nino conditions in May 1997. A number of El Nino forecast
activities supported by NOAA indicated the likelihood of a
moderate or strong El Nino this winter. The forecast model
operated at NOAA's National Centers for Environmental Prediction
used data collected by the TOPEX/Poseidon satellite.
An El Nino is thought to be triggered when steady westward
blowing trade winds weaken and even reverse direction. This
change in the winds allows the large mass of warm water that is
normally located near Australia to move eastward along the
equator until it reaches the coast of South America. This
displaced pool of unusually warm water affects evaporation,
where rain clouds form and, consequently, alters the typical
atmospheric jet stream patterns around the world. The change in
the wind strength and direction also impacts global weather
patterns.
"Since the beginning of NSCAT's operation in September 1996,
the scatterometer observed stronger than normal easterly winds
in the central and western tropical Pacific, which piled up warm
water in the west as indicated by the higher than normal sea
level and sea surface temperature," said Dr. W. Timothy Liu,
NSCAT project scientist at JPL.
Unfortunately, the NSCAT observations stopped in June 1997
when Japan's Advanced Earth Observing Satellite (ADEOS) suffered
a fatal solar array problem and the mission was lost.
Another key component to the JPL El Nino watch has been the
water vapor data collected from NASA's Upper Atmosphere Research
Satellite (UARS).
"JPL's Microwave Limb Sounder experiment on UARS detected an
unusually large build-up of water vapor in the atmosphere at
heights of approximately 12 kilometers (eight miles) over the
central-eastern tropical Pacific. Not since the last strong El
Nino in the winter of 1991-92 have we seen such a large buildup
of water vapor in this part of the atmosphere," said JPL's Dr.
William Read. "Increased water vapor at these heights can be
associated with more intense winter-time storm activity from the
`pineapple express,' a pattern of atmospheric motions that
brings tropical moisture from Hawaii to the southwestern United
States.
"This phenomena is an example of how the ocean and atmosphere
work together to dictate the severity of El Nino events."
###
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=SANA=
Дата: 19 января 1998 (1998-01-19)
От: Alexander Bondugin
Тема: New Millennium Program Prepares For Full Plate Of Missions
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From The "JPL Universe"
Special issue: 1997 in review
January 9, 1998
New Millennium Program prepares for full plate of missions
By JOHN G. WATSON
The adventurous New Millennium Program made great strides in
1997 in its preparations for a series of missions launching from
1998 to 2003, with many more in the pipeline.
The program is a flagship NASA venture whose goal is the
development and testing of revolutionary technologies in space
flight so that they may be confidently used in science missions
of the future. Through a series of deep space and Earth-orbiting
missions, the New Millennium Program will validate the essential
technologies and capabilities required for challenging, new
types of missions to be flown in the next century.
In November, Dr. Fuk Li was named program manager, after
serving as acting program manager for several weeks following
the retirement of veteran JPL manager Kane Casani. Li, a remote
sensing expert who most recently served as manager of JPL's
Earth Science Program office, has the challenging task of
overseeing a wide variety of "faster, better, cheaper" missions
whose key technologies typically have never been used in space
flight before.
A key element of the New Millennium Program is the teaming of
government with industry and academia to improve America's
technological infrastructure. For this purpose, a series of
Integrated Product Development Teams composed of private firms,
universities and research labs are now working to identify,
design and deliver technologies needed to enable future science
missions so that they can be tested through upcoming New
Millennium missions.
Those missions begin this summer with Deep Space 1, whose
launch period starts July 1. Flying by asteroid McAuliffe, then
by Mars and finally by comet West-Kohoutek-Ikemura, DS1 will be
the first spacecraft ever to rely on solar electric propulsion
rather than conventional propellant-based systems for its main
source of thrust.
Solar electric propulsion is but one of 12 advanced
technologies to be demonstrated on this high-risk mission.
