Rosetta - the most interesting space mission of 2014

    In 2014, there will be two exciting events in the solar system that are worth the wait. Ironically, they are both associated with comets. Today I’ll talk about one of them.



    This summer and autumn in space will culminate in one of the most interesting research operations, comparable in importance to the landing of the Curiosity rover - the implementation of the Rosetta multi-year program. This spacecraft launched in 2004 and flew for ten years in the inner solar system, making corrections and gravitational maneuvers, only to enter the orbit of comet (67P) Churyumov-Gerasimenko. Rosetta should overtake the comet, how to study from a distance, and drop the Philae lander. He will do his part of the research and together they will tell us about comets as much as possible in a robotic mission.


    Great photo

    Comet Churyumov-Gerasimenko is not some unique cosmic body requiring compulsory study. On the contrary, it is an ordinary short-period comet returning to the Sun every 6.6 years. It does not fly further than the orbit of Jupiter, but its trajectory is predictable, and successfully turned up to the launch window of the spacecraft. Rosetta had previously been planned for another comet, but problems with the booster forced a delay in launch, so the goal changed.

    A curious question - why did you have to fly to a comet for ten whole years if it flies more often? The reason for this is the Rosetta science program. All previous missions, starting with the US-European ICE and the Soviet Vega in the 80s, and ending with Stardust in 2011, took place on the oncoming or flying courses. For thirty years, scientists have been able to photograph near the cometary nucleus; could throw a metal blank onto a comet, and after a few years take a look at the result of the fall; could even bring some cometary dust from the tail to Earth. But to spend near the nucleus of a comet for a sufficiently long time, and to sit on it, a simple meeting is not enough. The speed of comets can reach tens or even hundreds of kilometers per second, the second spacecraft of the device itself is added to this, therefore, you can only bomb or land Bruce Willis “on the forehead” of the comet.
    The long way allowed Rosetta to get to the comet from behind and settle down nearby, following the same speed and course as Churyumova-Gerasimenko (67P).



    Along the way, beautiful views of the Earth were shot:


    Large photo .

    On board the three-ton spacecraft, 12 scientific instruments are placed that will allow us to study the temperature, composition, intensity of the comet's tail evaporation, and the surface of the nucleus. The radar experiment will make it possible to make a radar “ultrasound” of the cometary nucleus in order to determine its internal structure. But the most interesting, from the point of view of spectacular “picture”, results are expected from the optical camera OSIRIS (Optical, Spectroscopic, and Infrared Remote Imaging System). This is a dual photo device equipped with two cameras with 700 mm and 140 mm lenses and 2048x2048 pixels CCDs.



    During the time that Rosetta spent on the road, she did not mess around, but implemented a research program worthy of several independent missions. In general, she demonstrates an example of how useful it is to have a spacecraft with a long-range camera, rushing back and forth around the solar system.

    A year and a half after the start, she looked from afar on the implementation of the NASA Deep Impact mission. The impact of the impactor on the comet Tempel 1 caused a flash that is difficult to see with your eyes:



    but it was detected by more sensitive sensors:



    Two years later, Rosetta flew at a close distance from Mars and took simply gorgeous images of the planet in different spectral ranges. In optical Mars, it looks like this:



    And the ultraviolet channel allowed us to highlight details in the Martian atmosphere:



    A separate photo was made by the onboard camera of the Philae descent vehicle:



    It is curious that, depending on the camera, the color of the observed surface can change significantly. A similar pale beige color of Mars was given by the Mars Global Surveyor satellite camera. (As it turned out , the color was added artificially).

    After Mars, Rosetta “fell asleep” to wake up after a year and a half in 2008, for shooting the six-kilometer asteroid Steins flying over a distance of 800 km. True, a system failure prevented the shooting of an asteroid with a long-range camera, but the wide-angle one allowed us to take pictures in detail up to 80 meters per pixel, and to obtain valuable data about the object.



    Even from Earth it was determined that the asteroid belongs to the class-E. A close-up inspection confirmed this. It turned out Steins consists of silicates, poor in iron, but rich in magnesium, while some minerals suffered a heating of more than 1000 degrees Celsius. Observations of the surface and features of the rotation of the asteroid were able to confirm in practice the YORP effect. This effect occurs (more precisely, it is more noticeable) in small irregularly shaped asteroids. Uneven heating of the surface leads to the fact that the infrared radiation of the heated part creates reactive thrust, which increases the speed of rotation of the asteroid.

