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Strange how NASA have suddenly drawn our attention back to Chandrayaan-1. Wonder what thats for? We will find out in the days to follow.
You know, there were 40,000 images returned out of an estimated 80,000 they were going to return on this mission. Where are they all? If anyone knows pehaps they can post a link on this thread please.
Unfortunately, something failed and the mission was lost after only a short time. However, they now find it happily STILL orbiting the Moon almost where they thought it 'should' be but only half an orbit off.
I always understood the orbit of a spacecraft decayed if nothing was done to correct it and its been nearly 9 years now without any input from Earth. Oh.. of course, there is very little(1/6th) gravity on the Moon, thats why it is still orbiting.
Planetary org says they returned 15,000 images from the probe moon impact probe
Strange how NASA have suddenly drawn our attention back to Chandrayaan-1. Wonder what thats for? We will find out in the days to follow.
You know, there were 40,000 images returned out of an estimated 80,000 they were going to return on this mission. Where are they all? If anyone knows pehaps they can post a link on this thread please.
Unfortunately, something failed and the mission was lost after only a short time. However, they now find it happily STILL orbiting the Moon almost where they thought it 'should' be but only half an orbit off.
I always understood the orbit of a spacecraft decayed if nothing was done to correct it and its been nearly 9 years now without any input from Earth. Oh.. of course, there is very little(1/6th) gravity on the Moon, thats why it is still orbiting.
Planetary org says they returned 15,000 images from the probe moon impact probe
Chandrayaan-2 Second Indian Moon mission Link 1 Link 2
What?
Objects in low-Earth-orbit (LEO) see their orbits decay in a relatively short period of time due to atmospheric drag. There isn't much, but over time it adds up. An example would be Skylab, which was finally parked in an orbit of about 275 miles in 1974. Five years later, it re-entered the atmosphere due to orbital decay. Satellites in higher orbits, far above the atmosphere - such as GPS satellites, which orbit at over 12,000 miles - can stay there almost indefinitely (ie, long after they've either ceased to function or become technologically obsolete). The United States launched Vanguard 1 in 1958. It is in an elliptical orbit that swings it at perigee to within 360 miles of Earth. There is still some atmospheric drag even at that altitude, though it is extremely slight - Vanguard 1's estimated date of orbital decay, when it is expected to finally plunge towards Earth and burn up, is the year 2198.
The Moon has no atmosphere. Well, technically, the Moon does have an atmosphere, but it is so thin as to functionally be a vacuum. Now, no orbit is permanent. There will always be gravitational perturbations from the Sun or other planets in their orbits, which of course vary in their distance from Earth. And in the case of the Moon there are gravitational anomalies (mascons) which work to gradually degrade orbits of captured bodies. But the nine years that Chandrayaan-1 has been orbiting is nothing. There is nothing at all unusual about that.
And the fact that the Moon's gravity is 1/6th that of Earth has absolutely no bearing whatsoever in the matter.
I understood, perhaps incorrectly, that there is an attraction between large bodies and therefore the mass of the Moon would be likely to attract smaller masses. Isn't this what keeps planets at certain distances from the sun as they are orbiting?
I also understood the Lagrangian Point between the earth and the Moon was where the Earths attractive force ceases to have a greater influence on a space ship and after that point, the Moon was the 'attractor' ? Surely the nearer the spaceship is to the Moon, the more that force will be 'felt'?
I understood, perhaps incorrectly, that there is an attraction between large bodies and therefore the mass of the Moon would be likely to attract smaller masses. Isn't this what keeps planets at certain distances from the sun as they are orbiting?
All objects have mass and therefore any two objects will attract each other. The sun attracts the earth but the earth also attracts the sun. What keeps a satellite in orbit around the earth (or around the moon) is a balance between gravity and the momentum of the satellite that is in orbit around the earth. If the momentum is too little the satellite will fall out of orbit. If the momentum is too great the satellite will escape the gravitational pull of the earth and fly out into space. Essentially, a satellite in orbit around the earth falls around the earth. As a satellite orbits the earth gravity is constantly pulling the satellite towards it. But because of the satellite's momentum the earth's surface is constantly curving away from the satellite so that as it falls around the earth there is never any ground for the satellite to hit.
