109-464: OKEANOS ( Oversize Kite-craft for Exploration and Astronautics in the Outer Solar system ) was a proposed mission concept to Trojan asteroids , which share Jupiter's orbit, using a hybrid solar sail for propulsion; the sail was planned to be covered with thin solar panels to power an ion engine . In situ analysis of the collected samples would have been performed by either direct contact or using
218-471: A 20 km by 200 km area in the Woomera Prohibited Area , South Australia . Four ground teams surrounded this area and located the re-entry capsule by optical observation and a radio beacon. Then a team on board a helicopter was dispatched. They located the capsule and recorded its position with GPS. The capsule was successfully retrieved at 07:08 UTC (16:38 local) of 14 June 2010. The two parts of
327-640: A revised version of the Nice model Jupiter trojans are captured when Jupiter encounters an ice giant during the instability. In this version of the Nice model one of the ice giants (Uranus, Neptune, or a lost fifth planet ) is scattered inward onto a Jupiter-crossing orbit and is scattered outward by Jupiter causing the orbits of Jupiter and Saturn to quickly separate. When Jupiter's semi-major axis jumps during these encounters existing Jupiter trojans can escape and new objects with semi-major axes similar to Jupiter's new semi-major axis are captured. Following its last encounter
436-409: A September 2005 rendezvous with Itokawa. As it arrived, the spacecraft did not go into orbit around the asteroid, but remained in a station-keeping heliocentric orbit close by. Hayabusa surveyed the asteroid surface from a distance of about 20 km (13.7 mi), the "gate position". After this the spacecraft moved closer to the surface (the "home position"), and then approached the asteroid for
545-480: A cargo container which had air suspension to keep the capsule below 1.5 G shock during transportation. The capsule and its heat shield parts were transported to Japan by a chartered plane and arrived at the curation facility at the JAXA/ISAS Sagamihara Campus on 18 June. A Tokyo Metropolitan Government adviser and former lieutenant general, Toshiyuki Shikata, claimed that part of the rationale for
654-568: A deficit of periods in the range 8–10 hours. The Maxwellian distribution of the rotational periods of Jupiter trojans may indicate that they have undergone a stronger collisional evolution compared to the asteroid belt. In 2008 a team from Calvin College examined the light curves of a debiased sample of ten Jupiter trojans, and found a median spin period of 18.9 hours. This value was significantly higher than that for main-belt asteroids of similar size (11.5 hours). The difference could mean that
763-422: A dual purpose of solar sail propulsion and solar panel for power generation. If a lander had been included, its mass would have been no greater than 100 kg. The lander would have collected and analyzed samples from the asteroid. A more complex suggested concept would have had the lander take off again, rendezvous with the mothership and transfer the samples for their transport to Earth. The unique proposed sail
872-417: A factor of 2 if small Jupiter trojans are more reflective than large ones. The number of Jupiter trojans observed in the L 4 swarm is slightly larger than that observed in L 5 . Because the brightest Jupiter trojans show little variation in numbers between the two populations, this disparity is probably due to observational bias. Some models indicate that the L 4 swarm may be slightly more stable than
981-742: A fixed separation from Jupiter. They slowly librate around their respective equilibrium points, periodically moving closer to Jupiter or farther from it. Jupiter trojans generally follow paths called tadpole orbits around the Lagrangian points; the average period of their libration is about 150 years. The amplitude of the libration (along the Jovian orbit) varies from 0.6° to 88°, with the average being about 33°. Simulations show that Jupiter trojans can follow even more complicated trajectories when moving from one Lagrangian point to another—these are called horseshoe orbits (currently no Jupiter Trojan with such an orbit
1090-512: A higher position, then descended again to 500 m and released one of the target markers into space to test the craft's ability to track it (this was confirmed). From analysis of the closeup images, the Woomera Desert site (Point B) was found to be too rocky to be suitable for landing. The Muses Sea site (Point A) was selected as the landing site, for both first and, if possible, second landings. On 12 November, Hayabusa closed in to 55 m from
1199-437: A lander carrying a high-resolution mass spectrometer. A sample-return to Earth was an option under study. OKEANOS was a finalist for Japan's Institute of Space and Astronautical Science (ISAS) ' 2nd Large Mission Class to be launched in 2026, and possibly return Trojan asteroid samples to Earth in the 2050s. The winning mission was LiteBIRD . The OKEANOS mission was a concept first proposed in 2010 to fly together with
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#17328550839951308-412: A leak in the thruster system, the probe was put in a "safe hold mode". On 27 November, the probe experienced a power outage when trying to reorient the spacecraft, probably due to a fuel leakage. On 30 November, JAXA announced that control and communication with Hayabusa had been restored, but a problem remained with the craft's reaction control system , perhaps involving a frozen pipe. Mission control
1417-513: A reentry capsule. The lander would have been discarded after the sample transfer. GAP-2 and EXZIT were instruments for astronomical observations, and were not intended to be used for studying Trojan asteroids. The two would have conducted opportunistic surveys, taking advantage of the mission's trajectory. GAP-2 would have made it possible to locate the position of Gamma-ray bursts with high precision by pairing it with terrestrial observatories. EXZIT, as zodiacal light gets significantly weak beyond
