To asteroid Itokawa and back

Asteroid Itokawa is the smallest asteroid that a spacecraft has reached and studied. It is 600 meters long and belongs to the group of asteroids that pass by the Earth during their orbit around the Sun

Asteroid Itokawa is the smallest asteroid that a spacecraft has reached and studied. It is 600 meters long and belongs to the group of asteroids that pass by the Earth during their orbit around the Sun. This is the group of asteroids called the Neo group (Near Earth Objects). The spaceship he was directed to was a Japanese spaceship named Hayabusa. It was launched on May 9.5.2003, 2005 and arrived in September XNUMX.

The spacecraft was designed to orbit the asteroid for 3 months from September 2005 to November 2005 and during that time it would photograph and measure it. A total of 1600 were broadcast to Israel from its surface. The spacecraft was supposed to descend to a height of 100 meters from the surface and launch a number of small pellets. These will hit the ground and some of the dust that will be sprayed upwards will be absorbed in a special compartment in the spacecraft and returned to earth. The landing was supposed to take place in June 2007 in Australia. From the telemetry analysis done several years later, it became clear that this mission was a failure.

When the spacecraft reached a height of 100 meters from the ground, it was also supposed to launch a tiny vehicle called Minerva to the ground of the asteroid. This is a lander with a cylindrical structure weighing 600 grams. The car has no wheels. The intention was that he would use the momentum of a dumbbell inside him to move from one place to another. This is a completely new technique. The vehicle has 3 cameras located at a height of 5 cm from the base. One camera is located on one side of the vehicle and it can take pictures even when the vehicle makes its jumps. On the other side of the vehicle are installed two cameras that can observe a distance of 10-50 cm. The overlapping field of vision between them can give a sense of depth. The resolution in the mother cameras during the global mapping is 30 meters per pixel and during the descent to a height of 100 meters the resolution is 1.2 cm per pixel. The resolution of Minerva is 1 mm per pixel up to a distance of 10 cm. Minerva is able to examine the size of regolith grains (rock grains) covering the asteroid. At the upper end of the vehicle and at the lower end there are 6 thermometers that measure the temperature of the ground and it is possible to learn from this whether the surface of the ground is made of sand or is rocky. The vehicle was indeed released and broadcast that it had indeed left, but it was lost.

The spacecraft tried to approach the asteroid twice in order to release the balls, but the said attempt was unsuccessful. In retrospect it turned out that the second time the spacecraft actually landed on the asteroid and stayed on its surface for half an hour.

The findings of the measurements made by the spacecraft itself showed that the asteroid is a fragment of a larger body. It orbits the sun once in 556.36 days and its inclination angle is 1.62 °. The distance of its orbit from the sun is between 1.324 astronomical units and 1.695 astronomical units. Its density is 0.3 ± 2.5 g/cm12.5 and it rotates around itself once every XNUMX hours.

It is possible to see on its surface fragments of rocks of different sizes from grains up to those that are 50 meters long. Some of the surface is smooth and other parts are rough. In the rough parts you can see rocks stuck in it at right angles. At one end you can see a block of rock in a kind of rectangular configuration stuck in the ground. This phenomenon can indicate that in the place of the impact on the ground the impact is covered with a sticky substance. Maybe organic matter.

When the first photographs from the asteroid arrived the researchers were surprised. It turned out that the asteroid does not have a homogeneous structure. Its edges appear rounded, probably as a result of the impact of various bodies in space that acted like an erosive mechanism and rounded sections of it. It seems that various bodies that hit him left dust on him. This too was a surprise. It was not expected that a body with such a tiny gravity would be able to hold regolith.

Examination of extremely high-resolution, 6 mm per pixel, images showed that the asteroid is covered in millimeter-sized unconsolidated gravel grains found in its smooth areas, disproving the assumption that the entire asteroid is covered in grains. It is estimated that those parts separated from each other in a process of liquefaction (fluiazation) caused by vibrations induced by the impact of small meteorites. When grains oscillate they "liquefy" and behave like a granular fluid.

Although the spacecraft had considerable scientific achievements despite its failures in landing a tiny all-terrain vehicle and collecting samples, the return to Israel was fraught with quite a few problems and it was not at all certain that it would survive. It was feared that the spacecraft would not survive at all. The first malfunction occurred on 31.7.2005/3.10.2005/3 when one of the stabilization mechanisms stopped functioning and the other stopped functioning on 1.12.2005/8/XNUMX. The spacecraft was left with one stabilization mechanism and great care had to be taken while operating near the asteroid. It was necessary to postpone the return to Israel for XNUMX years. The spacecraft is stabilized using an emergency booster. Questions arose regarding the continued use of the spacecraft's battery. On December XNUMX, XNUMX, the flight controllers decided to use a low-gain antenna that works at a low rate of XNUMX bits per second, even though the communication line was weak and there were sometimes disconnections in communication. In addition, the attribution and supervision systems did not function properly. It was not clear what caused this. It was estimated that the excessive use of the power systems for the various units in the spacecraft were in reset mode, when their temperatures dropped due to the evaporation of leaked fuel and due to the failure to charge electricity from the batteries to the various systems of the spacecraft following a power drop.

From 8.12.2005 there was no contact with the spacecraft for 6 weeks due to a disturbance that caused its antenna not to be aimed at the Earth. The relationship was renewed on 23.1.2006 and it reached its full scope on 26.2.2006. It turned out that the spacecraft had suffered a loss of power and that the oxygen tank was empty. In addition, the maneuvering engines were weakened.

In an unusual step, it was decided to combine the partial functions of the A and B ion engines so that the spacecraft would have enough power to return to Earth. It was decided to combine the neutralizing factor of the ion engine A and the power source of engine B. The attempt was indeed successful and resulted in the successful landing on 13.6.2010/1500/XNUMX. The cell that was supposed to collect samples from the asteroid ground landed safely. The particles that were still found in the cell, about XNUMX, somehow got inside while the spacecraft was resting on the asteroid's ground.

Sources

Mazar H.-"Dust clouds and particles in the asteroid belt" All Stars of Light issue no. 3 volume 20 April-May June 1993 p. 66-67

Clark S.-"New hope for plucky Japanese asteroid mission" 19.11.2009
http://www.spaceflightnow.com/news/n0911/hayabusa

Clark S.- "Team trying to regain control of troubled asteroid probe" 11.3.2006
http://www.spaceflightnow.com/news/n0603/11hayabusa

Sherrif L. – “New flight control problem for Japan's asteroid probe” 7.10.2005
http://www.theregister.co.uk/2005/10/07/asteroid_altitude/print.html

image
http://spacenews.dancebeat.info/images/hayabusa_oct4-1.jpg

Itokawa (minor planet 25143)
http://www.daviddarling.unfo/encyclopedia/I/Itotawa.html

"JAXA unable to restore full-scale operations on a deteriorating Hayabusa" 12.12.2005
http://www.spacedaily.com/news/asteroid-05zj.html

"Latest Itokawa image reveals a strange asteroid with few craters" 12.9.2005
http://www.spacedaily.com/news/asteroid-05m.html

"Minerva explores the surface of ITOKAWA"
http://www.hayabusa.isas.jaxa.jp/index.html

"Scientists find migration regolith on tiny asteroid Itokawa" 22.4.2007
http://www.spacedaily.com/reports/ Scientists_ Find_ Migration_ Regolith _On _Ttiny_ Asteroid _Itokawa_999.html