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IDA-PIA00138.jpgAsteroid Ida's limb (HR)74 visiteThe Galileo imaging system captured this picture of the limb of the asteroid 243 Ida about 46 seconds after its closest approach on August 28, 1993, from a range of only 2480 Km. It is the highest-resolution image of an asteroid's surface ever captured and shows detail at a scale of about 25 meters per pixel. This image is one frame of a mosaic of 15 frames shuttered near Galileo's closest approach to Ida. Since the exact location of Ida in space was not well-known prior to the Galileo flyby, this mosaic was estimated to have only about a 50 percent chance of capturing Ida. Fortunately, this single frame did successfully image a part of the sunlit side of Ida. The area seen in this frame shows some of the same territory seen in a slightly lower resolution full disk mosaic of Ida returned from the spacecraft in September, 1993, but from a different perspective. Prominent in this view is a 2 Km deep "valley" seen in profile on the limb.
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Ida-MF-LXTT.jpgAsteroid "Ida" (possible Natural Colors; credits for the additional process. and color.: Dr Marco Faccin - Lunexit Team)98 visitenessun commentoMareKromium
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Itokawa-03.pngThe Southern Hemisphere of Itokawa66 visiteAfter reaching the sub-solar point, Hayabusa started to travel out of the ecliptic plane to observe the polar regions of Itokawa. This image shows the Southern Hemisphere
of Itokawa. Due to the low altitude and solar elevation angles, we can see detailed topography in the high-latitude regions. There are even some boulders on Muses-Sea, which looked very smooth in previous observations. Imagine one of these boulders flying in space. If it came to the Earth's vicinity, we would observe it as a tiny independent near-Earth asteroid. It has long been conjectured that meteorites are fragments of asteroids delivered to the Earth's surface, but it remains to be proven. The samples of Itokawa collected and returned by Hayabusa could provide the first direct evidence of the link between asteroids and meteorites.
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Itokawa-04.jpgOrbiting around Itokawa (1)73 visiteHayabusa arrived at its exploration target, near Earth asteroid Itokawa, on Sept., 12th, 2005 after having been propelled there via ion engines and an Earth swing-by. Since then, it has successfully performed orbital maneuvers, precisely keeping its position relative to Itokawa. The Hayabusa Project Team has made many discoveries while carrying out their ambitious scientific observations of Itokawa. This release summarizes and reports the major scientific and engineering achievements in advance of Hayabusa’s unprecedented and historic descent to the surfaceof Itokawa for sample collection middle to later this month (November 2005).
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Itokawa-05.jpgOrbiting around Itokawa (2)70 visiteHayabusa is a technology demonstration spacecraft focusing on key technologies that are required for future large-scale sample and return missions, yet is also making new scientific observations and discoveries. The technology demonstration component of the mission consists of 5 goals:
1) ion engine propulsion in interplanetary cruise;
2) ion engine propulsion in combination with an Earth gravity assist;
3) autonomous guidance and navigation using optical measurements;
4) collection of surface samples in an ultra-low gravity environment and
5) the direct recovery of these samples on the ground after its return from interplanetary flight.
To date the Hayabusa project has accomplished these demonstrations up through
the third goal.
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Itokawa-06.jpgOrbiting around Itokawa (3)65 visiteSpecifically, at the time of arrival at Itokawa, Hayabusa had driven its proprietary new ion engines for 26.000 hours, including their operation during an Earth flyby.
It has also perfectly completed a period of hybrid optical navigation followed by
precise guidance and navigation of the spacecraft during its station keeping period around Itokawa.
These engineering achievements are the primary mission of Hayabusa and their successful completion is a great achievement.
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Itokawa-07.jpgOrbiting around Itokawa (4)65 visiteThe deep-space exploration technologies that the Top World's Space Agencies are pursuing consist of 3 major elements:
1) high efficiency electric propulsion for cruise;
2) rendez-vous with target destinations and
3) round-trip flights back to the Earth.
As of this time Hayabusa has accomplished the first and second of these elements, leading the way for the Space Exploration Agencies of the World.
Furthermore, robotic sample collection and return from an extra terrestrial object has not been executed before, and is not currently planned, except for Hayabusa, which will attempt to gather a bulk sample from Itokawa.
