The European Space Agency crowns the rendezvous maneuvers a success; Another first will be achieved in November when a lander launched from Rosetta lands on the comet nucleus
After a decade-long journey in pursuit of its destination, today the European Space Agency's Rosetta spacecraft became the first spacecraft to orbit a comet, thereby opening a new chapter in the study of the solar system.
The Rosetta spacecraft and the comet P67 Churyumov-Gardimenko are 405 million km from Earth, about halfway between the orbits of Mars and Jupiter, as they speed toward the inner solar system at a speed of about 55 km/h.
The comet is on a six-and-a-half-year orbital path that brings it behind Jupiter to the point between the orbits of Mars and Earth at its closest approach to the Sun. Rosetta will accompany him for about a year as they circle the Sun and return to Jupiter again.
Comets are considered the building blocks of the solar system and it is possible that they were used to 'sow' the earth with water and possibly also with the ingredients necessary for life. However, many fundamental questions about comets are still open and the scientists hope that through close, comprehensive research, Rosetta will be able to solve these mysteries either from orbit or with the help of the Philae lander, which is still inside Rosetta and will land on the comet in November.
The journey to the comet was not on a direct route. Since its launch in 2004, the spacecraft had to use the Earth's gravity three times and once that of Mars to help it enter a rendezvous orbit with the comet. This complex orbit also allowed Rosetta to pass by asteroids Steins and Lutetia and capture unprecedented sights and important scientific data on these two objects.
"After ten years, five months and four days of traveling towards its destination, when it circled the sun five times and covered 6.4 billion kilometers we are happy to announce that we are finally there" said the director general of the European Space Agency Jean-Jacques Dordin.
"The European Rosetta made history by being the first spacecraft to meet a comet, an important milestone in our search for our origins. The discoveries can begin."
Today was the last of a series of ten ignitions and maneuvers that began in May of this year to gradually adjust Rosetta's speed and direction to match those of the comet. If one of these maneuvers failed, the mission would be lost, and the spacecraft would simply pass by the comet.
Comet P67 Churyumov-Gardimenko has begun to reveal its personality as Rosetta approaches it. Images taken by the Osiris camera between April and early June showed that its activity shows variations. The comet's halo—a spreading envelope of gas and dust—became bright and then dimmed again during these six weeks. At the same time, the first measurements from the microwave instrument on the Rosetta spacecraft, MIRO, hypothesize that the comet emits water vapor into space at a rate of 300 milliliters per second. The VIRIS visible light and infrared spectrometer measured the average temperature on the comet's surface and found that it is around minus 70 degrees Celsius, which indicates a cold and dusty surface rather than clean and full of ice.
After that, amazing photos taken from a distance of about 12 km begin to reveal that the core consists of two large parts connected by a kind of neck, which gives it the appearance of a rubber duck. Successive images showed more and more details, the last one, the highest resolution image downloaded from the spacecraft's computer today (see image at the beginning of the article).
"The first clear sight of the comet gives us a lot to think about," says Matt Taylor, a scientist at the European Space Agency's Rosetta project.
"Is this double structure due to the fact that the nucleus is made up of two comets that united in the history of the solar system, or is it one comet that has dramatically eroded and become asymmetric over time? According to the attribute, Rosetta is in the best place to study the unique bone."
The spacecraft is now 100 km from the surface of the comet's core, but it will get closer over the next six weeks. It will twice make a triangular orbit in front of the comet, first to a distance of 100 kilometers and then it will descend to a distance of 50 kilometers. At this point more and more instruments will be able to provide detailed scientific data on the comet, scanning the surface for the best landing site for Philae.
Eventually Rosette will approach the almost circular orbit at an altitude of 30 kilometers, and depending on the activity of the comet, maybe even closer. "We are faced with a challenge to learn about the unfamiliar environment of the comet, to begin orbiting and eventually to land," says Sylvain Ludois, Rosetta's director of operations.
At the end of August, the five best landing sites will be selected, and in mid-September, the preferred site will be selected from among them. The final schedule for the series of events - currently it is the release of Philly on November 11 - will be confirmed in mid-October.
"During the coming months, in addition to characterizing the comet's nucleus and determining the rules for the continuation of the mission, we will be making final preparations for a new historical landmark in the space program - landing on a comet," Matt said.
"After landing, Rosetta will continue to accompany the comet to its closest point to the Sun in August 2015 and beyond, observing its behavior from a short distance to provide us with a unique insight and real-time experience of how the comet changes as it moves around the Sun."
