Hayabusa (space probe)

Objectives

Equipped with two driving ionic, Hayabusa must validate the use of this engine on long distances. This type of engine being very effective, it will be probably used for the future missions of exploration of space.

Hayabusa also has a navigation system using at the same time radio and optical measurements to calculate its trajectory and to approach the asteroid, without having to be guided by an human being. The use of this new system thus is also tested by the probe.

The study of the asteroid will also be done remotely (using many embarked scientific apparatuses), but through the sampling.

The probe will turn over towards the Earth using its ionic engine, where it will release in the terrestrial atmosphere a capsule containing of the samples of the surface of the asteroid. This also constitutes an important experiment for space engineering.

The principal technological objective of this mission is thus to test state-of-the-art technologies necessary for the taking away and the return to earth of extraterrestrial samples.

The probe

The Hayabusa probe with the shape of a box of 1,5 meter of width like length and 1,05 meter in height.

Two solar panels out of gallium arsenide, of a total surface of 12 square meters spread each side of the probe. A parabolic aerial of high profit, of 1,5 meter diameter, is fixed on the top, ensuring the communications with the Earth, assisted of two another antennas of low profit fixed on another side. On the side opposed to that where the antenna with high profit is, a horn 40 centimetres in diameter at its end will make it possible to recover the samples of the asteroid.

Its weight during launching was of 530 kg, including 50 kg of fuel and 65 kg gas Xénon for the ionic engine.

Propulsion

Hayabusa is propelled during the ionic phases of movements by two driving. This type of engine functions schematically in the following way: in the ionic engine, the xenon is ionized by Micro-onde S, then the ions are accelerated in an intense electric field. Lastly, the ions are ejected by the conduit providing a maximum push of 20 mn. Although thorough is weak for it, it is the fact that it can be maintained in the duration and thus make it possible the probe to reach important speeds which returns this type of propulsion interesting for the space voyages.

The probe is equipped with another system of propulsion, running on the tetroxide of Azote/Hydrazine, which provides the additional push of 22 NR necessary for the operations.

Sampling

The Itokawa asteroid is so small and its gravity is so weak that the probe really will not land, it rather “will accost”.

We do not know what is made up the asteroid and we are unaware of also if its surface is made of hard stone or fine sand. Any pressure or forces that one would apply to the asteroid, in order to dig surface of it, would propel the probe in space. Another method was thus developed in order to take samples of them: to destroy an end of surface using a small projectile and to collect the fragments of them.

The procedure is the continuation: once the probe will be sufficiently close to surface, it will turn off its engine in order not to contaminate it. The remainder of the descent will be done in free “fall” (gravity being weak, about 1/100 000 of that reigning on Earth). As mentioned above, the probe is equipped with a horn 40 centimetres in diameter at its end. As soon as this horn passes very close to the ground, a projectile of a few grams will be drawn at a speed of 300 m/s. The impact of this projectile with surface will cause the emission of fragments and dust which will be recovered and transferred in a capsule via the horn. The scientists hope to roughly recover 1 gram of dust, coming from 3 different places. The time of contact on the asteroid is estimated at 1 second by taking away.

Let us note that this method of sampling is at the origin of the nickname given to the probe. Indeed, a Faucon ( Hayabusa ) plunges on its prey, the trap in its greenhouses and takes again its take-off without landing.

Scientific instruments

Several scientific instruments equip the probe, some are used for navigation.

Minerva

A rover provided by NASA was initially to be deposited on the asteroid in order to study surface of it. This project was however cancelled following budgetary restrictions. Another microphone-robot called Minerva (Acronym of Micro/Nano Experimental Robot Vehicle for Asteroid ) and developed by the JAXA, was to be released on the asteroid in order to study surface of it.

It is appeared as a Hexadécagone (a Polygone at 16 sides) 120 millimetres in diameter for 100 mm in height and a mass of only 591 Gram S. Its power supply is ensured by several small solar panels.

All the operations carried out on Itokawa must take account of extremely weak gravity reigning around this one. Like being driven on wheels, on the surface of a body, a minimum of gravity requires, another mode of displacement had to be developed. The robot was designed to move while leaping, with a maximum speed of 9 cm/s. Minerva was to calculate each jump with precision to avoid, that is to say of " to float " with the top of the ground of Itokawa, that is to say to put itself into orbit around this one.

Minerva is equipped with 3 cameras CCC, of which two are used together to generate a representation in 3D surface of Itokawa, they are able to see from 10 to 50 cm in front of them. The third camera observes more distant areas.

In addition to the images, statements of temperature were to be carried out with the six thermal sensors.

The Hayabusa probe was to be used as relay for the transmission of the data towards the Earth.

The dropping of this last in November 2005 however failed, that Ci not having been able to reach the surface of the asteroid.

Cost of the mission

The cost of the Hayabusa probe is roughly 12 billion Yen S.

Course of the mission

The Hayabusa probe was launched the May 9th 2003 by a rocket M-V starting from the Space center Kagoshima close to Uchinoura in Japan.

The May 19th 2004, the probe passed close to the Earth to use are gravitational Assistance and to place themselves on a new elliptic orbit carrying out it towards Itokawa. At the time of its passage near our planet, Hayabusa tested its optical navigation system (ONC and LIDAR) which enables him to calculate its relative position compared to a celestial body.

