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Cover: SOHO observes the Sun; The planets to scale
on 2 December 1995, SOHO observes the Sun's deep
interior and also its interactions all the way out to Earth’s orbit and
beyond, where the magnetised solar wind of atomic particles sweeps
through interplanetary space. More than 3200 scientists from around the
world have been involved with SOHO, which is a project of international
collaboration between ESA and NASA.
SEM273ULWFE: Credits: NASA/ESA
All Planet Sizes: This illustration shows the approximate sizes of
the planets relative to each other. Outward from the Sun, the planets
are Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus, Neptune, and
Pluto. Jupiter's diameter is about 11 times that of the Earth's and the
Sun's diameter is about 10 times Jupiter's. Pluto's diameter is slightly
less than one-fifth of Earth's. The planets are not shown at the
appropriate distance from the Sun. Image Credit: NASA Lunar and
January: Collecting Stardust from a Comet
PIA05578: Comet Wild 2 - Jet Release. This composite image
was taken by the navigation camera during the close approach phase of
Stardust's Jan 2, 2004 flyby of comet Wild 2. Several large depressed
regions can be seen. Comet Wild 2 is about five kilometers (3.1 miles)
in diameter. To create this image, a short exposure image showing
tremendous surface detail was overlain on a long exposure image taken
just 10 seconds later showing jets. Together, the images show an
intensely active surface, jetting dust and gas streams into space and
leaving a trail millions of kilometers long.
In addition to collecting samples, Stardust also took pictures during
its flyby. The images were startling because they showed a surface that
is unlike anything previously seen in space. Before Stardust, spacecraft
had imaged the surfaces of only two comets, Halley and Borrelly. Both of
these comets had elongated shapes, similar to peanuts, and their surface
features were relatively subtle. Unlike the previous comets, Wild 2 was
seen to have a slightly flattened shape and its surface was covered with
What we saw was a very rough surface that was not made of loose
material. It has strength and some areas have vertical cliffs and even
overhangs. We also saw that much of the comet's surface is covered with
depressions up to , a kilometer across, with steep walls and flat
floors. We believe that some of the depressions are impact craters but
they are unusual and not a single depression, anywhere on the comet, is
similar to typical impact craters seen on the Moon, Mars, satellites and
asteroids. A major surprise was the observation of ridges, mesas (flat
toped hills bounded by cliffs) and pinnacles rising more than 100 meters
above their surroundings. It is likely that these features are remnants
left after the loss of more than 100 meters of original surface. The
pinnacles are column-like features that have never been observed on
other solar system bodies, other than Earth.
Long exposure images showed sunlight reflecting off jets of dust
projecting into space. We were expecting one or two jets but we saw 20.
Jets are produced when gas escapes from localized regions and carries
dust and rocks outwards. The low-density gas is invisible but the
entrained dust scatters sunlight making it visible. The large number of
jets shows that gas sources on Wild2 are numerous and probably small.
Dust detectors on the spacecraft measured bursts of impacts when
Stardust flew through jets.
Scientists believe the cargo will help provide answers to fundamental
questions about comets and the origins of the solar system. Comets like
Wild 2 are a special interest to astrobiology because they are preserved
samples of the fundamental building blocks of the solar system. The
remarkable surface of this body is the result of billions of years of
residence beyond the orbit of Neptune and a brief recent history inside
the orbit of Jupiter.
Image and Text Credit: NASA/JPL-Caltech
February: Endurance Crater: "Burns Cliff"
Opportunity on 'Burns Cliff' (Simulated) .This synthetic image of NASA's Opportunity Mars
Exploration Rover inside Endurance Crater was produced using
"Virtual Presence in Space" technology. Developed at NASA's Jet
Propulsion Laboratory, Pasadena, Calif., this technology combines
visualization and image processing tools with Hollywood-style
special effects. The image was created using a photorealistic model
of the rover and an approximately full-color mosaic. The size of the
rover in the image is approximately correct and was based on the
size of the rover tracks in the mosaic.
Because this synthesis provides viewers with a sense of their own
"virtual presence" (as if they were there themselves), such views
can be useful to mission teams by enhancing perspective and a sense
Opportunity captured the underlying view of "Burns Cliff" after
driving right to the base of this southeastern portion of the inner
wall of "Endurance Crater."
PIA07110 combines frames taken by
Opportunity's panoramic camera between the rover's 287th and 294th martian days (Nov. 13 to 20, 2004).