Others include new telecommunications equipment; autonomous
optical navigation; advanced solar arrays; a miniature
integrated ion and electron spectrometer; microelectronic
devices; and a miniaturized camera and imaging spectrometer that
will take pictures and make chemical maps of the target asteroid
and comet.
Late last summer, the DS1 bus arrived at JPL from the Arizona
facilities of DS1's industry partner, Spectrum Astro, and the
spacecraft has since been almost fully assembled. It is now
preparing for testing in the 25-foot space simulator in Building
150 in preparation for its delivery to the Cape in early spring.
Deep Space 2 will send two small probes weighing two
kilograms (4.5 pounds) each aboard the 1998 Mars Surveyor lander
to study Mars' soil and atmosphere. In-situ instrument
technologies for making direct measurements of the Martian
surface will include a meteorological pressure sensor,
temperature sensors for measuring the thermal properties of the
Martian soil, and a subsurface soil collection and analysis
instrument.
1997 saw many crucial tests of the probe and instrumentation
design, nearly all taking place at the New Mexico Institute of
Mining Technology's Energetic Materials Research and Test Center
in Socorro, N.M. A critical test took place on Oct. 29, when two
of the most sensitive subsystems, a battery assembly and a tiny
motor and drill assembly for extracting a subterranean soil
sample, were successfully qualified. Fully integrated systems
testing will take place in 1998 in preparation for DS2's January
1999 launch.
An advanced, lightweight scientific instrument designed to
produce visible and short-wave infrared images of Earth's land
surfaces was selected as the New Millennium Program's first
Earth-observing mission. Launching in May 1999, Earth Orbiter 1
is managed by NASA's Goddard Space Flight Center in Greenbelt,
Md. Like DS1, it too will validate 12 technologies.
The mission will serve multiple purposes, including providing
remote-sensing measurements of Earth that are consistent with
data collected since 1972 by the Landsat series of satellites,
which is used by farmers, foresters, geologists and city
planners. In addition, it will acquire data with finer spectral
resolution, a capability long sought by many scientists studying
Earth and its environs, and it will lay the technological
groundwork for inexpensive, more compact imaging instruments in
the future.
In 1997, a successful EO-1 critical design was conducted.
Focal plane and telescope elements are on schedule to be
delivered to MIT's Lincoln Laboratory, the instrument
integrator, in the first half of 1998. All of the major
structural elements of the bus are fabricated, and the
mechanical assembly and flight electrical harness are now in
process. Spacecraft bus-level integration will begin this
spring, and the instrument is due for bus integration at the end
of 1998.
In mid-November, NASA announced that Earth Orbiter 2 will
encompass the Space-Readiness Coherent Lidar Experiment
(Sparcle), flying in the cargo bay of the space shuttle.
Scheduled to launch in 2001, its goal is to determine whether a
space-based sensor can accurately measure global winds within
Earth's atmosphere from just above the surface to a height of
about 16 kilometers (10 miles).
Among the many candidate New Millennium Program launches are
Deep Space 3, an interferometry mission encompassing three
spacecraft orbiting the sun in formation, and Deep Space
4/Champollion, the first landing of a science payload on the
nucleus of an active comet.
Landing in 2005, DS4 will analyze the nucleus; conduct an
atomic, molecular and mineralogical composition assessment down
to a depth of one meter; assess such physical properties as
thermal conductivity; send back both standard and stereographic
images; and attempt to return a nucleus sample to Earth by 2010.
1997's DS4 activities have included developing detailed
designs of the lander and carrier spacecraft, testing of
spacecraft anchoring systems at the China Lake Naval Weapons
Testing Center in Ridgecrest, Calif., and the construction of a
lab at JPL dedicated to the creation of cometary simulant
materials that replicate the possible properties of a comet
nucleus for further spacecraft anchor and drilling tests.