The July 31st 2005, one from its three Gyroscope S, breaks down, but the mission continues without problem, because the probe can function with only two gyroscopes.

Approach and the study

The probe achieved its goal the September 12th 2005. Once on the spot, Hayabusa will not be put into orbit around the asteroid but will traverse a heliocentric orbit near to this one. Initially, Hayabusa will remain with more than 10 kilometers of the asteroid and will carry out many scientific observations (of which measurements of the gravitational Champ, Topographie, etc). This information, interesting in themselves, also will use to locate the adequate sites for the sampling.

The October 2nd, the probe loses a second Volant of inertia, obliging it to use its chemical engines to stabilize its movement. This failure obliges to reduce the number of taking away from 3 to 2, for lack of fuels for the chemical engines. However, the phase of cartography should not be touched by this failure, considering which it is almost finished.

Because of the distance, it is impossible for the persons in charge on Earth to control the approach. Even if the station of control on Earth cannot operate the probe, it can order to him to suspend the descent in the event of danger. And it is what it is produced the November 4th, where the JAXA cancelled the operation of descent, following the detection of an error in the optical navigation system of the probe whereas it was to approximately 1 kilometer. The Japanese agency preferred to cancel the descent and to take it again later, by security measure and to avoid putting in Hayabusa danger. The team in load of Hayabusa relativized the gravity of the failure, which could appear tiny and be due to the complexity of the forms on the ground of Itokawa.

Failure of the sending of Minerva

The November 12th, Hayabusa starts again a general repetition of its descent. This time, all the parameters are correct and the dropping of the Minerva microphone-robot takes place. Unfortunately, this last will never touch the ground of the asteroid, to carry out its jumps there. Although the communications with the machine were established, this last finally derived, without to have been able to take readings. The persons in charge of the probe think that the order of dropping was given when the probe did not move any more towards the asteroid. Although Minerva is lost, the repetition of the descent it is unrolled correctly and the attempts at sampling is always planned for the 19 and November 25th.

Landing not controlled of Hayabusa

The November 19th, the first attempt at sampling takes place. With approximately 40 meters with the top of the asteroid, a reference mark ( Target Marker ) of 10 cm is sent on Itokawa. By reflecting a luminous ray sent by Hayabusa, the reference mark enables him to calculate the distance more precisely separating it from the “ground” and must facilitate the procedure of taking away.

With approximately 17 meters of altitude, the signal is stopped because the antenna with high profit was not aligned any more towards the Earth because of a change of slope of Hayabusa, to avoid an obstacle which a sensor would have detected. Moreover, the swing of the stations Goldstone (in California) and Usuda (with the Japan) of the Deep Space Network of NASA occurred at the same time, result, no data could not be received. That did not prevent the probe from continuing to go down slowly, for finally touching Itokawa with 21:10 YOU, rebounding very slowly twice and to stabilize themselves with 21:30 YOU.

The probe could not carry out its taking away, it would seem that it was posed of “guingois”, on the section of the solar panels. After approximately 30 minutes on the ground of Itokawa, Hayabusa receives an order of interruption of the descent which the control center of the JAXA had sent at the time of the loss of communication. The probe redécolle then, to place itself at approximately 100 kilometers of Itokawa.

Second attempt at taking away

The reference mark being in place, a new attempt at taking away is carried out as envisaged the November 25th. With 20:10 YOU, the probe stop his communications to carry out a modification of his orientation to prepare his contact with the ground. With 20:16 YOU, the communication begin again and to 20:20 YOU it probe indicate that it is going up.

The analysis of telemetry indicates that the probe carried out a taking away well and that two impactors were drawn. The probe with the air in good state, put besides some of its engines, which do not seem to function correctly. The team of Hayabusa carries out tests to define the true problem. Who could originate in a shock at the time of the landing not controlled of November 19th, day of the first attempt at taking away.

At the beginning of December, Jaxa retracts: it would seem finally that no impactor was drawn on the ground from the asteroid. Consequently, it is probable that the horn of taking away did not collect anything.

The return to earth

After having spent several months to study Itokawa, the probe was to start again its engines in first half of December, in order to return towards the Earth, which it would have thus reached during the summer 2007. Unfortunately, the starting window was missed because of the instability of the probe due to a fuel leak which has occurred on December 26th. Jaxa now hopes to bring back Hayabusa in 2010. The capsule containing or not samples of the surface of Itokawa will separate then from the probe at a distance of more than 200.000 kilometers of the Earth and will penetrate in the terrestrial atmosphere, boxing an extreme heat (3 000 °C) and brutal decelerations. A Parachute will slow down the fall of the capsule to arrive in Australia where its invaluable cargo will be studied under all the seams.

External bonds

'' Hayabusa - Muses-C '', of Catherine Ledent, on the Astrocosmos.net site (Of important parts of the article of Wikipédia base themselves on this article)
Animation showing the mode of displacement of Minerva, with format MPEG
'' Images of the Earth and the Moon '', snuff by Hayabusa, on the site of the JAXA
'' Hayabusa (Muses-C) '', on the site of NASA
'' the Japanese space probe Hayabusa sees its target: the asteroid Itokawa '', on the site Techno-Science.net

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