This is a composite of 46 different images, each acquired in seven
different Pancam filters. It is an approximately true-color
rendering generated from the panoramic camera's 750-nanometer,
530-nanometer and 430-nanometer filters. The mosaic spans more than 180
degrees side to side. Because of this wide-angle view, the cliff walls
appear to bulge out toward the camera. In reality the walls form a
gently curving, continuous surface.
March: Cascading Dunes in Rabe Crater
Crater lies among hundreds of thousands of
other impact craters in the rough-hewn southern highlands of Mars.
Spanning 108 kilometers (67 miles), Rabe is halfway between the martian
equator and the south pole, and west of the giant impact basin Hellas.
Two features distinguish Rabe Crater apart from most other craters on
Mars. The crater has a flat floor with a pit sunk into it, plus a large
field of dunes.
A pair of visible-wavelength images together with
numerous infrared ones created this false-color Thermal Emission Imaging
System (THEMIS) on NASA's Mars Odyssey spacecraft view that captures
portions of both the pit and the dune field. The colors portray the
overnight surface temperatures: bluer colors indicate cold places,
redder tints warm ones. This helps scientists distinguish areas covered
in fine-grain material, such as dust and sand, from those where harder
and rockier ground stands exposed.
The technique works because areas mantled in dust cool
off quickly after sundown, while rocks hold onto daytime heat much
better. When THEMIS looks down from orbit in the predawn hours, outcrops
of bedrock are still glowing with warmth, while dusty ground has long
since turned cold and dark.
Image and Text Credit: NASA/JPL/ASU
April: Martian Moonlet
SEMA161A90E: Phobos in colour, close-up . This image, taken by the
High Resolution Stereo Camera (HRSC) on board ESA’s Mars Express
spacecraft, is one of the highest-resolution pictures so far of the
Martian moon Phobos, the larger of Mars' two moons.
The image shows the Mars-facing side of the moon, taken from a
distance of less than 200 kilometres with a resolution of about seven
metres per pixel during orbit 756, on 22 August 2004.
This colour image was calculated from the three colour channels and
the nadir channel on the HRSC.
Phobos and Deimos are widely believed to be captured asteroids.
Phobos is an oblong shaped moon measuring 27 X 21 X 19 km. It orbits
Mars with a period of 7.3 hours, less than a Martian day. This makes the
moon appear to rise in the west and set in the east, usually twice a
day. It is so close to the surface that it cannot be seen above the
horizon from all points on the surface of Mars.
Phobos is heavily cratered with interesting parallel grooves about
150 m long and 25m deep. The grooves seem to radiate from the largest
crater to an oddly shaped area on the other end of the moon. Because of
this it is presumed that the grooves may have formed with the impact of
the largest crater.
And Phobos is doomed: because its orbit is below synchronous altitude
tidal forces are lowering its orbit (current rate: about 1.8 meters per
century). In about 50 million years it will either crash onto the
surface of Mars or (more likely) break up into a ring.
Image and Text Credit: ESA/DLR/FU Berlin (G. Neukum)
May: Virtual Spirit on the Flank of
PIA03231: This synthetic image
of the Spirit Mars Exploration Rover on the flank of "Husband Hill" was
produced using "Virtual Presence in Space" technology. Developed at
NASA's Jet Propulsion Laboratory, Pasadena, Calif., this technology
combines visualization and image-processing tools with Hollywood-style
special effects. The image was created using a photorealistic model of
the rover and a false-color mosaic. The size of the rover in the image
is approximately correct and was based on the size of the rover tracks
in the mosaic. The mosaic was assembled from frames taken by the
panoramic camera on the rover's 454th Martian day, or sol (April 13,
Image and Text Credit: NASA/JPL-Caltech/Cornell
June: Methane's Terrain on Titan
The European Space Agency's Huygens probe gently landed on the surface
of Titan on January 14, 2005. The probe ground track is indicated as
points in white. North is up.
Images recorded by Huygens' descent imager/spectral radiometer between
17 and 8 kilometers were assembled to produce the panoramic mosaic
PIA06438. Narrow dark linear markings, interpreted as channels, cut
through the brighter terrain. The complex channel network implies
precipitation (likely as methane "rain") and possibly springs.
The circle indicates the outline of the low-altitude panorama
PIA06439, composed of images between 7 and 0.5 kilometers. The ridge near the centre is cut by a
dozen darker lanes or channels. The landing site is marked with an "X"
near the continuation of one of the channels.