###
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=SANA=
Дата: 19 января 1998 (1998-01-19)
От: Alexander Bondugin
Тема: New Topex/Poseidon El Nino Image Now Online
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MEDIA RELATIONS OFFICE
JET PROPULSION LABORATORY
CALIFORNIA INSTITUTE OF TECHNOLOGY
NATIONAL AERONAUTICS AND SPACE ADMINISTRATION
PASADENA, CALIFORNIA 91109. TELEPHONE (818) 354-5011
http://www.jpl.nasa.gov
Contact: Mary Hardin
(818) 354-0344
INTERNET ADVISORY January 15, 1998
NEW TOPEX/POSEIDON EL NINO IMAGE NOW ONLINE
The most recent El Niсo image from the TOPEX/Poseidon
satellite is now online at:
http://www.jpl.nasa.gov/elnino
The image shows sea surface height relative to normal ocean
conditions on Jan. 8, 1998, and sea surface height is an
indicator of the heat content of the ocean. The volume of the
warm water pool related to the El Niсo has decreased by about 40
percent since its maximum in early November, but the area of the
warm water pool is still about one and a half times the size of
the continental United States. In addition, the maximum water
temperature in the eastern tropical Pacific, as measured by the
National Oceanic and Atmospheric Administration (NOAA), is still
higher than normal. Until these high temperatures diminish, the
El Niсo warm water pool still has great potential to disrupt
global weather because the high water temperatures directly
influence the atmosphere.
Oceanographers believe the recent decrease in the size of
the warm water pool is a normal part of El Niсo's natural rhythm.
TOPEX/Poseidon has been tracking these fluctuations of the El
Niсo warm pool since it began in early 1997. These sea surface
height measurements have provided scientists with their first
detailed view of how El Niсo's warm pool behaves because the
TOPEX/Poseidon satellite measures the changing sea surface height
with unprecedented precision.
The U.S./French TOPEX/Poseidon mission is managed by NASA's
Jet Propulsion Laboratory, a division of the California Institute
of Technology.
#####
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Дата: 19 января 1998 (1998-01-19)
От: Alexander Bondugin
Тема: Next Generation: Mars Surveyor '98
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From The "JPL Universe"
Special issue: 1997 in review
January 9, 1998
Next generation: Mars '98
The Mars Surveyor '98 program is the next generation of
spacecraft to be sent to Mars. Consisting of an orbiter--to be
launched Dec. 10, 1998, and lander, set for launch on Jan. 3,
1999--the Mars '98 mission will add to the knowledge gained by
the Global Surveyor and Pathfinder missions. The general science
theme for the 1998 Surveyor missions is "Volatiles and Climate
History."
The Mars '98 orbiter will arrive at Mars Sept. 23, 1999,
while the lander will touch down Dec. 3, 1999.
Upon arrival at Mars, the spacecraft will use a series of
aerobraking maneuvers to achieve a stable orbit, and then use
atmospheric instruments and cameras to provide detailed
information about the surface and climate of Mars.
The '98 orbiter mission will carry a rebuilt version of the
Mars Observer Pressure Modulated Infrared Radiometer (PMIRR), as
well as the Mars color imaging system. PMIRR will observe the
global distribution and time variation of temperature, pressure,
dust, water vapor and condensates in the Martian atmosphere. The
imaging system will observe synoptically Martian atmospheric
processes at global scale and study details of the interaction
of the atmosphere with the surface at a variety of scales in
both space and time. In addition to the science payload, the
orbiter spacecraft will provide an on-orbit data relay
capability for future U.S. and/or international surface
stations.
The lander will land near the southern polar cap and is
equipped with cameras, a robotics arm and instruments to measure
the composition of the Martian soil. Two small microprobes are
also piggybacking on the lander, which will penetrate into the
Martian subsurface to detect water ice.