For information on the European Space Agency website
More on the subject on the science website
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20 תגובות
A lion cub
You hit a good point, but your conclusions that it is a bluff are due to a lack of knowledge about the Rosetta spacecraft's trajectory planning.
If Rosetta were moving at the usual speeds of spacecraft in the solar system, its speed would be too great to be trapped in the gravitational field of Comet Chermoyev. Indeed, if Rosetta had sent directly to Chermoev, it would not have been caught in the comet's gravitational field. In order for the spacecraft to be trapped in the comet's gravitational field, its motion had to be drastically slowed down. There were two alternative options for deceleration: (1) add a large amount of fuel to it to perform braking, (2) slow down its movement while making sophisticated use of the gravity of large celestial bodies.
The second option is called "gravitational slingshot" or similar names.
The main drawback of gravitational bounce maneuvers is that they usually require a very long time. This is why Rosetta's travel time lasted about 10 years instead of half a year (half a year if the spacecraft had been braked without gravitational bouncers).
A lion cub
You hit a good point, but your conclusions that it is a bluff are due to a lack of knowledge about the Rosetta spacecraft's trajectory planning.
If Rosetta were moving at the usual speeds of spacecraft in the solar system, its speed would be too great to be trapped in the gravitational field of Comet Chermoyev. Indeed, if Rosetta had sent directly to Chermoev, it would not have been caught in the comet's gravitational field. In order for the spacecraft to be trapped in the comet's gravitational field, its motion had to be drastically slowed down. There were two alternative options for deceleration: (1) add a large amount of fuel to it to perform braking, (2) slow down its movement while making sophisticated use of the gravity of large celestial bodies.
The second option is called "gravitational slingshot" or similar names.
The main drawback of gravitational bounce maneuvers is that they usually require a very long time. This is why Rosetta's travel time lasted about 10 years instead of half a year (half a year if the spacecraft had been braked without gravitational bouncers).
A supplement to Mickey's detailed explanation and a well-founded answer to the lion cub.
Escape speed is one thing and orbital speed is another thing that depends on the radius of the circle. When the mass of the spacecraft is negligible compared to the mass of the comet (which is the case here), the speed in a circular orbit will be (Vo=SQRT(G*M/R) where G-the global gravitational constant, M-the mass of the comet and R the distance of the satellite from its center. In our case, the speed of Rosetta At a distance of 30 km from the center of the comet it will be only 8.36 cm/second and it will complete a complete orbit around the comet in 26.1 days. Although this is a very low speed, it can be checked and corrections made when necessary. It should be noted, however, that this is the speed of the satellite around the comet when the comet with His satellite moves at enormous speed in orbit around the sun.
Hope everything is clear now.
live a lion,
You are right that it is apparently difficult to circle this comet, but it is still possible under certain conditions and constraints.
I will try to explain briefly taking into account the data I have now collected on the Internet to give an answer
A little more accurate and also a little more satisfying (at least from what I read here in the comments):
1. Because this comet has an escape velocity of 0.46 m/s. That is, if the vertical speed of a certain body,
Said gradient to the gravitational field, on the surface of the comet's surface is greater than this speed, so the body can actually escape
Due to the comet's gravity. Just to give proportion, the escape velocity from Earth is 11,186 m/s,
From the surface of the moon it is 2,400 m per second and from Pluto it is 1,200 m per second.
2. Since the force of gravity is a relative force between the masses of the bodies and inversely proportional to the distance between them, the force of gravity that "feels"
Relative to other bodies in space, such as the Sun and the other planets in the Sun's orbit, the spacecraft is negligible. So, right now
The relationship of forces (literally) in this issue, is solely between the spacecraft and the comet for the sake of the matter. Of course, in simulations
Realities where very high precision is required, consider everything as much as possible.
3. If the speed of the spacecraft in the direction of the gradient vector of the comet's gravity field is equal to the speed
The escape is 0.46 m/s, so the spacecraft will actually become a satellite of the comet. If this speed is smaller
So the spacecraft will be captured by the comet's gravity and if it is greater than this speed then the spacecraft will overcome gravity
of the comet and actually "run away" from it.
4. Although it is very difficult to achieve such accuracy and maintain such speed, it is still possible by using very precise sensors that exist in our time,
which actually constantly measure the distance from the ground with very high precision and thus it is possible to assess whether you are getting closer or further away
from the comet In fact, any such correction made by turning on burners wastes energy, therefore the higher the accuracy in the measurement
And the accuracy in maneuvers is also higher, so in fact there will be less "waste" of energy for the spacecraft.