1526-435: A relative speed of 3 m per second. On 1 June, Hayabusa project manager Junichiro Kawaguchi reported that they confirmed two out of four ion engines were working normally, which would have been sufficient for the return journey. On 30 January 2007, JAXA reported that 7 out of 11 batteries were working and the return capsule was sealed. On 25 April, JAXA reported that Hayabusa started the return journey. On 29 August, it
1635-503: A result, the target asteroid was changed to 1998 SF 36 . In 2002, launch was postponed from December 2002 to May 2003 to recheck O-rings of reaction control system since one of it was found using different material than specified. On 9 May 2003 04:29:25 UTC, MUSES-C was launched by an M-V rocket, and the probe was named " Hayabusa ". Ion thruster checkout started on 27 May 2003. Full power operation started on 25 June. Asteroids are named by their discoverer. ISAS asked LINEAR ,
1744-540: A result, when the MINERVA release command arrived, MINERVA was released while the probe was ascending and at a higher altitude than intended, so that it escaped Itokawa's gravitational pull and tumbled into space. Had it been successful, MINERVA would have been the first hopping space rover. The Soviet mission Phobos 2 also encountered a malfunction while attempting to deploy a hopping rover. Scientists' understanding of asteroids depends greatly on meteorite samples, but it
1853-454: A sample to be taken, but there is a high probability that some dust may have whirled up into the sampling horn when it touched the asteroid, so the sample canister attached to the sampling horn was sealed. On 25 November, a second touchdown attempt was performed. It was initially thought that this time, the sampling device was activated; however, later analysis decided that this was probably another failure and that no pellets were fired. Due to
1962-515: A sample-return using a lander. This lander concept was a collaboration among the German Aerospace Center (DLR) and Japan's JAXA , starting in 2014. The spacecraft would have deployed a 100 kg lander on the surface of a 20–30 km Trojan asteroid to analyze its subsurface volatile constituents, such as water ice, using a 1-meter pneumatic drill powered by pressurized nitrogen gas. Some subsurface samples would have been transferred to
2071-450: A series of soft landings and for the collection of samples at a safe site. Autonomous optical navigation was employed extensively during this period because the long communication delay prohibits Earth-based real-time commanding. At the second Hayabusa touched down with its deployable collection horn, the spacecraft was programmed to fire tiny projectiles at the surface and then collect the resulting spray. Some tiny specks were collected by
2180-542: A target marker, and release of the Minerva minilander. The descent went well initially, and navigation images with wide-angle cameras were obtained. However, at 01:50 UTC ( 10:50 am JST ) on 4 November, it was announced that due to a detection of an anomalous signal at the Go/NoGo decision, the descent, including release of Minerva and the target marker had been canceled. The project manager, Junichiro Kawaguchi, explained that
2289-452: A variation of this theory Jupiter captures trojans during its initial growth then migrates as it continues to grow. During Jupiter's migration the orbits of objects in horseshoe orbits are distorted causing the L4 side of these orbits to be over occupied. As a result, an excess of trojans is trapped on the L4 side when the horseshoe orbits shift to tadpole orbits as Jupiter grows. This model also leaves
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#17328550839952398-477: Is 0.056 ± 0.003 for the objects larger than 57 km, and 0.121 ± 0.003 (R-band) for those smaller than 25 km. The asteroid 4709 Ennomos has the highest albedo (0.18) of all known Jupiter trojans. Little is known about the masses, chemical composition, rotation or other physical properties of the Jupiter trojans. The rotational properties of Jupiter trojans are not well known. Analysis of
2507-465: Is caused by (1) the assumption that all Jupiter trojans have a low albedo of about 0.04, whereas small bodies may have an average albedo as high as 0.12; (2) an incorrect assumption about the distribution of Jupiter trojans in the sky. According to the new estimates, the total number of Jupiter trojans with a diameter larger than 2 km is 6,300 ± 1,000 and 3,400 ± 500 in the L 4 and L 5 swarms, respectively. These numbers would be reduced by
2616-461: Is known, though one is known for Neptune ). Discerning dynamical families within the Jupiter trojan population is more difficult than it is in the asteroid belt, because the Jupiter trojans are locked within a far narrower range of possible positions. This means that clusters tend to overlap and merge with the overall swarm. By 2003 roughly a dozen dynamical families were identified. Jupiter-trojan families are much smaller in size than families in
2725-470: Is normally understood to specifically mean the Jupiter trojans because the first Trojans were discovered near Jupiter's orbit and Jupiter currently has by far the most known Trojans. In 1772, Italian-born mathematician Joseph-Louis Lagrange , in studying the restricted three-body problem , predicted that a small body sharing an orbit with a planet but lying 60° ahead or behind it will be trapped near these points. The trapped body will librate slowly around
2834-409: Is open to question, because multiple weak resonances with Jupiter and Saturn cause them to behave chaotically over time. Collisional shattering slowly depletes the Jupiter trojan population as fragments are ejected. Ejected Jupiter trojans could become temporary satellites of Jupiter or Jupiter-family comets . Simulations show that the orbits of up to 17% of Jupiter trojans are unstable over the age of
2943-437: Is set to explore seven Jupiter trojans. It was launched on October 16, 2021, and will arrive at the L 4 Trojan cloud in 2027 after two Earth gravity assists and a fly-by of a main-belt asteroid. It will then return to the vicinity of Earth for another gravity assist to take it to Jupiter's L 5 Trojan cloud where it will visit 617 Patroclus . Hayabusa Hayabusa ( Japanese : はやぶさ , " Peregrine falcon ")