The science package for the lander includes the Mars Volatile
and Climate Surveyor (MVACS) integrated lander payload, the Mars
Descent Imager (MARDI) and an atmospheric lidar experiment
provided by the Russian Space Agency Institute for Space
Science. The integrated lander payload includes a surface stereo
imager with Mars Pathfinder heritage; a meteorology package; an
instrumented robotic arm for sample acquisition, soil
manipulation and closeup imaging of the surface and subsurface;
and the thermal and evolved gas analysis experiment for
determining the nature and abundance of volatile material in the
Martian soil.
The images obtained while the lander descends to the surface
will establish the geological and physical context of the
landing site. The atmospheric lidar experiment will determine
the dust content of the Martian atmosphere above the landing
site.
Dr. John McNamee of JPL is Mars Surveyor '98 project manager.
###
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=SANA=
Дата: 19 января 1998 (1998-01-19)
От: Alexander Bondugin
Тема: Origins Advances Its Study Of Star, Galaxy and Life Formation
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From The "JPL Universe"
Special issue: 1997 in review
January 9, 1998
Origins advances its study of star, galaxy and life formation
By JANE PLATT
1997 was a busy year for the Origins program, an ambitious
and intriguing series of missions to teach us more about star
and galaxy formation and extend the search for life beyond our
solar system.
For the first of the Origins missions, the Space Infrared
Telescope Facility (SIRTF), the year was spent with planning and
design during the project's Phase B. SIRTF passed its
preliminary design review and non-advocate review in late
September, and will undergo its critical design review in the
fall of 1998. The development of SIRTF's large, sensitive
infrared detector arrays was completed and construction of the
flight detectors was initiated. SIRTF will enter Phase C/D in
April 1998.
With a planned launch in 2001, SIRTF will explore galaxy
evolution and star formation in other galaxies, and will probe
the distant reaches of the observable universe to study some of
the most luminous galaxies known. Within our own galaxy, SIRTF
will search for brown dwarfs, and will detect and characterize
extra-solar disks that may represent new solar systems forming.
SIRTF will complete NASA's Great Observatories Program, a suite
of observatories designed to study the universe at all
wavelengths. The other observatories in this family are the
Hubble Space Telescope, the Advanced X-ray Astrophysics
Facility, and The Compton Gamma Ray Observatory.
NASA has selected the Infrared Processing and Analysis Center
(IPAC), which is operated jointly by Caltech and JPL, to be the
home institution for the SIRTF science center.
Dr. Tom Soifer of Caltech has been named director of the
center, which will be responsible for operating SIRTF and
processing its data. The SIRTF mission is managed by JPL for
NASA's Office of Space Science.
Another in the series of Origins missions, the Space
Interferometry Mission, entered Phase A in October 1997. Chris
Jones, the former Cassini spacecraft development manager, was
appointed project manager for SIM, which will have an
unprecedented ability to pinpoint stars and determine with high
accuracy ages and distances in the universe. Within the Milky
Way galaxy, SIM will search for signs of planet formation in
disks of material orbiting other stars. The spacecraft will look
for the wobble of stars that are caused by planets orbiting
around them.
As the world's first long baseline optical space
interferometer, SIM will serve as a technological stepping stone
for the Terrestrial Planet Finder, a future Origins mission
designed to capture a "family portrait" of other planetary
systems. The Planet Finder would characterize the atmospheres of
newly-discovered "Earthlike" planets to determine which of them
might be habitable.
The planned Keck interferometer successfully completed its
preliminary design review in September, with a critical design
review scheduled next summer. The Keck project will link the two
10-meter (393-inch) telescopes at Hawaii's Keck Observatory on
Mauna Kea into one interferometer, later adding four 2-meter
(79-inch) outrigger telescopes to complete the six-element
imaging array. The project has begun the process of applying to
Hawaii's conservation district for permits to install the
outriggers. The linking of the two main telescopes is scheduled
for completion in 2000, with 2002 set as the target date for the
outriggers to begin operations.
