In the near future, all systems of the Rosetta probe will be turned off, and the probe itself will be buried today, September 30, at 13:40 Moscow time on comet 67P / Churyumov - Gerasimenko. Life recalls the main milestones of this grandiose space experiment lasting twelve years.
dream of a comet
More than 12 years ago, on March 2, 2004, an Ariane-5 launch vehicle carrying the Rosetta space probe was launched from the Kourou launch site in French Guiana. Ahead of the probe were ten years of travel through space and a meeting with a comet. It was the first spacecraft launched from Earth, which was supposed to reach a comet, land a descent vehicle on it and tell the earthlings a little more about these celestial bodies arriving in the solar system from deep space. However, the history of "Rosetta" began much earlier.
Russian trace
In 1969, photographs of comet 32P / Comas Sola taken by a Soviet astronomer Svetlana Gerasimenko in the Alma-Ata observatory, another Soviet astronomer Klim Churyumov, at the very edge of the picture, a comet unknown to science was found. After its discovery, it was entered in the register under the name 67P / Churyumova - Gerasimenko.
67P means that this is the sixty-seventh short-period comet discovered by astronomers. Unlike long-period comets with a short period of revolution, they orbit the Sun in less than two hundred years. 67P and generally rotates very close to the star, making a revolution in six years and seven months. This feature made the Churyumov-Gerasimenko comet the main target for the first landing of the spacecraft.
Do not eat, so bite
Initially, the European Space Agency planned the CNSR (Comet Nucleus Sample Return) mission to collect and return comet nucleus samples to earth together with NASA. But NASA could not stand the budget, and left alone, the Europeans considered that they could not pull the return of the samples. It was decided to launch a probe, land a descent module on the comet and get as much information as possible on the spot without returning.
For this purpose, the probe "Rosetta" and the descent module "Fily" were created. Initially, their goal was a completely different comet - 46P / Virtanen (it has an even shorter orbital period: only five and a half years). But, alas, after the failure of the launch vehicle engines in 2003, time was lost, the comet left the trajectory, and in order not to wait for it, the Europeans switched to 67R / Churyumova - Gerasimenko. On March 2, 2004, a historic launch took place, attended by Klim Churyumov and Svetlana Gerasimenko. "Rosetta" began its journey.
space rosette
The Rosetta probe was named after the famous Rosetta Stone, which helped scientists understand the meaning of ancient Egyptian hieroglyphs. It was collected in a clean room (a special room where a minimum of possible dust particles and microorganisms is maintained), since it was possible to find molecules on the comet - the precursors of life. It would be very disappointing to find terrestrial microorganisms with a probe instead.
The weight of the probe was 3,000 kilograms, and the area of Rosetta's solar arrays was 64 square meters. 24 engines were supposed to correct the course of the device at the right time, and 1670 kilograms of fuel (the purest monomethylhydrazine) - to provide maneuvers. Among the payload are scientific instruments, a unit for communication with the Earth and the descent module, the Philae descent module itself, weighing 100 kilograms. The main work on the creation of scientific instruments and assembly was carried out by the Finnish company Patria.
Dear uneasy
The flight pattern of the Rosetta is more like a task in a children's book: "help the spacecraft find its comet", where you have to drag your finger along a confusing trajectory for a long time. Rosetta made four revolutions around the Sun, using the gravity of the Earth and Mars to accelerate in order to develop enough speed to fly to the comet.
catch up with the celestial body. Only in this case, Rosetta would be captured by the gravitational field of the comet and become its artificial satellite. During the flight, the probe made four gravitational maneuvers, an error in any of which would put an end to the entire mission.
Filami on the water
Scientists from ten countries, including Russia, took part in the creation of the Philae lander. The name went to the module as a result of the competition. A 15-year-old Italian woman suggested continuing the theme of archaeological mysteries with the ancient Egyptian island of Philae, where an obelisk that required decipherment was also found.
Despite its light weight, the baby descended on the comet carried almost 27 kilograms of payload: a dozen instruments for studying the comet. These include a gas chromatograph, a mass spectrometer, a radar, six microcameras for surface imaging, density sensors, a magnetometer and a drill.