3052-535: Is significantly higher than that of 617 Patroclus. Such a difference in densities suggests that density may not be a good indicator of asteroid origin. Two main theories have emerged to explain the formation and evolution of the Jupiter trojans. The first suggests that the Jupiter trojans formed in the same part of the Solar System as Jupiter and entered their orbits while it was forming. The last stage of Jupiter's formation involved runaway growth of its mass through
3161-408: Is very difficult to match up meteorite samples with the exact asteroids from which they came. Hayabusa helped solve this problem by bringing back pristine samples from a specific, well-characterized asteroid. Hayabusa bridged the gap between ground observation data of asteroids and laboratory analysis of meteorite and cosmic dust collections. Also comparing the data from the onboard instruments of
3270-456: The Hayabusa mission was the first one to return an asteroid sample to Earth for analysis. In addition, Hayabusa was the first spacecraft designed to deliberately land on an asteroid and then take off again ( NEAR Shoemaker made a controlled descent to the surface of 433 Eros in 2000, but it was not designed as a lander and was eventually deactivated after it arrived). Technically, Hayabusa
3379-460: The Hayabusa with the data from the NEAR Shoemaker mission will put the knowledge on a wider level. The Hayabusa mission has a very deep engineering importance for JAXA, too. It allowed JAXA to further test its technologies in the fields of ion engines , autonomous and optical navigation, deep space communication, and close movement on objects with low gravity among others. Second, since it
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3488-582: The Jupiter Magnetospheric Orbiter (JMO) as part of the cancelled Europa Jupiter System Mission – Laplace . In its latest formulation, the OKEANOS mission and LiteBIRD were the two finalists of Japan's Large Mission Class by the Ministry of Education, Culture, Sports, Science and Technology . LiteBIRD, a cosmic microwave background astronomy telescope, was selected. Analyzing the composition of
3597-496: The Jupiter Trojans may help scientists understand how the Solar System was formed. It would also help determine which of the competing hypotheses is right: remnant planetesimals during the formation of Jupiter, or fossils of building blocks of Jupiter, or captured trans-Neptunian objects by planetary migration. The latest proposal included a lander to perform in situ analyses. There were several options for this mission, and
3706-512: The SETI Institute as the project scientist. Since the reaction control system no longer functioned, the 510 kilograms (1,120 lb) space probe re-entered the Earth's atmosphere similar to the approach of an asteroid along with the sample re-entry capsule, and, as mission scientists expected, the majority of the spacecraft disintegrated upon entry. The return capsule was predicted to land in
3815-467: The Trojan War was suggested by Johann Palisa of Vienna , who was the first to accurately calculate their orbits. Asteroids in the leading (L 4 ) orbit are named after Greek heroes (the "Greek node or camp" or " Achilles group"), and those at the trailing (L 5 ) orbit are named after the heroes of Troy (the "Trojan node or camp"). The asteroids 617 Patroclus and 624 Hektor were named before
3924-666: The asteroid belt . Like main-belt asteroids, Jupiter trojans form families . As of 2004 , many Jupiter trojans showed to observational instruments as dark bodies with reddish, featureless spectra . No firm evidence of the presence of water, or any other specific compound on their surface has been obtained, but it is thought that they are coated in tholins , organic polymers formed by the Sun's radiation. The Jupiter trojans' densities (as measured by studying binaries or rotational lightcurves) vary from 0.8 to 2.5 g·cm . Jupiter trojans are thought to have been captured into their orbits during
4033-415: The ion engines to the bi-propellant thrusters for orbital maneuvering. From 4 September, Hayabusa 's cameras were able to confirm Itokawa's elongated shape. From 11 September, individual hills were discerned on the asteroid. On 12 September, Hayabusa was 20 km (12 mi) from Itokawa and JAXA scientists announced that Hayabusa had officially "arrived". On 15 September 2005, a 'color' image of
4142-480: The telemetry log data was faulty. On 6 December, Hayabusa was 550 km from Itokawa. JAXA held a press conference about the situation so far. On 8 December, a sudden orientation change was observed, and communication with Hayabusa was lost. It was thought likely that the turbulence was caused by evaporation of 8 or 10 cc of leaked fuel. This forced a wait of a month or two for Hayabusa to stabilize by conversion of precession to pure rotation, after which
4251-486: The 4.4–40 km range the Jupiter trojans' size distribution resembles that of the main-belt asteroids. Nothing is known about the masses of the smaller Jupiter trojans. The size distribution suggests that the smaller Trojans may be the products of collisions by larger Jupiter trojans. Jupiter trojans have orbits with radii between 5.05 and 5.35 AU (the mean semi-major axis is 5.2 ± 0.15 AU), and are distributed throughout elongated, curved regions around
4360-866: The Greece/Troy rule was devised, resulting in a "Greek spy", Patroclus , in the Trojan node and a "Trojan spy", Hector , in the Greek node. In 2018, at its 30th General Assembly in Vienna, the International Astronomical Union amended the naming convention for Jupiter trojans, allowing for asteroids with H larger than 12 (that is, a mean diameter smaller than approximately 22 kilometers, for an assumed albedo of 0.057) to be named after Olympic athletes, because there are now far more known Jupiter trojans than available names of Greek and Trojan warriors that fought in
