## Chandrayan-1 moon mission

Drevin
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### Re: Chandrayan-1 mission launched succesfully

It looks like the firing of the LAM is not only increasing the apogee as it should but also the perigee (336 to 348 km). If the engine is fired at perigee as I think it normally should be, would that not only increase the apogee?

Perigee is a 'point' on the elliptical orbit, the engine was firing away for 9 minutes or so right ? The satellite must have moved a considerable distance beyond this 'point' during this firing. This will naturally lead to the idea of a dynamic perigee, won't it for all practical purposes increase the perigee, but will never decrease it with each impulse given.

To take a geometric view of the situation, draw a half-circle touching the perigee of the elliptical orbit. Any instantaneous engine firing will move the object at perigee to the space out of the circle. This automatically implies a larger distance from the reference center of the circle drawn or the foci of the elliptical orbit. A cumulative sequence of firings will leave the perigee growing in value.

If you could have given an instantaneous impulse at the perigee point rather than over the 9 minutes, then and only then can you have preserved the original perigee value.

Could it be more easily explainable by saying that the apogee and perigee values are related to each other thru an equation determined by mechanics of an elliptical orbit. So that vast increases in apogee result in corresponding miniscule changes in the perigee value.

jmt

found some relevant equations to elliptical orbit

apogee=a(1+e) and
perigee=a(1-e)
e = eccentricity
a = half length of major axis of the ellipse.
(sum of apogee and perigee=2a=length of major axis of ellipse)

Note: apogee and perigee distances are on opposite sides of the earth with the earth being inside the elipse.

SSridhar
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### Re: Chandrayan-1 mission launched succesfully

Drevin, Bade's explanation is correct. The motor firing at perigee is not a point impulse action. That's why some minor difference happens. When LAM is fired at perigee, both the semi major axis & semiminor axes will change.

Drevin
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### Re: Chandrayan-1 mission launched succesfully

Yes I know Sridhar sir, but he's not super clear thats why i relied on math. No offence Badeji. Extra kinetic energy from the burn coupled with the larger elliptical orbit leads to the increase in perigee distance. (Combination of geometry and spacecraft acceleration)

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### Re: Chandrayan-1 mission launched succesfully

SSridhar-ji, thanks, your explanation works for me.
Drevin-ji, I think Bade-ji's second explanation on perigee/apogee also works pretty well, especially with SS-ji's clarification. In the real universe, pure maths can be quite fallible!

I can only assume that the apollo missions wanted to get to the moon as fast as possible at the expense of energy in order to minimise the life support requirements and reduce overall risk, and hence used other orbits. these complications don't exist for unmanned systems.

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### Re: Chandrayan-1 mission launched succesfully

Lalmohan wrote:I can only assume that the apollo missions wanted to get to the moon as fast as possible at the expense of energy in order to minimise the life support requirements and reduce overall risk, and hence used other orbits. these complications don't exist for unmanned systems.

Quite right. We had a PSLV that could place the Chandrayaan-I in an elliptical GTO parking orbit from which it was sent subsequently into a Trans Lunar Trajectory while the Americans had the benefit of the huge Saturn V booster plus other things for a direct transfer.

Drevin
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### Re: Chandrayan-1 mission launched succesfully

In the real universe, pure maths can be quite fallible!

don't care. i saw confusion hence the posts. natural participation in the forum functioning. thats what i am here for .....participating .... i never was a lurker .... infact i don't have time to lurk .... too big a luxury for an employed guy.

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### Questions

Few questions:

[1] Does the Chandrayan carry a photo camera among other instruments? I was thinking that it would be nice to have some photos of the blue planet taken from our space vehicle as it speeds away towards the moon.

Right now it is all dry data. Images have their own value and impact.

[2] From this image posted earlier, it is evident that Chandrayan will be coming close to Earth repeatedly till it is established in lunar orbit. But does this not greatly increase the danger of being hit by space debris?

[3] Also posted earlier, is this information (right column) accurate? If so, how is this website getting such accurate data?

Sid
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### Re: Chandrayan-1 mission launched succesfully

Got this observation from another forum. As per this live tracking site Chandrayaan still have 300 KM * 37800 KM earth orbit.

Is it supposed to be like this or this site is crap?? Any gurus on this?

http://n2yo.com/?s=33405

Lalmohan
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### Re: Chandrayan-1 mission launched succesfully

Shivani, there is i believe a map of all known space debris of any significance. presumably orbits are designed to cope with that. much of it i assume is decaying and falling back down as extra shooting stars. Chandrayaan is not coming near to the cluttered altitude (100-200kms) so should be relatively safe

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### Re: Chandrayan-1 mission launched succesfully

Regarding the increase in perigee: Thanks for the explanation. Yes of course, I should have realized that the 9+ min firing is of significant duration that will change the perigee as you pointed out. I think that will also change the orientation of the new orbit vis-a-vis the previous one, no? Would the new intermediate orbits added after launch have anything to do with better calibrating those effects?