"Phila" is more like a Swiss penknife with paws. In addition, two harpoons were built into it for fixing on the surface of the comet and three drills on the landing legs. In addition, shock absorbers were supposed to extinguish the shock on the surface, and the rocket engine was supposed to press the module against the comet for a few seconds. However, everything went wrong.
Small step for the lander
On August 6, 2014, Rosetta caught up with the comet and approached it at a distance of one hundred kilometers. Comet Churyumova - Gerasimenko has a complex shape, similar to a poorly made dumbbell. Its largest part measures four by three kilometers, and the smaller one - two by two kilometers. Philae was supposed to land on most of the comet, in Site A, where there were no large boulders.
On November 12, at a distance of 22 kilometers from the comet, the Rosetta sent the Philas to land. The probe flew up to the surface at a speed of one meter per second, tried to gain a foothold with augers, but for some reason the engine did not work and the harpoons did not activate. The probe was torn off the surface, and after making three touches, he sat down at all where it was planned. The main problem with the landing was that Philae ended up in a shadowy part of the comet, where there was no light to recharge.
In general, landing on a comet is the most complicated technical event, and even such a result shows the highest skill of the specialists who carried it out. Information reaches the Earth with a delay of half an hour, so all possible commands are given in advance or reach with a huge lag.
Imagine that you need to drop a load from an airplane flying 22 kilometers from the surface of the earth (well, just imagine this), which should exactly fall into a small area. Moreover, your cargo is a rubber ball, which, at the slightest mistake, strives to bounce off the surface, and the plane responds to commands after an hour.
It wasn't the comet
However, on Earth, the first comet landing in human history caused much less emotion than the shirt of the British scientist Matt Taylor, who led the landing. The Hawaiian shirt with half-naked beauties made people talk about disrespect for women, objectification, sexism, anti-feminism and other "isms". It even got to the point that Matt Taylor was forced to tearfully apologize to those who were frapped by his choice of clothing. At the same time, almost no attention was paid to one of the greatest cosmic achievements.
60 hours
Since the Philae landed in a shaded area, there was no way to charge the batteries. As a result, less than three days of work on internal batteries remained for scientific work. During this time, scientists managed to obtain a lot of data. Organic compounds were found on 67P, four of which (methyl isocyanate, acetone, propionaldehyde, and acetamide) had never before been found on the surface of comets.
Gas samples were taken, which were found to contain water vapor, carbon dioxide, carbon monoxide and several other organic components, among which there is formaldehyde. This is a very important find, as the discovered materials can serve as a building material for the creation of life.
After 60 hours of experiments, the descent vehicle turned off and switched to the energy conservation mode. The comet was heading closer to the Sun, and the scientists had the hope that after some time there would be enough energy to launch it again.
Instead of an epilogue
In June 2015, seven months after the last communication session, Phil announced that he was ready to go. During the month, two short communication sessions took place, during which only telemetry was transmitted. On July 9, 2015, communication with the lander was lost forever. Scientists did not stop trying to reach the module throughout the year, but, alas, to no avail.On July 27, 2016, scientists turned off the communication unit on the Rosetta, recognizing the hopelessness of the attempts. Philae remained on the comet.
67R / Churyumova - Gerasimenko began to move away from the sun, and the Rosetta, which is in its orbit, also no longer has enough energy. She completed all the scientific experiments, and today, having turned off all the sensors, the scientists will land the probe on the eternal parking lot on the surface of the comet as a monument to human thought and ambitions.
Thus ends a twelve-year-long space journey, one of the most daring and successful experiments of mankind.
"Rosetta" (Rosetta) is a spacecraft designed to study a comet. Designed and manufactured by the European Space Agency. It consists of two parts: the Rosetta probe itself ( Rosetta space probe) and the Philae lander ( Philae lander) .
The spacecraft was launched on March 2, 2004 to comet 67P/Churyumov-Gerasimenko. Rosetta is the first spacecraft to orbit a comet. In addition, as part of the program of the year, the world's first landing of a descent vehicle on the surface of a comet took place (November 12, 2014).
Story
In 1986, a significant event occurred in the history of space exploration: Halley's comet approached the Earth at a minimum distance. It was explored by spacecraft from different countries. Scientists have obtained valuable information about the composition and origin of comets.