4469-638: The Jupiter trojan population 3–4 orders of magnitude too large. The second theory proposes that the Jupiter trojans were captured during the migration of the giant planets described in the Nice model . In the Nice model the orbits of the giant planets became unstable 500–600 million years after the Solar System's formation when Jupiter and Saturn crossed their 1:2 mean-motion resonance . Encounters between planets resulted in Uranus and Neptune being scattered outward into
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4578-622: The Jupiter trojans possess a lower average density, which may imply that they formed in the Kuiper belt (see below). Spectroscopically , the Jupiter trojans mostly are D-type asteroids , which predominate in the outer regions of the asteroid belt. A small number are classified as P or C-type asteroids . Their spectra are red (meaning that they reflect more light at longer wavelengths) or neutral and featureless. No firm evidence of water, organics or other chemical compounds has been obtained as of 2007 . 4709 Ennomos has an albedo slightly higher than
4687-494: The Jupiter-trojan average, which may indicate the presence of water ice. Some other Jupiter Trojans, such as 911 Agamemnon and 617 Patroclus , have shown very weak absorptions at 1.7 and 2.3 μm, which might indicate the presence of organics. The Jupiter trojans' spectra are similar to those of the irregular moons of Jupiter and, to a certain extent, comet nuclei , though Jupiter trojans are spectrally very different from
4796-451: The L 4 Lagrangian point of the Sun – Jupiter system, later named 588 Achilles . In 1906–1907 two more Jupiter trojans were found by fellow German astronomer August Kopff ( 624 Hektor and 617 Patroclus ). Hektor, like Achilles, belonged to the L 4 swarm ("ahead" of the planet in its orbit), whereas Patroclus was the first asteroid known to reside at the L 5 Lagrangian point ("behind"
4905-438: The L 5 swarm. The largest Jupiter trojan is 624 Hektor , which has a mean diameter of 203 ± 3.6 km. There are few large Jupiter trojans in comparison to the overall population. With decreasing size, the number of Jupiter trojans grows very quickly down to 84 km, much more so than in the asteroid belt. A diameter of 84 km corresponds to an absolute magnitude of 9.5, assuming an albedo of 0.04. Within
5014-496: The MUSES-C project started in fiscal year 1996. Asteroid Nereus was the first choice of target, 1989 ML was the secondary choice. In early development phase, Nereus was considered out of reach and 1989 ML became the primary target. A launch failure of M-V in July 2000 forced MUSES-C's launch to be delayed from July 2002 to November/December, putting both Nereus and 1989 ML out of reach. As
5123-463: The Solar System. Levison et al. believe that roughly 200 ejected Jupiter trojans greater than 1 km in diameter might be travelling the Solar System, with a few possibly on Earth-crossing orbits. Some of the escaped Jupiter trojans may become Jupiter-family comets as they approach the Sun and their surface ice begins evaporating. On 4 January 2017 NASA announced that Lucy was selected as one of their next two Discovery Program missions. Lucy
5232-520: The South Australian outback while the spacecraft broke up and incinerated in a large fireball. An international team of scientists observed the 12.2 km/s entry of the capsule from 11.9 km (39,000 ft) on board NASA's DC-8 airborne laboratory, using a wide array of imaging and spectrographic cameras to measure the physical conditions during atmospheric reentry in a mission led by NASA's Ames Research Center , with Peter Jenniskens of
5341-435: The Trojan war. Estimates of the total number of Jupiter trojans are based on deep surveys of limited areas of the sky. The L 4 swarm is believed to hold between 160,000 and 240,000 asteroids with diameters larger than 2 km and about 600,000 with diameters larger than 1 km. If the L 5 swarm contains a comparable number of objects, there are more than 1 million Jupiter trojans 1 km in size or larger. For
5450-460: The accretion of large amounts of hydrogen and helium from the protoplanetary disk ; during this growth, which lasted for only about 10,000 years, the mass of Jupiter increased by a factor of ten. The planetesimals that had approximately the same orbits as Jupiter were caught by the increased gravity of the planet. The capture mechanism was very efficient—about 50% of all remaining planetesimals were trapped. This hypothesis has two major problems:
5559-411: The asteroid Itokawa. According to Japanese scientists, the composition of Hayabusa 's samples was more similar to meteorites than known rocks from Earth. Their size is mostly less than 10 micrometers. The material matches chemical maps of Itokawa from Hayabusa' s remote sensing instruments. The researchers found concentrations of olivine and pyroxene in the Hayabusa samples. Further study of
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#17328550839955668-520: The asteroid belt, would have enabled the telescope to observe the cosmic infrared background . MGF-2 was a possible a successor of the MGF instrument on board the Arase satellite, and ALADDIN-2, GAP-2 were possible successors of the respective instruments onboard IKAROS . Jupiter trojan The Jupiter trojans , commonly called trojan asteroids or simply trojans , are a large group of asteroids that share
5777-591: The asteroid belt; the largest identified family, the Menelaus group, consists of only eight members. In 2001, 617 Patroclus was the first Jupiter trojan to be identified as a binary asteroid . The binary's orbit is extremely close, at 650 km, compared to 35,000 km for the primary's Hill sphere . The largest Jupiter trojan— 624 Hektor — is probably a contact binary with a moonlet. Jupiter trojans are dark bodies of irregular shape. Their geometric albedos generally vary between 3 and 10%. The average value