5. But the real problem in this whole story is that it is not a comet that has a spherical body, so the gravitational field here is also
not spherical. From this it follows that it is difficult to navigate the spacecraft in a satellite way around it, so that the direction of its movement will be vertical to the direction of the vector
The gradient of the comet's gravitational field. To overcome this problem, the deviation should be reduced as much as possible,
And the intuitive method is actually by getting as close to the surface of the comet as possible. So in fact, the curvature of the field will be negligible,
That is, sinx = x and the understanding will understand.
Hope I helped 🙂
A. Ben Ner
Small but important fix. The weight decreases over time due to the use of fuel to perform course corrections whether it is course corrections or whether the main engine is used or the navigation engines are used. If my memory does not deceive me, it has been a long time since I wore the chairs of the academy (I was born in 156 BC). Differential and integral calculus are used here.
A lion cub
Your claim is wrong even though it stems from real physical intuition
Although it is true that the comet's gravitational force is small compared to planets orbiting the sun
Such as Mars and even the Moon, however, it is greater than 0.
Therefore, if the force of gravity is small, it must be demanded that the force opposing it,
The centrifugal force resulting from the rotation of the rosette around the comet will be smaller and less equal
or greater in magnitude (but opposite in direction) to the force of gravity. This is XNUMXth grade physics
If my memory serves me correctly.
This requirement dictates that, the rosette will be as light as possible in its weight, and given
Its weight (almost constant), then its rotation speed around the comet will be relatively slow
For the speed it was required to rotate it orbited heavier celestial bodies.
Well, it is possible that the European Space Agency has someone who knows how to calculate it.
Fact - the Rosetta is there.
Miracles
"Tend" is in the past tense, "tend" is in the future tense. As for the word "why". By the intention you are referring to, if you punctuate the word then under the letter "L" there should be a pivot. With the intention that I am referring to under the "L" there should be a pinch and then you don't necessarily have to put a question mark, as for the word "spherical" you are right it is possible and even desirable to write "spherical". Besides, if you want to hear what is beautiful, it is not in astronomy, I am attaching a link
https://www.youtube.com/watch?v=CH4_zH9-vfI
Hint I don't know Russian, maybe you do
Life
In addition - "Why not believe the European Space Agency." - missing question marks, and I also think it is more correct to try "why"... (Why - for what purpose? Why - because of what?).
And "spherical" - you probably meant "spherical", didn't you?
Only - don't take me seriously, Hebrew is not my strong point...
Life
If you want to be precise - you should say "try" and not "don't try"...
Haim,
It was a joke, obviously he believed the "European Space Agency" and not our lovable lion cub here
MouthHole
Why not believe the European Space Agency. They have done successful things in the study of the solar system. Like putting spacecraft into orbit around Mars and Venus and the Huygens spacecraft that landed on Titan. As for asteroids, the American NEAR spacecraft was put into orbit around the 33 km diameter asteroid Eros. The European Mars Express spacecraft that was put into orbit around Mars, during its orbits around Mars we maneuvered it so that it passed at a distance of 96 km from Phobos, a body that is 26 km long. Regarding tiny bodies such as asteroids it is difficult to speak in terms of diameter since they are not spherical bodies.
Haim, I apologize, I am dyslexic in my profession.
Anyway, if it's from the European Space Agency, then I don't believe them and straight up going to do the math 🙂
post Scriptum.
Thanks for the corrections (no sarcasm here).
MouthHole
First, write disturbed and not disturbed. Second, the spacecraft was built in Germany within the framework of the European Space Agency. Please be precise in the details. Try to write without spelling mistakes next time. In my profession I am a linguistic editor.
Miracles, I guess he just is, but somehow, intuitively, what he says feels right. Of course I don't believe Gore is right, because otherwise they wouldn't have been able to do it. But it 'sounds' somewhat logical 🙂
But I'm not a moron, and I'm too lazy to calculate (meaning - it's not important enough for me to check), I believe in NASA this time 🙂
Lion cub
Did you do the math or are you just guessing?
How can you orbit a comet? Its mass is so small that it has no gravitational force or has a very, very small force.
A spacecraft satellite has an enormous speed and cannot be deflected into a circular rotation. Something here is a bluff.
Sending a probe that crashes is also difficult because it might miss the comet.
Anyway thanks for the info.