However, many questions remained unsolved, so NASA and ESA began working together on new space exploration. NASA has been concentrating efforts on the asteroid flyby and comet rendezvous program. The ESA was developing a comet nucleus sample return program. In 1992, however, NASA stopped development due to budgetary constraints. ESA began independent development of spacecraft. By 1993, it became clear that with the existing budget of the ESA, a flight to a comet with the subsequent return of soil samples was impossible, so the apparatus program was subjected to major changes. Finally, it looked like this: the approach of the apparatus first with asteroids, and then with a comet, and then - research on the comet, including a soft landing of the descent vehicle.
The purpose of the flight
P provided for a flight to the comet 67P / Churyumov - Gerasimenko, with a launch on February 26, 2004 and a meeting with the comet in 2014. Rosetta was launched on March 2, 2004 from the Kourou spaceport. Rosetta was supposed to approach the comet and launch the Philae lander towards it.
"Fila" had to approach the comet with a relative speed of about 1 m / s and, upon contact with the surface, release two harpoons, since the comet's weak gravity is not able to hold the device, and it can simply bounce. After landing "Phila" it was planned to start the implementation of the scientific program:
- determination of comet nucleus parameters;
- study of the chemical composition;
- study of the change in the activity of a comet over time.
It is worth noting that the Rosetta flight program is very complex. It included four gravitational maneuvers near Earth and Mars, and even small deviations could affect success.
Construction and design
Rosetta was assembled in a clean room. Sterilization was not as important, since comets are not considered as objects where you can find living microorganisms, but they are hoped to find molecules that are the precursors of life. The main propulsion system consists of 24 two-component engines. The cellular aluminum hull and electrical wiring on board were made by the Finnish company Patria.
Lander scientific equipment
The total mass of the descent vehicle is 100 kg. The 26.7 kg payload consists of ten scientific instruments.
The work of the apparatus near the comet (2014)
Image taken by the CIVA camera of the Philae lander from a distance of 16 km from comet 67P/Churyumov-Gerasimenko
- In July, Rosetta received the first data on the state of the Churyumov-Gerasimenko comet. The device determined that the comet's nucleus, which has an "irregular" shape, releases about 300 milliliters of water into the surrounding space every second.
- On August 7, Rosetta approached the comet's nucleus at a distance of about 100 km.
- A decision was made to land on the surface of the comet's nucleus on November 12.
- On November 12, ESA reported the undocking of the Philae spacecraft from the Rosetta probe, a signal about this was received at 10:03 local time at the European Space Flight Control Center in Darmstadt. The descent to the surface of the comet's nucleus took him about seven hours. During this time, the device took pictures of both the comet itself and the Rosetta probe. The landing of the module was complicated by the failure of the rocket engine pressing the apparatus to the ground, which increased the risk of bouncing off the comet. In addition, the harpoons that were supposed to fix the Philae on the surface of the comet did not work. At 16:03 UTC, the vehicle landed.
- On November 14, the Philae lander completed its main scientific tasks and transmitted all the results from the ROLIS, COSAC, Ptolemy, SD2 and CONSERT scientific instruments to Earth via Rosetta. In addition, the craft was raised 4 cm and rotated 35° in an attempt to increase the illumination of the solar arrays.
- On November 15, Philae went into idle mode (all scientific instruments and most onboard systems off) due to onboard battery exhaustion (contact lost at 00:36 UTC). The illumination of solar panels (and, accordingly, the power generated by them) is too low to charge the batteries and continue working. Therefore, communication sessions with the device in the near future are unlikely. It is possible that as the comet approaches the Sun, the amount of generated energy will increase to values sufficient to turn on the apparatus - such a development of events was taken into account when designing it.
Image copyright EKA Image caption The picture was taken 10 seconds before the impact with the comet.
The Rosetta space probe collided with the Churyumov-Gerasimenko comet, which it followed for 12 years.
In the process of approaching the surface of the comet - a sphere with a diameter of 4 km, consisting of ice and dust - the probe was still transmitting photographs to Earth.
The mission control center of the European Space Agency (ESA), which is located in the German city of Darmstadt, gave the command to change course on Thursday afternoon.
Final confirmation that a controlled impact had finally occurred came from Darmstadt after radio contact with the probe was suddenly cut off.