Hayabusa’s success clearly shows that Japan’s deep space exploration technology has reached the level of the World’s most developed Space Agencies, and that Japan is now in a Leadership Position in some select engineering fields.
Thus Hayabusa opens a New Era in the exploration of the Solar System.
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Itokawa-08.jpgSurface details (1)63 visiteFor the scientific aspects of the mission, Hayabusa carries 4 instruments that have
performed successful observations to date:
1) AMICA, a Visible Imager with multi-band filters, has exposed 1500 images amounting to almost 1 GB of data;
2) NIRS, a near infrared spectrometer that has already taken 75.000 measurements distributed globally over the body;
3) LIDAR, a laser altimeter that has accumulated 1,4 million measurements globally, and
4) XRS, an X-ray spectrometer that has already received and integrated its signal for 700 hours.
In addition to these, spacecraft tracking data has been used to measure properties of the asteroid as well.
These unprecedented scientific measurements are briefly described and reported in what follows.
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Itokawa-09.jpgSurface details (2)63 visiteA) Morphological and geological discoveries about Itokawa: the a-priori theoretical assumption that small near-Earth asteroids should have geologically homogeneous features was completely overturned by the observation of a wide variety of surface features and types at Itokawa. The surface is covered with huge boulders and, for the first time, naked surfaces not covered with regolith have been exposed. Previously visited asteroidswere covered with thick regolith, thus Itokawa’s surface is like nothing that has seen before, which is quite fortunate for the Hayabusa Mission. The opportunity to observe the true asteroid surface, which isusually concealed from view, advancesour understanding of spectroscopic observations of asteroids taken from Earth, and allows us to expand our knowledge of near Earth asteroids.
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Itokawa-10.jpgSurface details (3)66 visite(B) Taking advantage of the observations made with the onboard instruments, sufficiently detailed information about the sampling sites has been obtained, and the relation between the potential samples and the spectroscopic data has been correctly correlated. As a technology demonstration mission, Hayabusa has already finished the preliminary steps towards the primary sample and return goal. These samples will provide important scientific clues concerning the puzzlingly inconsistent correlations between S-type asteroids and ordinary chondrites, and lead to an improved understanding of the space weathering effect, which may clarify our understanding of the early Solar System and Earth.
(C) Combinations of the Itokawa images along with spacecraft navigation information has enabled shape and gravity models to be numerically defined. The Science Team has started to study and identify the special mechanisms that can move boulders and regolith in the ultra-low gravity environment associated with small objects.
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Itokawa-11.jpgThe Landing Procedure64 visiteThe gravity and slope information and estimates of the density of boulders and regolith distribution on the surface, combined with comparisons with meteorites, will advance our interpretation and understanding of asteroid planetology.
D) Using the laser altimeter and optical navigation camera, along with range and range-rate measurements fromground-tracking stations, have led to a successful mass and density estimate for Itokawa. The density has been estimated to be 2,3 +/-0,3 gram/cc, which is a little lower than that measured for rocks on the ground or for other S-type asteroids measured to date. This may indicate that there is substantial porosity for this body and forces conventional views of these small objects to be changed drastically. When the samples are successfully returned and recovered, the actual porosity will be clarified and our knowledge of how the Earth relates to meteorites will be greatly improved.
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Itokawa-12.jpgNear Infrared Spectra of Candidates for Sampling Sites65 visiteIn view of the scientific results described above, JAXA has determined the landing/sampling sites candidates and the descent target point for rehearsal, along with their planned dates and times.
The landing/sampling sites must be free of obstacles and smooth enough to ensure safety, a top priority, while at the same time the surface inclination and the ground station coverage for Hayabusa must be taken into account. Taking these issues into consideration, the candidate
sites and schedule were determined.
The first site candidate is the regolith expanse in the middle of Itokawa, known as the MUSES-SEA Area and the second candidate site is the Woomera desert at the tip end of Itokawa, where the terrain is broad and flat. The rehearsal target is the area located close to the spin axis, a little east of the first site. The date and time of the planned events
(JST) are as follows:
1. Rehearsal Descent: Nov. 4, '05 - h.14:00
2. 1st Touch-down: Nov. 12, '05 - h. 15:00
3. 2nd Touch-down: Nov. 25., '05 - h. 15:00
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