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### Re: Chandrayan-1 mission launched succesfully

Yes and your guess is good as anyone else's for the second question, lacking more definite information from ISRO which is public.

Vipul
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### Re: Chandrayan-1 mission launched succesfully

'Chandrayaan orbit to be raised to 267,000 km on Wednesday'.

The earth orbit of India's first lunar spacecraft will be raised to 267,000 km on Wednesday, an official here said.

"The Chandrayaan spacecraft, orbiting at a distance of around 165,000 km apogee (farthest point from earth) will be raised Wednesday to around 267,000 km. As of now, everything is normal and as per our expectations," Chandrayaan-1 project director M. Annadurai said.

The third orbit-raising was done Oct 26 and the spacecraft was raised up to 164,600 km, instead of 199,277 km apogee as originally announced by the Indian Space Research Organisation (ISRO).

"The important date for us is Nov 3 when the final orbit manoeuvre will happen. Between Oct 22 and Nov 3 we have the leeway to carry out the orbit raising activity," he said.On Nov 3, the ISRO will take the spacecraft to 384,000 km apogee.

The subsequent firing of spacecraft motors will take it near the lunar orbit and it is expected to get into lunar orbit Nov 8.

During the lunar orbit, the spacecraft's motors will be fired five times - called lunar burn - to take it to 100 km of the moon's radius.

"We expect that to happen November 14 or November 15," Annadurai said.

According to him the spacecraft has sufficient fuel on board."Going up, the spacecraft spends less fuel to travel the same distance," he added.

On Oct 23, the spacecraft's motors were fired for 18 minutes to take it to 37,900 km apogee.

Subsequently, the spacecraft motors were fired for 16 minutes and 9.5 minutes Oct 25 and Oct 26 respectively to take it to 74,715 km and 164,600 km respectively.

"On Wednesday we will fire the spacecraft motors for 190 seconds (3.17 minutes) to take it to 267,000 km. On Nov 3, the motor firing will be for around 150 seconds (2.5 minutes) to take the spacecraft to 384,000 km," Annadurai said.

Till date, the spacecraft has expended around 340 kg of fuel of the lift off capacity of 819 kg.The spacecraft's motor firing Wednesday and Nov 3 would consume around 40-50 kg of fuel.

"Another 100 kg fuel might be expended to put Chandrayaan into its intended orbit near the moon, leaving sufficient quantities of fuel for the spacecraft to orbit for two years," he added.

narayana
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### Re: Chandrayan-1 mission launched succesfully

During the lunar orbit, the spacecraft's motors will be fired five times - called lunar burn - to take it to 100 km of the moon's radius.

"We expect that to happen November 14 or November 15," Annadurai said.

it was supposed to be November 8th,now shifted to Nov 14 or 15th,is everything ok with the mission?

SSridhar
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### Re: Chandrayan-1 mission launched succesfully

narayana wrote:
During the lunar orbit, the spacecraft's motors will be fired five times - called lunar burn - to take it to 100 km of the moon's radius.

"We expect that to happen November 14 or November 15," Annadurai said.

it was supposed to be November 8th,now shifted to Nov 14 or 15th,is everything ok with the mission?

I do not see any shift. The last perigee firing on the earthbound orbit will be on the 3rd. It will take about 5 days to enter the lunar orbit after that which will be around the 8th. The series of lunar burns will take place after that to get a 100 km polar selenocentric orbit by 14th or 15th. Many things depend on the arrival geometry.

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### Re: Chandrayan-1 mission launched succesfully

so far nothing wrong

8th was the time expected to reach lunar gravitational field or so called lunar capture

as far as I understand the motor is fired at the perigee and as the orbits are getting more and more elliptical the time for the spacecraft to come back for next perigee burn to raise the apogee becomes longer .