"Goodbye, Rosetta! You've done your part. Here it is, space science at its best," said mission leader Patrick Martin.
The Rosetta project lasted 30 years. Some of the scientists who followed the Rosetta-comet impact in Darmstadt devoted much of their careers to the mission.
The approach speed of the probe to the comet was extremely low, only 0.5 meters per second, the distance was about 19 kilometers.
According to ESA representatives, Rosetta was not designed to land on the surface and could not continue to function after the collision.
That's why the probe was pre-programmed to shut down completely automatically upon contact with a celestial body.
Comet 67 R (Churyumova-Gerasimenko)
- Comet rotation cycle: 12.4 hours.
- Mass: 10 billion tons.
- Density: 400 kg per cubic meter (about the same as some types of wood).
- Volume: 25 cu. km.
- Colour: Coal - judging by her albedo (reflectivity of the body surface).
Rosetta followed the comet for 6 billion kilometers. The probe was in its orbit for more than two years.
It became the first spacecraft to orbit a comet.
Within 25 months, the probe sent over 100 thousand images and readings of measuring instruments to Earth.
The probe collected previously inaccessible data about the celestial body, in particular, about its behavior, structure and chemical composition.
In November 2014, Rosetta launched a small robot called Philae to the comet's surface to collect soil samples, the first of its kind in the world.
Comets, as scientists suggest, have been preserved since the formation of the solar system in almost their original form, so the data transmitted by the probe to Earth will help to better understand the cosmic processes that took place 4.5 billion years ago.
"The data transmitted by Rosetta will be used for decades," said flight director Andrea Accomazzo.
Last Stand
The probe was at a distance of 573 million km from the Sun and moved farther and farther from it, approaching the boundaries of the solar system.
The spacecraft ran on solar panels that could no longer be recharged efficiently.
In addition, the data transfer speed has become extremely low: only 40 kb per second, which is comparable to the speed of accessing the Internet through a telephone line.
In general, Rosetta, launched into space in 2004, has recently been in not the best technical condition, as it has been exposed to radiation and extreme temperatures for many years.
According to project coordinator Matt Taylor, the team discussed the idea of putting the probe on standby and reactivating it when the Churyumov-Gerasimenko comet next enters the inner solar system.
However, scientists did not have any confidence that Rosetta would then work in the same mode.
Therefore, the researchers decided to give "Rosette" a chance to prove themselves in the "last battle" and "pass away with brilliance", no matter how bitter it may sound.
Over the past decades, autonomous spacecraft have made many landings on the planets of the solar system and some of their satellites. And soon the leg… that is, the landing leg of a man-made spacecraft will for the first time leave its mark on the icy path of the nucleus of comet 67P/Churyumov-Gerasimenko.
Rosetta, ESA, 2004: Rosetta is the first mission to include not only remote study, but also a landing in 2014 on the Churyumov-Gerasimenko comet under study.
Dmitry Mamontov
There was no famous "Let's go!" or "One small step for a man ..." - on the screen, the countdown numbers simply passed zero, and the countdown changed sign from minus to plus. No other visible effects, but the engineers at the European Space Agency's (ESA) mission control visibly tensed up. At that moment, the Rosetta spacecraft, located more than 400 million kilometers from us, began the deceleration maneuver, but it took 22 minutes for the radio signal to reach the Earth. And seven minutes later, Sylvan Lodue, the operator of the spacecraft, looking at the telemetry data display, stood up and solemnly said: “Ladies and gentlemen, I can officially confirm: we have arrived at the comet!”
International Cometary Explorer (ICE) NASA/ESA, 1978. The American-European ICE flew through the tail of comet Giacobini-Zinner in 1985, and later, in 1986, flew through the tail of Halley's comet at a distance of 28 million km from the nucleus.
Vega-1, Vega-2 of the USSR, 1984. After a visit to Venus, Soviet spacecraft headed for Halley's comet to fly in March 1986 at a distance of 9,000 km from the nucleus (Vega-1) and 8,000 km (Vega-2 ).
Sakigake, Suisei ISAS, 1985. Japanese probes were sent to Halley's comet. In 1986, Suisei passed 150 thousand km from the nucleus, studying the interaction of the comet with the solar wind, Sakigake flew at a distance of 7 million km from the nucleus.
