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Itokawa.jpgHayabusa's "shadow"!54 visiteWhat's that unusual looking spot on asteroid Itokawa? It's the shadow of the robot spacecraft Hayabusa that took the image. Japan's Hayabusa Mission arrived at the asteroid in early September and has been imaging and maneuvering around the floating space mountain ever since. The above picture was taken earlier this month (November 2005).
Asteroid Itokawa spans about 300 mt.
One scientific goal of the Hayabusa mission is to determine out how much ice, rock and trace elements reside on the asteroid's surface, which should give indications about how asteroids and planets formed in the early Solar System. A can-sized robot MINERVA that was scheduled to hop around the asteroid's surface has not, so far, functioned as hoped. Later this month, Hayabusa is scheduled to descend to asteroid Itokawa and collect surface samples in a return capsule. In December, Hayabusa will fire its rockets toward Earth and drop the return capsule down to Earth's Australian outback in 2007 June.
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Itokawa~0.jpgClosing on Itokawa54 visiteItokawa: un asteroide che sembra contraddire tutto quanto viene dato per acquisito nel campo delle forme esteriori e dei rilievi superficiali dei corpi (teoricamente) esposti a pesantissimi azioni di impatto sin dagli albori della loro esistenza. Pensate a 433-Eros, oppure a Ceres, o Dactyl o a qualsiasi altro corpo similare che abbiamo avuto occasione di vedere da distanza ravvicinata. Forse il solo asteroide AnneFrank non sembra presentare una particolare craterizzazione (ma le immagini, di cattiva qualità, non possono essere considerate definitorie) e quindi si viene a porre nel novero delle rarità. Tuttavia, quello che vediamo adesso, è ben più che un'eccezione e molto di più di un'Anomalìa: Itokawa NON ha alcun cratere superficiale visibile e le sue forme, spigolose ed a tratti aguzze, costituiscono una novità assoluta per i Ricercatori e gli Studiosi di Scienze Planetarie.
Original caption:"Where are the craters on asteroid Itokawa? No one knows. The Japanese robot probe Hayabusa recently approached the Earth-crossing asteroid and is returning pictures showing a surface unlike any other Solar System body yet photographed -- a surface possibly devoid of craters. One possibility for the lack of common circular indentations is that asteroid Itokawa is a rubble pile -- a bunch of rocks and ice chunks only loosely held together by a small amount of gravity. If so, craters might be filled in whenever the asteroid gets jiggled by a passing planet -- Earth in this case. Alternatively, surface particles may become electrically charged by the Sun, levitate in the microgravity field, and move to fill in craters. Over the weekend, Hayabusa lowered itself to the surface of the strange asteroid in an effort to study the unusual body and collect surface samples that could be returned to Earth in 2007".
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Iustitia.jpgIustitia (Imagination)79 visitenessun commentoMareKromium
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KBO-1-Artist_Conception.jpgKuiper's Belt Object occulting a Star56 visiteThis is an artist's impression of a 0,5-mile-diameter Kuiper Belt Object (KBO) that was detected by NASA's Hubble Space Telescope. The icy relic from the early Solar System is too small for Hubble to photograph. The object was detected when it passed in front of a background star, temporarily disrupting the starlight.MareKromium
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KBO-2-Artist_Conception.jpgKuiper's Belt Object occulting a Star55 visiteNASA's Hubble Space Telescope has discovered the smallest object ever seen in Visible Light in the Kuiper Belt, a vast ring of icy debris that is encircling the outer rim of the Solar System, just beyond Neptune.
The needle-in-a-haystack object found by Hubble is only 3200 feet across and a whopping 4,2 Billion Miles away. The smallest Kuiper Belt Object (KBO) seen previously in reflected light is roughly 30 miles across, or 50 times larger.
This is the first observational evidence for a population of comet-sized bodies in the Kuiper Belt that are being ground down through collisions. The Kuiper Belt is therefore collisionally evolving, meaning that the region's icy content has been modified over the past 4,5 BYs.
The object detected by Hubble is so faint — at 35th magnitude — it is 100 times dimmer than what Hubble can see directly.
So then how did the space telescope uncover such a small body?MareKromium
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KBO-3-Artist_Conception.jpgKuiper's Belt Object occulting a Star54 visiteIn a paper published in the December 17th issue of the journal Nature, Hilke Schlichting of the California Institute of Technology in Pasadena, Calif., and her collaborators are reporting that the telltale signature of the small vagabond was extracted from Hubble's pointing data, not by direct imaging.
Hubble has three optical instruments called Fine Guidance Sensors (FGS). The FGSs provide high-precision navigational information to the space observatory's attitude control systems by looking at select guide stars for pointing. The sensors exploit the wavelike nature of light to make precise measurement of the location of stars.
Schlichting and her co-investigators determined that the FGS instruments are so good that they can see the effects of a small object passing in front of a star. This would cause a brief occultation and diffraction signature in the FGS data as the light from the background guide star was bent around the intervening foreground KBO.
They selected 4,5 years of FGS observations for analysis. Hubble spent a total of 12.000 hours during this period looking along a strip of sky within 20° of the Solar System's Ecliptic Plane, where the majority of KBOs should dwell. The team analyzed the FGS observations of 50.000 guide stars in total.