    It is curious that, based on the theory of the YORP effect, Steins should have had the shape of a double cone, but a large impact crater at the south pole “flattened” the asteroid and gave it the shape of a “diamond”. The same blow seems to have split the cosmic body in half, but it continues to hold on due to the forces of gravity, although scientists have examined signs of a giant crack cutting through the Steins.



    In the spring of 2010, Rosetta allowed for better identification of the comet-like body P / 2010 A2 found in the asteroid belt. This “comet” made a noise in the camp of astronomers in 2010, when it began to behave in a completely different way.


    Hubble telescope shot.

    Despite the fact that the Rosetta camera can not be compared with the Hubble, observations made from a different angle made it possible to determine that we are not facing a comet, but the result of a space accident when a small fragment about a meter in size crashed into a 150-meter asteroid.

    But the asteroid “star” of 2010 was (21) Lutetia. This is a hundred-kilometer asteroid that Rosetta examined from a distance of 3170 km. This time, the 700 mm camera worked perfectly, so even from this distance it turned out to remove surface details up to 60 m per pixel.



    Lutetia is a very interesting and mysterious object, the study of which has raised many questions. Earlier, astronomers from the Earth defined its spectral class as M - asteroids with a large number of metals, while Rosetta spectral studies indicated more likely a class of C - carbon chondrites. Surface images have led to the conclusion that Lutetia is covered for 3 km with a thick carpet of fragmented regolith that hides bedrock. Analysis of the mass made it possible to determine its density: higher than stone, but lower than metal asteroids, which also led to bewilderment. As a result, scientists decided that we are faced with one of the few planetesimals left from the inception of the Solar System - “planet nuclei".


    Great photo .

    Once Lutetia began the process of differentiation of matter, moving heavy metal rocks to the center and bringing light stone to the surface. However, it was too far from the orbits of formation of the stone planets of the solar system and too close to Jupiter, whose gravitational perturbations did not allow to gain the required mass. Moreover, it is believed that earlier the Lutetia form was approaching the sphere, but repeated collisions in the asteroid belt over 3.5 billion years disfigured its appearance.

    After the inspection, Lutetia Rosetta fell asleep again to wake up only on January 20, 2014. Now the equipment is being checked and no malfunctions have been identified, which seems like a fantastic result for a spacecraft that spent ten years in outer space and flew through the asteroid belt twice.

    What lies ahead? Make notes on the calendar.



    May 2014: another important point for the mission is the latest trajectory corrections for approaching the comet. At the end of May, the distance between the “hunter and the victim” will be about 100 thousand km. I think by that time the first pictures of the comet and its nucleus will begin to arrive. There will be another 450 million kilometers from them to the Earth, therefore it will be possible to observe the comet on your own only with powerful telescopes.

    August 2014: Rosetta enters a comet. Of course, while in a coma. It is believed that particles of dust and ice coma can damage the spacecraft, but this is in the case of oncoming trajectories. For Rosetta, the speed of the comet will be almost zero, so serious damage is not expected. But these days, the most spectacular images of the approaching and rotating cometary nucleus are expected. If the cameras work normally, we can see not only the surface of the nucleus, but also the processes that take place on it, as we approach the Sun. Gas and dust jets, beating from the depths, should look simply gorgeous.

    November 2014: the most stressful days, hours, minutes. There is a close approach to the comet up to 3 km and the Philae descent vehicle is reset. He must sit on the core, drill it, take a picture, enlighten it with radar, take soil samples ... In short, if the mission is successful, then this will be a real triumph of interplanetary science.



    2015: Rosetta will continue to follow with the comet for as long as it can. The longevity of Philae is in question, a lot depends on the landing site, the rotation mode of the core, and the conditions on the surface. When approaching the Sun, he should have enough energy to work, but, as he moves away, the battery efficiency will drop. If she can sit down and stretch for at least a month, this will be a present for the creators and for dozens of scientists from Europe and the USA.

    Unfortunately, it will be almost impossible to observe a comet from Earth without serious equipment. Therefore, we can only wait, follow the news, and wish good luck to the European Space Agency. Fly, Rosetta! Fly!

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