Giotto ESA, 1985. In 1986, a European apparatus photographed the nucleus of Comet Halley from a distance of only 600 km, and later, in 1992, passed at a distance of 200 km from Comet Grigg-Skjellerup.
Deep Space 1 NASA, 1998. In 1999, this apparatus approached the asteroid 9969 Braille at a distance of 26 km. In September 2001, he flew at a distance of 2200 km from the Borrelli comet.
Stardust NASA, 1999. The first mission, the purpose of which was not only a 150 km approach to the nucleus of comet Wild-2 in 2004, but also the delivery of a sample of cometary material to Earth (in 2006). Later, in 2011, it approached comet Tempel-1.
Contour (Comet Nucleus Tour) NASA, 2002. It was planned that Contour would fly near the nuclei of two comets - Encke and Schwassmann-Wachmann-3, after which it would be directed to the third (Comet d'Arrest was considered as the most likely target). But during the transition to the trajectory leading to the first target, communication with the device was lost.
Deep Impact NASA, 2005. In 2005, the Deep Impact spacecraft approached the nucleus of comet Tempel 1 and fired a special striker at it. The composition of the substance knocked out by the impact was analyzed using onboard scientific instruments. Later, the device was sent to the comet Hartley-2, from the nucleus of which it passed at a distance of 700 km in 2010.
From antiquity to the present day
Comets are among the celestial objects that can be seen with the naked eye, and therefore they have always been of particular interest. These celestial bodies are described in many historical sources, often in very colorful language. “She shone with daylight and dragged a tail like the sting of a scorpion,” the ancient Babylonians wrote about the comet of 1140 BC. At different times, they were considered either signs or messengers of misfortune. Now scientists, based on the scientific data accumulated during the study of comets, believe that comets played a key role in the emergence of life on Earth, delivering water and, possibly, the simplest organic molecules to our planet.
The first data on the composition of cometary matter were obtained using spectroscopic instruments back in the 19th century, and with the beginning of the space age, mankind had the opportunity to directly see and “feel” (if not with their own eyes and hands, then with scientific instruments) comet tails and samples of cometary matter . Since the late 1970s, several spacecraft have been launched to study comets in various ways, from taking photographs from small (by space standards) distances to collecting samples and delivering samples of cometary material to Earth. But in 1993, the European Space Agency decided to take aim at a much more ambitious goal - instead of delivering samples to an earthly laboratory, engineers proposed taking the laboratory to a comet. In other words, as part of the Rosetta space mission, the Philae lander was supposed to land on the surface of a miniature ice world - the nucleus of a comet.
10 years of flight
The development of the mission lasted ten years, and by 2003 the Rosetta spacecraft was ready for launch. Launching it into space using the Ariane??5 launch vehicle was planned for January 2003, but in December 2002 the same rocket exploded during launch. The event had to be postponed until the causes of the malfunctions were clarified, and the three-ton spacecraft was launched into parking orbit only in March 2004. From here he began his journey to the goal - comet 67P / Churyumov-Gerasimenko, but in a very roundabout way. “There are no rockets powerful enough to directly launch a craft into a comet’s trajectory,” explains Andrea Accomazzo, flight director for the Rosetta mission. - Therefore, the device had to perform four gravitational maneuvers in the gravitational field of the Earth (2005, 2007, 2009) and Mars (2007). Such maneuvers make it possible to transfer part of the planet's energy to the spacecraft, accelerating it. Twice the device crossed the asteroid belt, and so that this part of the flight would not be wasted, it was decided at the same time to explore some objects of the belt - the asteroids Lutetia and Stines.