5886-608: The asteroid surface for about 30 minutes (see below ). The Hayabusa spacecraft was launched on 9 May 2003 at 04:29:25 UTC on an M-V rocket from the Uchinoura Space Center (still called Kagoshima Space Center at that time). Following launch, the spacecraft's name was changed from the original MUSES-C to Hayabusa , the Japanese word for falcon . The spacecraft's xenon ion engines (four separate units), operating near-continuously for two years, slowly moved Hayabusa toward
5995-558: The asteroid was released (which is, however, grey in coloring). On 4 October, JAXA announced that the spacecraft had successfully moved to its 'Home Position' 7 km from Itokawa. Closeup pictures were released. It was also announced that the spacecraft's second reaction wheel, governing the Y-axis, had failed, and that the craft was now being pointed by its rotation thrusters. On 3 November, Hayabusa took station 3.0 km from Itokawa. It then began its descent, planned to include delivery of
6104-460: The asteroid's shape, spin, topography, color, composition, density, and history. In November 2005, it landed on the asteroid and collected samples in the form of tiny grains of asteroidal material, which were returned to Earth aboard the spacecraft on 13 June 2010. The spacecraft also carried a detachable minilander, MINERVA , which failed to reach the surface. NASA 's Galileo and NEAR Shoemaker spacecraft had visited asteroids before, but
6213-437: The asteroid's surface. MINERVA was released but due to an error failed to reach the surface. On 19 November, Hayabusa landed on the asteroid. There was considerable confusion during and after the maneuver about precisely what had happened, because the high-gain antenna of the probe could not be used during final phase of touch-down, as well as the blackout during handover of ground station antenna from DSN to Usuda station. It
6322-439: The beacon signal. On 6 February, an ejection of xenon propellant was commanded for attitude control to improve communication. The spin axis change rate was about two degrees per day. On 25 February, telemetry data was obtained through the low-gain antenna. On 4 March, telemetry data was obtained through the medium-gain antenna. On 6 March, Hayabusa' s position was established at about 13,000 km ahead of Itokawa in its orbit with
6431-504: The capsule coasted on a ballistic trajectory, re-entering the Earth's atmosphere at 13:51, 13 June 2010 UTC. It is estimated that the capsule experienced peak deceleration of about 25 G and heating rates approximately 30 times those experienced by the Apollo spacecraft . It landed via parachute near Woomera , Australia. In relation to the mission profile, JAXA defined the following success criteria and corresponding scores for major milestones in
6540-501: The center of the sail, equipped with a solar-electric ion engine for maneuvering and propulsion, especially for a possible sample-return trip to Earth. The spacecraft would have used solar sail technology initially developed for the successful IKAROS (Interplanetary Kite-craft Accelerated by Radiation of the Sun) that launched in 2010, whose solar sail was 14 m × 14 m in size. As with the IKAROS,
6649-428: The density of the binary Jupiter trojan 617 Patroclus as being less than that of water ice (0.8 g/cm ), suggesting that the pair, and possibly many other Trojan objects, more closely resemble comets or Kuiper belt objects in composition—water ice with a layer of dust—than they do the main-belt asteroids. Countering this argument, the density of Hektor as determined from its rotational lightcurve (2.480 g/cm )
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#17328550839956758-572: The discoverer of 1998 SF 36 , to offer the name after Hideo Itokawa , and on 6 August, Minor Planet Circular reported that the target asteroid 1998 SF 36 was named Itokawa . In October 2003, ISAS and two other national aerospace agencies in Japan were merged to form JAXA . On 31 March 2004, ion thruster operation was stopped to prepare for the Earth swing-by. Last maneuver operation before swing-by on 12 May. On 19 May, Hayabusa performed Earth swing-by. On 27 May, ion thruster operation
6867-568: The early stages of the Solar System's formation or slightly later, during the migration of giant planets. The term "Trojan Asteroid" specifically refers to the asteroids co-orbital with Jupiter, but the general term " trojan " is sometimes more generally applied to other small Solar System bodies with similar relationships to larger bodies: Mars trojans , Neptune trojans , Uranus trojans and Earth trojans are known to exist. Temporary Venus trojans and Saturn trojans exist, as well as for 1 Ceres and 4 Vesta . The term "Trojan asteroid"
6976-400: The first stage of Trajectory Correction Maneuver (TCM-0) which led to a rough Earth rim trajectory was completed. It was planned to be 60 days until reentry. By 4 May, the probe completed its TCM-1 maneuver to align precisely to the Earth rim trajectory. On 22 May, TCM-2 started, continued for about 92.5 hours, and finished on 26 May. It was followed by TCM-3 from 3 through 5 June to change
7085-524: The four engines. The electric engine system would have been an improved version of the engine from the Hayabusa mission, used for maneuvering, and especially for an optional sample-return trip to Earth. A study indicated the need for 191 kg of xenon propellant if it had been decided to bring a sample back to Earth. The mission concept considered several scenarios, targets, and architectures. The most ambitious scenario contemplated in situ analysis and
7194-411: The heat shield, which were jettisoned during the descent, were also found. After confirming that the explosive devices used for parachute deployment were safe, the capsule was packed inside a double layer of plastic bags filled with pure nitrogen gas to reduce the risk of contamination. The soil at the landing site was also sampled for reference in case of contamination. Then the capsule was put inside
7303-408: The ice giant can pass through one of the libration points and perturb their orbits leaving this libration point depleted relative to the other. After the encounters end some of these Jupiter trojans are lost and others captured when Jupiter and Saturn are near weak mean motion resonances such as the 3:7 resonance via the mechanism of the original Nice model. The long-term future of the Jupiter trojans