The Keck interferometer will survey 500 nearby stars, using
astrometry for extra-solar planet detection. It will look for
the wobble caused by planets of a mass as low as Uranus out to a
distance of 10 parsecs. The so-called "warm Jupiters," the type
of planets currently being detected indirectly, will be seen
directly using the six-element interferometer.
In addition, the Keck interferometer will determine the
extent of the zodiacal dust clouds believed to shroud other
solar systems, gathering information that will affect the design
of the Terrestrial Planet Finder.
New images of various celestial objects were captured by the
2-Micron All-Sky Survey (2MASS), which began operations in 1997
using the first of a pair of twin telescopes. The two 1.3 meter
(51-inch) telescopes will peer through the Milky Way galaxy's
curtain of interstellar dust to conduct a near-infrared survey
of the entire celestial sky. Operations began in 1997 at the
Smithsonian Astrophysical Observatory site atop Mount Hopkins
near Tucson, Ariz., while the other 2MASS telescope, at a
National Optical Astronomy Observatories site in Cerro Tololo,
Chile, will begin operating in February of 1998. 2MASS, which is
primarily funded by NASA, is based at the University of
Massachusetts, Amherst. IPAC is processing the 2MASS data.
The survey is designed to catalogue 300 million stars and 1
million galaxies in the local universe, along with such exotic
targets as quasars, black holes and brown dwarfs. It will also
observe many known asteroids and possibly some comets.
It's expected that 2MASS will discover new infrared sources
that may form the basis for future space observatories, like the
Advanced X-Ray Facility (AXAF), the Space Infrared Telescope
Facility and the Next Generation Space Telescope.
Another project supported by Caltech's IPAC is the Wide-Field
Infrared Explorer (WIRE), which has a mission to discover how
galaxies change through time and to detect the birth of new
galaxies, called proto-galaxies.
Within weeks of the September 1998 launch of the WIRE
spacecraft into low Earth orbit, this small telescope will
detect tens of thousands of starburst galaxies--galaxies where
stars are forming at a much higher rate than usual--as well as an
unknown number of proto-galaxies.
###
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=SANA=
Дата: 19 января 1998 (1998-01-19)
От: Alexander Bondugin
Тема: Galileo Starts Two-Year Extended Europa Mission
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From The "JPL Universe"
Special issue: 1997 in review
January 9, 1998
Galileo starts two-year extended Europa mission
By JANE PLATT
After yielding a rich harvest of science results in 1997,
NASA's Galileo spacecraft wrapped up its primary mission on Dec.
7 and began a two-year follow-on journey, known as the Galileo
Europa mission.
The transition from primary to extended mission brought a
change in management. Bob Mitchell, who served as mission
director for the last year of Galileo's primary mission, was
appointed project manager for the Galileo Europa Mission, taking
over from Bill O'Neil, who served as Galileo project manager for
the flight to Jupiter and the two-year primary mission at
Jupiter. O'Neil will serve as a consultant on the senior staff
of JPL's Telecommunications and Mission Operations Directorate
pending his next assignment at the Laboratory.
"A great bounty of Jupiter system science has been obtained
and the continuing study of these data will surely add many more
important discoveries," O'Neil said of the mission. "I've been
involved with the Galileo mission since its beginning in 1977,
and have been at the helm since 1990 for the flight to Jupiter,
the first-ever outer planet entry and orbit insertion, and
throughout the two-year primary mission tour of the Jovian
system. I feel extraordinarily fortunate to have had this
priceless, truly unique experience. But it is time for new
challenges. I am delighted to turn the reins over to Bob
Mitchell. Having worked closely with Bob for more than 25 years,
I know that he will do a superb job leading the team."
"Accomplishing what we have set out to do with such a small
team is going to be a real challenge," Mitchell said. "But we
have an excellent team in place, and I'm looking forward to it."