To study the nucleus of a comet: ALICE UV-range video spectrometer for the search for noble gases in the composition of the comet's substance. OSIRIS (Optical, Spectroscopic, and Infrared Remote Imaging System) Visible and IR camera with two lenses (700 and 140 mm), with a 2048x2048 pixel matrix. VIRTIS (Visible and Infrared Thermal Imaging Spectrometer) Low-resolution multispectral camera and high-resolution spectrometer for thermal imaging of the nucleus and study of the IR spectrum of coma molecules. MIRO (Microwave Instrument for the Rosetta Orbiter) 3 cm radio telescope for detecting microwave radiation characteristic of water, ammonia and carbon dioxide molecules. CONSERT (Comet Nucleus Sounding Experiment by Radiowave Transmission) Radar for "transmission" and obtaining a tomogram of the nucleus of a comet. The emitter is installed on the Philae lander, and the receiver is on the orbiting satellite. RSI (Radio Science Investigation) Using the communication system of the apparatus to study the nucleus and coma. To study gas and dust clouds: ROSINA (Rosetta Orbiter Spectrometer for Ion and Neutral Analysis) Magnetic mass spectrometer and time-of-flight mass spectrometer for studying the molecular and ionic composition of gases. MIDAS (Micro-Imaging Dust Analysis System) High-resolution atomic force microscope for studying dust particles. COSIMA (Cometary Secondary Ion Mass Analyzer) Mass analyzer of secondary ions for studying the composition of dust particles. GIADA (Grain Impact Analyzer and Dust Accumulator) Impact analyzer and dust particle accumulator for measuring their optical properties, velocity and mass. RPC (Rosetta Plasma Consortium) Instrument for studying the interaction with the solar wind.
Rosetta became the first spacecraft to travel to the outer solar system with solar panels rather than a radioisotope thermoelectric generator on board as a power source. At a distance of 800 million km from the Sun (this is the farthest point of the mission), the illumination does not exceed 4% of the earth, so the batteries have a large area (64 m 2). In addition, these are not ordinary batteries, but specially designed for operation in low-intensity and low temperature conditions (Low-intensity Low Temperature Cells). But even so, in order to save energy in May 2011, when Rosetta reached the finish line to the comet, the device was put into hibernation for 957 days: all systems were turned off except for the command receiving system, the control computer and the power supply system.
First satellite
In January 2014, Rosetta was "awakened", preparations began for a series of rendezvous maneuvers - braking and speed equalization, as well as the planned inclusion of scientific instruments. Meanwhile, the final goal of the journey became visible only a few months later: in the image taken by the OSIRIS camera on June 16, the comet occupied only 1 pixel. A month later, it barely fit in 20 pixels.
APXS (Alpha X-ray Spectrometer) Alpha and X-ray spectrometer for studying the chemical composition of the soil under the apparatus (submerged to 4 cm). COSAC (COmetary SAmpling and Composition) Gas chromatograph and time-of-flight spectrometer for the detection and analysis of complex organic molecules. PTOLEMY Gas analyzer for measuring isotopic composition. CIVA (Comet Nucleus Infrared and Visible Analyzer) Six microcameras for panning the surface, a spectrometer for studying the composition, texture and albedo of samples. ROLIS (Rosetta Lander Imaging System) High resolution camera for descending and stereo surveying of sampling sites. CONSERT (COMet Nucleus Sounding Experiment by Radiowave Transmission) Radar for "transmission" and obtaining a tomogram of the comet's nucleus. The emitter is installed on the Philae lander, and the receiver is on the orbiting satellite. MUPUS (MUlti-PUrpose Sensors for Surface and Sub-Surface Science) A set of sensors on the supports, the sampler and the outer surfaces of the apparatus for measuring the density, mechanical and thermal properties of the soil. ROMAP (Rosetta Lander Magnetometer and Plasma Monitor) Magnetometer and plasma monitor for studying the magnetic field and the interaction of a comet with the solar wind. SESAME (Surface Electric Sounding and Acoustic Monitoring Experiment) A set of three instruments for studying soil properties: Cometary Acoustic Sounding Surface Experiment (CASSE) - using sound waves, Permittivity Probe (PP) - using electric current, Dust Impact Monitor (DIM) measures the incidence of dust on a surface. SD2 (Drill, Sample, and Distribution subsystem) A sample drill capable of taking samples from a depth of up to 20 cm and delivering them to ovens for heating and to various instruments for further analysis.