7412-484: The ion engine D automatically stopped working due to an anomaly from degradation. On 19 November 2009, JAXA announced that they managed to combine the ion generator of ion engine B and the neutralizer of ion engine A. It was suboptimal but expected to be sufficient to generate the necessary delta-v . Out of 2,200 m/s delta-v necessary to return to the Earth, about 2,000 m/s had been performed already, and about 200 m/s were still necessary. On 5 March 2010, Hayabusa
7521-465: The lander would have included a panoramic camera (visible and infrared), an infrared microscope, a Raman spectrometer , a magnetometer , and a thermal radiometer. The lander would have operated for about 20 hours using battery power. If a sample-return was to be performed, the lander would have taken off then, rendezvous and deliver the surface and subsurface samples to the mothership hovering above (at 50 km) for subsequent delivery to Earth within
7630-434: The milestones are a series of world's first-time experiments built on it. Hayabusa carried a tiny mini- lander (weighing only 591 g (20.8 oz), and approximately 10 cm (3.9 in) tall by 12 cm (4.7 in) in diameter) named " MINERVA " (short for MI cro- N ano E xperimental R obot V ehicle for the A steroid). An error during deployment resulted in the craft's failure. This solar-powered vehicle
7739-400: The mission prior to the launch of the Hayabusa spacecraft. As it shows, the Hayabusa spacecraft is a platform for testing new technology and the primary objective of the Hayabusa project is the world's first implementation of microwave discharge ion engines . Hence 'operation of ion engines for more than 1000 hours' is an achievement that gives a full score of 100 points, and the rest of
7848-560: The most ambitious one proposed to retrieve and send samples to Earth for extensive investigations. Had it been selected in April 2019 for development, the spacecraft would have launched in 2026, and may had offered some synergy with Lucy spacecraft that will flyby multiple Jupiter Trojans in 2027. The spacecraft was projected to have a mass of about 1,285 kg (2,833 lb) including a possible lander and would have been equipped with solar electric ion engines . The 1600 m sail would have had
7957-451: The number of trapped bodies exceeds the observed population of Jupiter trojans by four orders of magnitude , and the present Jupiter trojan asteroids have larger orbital inclinations than are predicted by the capture model. Simulations of this scenario show that such a mode of formation also would inhibit the creation of similar trojans for Saturn , and this has been borne out by observation: to date no trojans have been found near Saturn. In
8066-439: The objects brighter than absolute magnitude 9.0 the population is probably complete. These numbers are similar to that of comparable asteroids in the asteroid belt. The total mass of the Jupiter trojans is estimated at 0.0001 of the mass of Earth or one-fifth of the mass of the asteroid belt. Two more recent studies indicate that the above numbers may overestimate the number of Jupiter trojans by several-fold. This overestimate
8175-404: The on board mass spectrometer for volatile analysis. The lander's scientific payload mass, including the sampling system, would not have exceeded 20 kg. The lander would have been powered by batteries and was planned to perform an autonomous descent, landing, sampling and analysis. Some samples were to be heated up to 1000 °C for pyrolysis for isotopic analysis. The conceptual payload for
8284-406: The optical navigation system was not tracking the asteroid very well, probably caused by the complex shape of Itokawa. A delay of a few days was required to evaluate the situation and reschedule. On 7 November, Hayabusa was 7.5 km from Itokawa. On 9 November, Hayabusa performed a descent to 70 m to test the landing navigation and the laser altimeter. After that, Hayabusa backed off to
8393-453: The particles found in one of two compartments inside the Hayabusa sample return capsule came from Itokawa. Analysis with a scanning electron microscope identified about 1,500 grains of rocky particles, according to the JAXA press release. After further studying the analysis results and comparison of mineral compositions, most of them were judged to be of extraterrestrial origin, and definitely from
8502-441: The planet Jupiter 's orbit around the Sun . Relative to Jupiter, each trojan librates around one of Jupiter's stable Lagrange points : either L 4 , existing 60° ahead of the planet in its orbit, or L 5 , 60° behind. Jupiter trojans are distributed in two elongated, curved regions around these Lagrangian points with an average semi-major axis of about 5.2 AU . The first Jupiter trojan discovered, 588 Achilles ,
8611-457: The planet). By 1938, 11 Jupiter trojans had been detected. This number increased to 14 only in 1961. As instruments improved, the rate of discovery grew rapidly: by January 2000, a total of 257 had been discovered; by May 2003, the number had grown to 1,600. As of October 2018 there are 4,601 known Jupiter trojans at L 4 and 2,439 at L 5 . The custom of naming all asteroids in Jupiter's L 4 and L 5 points after famous heroes of
8720-493: The point of equilibrium in a tadpole or horseshoe orbit . These leading and trailing points are called the L 4 and L 5 Lagrange points . The first asteroids trapped in Lagrange points were observed more than a century after Lagrange's hypothesis. Those associated with Jupiter were the first to be discovered. E. E. Barnard made the first recorded observation of a trojan, (12126) 1999 RM 11 (identified as A904 RD at
8829-469: The primordial Kuiper belt , disrupting it and throwing millions of objects inward. When Jupiter and Saturn were near their 1:2 resonance the orbits of pre-existing Jupiter trojans became unstable during a secondary resonance with Jupiter and Saturn. This occurred when the period of the trojans' libration about their Lagrangian point had a 3:1 ratio to the period at which the position where Jupiter passes Saturn circulated relative to its perihelion. This process