To the right is
PIA07232, the first color view of Titan's surface. This is
the colored view, following processing to add reflection spectra data,
and gives a better indication of the actual color of the surface.
Initially thought to be rocks or ice blocks, they are more pebble-sized.
The two rock-like objects just below the middle of the image are about
15 centimeters (left) and 4 centimeters (center) across respectively, at a distance of about 85 centimeters from Huygens. The surface is darker than
originally expected, consisting of a mixture of water and hydrocarbon
ice. There is also evidence of erosion at the base of these objects,
indicating possible fluvial activity.
Image and Text Credit: NASA/JPL/ESA/University of Arizona
July: Deep Space Fireworks
PIA02137: This spectacular
image of comet Tempel 1 was taken 67 seconds after it obliterated
Impact's impactor spacecraft. The image was taken by the high-resolution
camera on the mission's flyby craft. Scattered light from the collision
saturated the camera's detector, creating the bright splash seen here.
Linear spokes of light radiate away from the impact site, while
reflected sunlight illuminates most of the comet surface. The image
reveals topographic features, including ridges, scalloped edges and
possibly impact craters formed long ago.
Upon impact, there was a brilliant and rapid release of dust that
momentarily saturated the cameras onboard the spacecraft. Audiences
around the world watched as dramatic images were returned in near real
time on NASA TV and over the Internet. All available orbiting telescopes
watched from space, including the Spitzer, Hubble and Chandra
telescopes. A number of Earthbound astronomers at larger and smaller
telescopes positioned their instruments and succeeded in capturing a
wide-field view of the impact. Although the comet brightened upon
impact, it wasn’t observable with the unaided eye at Earth.
and brightness of the released debris indicates that beneath the surface
of the comet, there is microscopic dust; water and carbon dioxide ice;
and hydrocarbons. Signatures of these species were seen in spectra
immediately after impact. New information since encounter tells us that
the forces holding the comet together are gravitational forces, and the
comet is extremely weak—weaker than snow.
Image and Text Credit: NASA/JPL-Caltech/UMD
August: Solar Coronal Mass Ejections
Coronal mass ejections sometimes reach
out in the direction of Earth
SEMFU62A6BD: This illustration shows a coronal mass ejection blasting off the Sun’s
surface in the direction of Earth. This left portion is composed of a
SOHO EIT 304 image superimposed on a LASCO C2 coronagraph. Two to four days
later, the CME cloud is shown striking and beginning to be mostly
deflected around the Earth’s magnetosphere. The blue paths emanating
from the Earth’s poles represent some of its magnetic field lines. The
magnetic cloud of plasma can extend to 30 million miles wide by the time
it reaches earth. These storms, which occur frequently, can disrupt
communications and navigational equipment, damage satellites, and even
Image and Text Credit: SOHO/LASCO/EIT (ESA & NASA)
September: Lava Channels in Tharsis
Lava Channels On a Volcano:
At first glance, the channels snaking across this
false-color Mars Odyssey THEMIS image look carved by water. But the channels lie on
the slopes of Ascraeus Mons, a gigantic volcano, and scientists are
looking more to lava flows for a source than to water.
Ascraeus lies in Tharsis, the most volcanic part of
Mars. The volcano's summit lies out of the frame at bottom, and its
flank runs downhill toward the top of the picture. The image spans 18 km
(11 miles) wide by 66 km (41 miles) high.
A close look at the ground reveals many small lava
flows following the same trend as the channels. Ascraeus is a shield
volcano, built like the Hawaiian islands from countless thin sheets of
Such lava flows are fed by natural pipes or tubes that
develop within the flows. These conduct lava from its source to the
spreading flow fronts.
In places, however, a lava tube's roof may fall in,
opening a pit. Where a longer section of roof collapses, the pit becomes
an oval. If the flow in the tube erodes the roof sufficiently, many pits
and ovals will merge to form an open channel.
This false-color THEMIS image also tells about the
volcano's surface material. It combines a view at visible wavelengths
with nighttime temperatures shown in color. Bluish tints indicate colder
ground, while redder ones point to warmer areas.
At night on Mars, fine-grain materials such as dust
give up heat easily and turn cold. Rocky ground, however, remains warm
because it does a better job of holding onto daytime heat from the Sun.