Quote:
I also understood the Lagrangian Point between the earth and the Moon was where the Earths attractive force ceases to have a greater influence on a space ship and after that point, the Moon was the 'attractor' ? Surely the nearer the spaceship is to the Moon, the more that force will be 'felt'?
Pretty much so, yes. There are five Lagrange points between the earth and the moon. L4 and L5 are stable equilibrium points and L1, L2, and L3 are unstable points. A diagram of the earth/moon Lagrange points, and further information are provided in the link below.
A Lagrange point is a location in space where the combined gravitational forces of two large bodies, such as Earth and the sun or Earth and the moon, equal the centrifugal force felt by a much smaller third body. The interaction of the forces creates a point of equilibrium where a spacecraft may be "parked" to make observations. Lagrange Points: Parking Places in Space
But the nine years that Chandrayaan-1 has been orbiting is nothing. There is nothing at all unusual about that.
This thing has supposedly had no communications at all with Earth so there have been no adjustments whatsoever to the orbit it was left in when the accident happened. Isn't that unusual that it is still up there after nearly 9 years in that case?
Obviously, it probably depends on the size of the spacecraft as well, but I thought that every few years the Earth ones had to have their orbits adjusted so they didn't fall out of orbit because they were being attracted to the Earth as explained above.
So how long are we talking about here? For a rogue satellite to degrade from its orbit around the Moon and drop out and crash? I thought it would be years but you seem to be suggesting it is likely to be decades? Centuries?
This thing has supposedly had no communications at all with Earth so there have been no adjustments whatsoever to the orbit it was left in when the accident happened. Isn't that unusual that it is still up there after nearly 9 years in that case?
Obviously, it probably depends on the size of the spacecraft as well, but I thought that every few years the Earth ones had to have their orbits adjusted so they didn't fall out of orbit because they were being attracted to the Earth as explained above.
So how long are we talking about here? For a rogue satellite to degrade from its orbit around the Moon and drop out and crash? I thought it would be years but you seem to be suggesting it is likely to be decades? Centuries?
Not long before contact with Chandrayaan-1 was lost its orbiting altitude had been increased from 100 km above the moon's surface to 200 km. Since the moon has no atmosphere to speak of which would create drag, the spacecraft can orbit the moon for a very long time. Much longer than 9 years.
The last time the Hubble space telescope was serviced was in May 2009, but I don't know if it received an altitude boost at that time or not. Since a space shuttle was necessary to boost the telescope's orbit and the space shuttle fleet has been retired, there is no way to maneuver it into a higher orbit. It orbits at around 353 miles which is in the Thermosphere. Most projection models suggest that Hubble will remain in orbit until the mid 2030's.
I wonder what happened to all the 70,000 images it sent before it died.
There are 5 images of the Moon on the official ISRO Indian Space Agency website and I dont seem to be able to find the official repository. I would have expected to find it listed here but the data from the mission seems to have been left out.
...has made 3,000 revolutions around the Moon. Besides sending more than 70,000 images of the lunar surface which provide breathtaking views of lunar mountains and craters,...
and the reason for failure of the comms module was...Link
Quote:
Asked about the ISRO’s admission that a “miscalculation of the moon’s temperature” led to the satellite’s abrupt end on August 29, ISRO Chairman G. Madhavan Nair said: “Unfortunately, the reflection from the moon was much larger than expected and higher than what the literature data indicated.”
How many spacecraft went to the Moon before 2003 when this mission was started?
I wonder what happened to all the 70,000 images it sent before it died.
There are 5 images of the Moon on the official ISRO Indian Space Agency website and I dont seem to be able to find the official repository. I would have expected to find it listed here but the data from the mission seems to have been left out.
Link
and the reason for failure of the comms module was...Link
How many spacecraft went to the Moon before 2003 when this mission was started?
You might try asking NASA about those 70,000 images.
I will, and I have also asked the Indian Space Agency. No answer yet...
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