The first flyby of the Galileo Europa Mission took place on
Dec. 16, when the spacecraft swooped past Europa at an altitude
of 200 kilometers (124 miles), making it the closest Europa
encounter of the entire Galileo mission. The extended mission
will include seven more Europa flybys, four encounters with
Callisto, and one or two close flybys of Io, depending on
spacecraft health.
Pictures and other data returned by Galileo during its
primary mission continued to fascinate the public in 1997. New
images of Europa revealed evidence of ice flows, a complex
network of crisscrossed ridges, chunky ice rafts and relatively
smooth, crater-free patches. The areas of rafting added to the
mounting evidence of liquid oceans under Europa's icy crust at
some point in its history. The presence of oceans would increase
the odds that life could have existed there.
"We're intrigued by these blocks of ice, similar to those
seen on Earth's polar seas during springtime thaws," said Dr.
Ronald Greeley, an Arizona State University geologist and
Galileo imaging team member. "The size and geometry of these
features lead us to believe there was a thin icy layer covering
water or slushy ice, and that some motion caused these crustal
plates to break up."
Galileo investigators discovered a hydrogen atmosphere around
Ganymede and both hydrogen and carbon dioxide in an atmosphere
on Callisto. The spacecraft also found that Europa has an
ionosphere, produced by ionization of its tenuous oxygen
atmosphere. This finding came after a series of six occultation
experiments, when the radio signal was interrupted while Europa
was positioned between Galileo and Earth. These experiments were
performed during Galileo's encounters with Europa in December
1996 and February 1997.
"While this discovery does not relate to the question of
possible life on Europa, it does show us there are complex
surface and atmospheric processes occurring there, and Europa is
not just some dead hunk of material," said lead investigator Dr.
Arvydas Kliore of JPL.
Galileo also transmitted new evidence of numerous high-
temperature volcanoes on Jupiter's volatile moon, Io. One recent
discovery revealed a new dark spot the size of Arizona on Io.
The visible change occurred between Galileo's seventh and tenth
orbits of Jupiter, and produced a dark area about 400 kilometers
(249 miles) in diameter, surrounding a volcanic center named
Pillan Patera.
"This is the largest surface change on Io observed by Galileo
during its entire two-year tour of the Jovian system," said
Galileo imaging team member Dr. Alfred McEwen, a University of
Arizona research scientist.
Other significant results from Galileo this past year
included the confirmation of the spacecraft's 1996 discovery of
a magnetic field and magnetosphere on Ganymede, and the
discoveries that all the Galilean moons except Callisto have a
core. Callisto did show signs of surface erosion and blanketing
at fine scale.
"Before Galileo, we could only make educated guesses about
the structure of the Jovian moons," said Dr. John Anderson, a
JPL planetary scientist. "Now, with the help of the spacecraft,
we can measure the gravitational fields of the satellites and
determine their interior structure and density. We can determine
how the matter is distributed inside."
Galileo's instruments also detected some interesting, Earth-
like phenomena on Jupiter, including the presence of lightning
and aurora. Recent findings confirm the suspicion that the
thunderstorms provide energy for the low pressure centers on
Jupiter, which in turn feed the Great Red Spot, white ovals and
other large storms.
In 1997, Galileo also found clusters of volcanic vents and
hot spots in greatest concentration on Io in the areas closest
and farthest from Jupiter. Other discoveries include evidence of
salt and carbon dioxide in Europa's icy crust and landslides on
Callisto.
While the spacecraft was busy making scientific history,
Galileo team members made history of their own in January.
O'Neil, Johnson, and others met with Pope John Paul II during a
trip to Italy.
"None of us ever anticipated that Project Galileo would
result in a papal audience, "O'Neil said. "The Pope seemed very
interested in learning about Galileo results. He encouraged
continuing exploration of the universe."
O'Neil and Johnson received honorary doctorates from the
University of Padova and attended the Three Galileos Conference,
a meeting designed to honor Galileo the man, Galileo the
mission, and Galileo the new national telescope of Italy.
###
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