(While Ascraeus is young in geologic terms, its lava flows have been
cold, hard rock for ages.)
Here the colors show a broad, dust-covered surface
(blue), cut by channels whose sides contain a mix of rocks and dust
(yellow). Only in a few places can we see exposures of rock (reddish
orange) poking through.
Image and Text Credit: NASA/JPL/ASU
October: Skating on Mars? Water Ice at the North Pole
Water ice in crater at Martian north
pole ---- Perspective view of crater with water ice - looking east
SEMTVM6DIAE: The HRSC on ESA's Mars Express obtained this perspective
view on 2 February 2005 during orbit 1343 with a ground resolution of
approximately 15 metres per pixel.
It shows an unnamed impact crater located on Vastitas
Borealis, a broad plain that covers much of Mars's far northern
latitudes, at approximately 70.5° North and 103° East.
The crater is 35 kilometres wide and has a maximum
depth of approximately 2 kilometres beneath the crater rim. The circular
patch of bright material located at the centre of the crater is residual
The colours are very close to natural, but the
vertical relief is exaggerated three times. The view is looking east.
Credits: ESA/DLR/FU Berlin (G. Neukum)
November: The Face of Beauty
Few sights in the solar system are more strikingly beautiful than softly
hued Saturn embraced by the shadows of its stately rings.
The gas planet's subtle northward gradation from gold to azure is a
striking visual effect that scientists don't fully understand. Current
thinking says that it may be related to seasonal influences, tied to the
cold temperatures in the northern (winter) hemisphere. Despite
revelations, Saturn remains a world of mystery.
Currently, the rings' shadows shield the mid-northern latitudes from
the harshest of the sun's rays. As Saturn travels around the sun in its
29-year orbit, the shadows will narrow and head southward, eventually
blanketing the opposite hemisphere.
Images taken with blue, green and red spectral filters were used to
create this color view, which approximates the scene as it would appear
to the human eye. The view was brightened to enhance detail visible in
the rings and within their shadows.
The images were obtained with the Cassini wide-angle camera from a
distance of approximately 999,000 kilometers (621,000 miles) from Saturn
on May 4, 2005, as the spacecraft cruised a few degrees above the ring
plane. The image scale is about 60 kilometers (37 miles) per pixel on
Image and Text Credit: NASA/JPL/Space Science Institute
December: Swinging Past the Home Planet
Galapagos Islands: The Mercury-bound
MESSENGER spacecraft captured
several stunning images of Earth during a gravity assist swingby of its
home planet on Aug. 2, 2005. One picture, snapped when MESSENGER was
34,692 miles (55,831 kilometers) above Earth, shows the Galapagos
Islands as tiny specks peeking through an opening in clouds of the
brightly lit dayside of the planet. The line dividing day and night cuts
a swath through South America, with night about to fall on the western
half of the continent. The large bright spot to the west of South
America is the Sun’s light scattering off ocean waves.
Earth flyby not only adjusted the spacecraft’s path to Mercury – the
gravity assist maneuver allowed the spacecraft team to test several
MESSENGER science instruments by observing its home planet.
The Mercury Dual Imaging System’s wide-angle camera passed with
flying colors, snapping a number of images across its full multispectral
capability. The camera is designed to characterize minerals that may
have formed in Mercury’s crust. Telescope measurements from Earth
suggest that Mercury’s surface resembles the highlands on our moon:
abundant feldspar (anorthite) with limited amounts of iron-rich minerals
such as pyroxene and olivine. The MESSENGER team carefully picked 11
filters across visible and near-infrared wavelengths (400 to 1,100
nanometers) known to indicate these and other common silicate minerals.
This three-band composite is made from filters with peak sensitivities
near 480 nm, 560 nm and 630 nm. These filters help distinguish materials
with distinct visible color differences (ilmenite, volcanic glasses) but
are also very close to the sensitivity of the human eye. (Natural color
is somewhat subjective, so this combination of bands is “approximate”
Once in orbit around Mercury, MESSENGER will map the entire surface in
all 11 wavelengths – and at resolutions 10 times better than seen in
this view of Earth.
Credit: NASA/Johns Hopkins University Applied
Physics Laboratory/Carnegie Institution of Washington/Northwestern
Meet The Spacecraft
SOHO (Cover, August)
2 December 1995 the joint ESA-NASA Solar Heliospheric Observatory (SOHO)
was launched by an Atlas II-AS rocket from Cape Canaveral in Florida,
US. SOHO was designed to answer the following three fundamental
scientific questions about the Sun:
What is the structure and dynamics of the solar interior?