8938-436: The probe, the data from the landing attempt were downloaded and analyzed, and on 23 November, JAXA announced that the probe had indeed landed on the asteroid's surface. Unfortunately, the sampling sequence was not triggered since a sensor detected an obstacle during descent; the probe tried to abort the landing, but since its orientation was not appropriate for ascent, it chose instead a safe descent mode. This mode did not permit
9047-534: The redder Kuiper belt objects. A Jupiter trojan's spectrum can be matched to a mixture of water ice, a large amount of carbon-rich material ( charcoal ), and possibly magnesium -rich silicates . The composition of the Jupiter trojan population appears to be markedly uniform, with little or no differentiation between the two swarms. A team from the Keck Observatory in Hawaii announced in 2006 that it had measured
9156-402: The reentry and landing part of the mission was to demonstrate "that Japan's ballistic missile capability is credible." Before the capsule was extracted from the protecting plastic bag, it was inspected using X-ray CT to determine its condition. Then the sample canister was extracted from the reentry capsule. The surface of the canister was cleaned using pure nitrogen gas and carbon dioxide; it
9265-449: The rotation axis needed to be directed toward the Sun and Earth within a specific angular range. The probability of achieving this was estimated at 60% by December 2006, 70% by spring 2007. On 7 March 2006, JAXA announced that communication with Hayabusa had been recovered in the following stages: On 23 January, the beacon signal from the probe was detected. On 26 January, the probe responded to commands from ground control by changing
9374-426: The rotational light curves of 72 Jupiter trojans gave an average rotational period of about 11.2 hours, whereas the average period of the control sample of asteroids in the asteroid belt was 10.6 hours. The distribution of the rotational periods of Jupiter trojans appeared to be well approximated by a Maxwellian function , whereas the distribution for main-belt asteroids was found to be non-Maxwellian, with
9483-456: The samples by splitting particles and examining their crystal structure at SPring-8 . The 26 August 2011 issue of Science devoted six articles to findings based on dust collected by Hayabusa . Scientists' analysis of the dust from Itokawa suggested that it had probably originally been part of a larger asteroid. Dust collected from the asteroid surface was believed to have been exposed there for about eight million years. Dust from Itokawa
9592-419: The samples had to wait until 2011 because researchers were still developing special handling procedures to avoid contaminating the particles during the next phase of research. In 2013 JAXA announced that 1500 extraterrestrial grains had been recovered, comprising the minerals olivine , pyroxene , plagioclase and iron sulfide . The grains were about 10 micrometers in size. JAXA performed detailed analyses of
9701-428: The scientists investigated the feasibility of a sample return mission to Anteros and concluded that the technology was not yet developed. Between 1987 and 1994, joint ISAS / NASA group studied several missions: an asteroid rendezvous mission later became NEAR , and a comet sample return mission later became Stardust . In 1995, ISAS selected asteroid sample return as an engineering demonstration mission, MUSES-C, and
9810-443: The solar angle of the sail would have been changed by dynamically controlling the reflectivity of liquid crystal displays (LCD) on the outer edge of the sail so that the sunlight pressure would produce torque to change its orientation. The ion engine intended for the mission was called μ10 HIsp. It was planned to have a specific impulse of 10,000 seconds, power of 2.5 kW, and a maximum thrust magnitude of 27 mN for each of
9919-418: The spacecraft for analysis back on Earth. After a few months in proximity to the asteroid, the spacecraft was scheduled to fire its engines to begin its cruise back to Earth. This maneuver was delayed due to problems with attitude control (orientation) and the thrusters of the craft. Once it was on its return trajectory, the re-entry capsule was released from the main spacecraft three hours before reentry, and
10028-563: The time), in 1904, but neither he nor others appreciated its significance at the time. Barnard believed he had seen the recently discovered Saturnian satellite Phoebe , which was only two arc-minutes away in the sky at the time, or possibly an asteroid. The object's identity was not understood until its orbit was calculated in 1999. The first accepted discovery of a trojan occurred in February 1906, when astronomer Max Wolf of Heidelberg-Königstuhl State Observatory discovered an asteroid at
10137-402: The trajectory from the Earth rim to Woomera, South Australia , TCM-4 was performed on 9 June for about 2.5 hours for a precision descent to Woomera Prohibited Area . The reentry capsule was released at 10:51 UTC on 13 June. The reentry capsule and the spacecraft reentered Earth's atmosphere on 13 June 2010 at 13:51 UTC (23:21 local). The heat-shielded capsule made a parachute landing in
10246-408: The two Lagrangian points; each swarm stretches for about 26° along the orbit of Jupiter, amounting to a total distance of about 2.5 AU. The width of the swarms approximately equals two Hill's radii , which in the case of Jupiter amounts to about 0.6 AU. Many of Jupiter trojans have large orbital inclinations relative to Jupiter's orbital plane—up to 40°. Jupiter trojans do not maintain
10355-496: Was a robotic spacecraft developed by the Japan Aerospace Exploration Agency (JAXA) to return a sample of material from a small near-Earth asteroid named 25143 Itokawa to Earth for further analysis. Hayabusa , formerly known as MUSES-C for Mu Space Engineering Spacecraft C , was launched on 9 May 2003 and rendezvoused with Itokawa in mid-September 2005. After arriving at Itokawa, Hayabusa studied