On August 6, the device made a braking maneuver, equalized the speed with the comet and became its "honorary escort". “Rosetta traces curvilinear triangles from about 100 km from the comet on the solar side to capture all the details of its illuminated surface,” explains Frank Budnik, mission flight dynamics specialist. - On each side of this triangle, the device drifts for three or four days, then the direction of flight is changed with the help of engines. The trajectory is slightly curved by the comet's gravity, and thanks to this we can calculate its mass in order to put the device into a stable low orbit later. At the same time, Rosetta will be the first ever artificial satellite of a comet.”
Key in pocket
Mission Rosetta is named after the Rosetta Stone, a stone tablet found in 1799 by a French officer in Egypt. The tablet is engraved with the same text - in the well-known ancient Greek language, ancient Egyptian hieroglyphs and Egyptian demotic writing. The Rosetta Stone served as a key, thanks to which linguists were able to decipher the ancient Egyptian hieroglyphs. The Rosetta Stone has been in the British Museum since 1802. The Philae lander got its name from the Egyptian island of Philae, where a surviving obelisk with inscriptions in ancient Greek and ancient Egyptian was found in 1815, which (along with the Rosetta Stone) helped linguists decipher it. Just as the Rosetta Stone gave the key to understanding the languages of ancient civilizations, which made it possible to reconstruct the events of many thousands of years ago, scientists hope that its cosmic namesake will provide the key to understanding comets, the ancient “building blocks” of the solar system that was born 4.6 billion years ago.
reconnaissance from orbit
But entering the orbit of a comet is only the first stage, anticipating the most important part of the mission. According to the plan, until November, Rosetta will study the comet from its orbit, as well as map its surface in preparation for landing. “Before arriving at the comet, we knew quite a bit about it, even its shape - “double potato” - became known only with close acquaintance,” Stefan Ulamek, head of the Philae landing team, tells Popular Mechanics. “When choosing a landing site, we are guided by a set of requirements. First, it is necessary that the surface, in principle, be reachable from the orbit in which the apparatus will be located. Secondly, a relatively flat area within a radius of several hundred meters is needed: due to flows in a gas cloud, the device can be blown to the side during a rather long (up to several hours) descent. Thirdly, it is desirable that the illumination changes at the landing site and the day changes into night. This is important because we want to study how the comet's surface behaves under this change. However, we are also considering options for purely “daytime” places. We are lucky that the nucleus of the comet rotates stably around one axis, which makes the task much easier.”
Very soft landing
After the landing site is chosen, the main event will take place in November - the 100-kg Philae module will separate from the apparatus and, releasing three legs, will make the first ever landing on the comet nucleus. “When we started this project, we were completely unaware of many of the details of the process,” says Stefan Ulamek. “No one has landed on a comet before, and we still don’t know what its surface is: whether it is hard like ice, or loose like freshly fallen snow, or something in between. Therefore, the lander is designed to attach itself to almost any surface. After separation from the Rosetta spacecraft and extinction of orbital velocity, the Philae module will begin its descent towards the comet under the influence of its small gravity, after which it will land at a speed of about 1 m/s.
An image of comet 67P/Churyumov-Gerasimenko taken on August 16 by the OSIRIS camera with a long-focus lens from a distance of 100 km. The size of the comet's nucleus is 4 km, so the resolution of the image is about 2 m per pixel. Using a series of images of the comet, scientists have already mapped out five possible landing sites. The final choice will be made later.
At this point, it is very important to prevent the device from "bouncing" and fix it on the surface of the comet, and several different systems are provided for this. The push when touching the landing legs will be extinguished by the central electrodynamic shock absorber, at the same moment the nozzle on the upper end of the Philae will work, the jet thrust from the release of compressed gas will press the device to the surface for several seconds while it will throw out two harpoons - the size of a pencil - on cables. The length of the cables (about 2 m) should be enough to securely hold the harpoons, even if the surface is covered with a layer of loose snow or dust. Ice screws are located on three landing legs, which will also be screwed into the ice during landing. All of these systems have been tested on the German Space Agency's (DLR) Landing Simulator in Bremen, on both hard and loose surfaces, and we hope they will not fail in real-life conditions."
But that will be a little later, but for now, as Mark McCorian, Senior Research Fellow at the ESA Directorate of Automated Research, says, “we are like children who have been driving for ten years, and now finally arrived at scientific Disneyland, where in November we the most exciting attraction awaits.”
Editor's note: up-to-date landing information is available at the link.