Why does the solar corona exist and how is it heated to the
extremely high temperature of about 1 000 000 °C?
Where is the solar wind produced and how is it accelerated?
Clues on the solar interior come from studying seismic waves that are
produced in the turbulent outer shell of the Sun and which appear as
ripples on its surface.
obtain a 24 hours a day, 365 days a year view of the Sun SOHO is placed
at a permanent vantage point 1.5 million kilometers sunward of the Earth
in a halo orbit around the L1 Lagrangian point. SOHO was initially
designed to observe the Sun continuously for at least two years. All
previous solar observatories have orbited the Earth, from where their
observations were periodically interrupted as our planet eclipsed the
Sun. The advantage of SOHO has been its continual monitoring of the Sun
throughout the current solar cycle.
SOHO is made up of two modules. The Service Module forms the lower
portion of the spacecraft and provides power, thermal control, pointing
and telecommunications for the whole spacecraft and support for the
solar panels. The Payload Module sits above it and houses all the
Control of the spacecraft was lost in June 1998, and only restored
three months later through efforts of the SOHO recovery team. All 12
instruments were still us-able, most with no ill effects. Two of the
three on-board gyroscopes failed immediately and a third in December
1998. After that, new on-board software that no longer relies on
gyroscopes was installed in February 1999. It allowed the spacecraft to
return to full scientific operations, while providing an even greater
margin of safety for spacecraft operations. This made SOHO the first
three-axis stabilised spacecraft operated without gyroscopes, breaking
new ground for future spacecraft designs.
The scientific payload of SOHO comprises 12 complementary
instruments, developed and furnished by 12 international consortia
involving 29 institutes from 15 countries. Nine consortia are led by
European scientists, the remaining three by US scientists. More than
1500 scientists in countries all around the world are either directly
involved in SOHO's instruments or have used SOHO data in their research
has provided an unprecedented breadth and depth of information about the
Sun, from its interior, through the hot and dynamic atmosphere, to the
solar wind and its interaction with the interstellar medium. These
findings have been documented in an impressive, still growing body of
scientific and popular literature:
Besides watching the Sun, SOHO has become the most prolific
discoverer of comets in astronomical history: as of November 2005,
more than 1000 comets
had been found by SOHO.
Revealing the first images ever of a star’s convection zone (its
turbulent outer shell) and of the structure of sunspots below the
Providing the most detailed and precise measurements of the
temperature structure, the interior rotation, and gas flows in the
Measuring the acceleration of the slow and fast solar wind
Identifying the source regions and acceleration mechanism of the
fast solar wind in the magnetically "open" regions at the Sun's
Discovering new dynamic solar phenomena such as coronal waves and
Revolutionising our ability to forecast space weather, by giving up
to three days notice of Earth-directed disturbances, and playing a
lead role in the early warning system for space weather
Monitoring the total solar irradiance (the ‘solar constant’) as well
as variations in the extreme ultra violet flux, both of which are
important to understand the impact of solar variability on Earth’s
Image and Text Credit: SOHO/LASCO/EIT (ESA & NASA)
is the first U.S. space mission dedicated solely to the exploration of a
comet, and the first robotic mission designed to return extraterrestrial
material from outside the orbit of the Moon.
January 2, 2004, after five years in space and billions of kilometers of
travel, Stardust finally reached its target for a brief but daring
encounter. The spacecraft flew within 236 km of the comet Wild 2 and
survived the high speed impact of millions of dust particles and small
rocks up to nearly half a centimeter across. With its tennis racket
shaped collector extended, Stardust captured thousands of comet
particles to be returned to Earth on January 15, 2006 after a 2.88
billion mile round-trip journey.
In order to meet up with comet Wild 2, the spacecraft made three
loops around the Sun. On the second loop, its trajectory intersected the
comet. During the meeting, Stardust performed a variety of tasks
including reporting counts of comet particles encountered by the
spacecraft with the Dust Flux Monitor, and real-time analyses of the
compositions of these particles and volatiles taken by the Comet and
Interstellar Dust Analyzer (CIDA). Using a substance called aerogel,
Stardust captured these samples and stored them for safe keeping on its
long journey back to Earth.