10464-432: Was a hybrid that would have provided both photon propulsion and electric power. JAXA referred to the system as a Solar Power Sail. The sail would have been made of a 10 μm-thick polyimide film measuring 40 × 40 meters (1600 m), covered with 30,000 solar panels 25 μm thick, capable of generating up to 5 kW at the distance of Jupiter , 5.2 Astronomical Units from the Sun . The main spacecraft would have been located at
10573-405: Was also reversible allowing a fraction of the numerous objects scattered inward by Uranus and Neptune to enter this region and be captured as Jupiter's and Saturn's orbits separated. These new trojans had a wide range of inclinations, the result of multiple encounters with the giant planets before being captured. This process can also occur later when Jupiter and Saturn cross weaker resonances. In
10682-448: Was announced that Ion Engine C onboard Hayabusa, in addition to B and D, had been successfully re-ignited. On 29 October, JAXA reported that the first phase of trajectory maneuver operation had finished and the spacecraft was now put in a spin-stabilized state. On 4 February 2009, JAXA reported success in reignition of the ion engines and starting the second phase of the trajectory correction maneuver to return to Earth. On 4 November 2009,
10791-403: Was blown to correct the spin, and it was confirmed successful. On 5 December, attitude control was corrected enough to regain communication through the medium gain antenna. Telemetry was obtained and analyzed. As the result of telemetry analysis, it was found that there was a strong possibility that the sampler projectile had not penetrated when it landed on 25 November. Due to the power outage,
10900-525: Was designed to take advantage of Itokawa's very low gravity by using an internal flywheel assembly to hop across the surface of the asteroid, relaying images from its cameras to Hayabusa whenever the two spacecraft were in sight of one another. MINERVA was deployed on 12 November 2005. The lander release command was sent from Earth, but before the command could arrive, Hayabusa 's altimeter measured its distance from Itokawa to be 44 m (144 ft) and thus started an automatic altitude keeping sequence. As
11009-421: Was found to be "identical to material that makes up meteorites." Itokawa is an S-type asteroid whose composition matches that of an LL chondrite . In Japan, rival film companies announced the production of three different feature length theatrical films based on the story of Hayabusa , one of which, Hayabusa: Harukanaru Kikan (2012), starred Ken Watanabe . The Lego construction toy company released
11118-445: Was initially reported that Hayabusa had stopped at approximately 10 meters from the surface, hovering for 30 minutes for unknown reasons. Ground control sent a command to abort and ascend, and by the time the communication was regained, the probe had moved 100 km away from the asteroid. The probe had entered into a safe mode , slowly spinning to stabilize attitude control . However, after regaining control and communication with
11227-486: Was not designed to "land"; it simply touches the surface with its sample capturing device and then moves away. However, it was the first craft designed from the outset to make physical contact with the surface of an asteroid. Junichiro Kawaguchi of the Institute of Space and Astronautical Science was appointed to be the leader of the mission. Despite its designer's intention for momentary contact, Hayabusa landed and sat on
11336-459: Was on a trajectory that would have passed within the lunar orbit. Ion engine operation was suspended to measure the precise trajectory in preparation to perform Trajectory Correction Maneuver 1 to the Earth-rim trajectory. On 27 March, 06:17 UTC, Hayabusa was on a trajectory which would pass 20,000 km from Earth center, completing the orbit transfer operation from Itokawa to Earth. By 6 April,
11445-423: Was spotted in 1906 by German astronomer Max Wolf . More than 9,800 Jupiter trojans have been found as of May 2021 . By convention, they are each named from Greek mythology after a figure of the Trojan War , hence the name "trojan". The total number of Jupiter trojans larger than 1 km in diameter is believed to be about 1 million , approximately equal to the number of asteroids larger than 1 km in
11554-464: Was started again. On 18 February 2005, Hayabusa passed aphelion at 1.7 AU. On 31 July, the X-axis reaction wheel failed. On 14 August, Hayabusa 's first image of Itokawa was released. The picture was taken by the star tracker and shows a point of light, believed to be the asteroid, moving across the starfield. Other images were taken from 22 to 24 August. On 28 August, Hayabusa was switched over from
11663-465: Was the first-ever preplanned soft contact with the surface of an asteroid (the NEAR Shoemaker landing on 433 Eros was not preplanned) it has enormous influence on further asteroid missions. The Hayabusa mission profile was modified several times, both before and after launch. The asteroid exploration mission by the Institute of Space and Astronautical Science (ISAS) originated in 1986–1987 when
11772-440: Was then placed in the canister opening device. The internal pressure of the canister was determined by a slight deformation of the canister as the pressure of the environment nitrogen gas in the clean chamber was varied. The nitrogen gas pressure was then adjusted to match the internal canister pressure to prevent the escape of any gas from the sample upon the opening of the canister. On 16 November 2010, JAXA confirmed that most of
11881-399: Was working to resolve the problem before the craft's upcoming launch window for return to Earth. On 2 December, an attitude (orientation) correction was attempted, but the thruster did not generate enough force. On 3 December, the probe's Z-axis was found to be 20 to 30 degrees from the Sun direction and increasing. On 4 December, as an emergency measure, xenon propellant from the ion engines
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