Scouring the huge database, Schlichting and her team found a single 0,3-second-long occultation event. This was only possible because the FGS instruments sample changes in starlight 40 times a second. The duration of the occultation was short largely because of the Earth's orbital motion around the Sun.
They assumed the KBO was in a circular orbit and inclined 14° to the Ecliptic. The KBO's distance was estimated from the duration of the occultation, and the amount of dimming was used to calculate the size of the object. "I was very thrilled to find this in the data", says Schlichting.
Hubble observations of nearby stars show that a number of them have Kuiper Belt–like disks of icy debris encircling them. These disks are the remnants of planetary formation. The prediction is that over billions of years the debris should collide, grinding the KBO-type objects down to ever smaller pieces that were not part of the original Kuiper Belt population.
The finding is a powerful illustration of the capability of archived Hubble data to produce important new discoveries. In an effort to uncover additional small KBOs, the team plans to analyze the remaining FGS data for nearly the full duration of Hubble operations since its launch in 1990.MareKromium
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L-Itokawa.jpgThe Target Marker separated from Hayabusa (close-up)55 visiteThe Target Marker that separated from Hayabusa carried the names of 880.000 people who participated in the campaign from the World.
It was placed in the South-West area of the MUSES-Sea.
When it hit to the surface, the descent speed was about 9 cm/sec. The Target Marker was specifically designed and fabricated with an aluminum shell filled with polyimide balls (so to absorb kinetic energy through multi-collisions). This design is capable to dramatically suppress the bouncing of the probe and its function has been tested and verified via drop tower tests in a vacuum chamber on Earth.
The Target Marker (è il minuscolo punto luminoso - cerchiato in nero - che si vede accanto all'ombra di Hayabusa nel close-up di Sx) was illuminated by onboard flash lamps every 2' (...).
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LL-Itokawa.jpgTarget Marker located on Itokawa (1)56 visiteOn Nov. 26, spacecraft "Hayabusa" challenged the second trial to execute landing on and sampling from the asteroid Itokawa. Hayabusa team confirmed the whole process to have been implemented and it is sure that the team succeeded in sampling materials on the surface of an asteroid for the first time in World History. Detailed data to be sent from Hayabusa will further verify the sampling.
Hayabusa started its last descent phase from the altitude of 1 km above Itokawa by command from Earth around 10:00 p.m. Nov.25 (JST). It was followed by starting the vertical descent from around 6:00 a.m. Nov.26., and, around 6:25 a.m., Sagamihara Deep Space Control Room sent a command to continue the descent.
Hayabusa challenged landing and sampling operation after a hovering phase. Hayabusa team is now sure, through the analysis of telemetry data, that a series of sequence for sampling was successfully done. Hayabusa then flew up to several kilometers altitude with normal solar paddles power, spacecraft attitude, etc.
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LLL-Itokawa.jpgTarget Marker located on Itokawa (2)55 visiteThe spacecraft shifted to safe-hold mode because of its attitude dispersion during ascent, and Sagamihara Deep Space Control Room is now carrying out the recovery operation to three-axis control mode.
It therefore takes a few more days to obtain detailed data relating the procedure. Instruments onboard are functioning very well so far.
Spacecraft Hayabusa could find, on the surface of Itokawa, the Target Marker dropped on Nov. 20 among the images taken during descent phase on Nov. 26.
On the Target Marker are etched 880.000 names from 149 Countries.
The previous images show the area named "MUSES Sea" and they were taken at 04:58 of Nov. 20, 2005 (left) and at 06:24 of Nov. 26, 2005 (right).
In this frame, the white light spot inside the red circle is the Target Marker with the 880.000 names!
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LLM-Itokawa.jpg25143-Itokawa53 visiteA Japanese spacecraft has provided one of the best arguments yet in favor of a conception of asteroids which was pioneered by PSI (Planet Science Institute) scientists Don Davis and Clark Chapman in the late 70's. The evidence comes in startling closeup pictures of the tiny asteroid 25143-Itokawa, photographed by the Japanese Hayabusa spacecraft during a two-month encounter in late 2005. The asteroid illustrates the concept of a "Rubble-Pile" asteroid, which is composed of a mixture of boulders and dust gravitationally bound together.
The scientific results, recently highlighted in the journal Science, show that, unlike other asteroids recently imaged by spacecraft, which are mostly rounded and potato-like, dotted by craters, and with a few scattered boulders on the surface, Itokawa appears to be composed of massive splinter-like boulders protruding from a matrix of smaller fragments.
The largest boulders sticking out of the body appear to be some tens of meters across.
The Hayabusa science team includes PSI scientists Paul Abell and Bob Gaskell, and PSI affiliate scientists Hirdy Miyamoto and Faith Vilas.
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LLN-Itokawa-ST_2506464135_v.pngApproaching Itokawa (1 - natural colors; elab. Lunexit)54 visitenessun commentoMareKromium
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LLN-Itokawa-ST_2506540935_v.pngApproaching Itokawa (2 - natural colors; elab. Lunexit)53 visitenessun commentoMareKromium
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