The Sample Return Capsule is a compact, 57kg system, consisting
primarily of a sample canister with an aeroshield/basecover, plus
navigation recovery aids, an event sequencer and a small parachute
system. After re-entry the SRC will continue to free-fall until
approximately 3 km, at which point the parachute deployment sequence
will initiate for a soft landing in Utah.
Image and Text Credit: NASA/JPL-Caltech
Mars Exploration Rovers (February, May)
The names for the
Exploration Rovers - Spirit and Opportunity - were
selected from nearly 10,000 entries in a contest sponsored by
NASA, the Lego Company, and the Planetary Society. 9-year-old Sofi Collis, in the winning essay, wrote, "In America, I can
make all my dreams come true. Thank you for the 'Spirit' and the
The two identical rovers were originally
thought to be able to trek up to 100 meters a day ("sol") across
the martian surface, but on March 31, 2005 Opportunity traveled
a distance of 220 metersin a single day. This is farther than
the 1997 Mars Pathfinder rover Sojourner''s travel throughout
its entire mission. Each rover carries a sophisticated set of
instruments – the Athena Science Payload – that has allowed it
to search for evidence of liquid water in the planet's past.
On June 10, 2003, the first Mars Exploration Rover (MER)
spacecraft Spirit was launched on a Delta II rocket from Cape
Canaveral, Florida. After a seven month flight, it entered the
martian atmosphere in January 3, 2004. The second lander and
rover, Opportunity, followed on January 24.
The rovers each had
a spectacular landing, similar to that of the Pathfinder
spacecraft. After entering the atmosphere, the rovers deployed
their parachutes and airbags, hitting the surface with enough
force to bounce back up a hundred feet in the martian air. After
finally settling down, the lander petals opened to reveal the
rovers folded inside like origami. The rovers had to unfold
themselves carefully, deploying their camera masts, antennae,
wheels, and solar arrays.
The landing portion of the mission featured a design that is
dramatically different from that of Mars Pathfinder. Where
Pathfinder had a lander and the small Sojourner rover, each MER
spacecraft carried just a large, long-range rover. The rover has
a mass of nearly 180 kilograms (about 380 pounds).
Each rover can take a 360-degree visible color and infrared
image panorama. Athena scientists can choose rock and soil
targets and command the rovers to explore their surroundings.
The landers have long since been left behind, as both Spirit and
Opportunity have searched out enticing clues in the soil.
rover reaches a target, its multi-jointed arm deploys and the
target is examined with a microscope and two spectrometers. The
"RAT" (Rock Abrasion Tool) is used to expose fresh rock surfaces
for study. Images and spectra of interesting rocks and soils are
It was originally believed that the rovers would
only have the solar power capability to last for around 90 sols,
or the early summer of 2004, but regular "cleaning events" and
careful maneuvering have allowed them to continue for more than
a martian year (670 sols).
Image and Text Credit: NASA/JPL/Cornell
Mars Express (April, October)
Express is Europe’s first spacecraft to the Red Planet. The orbiter
instruments are remotely investigating the Martian atmosphere, surface
and subsurface. Beagle 2, the lander, was expected to perform
on-the-spot measurements and also search for signs of past life.
One of the main objectives is to search for traces of water in the
subsurface, through the atmosphere, and all the way up to free space.
Seven scientific instruments on board the orbiting spacecraft will
perform a series of remote sensing experiments designed to shed new
light on the Martian atmosphere, the atmospheric structure, and geology.
Scientists hope that Mars Express will detect the presence of water
below the surface in the form of underground rivers, pools, aquifiers,
Express travelled to the Red Planet in seven months arriving in in Mars
orbit on 25 December 2003. It set off on its journey from the Baikonur
launch pad in Kazakhstan on a Soyuz-Fregat launcher on 2 June 2003.
After reaching an altitude of about 200 kilometres, the Fregat upper
stage (which carries the spacecraft) fired its own motors to circularise
the orbit 200 kilometres above the Earth. Just before completing the
first orbit, it fired again to send itself and its cargo into an escape
orbit, en-route for Mars.
Just before arrival at Mars, Mars Express released the Beagle 2
lander on a trajectory that would enter the Martian atmosphere and
endure a bumpy ride through the Martian atmosphere down to the correct
landing site on the surface. Beagle 2 reached the surface on December
25, 2003, but no signal was ever received from the Beagle 2 lander, and
it was declared lost.
Mars Express is designed to record data for at least one Martian
year, or 687 Earth days. The spacecraft also carries a data relay system
for communicating with Earth.
Mars Odyssey (March, September)
Odyssey is an orbiter carrying science experiments designed to make
global observations of Mars to improve our understanding of the planet's
climate and geologic history, including the search for water and
evidence of life-sustaining environments.
Odyssey was launched April 7, 2001 on a Delta II rocket from Cape
Canaveral, Florida, and reached Mars on October 24, 2001, 0230 Universal
Time (October 23, 7:30 pm PDT/ 10:30 EDT). The spacecraft's main engine
fired to brake the spacecraft's speed and allowed it to be captured into
orbit around Mars. Odyssey used a technique called "aerobraking" that
gradually brought the spacecraft closer to Mars with each orbit. By
using the atmosphere of Mars to slow down the spacecraft in its orbit
rather than firing its engine or thrusters, Odyssey was able to save
more than 200 kilograms (440 pounds) of propellant.
Aerobraking ended in January, and its science mapping mission began
in February 2002. The primary science mission continued through August
2004 and Odyssey is currently in its extended mission. In its extended
mission, Mars Odyssey continues to map chemical elements and minerals on
the surface of Mars, look for water in the shallow subsurface, and
analyze the radiation environment to determine its potential effects on
human health. Odyssey also serves as a communications relay for
the Mars Exploration Rovers (Spirit and Opportunity) and future
Named after 2001: A Space Odyssey, the movie that inspired a
generation to believe in a future where travelers on their way to
Jupiter could call loved ones from space hotels via live television
links, NASA's 2001 Odyssey orbiter mission has actually brought that
fantasy one step closer to reality -- via Mars.
Image and Text Credit: NASA/JPL
Huygens probe was delivered to Saturn's moon Titan by the Cassini
spacecraft, which is managed by NASA's Jet Propulsion Laboratory,
Pasadena, Calif. The images were taken with the Descent Imager/Spectral
Radiometer, one of two NASA instruments on the probe.
The Cassini-Huygens mission is a cooperative project of NASA, the
European Space Agency and the Italian Space Agency. The Jet Propulsion
Laboratory, a division of the California Institute of Technology in
Pasadena, manages the Cassini-Huygens mission for NASA's Science Mission
Directorate, Washington, D.C. The Cassini orbiter and its two onboard
cameras were designed, developed and assembled at JPL. The Descent
Imager/Spectral team is based at the University of Arizona, Tucson, Ariz.
For more information about the Cassini-Huygens mission visit
Image and Text Credit: NASA/ESA
Deep Impact (July)
On the evening of July 3, 2005,
Deep Impact, a NASA
Discovery Mission, performed an incredibly complex experiment in space
to probe beneath the surface of a comet and reveal the secrets of its
interior. As a larger “flyby” spacecraft released a smaller “impactor”
spacecraft into the path of comet Tempel 1, the experiment became one of
a cometary bullet chasing down a spacecraft bullet while a third
spacecraft bullet sped along to watch.
Deep Impact was launched aboard a Delta II rocket on January 12 2005.
Five months later, it started collecting images of the comet before the
impact. In early July 2005, 24 hours before impact, the flyby spacecraft
pointed its high-precision tracking telescopes at the comet and released
the impactor on a course to hit the comet's sunlit side.
impactor was a battery-powered spacecraft that operated independently of
the flyby spacecraft for just one day. It is called a "smart" impactor
because, after its release, it took over its own navigation and
maneuvered into the path of the comet. A camera on the impactor captured
and relayed images of the comet's nucleus just seconds before collision.
The impactor spacecraft was composed mainly of copper, which is not
expected to appear in data from a comet's composition. For its short
period of operation, the impactor used simpler versions of the flyby
spacecraft's hardware and software - and fewer backup systems. The
impact was not forceful enough to make an appreciable change in the
comet's orbital path around the Sun.
After release of the impactor,
the flyby spacecraft maneuvered to a new path that, at closest approach
passed 500 km from the comet. The flyby spacecraft observed and recorded
data about the impact, the ejected material blasted from the crater, and
the structure and composition of the crater's interior. After its
shields protected it from the comet's dust tail passing overhead, the
flyby spacecraft turned to look at the comet again. The flyby spacecraft
collected additional data from the other side of the nucleus and
observed changes in the comet's activity. While the flyby spacecraft and
impactor did their jobs, professional and amateur astronomers at large
and small telescopes on Earth observed the impact and its aftermath, and
results were broadcast live over the Internet.
Two instruments on the
flyby spacecraft observed the impact, crater and debris with optical
imaging and infrared spectral mapping. The flyby spacecraft uses an
X-band radio antenna (transmission at about eight gigahertz) to
communicate to Earth as it also listened to the impactor on a different
frequency. For most of the mission, the flyby spacecraft communicates
through the 34-meter antennae of NASA's Deep Space Network. During the
short period of encounter and impact, when there was a huge increase in
volume of data, overlapping antennas around the world were used. Primary
data was transmitted immediately and other data was transmitted over the
Image and Text Credit: NASA/JPL-Caltech/UMD
Cassini-Huygens mission is a cooperative project of NASA, the European
Space Agency and the Italian Space Agency. The Jet Propulsion
Laboratory, a division of the California Institute of Technology in
Pasadena, manages the mission for NASA's Science Mission Directorate,
The Cassini orbiter and its two onboard cameras were
designed, developed and assembled at JPL. The imaging operations center
is based at the Space Science Institute in Boulder, Colo.
PIA03883: Artists's Conception of Cassini Saturn Orbit
Insertion. This is an artists concept of Cassini during the Saturn
Orbit Insertion(SOI) maneuver on July 1, 2004, just after the main
engine began firing. The spacecraft is moving out of the plane of
the page and to the right (firing to reduce its spacecraft velocity
with respect to Saturn) and has just crossed the ring plane.
The SOI maneuver, which was approximately 90 minutes long,
allowed Cassini to be captured by Saturn's gravity into a five-month
orbit. Cassini's close proximity to the planet after the maneuver
offered a unique opportunity to observe Saturn and its rings at
extremely high resolution.
Image and Text Credit: NASA/JPL/Space Science
MESSENGER - set to become the
first spacecraft to orbit the planet Mercury - was launched on August 3,
2004 aboard a Boeing Delta II rocket from Cape Canaveral. MESSENGER,
short for MErcury Surface, Space ENvironment, Geochemistry, and Ranging,
is the seventh mission in NASA's Discovery Program of lower cost,
scientifically focused exploration projects. Johns Hopkins University
Applied Physics Laboratory (APL) manages the mission for NASA's Office
of Space Science, built the spacecraft and will operate MESSENGER during
flight. MESSENGER is the 61st spacecraft built at APL.
1,100-kilogram spacecraft carries a package of seven science instruments
to determine Mercury's composition; image its surface globally and in
color; map its magnetic field and measure the properties of its core;
explore the mysterious polar deposits to learn whether ice lurks in
permanently shadowed regions; and characterize Mercury's tenuous
atmosphere and Earth-like magnetosphere.
a 4.9-billion mile (7.9-billion kilometer) journey that includes 15
trips around the sun, MESSENGER will fly past Earth once, Venus twice
and Mercury three times before easing into orbit around its target
planet. The Earth flyby, in August 2005, and the Venus flybys, in
October 2006 and June 2007, will use the pull of the planets' gravity to
guide MESSENGER toward Mercury's orbit. The Mercury flybys in January
2008, October 2008 and September 2009 help MESSENGER match the planet's
speed and location for an orbit insertion maneuver in March 2011. The
flybys also allow the spacecraft to gather data critical to planning a
yearlong orbit phase.
The "brains" of the spacecraft are redundant integrated electronics
modules (IEMs) that house two processors each -- a 25-megahertz (MHz)
main processor and a 10-MHz fault-protection processor.
Attitude determination -- knowing where the spacecraft is and in which
direction it's facing -- is performed using star-tracking cameras and an
Inertial Measurement Unit containing four gyroscopes and four
accelerometers, with six Digital Solar Sensors as a backup. Attitude
control is mostly accomplished using four reaction wheels inside the
spacecraft and, when necessary, MESSENGER's small thrusters. MESSENGER
will receive commands and send data primarily through its circularly
polarized X-band phased-array antennas.
A key MESSENGER design element deals with the intense heat at
Mercury. The Sun is up to 11 times brighter than we see on Earth and
surface temperatures can reach 450 degrees Celsius (about 840 degrees
Fahrenheit), but MESSENGER will operate at room temperature behind a
sunshade made of heat-resistant ceramic cloth.
Credit: NASA/Johns Hopkins University Applied
Physics Laboratory/Carnegie Institution of Washington/Northwestern
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