Shankar
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### Re: Chandrayan-1 mission launched succesfully

of course the transit time could have been shorter if we attempted a direct sling shot from earth parking orbit or geo transfer orbit but that was not done to take care of certain unknown effects mainly solar and gravitational pull of other bodies around which may or may not cause deviation from intended path and also to stay within the limitations of the spacecraft on board fuel capacity .

this method I think uses earths gravity more effectively to reach moon -somewhat slow but how does it matter as long as the objective is reached .

when a bigger rocket is used like GSLV and a bigger lunar craft with more on board fuel then the transit time will come down significantly as the number or orbits and may the orbit profile itself will be changed

at the moment what is important is we allow a lunar capture or get into effective lunar gravitational field around 8th and initiate the first lunar burn of LAM to effectively get into 1000 km lunar orbit and then slowly de accelerate to achieve the 100 km lunar polar orbit

UPrabhu
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### Re: Chandrayan-1 mission launched succesfully

http://www.khabrein.info/index.php?opti ... &Itemid=62

Oh so there indeed was shortfall in 3rd orbit raise.. as some slides show third orbit to be more than 190K

SSridhar
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### Re: Chandrayan-1 mission launched succesfully

Oh so there indeed was shortfall in 3rd orbit raise.. as some slides show third orbit to be more than 190K

From Vipul's post above, I inferred that ISRO decided to raise the orbit only to 164K, for whatever reason, instead of the earlier announced 199K Km.
Last edited by SSridhar on 29 Oct 2008 13:57, edited 1 time in total.

jerry
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### Re: Chandrayan-1 mission launched succesfully

Shankar
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### Re: Chandrayan-1 mission launched succesfully

I dont know -some confusion

the respective apogees are

74000 km

164 000 km

267 000 km

384 000 km x 2000 km

As per published data there is no shortfall - but ?

SSridhar
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### Re: Chandrayan-1 mission launched succesfully

I think the confusion comes from an earlier ISRO plan of having only three orbit raising manoueveres from the GTO, i.e 74K, 199K & 384K Kms. They later decided to add two more intermediate orbits between 74K & 384K, which were 164K & 267K Kms. So, there is actually no shortfall from firing. It is all WAD (working as designed).

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### Re: Chandrayan-1 mission launched succesfully

Fly me to the diety

The New York Times

October 29, 2008
Op-Ed Contributor
Fly Me to the Deity

AN unmanned spacecraft from India — that most worldly and yet otherworldly of nations — is on its way to the moon. For the first time since man and his rockets began trespassing on outer space, a vessel has gone up from a country whose people actually regard the moon as a god.

The Chandrayaan (or “moon craft”) is the closest India has got to the moon since the epic Hindu sage, Narada, tried to reach it on a ladder of considerable (but insufficient) length — as my grandmother’s bedtime version of events would have it. So think of this as a modern Indian pilgrimage to the moon.

As it happens, a week before the launching, millions of Hindu women embarked on a customary daylong fast, broken at night on the first sighting of the moon’s reflection in a bowl of oil. (This fast is done to ensure a husband’s welfare.) But reverence for the moon is not confined to traditional Indian housewives: The Web site of the Indian Space Research Organization — the body that launched the Chandrayaan — includes a verse from the Rig Veda, a sacred Hindu text that dates back some 4,000 years: “O Moon! We should be able to know you through our intellect,/ You enlighten us through the right path.”

One is tempted, in all this, to dwell on the seeming contradiction between religion and science, between reason and superstition. And yet, anyone who has been to India will have noted also its “modernity of tradition.” The phrase, borrowed from the political scientists Lloyd and Susanne Rudolph, might explain the ability of devout Hindus — many of them, no doubt, rocket scientists — to see no disharmony between ancient Vedic beliefs and contemporary scientific practice.

The Hindu astrological system is predicated on lunar movements: so the moon is a big deal in astrology-obsessed India. That said, the genius of modern Hinduism lies in its comfort with, and imperviousness to, science. A friend tells me of an episode from his childhood in Varanasi, the sacred Hindu city. Days after Apollo 11 landed on the moon, a model of the lunar module was placed in a courtyard of the most venerable temple in the city. The Hindu faithful were hailing man-on-the-moon; there was no suggestion that the Americans had committed sacrilege. (Here, I might add — with a caveat against exaggeration — that science sometimes struggles to co-exist with faith in the United States in ways that would disconcert many Indians.)

Of course, the Chandrayaan is also a grand political gesture — space exploration in the service of national pride. This kind of excursion may provoke yawns at NASA, but judging from round-the-clock local coverage it has received, the mission has clearly inflamed the imagination and ambition of Indians. Yes, even moon-worshipping ones.

Tunku Varadarajan, a professor of business at New York University and a research fellow at Stanford’s Hoover Institution, is the opinion editor at Forbes.com.

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### Re: Chandrayan-1 mission launched succesfully

Chandrayaan-1’s Orbit Closer to Moon - ISRO
The fourth orbit raising manoeuvre of Chandrayaan-1 spacecraft was carried out today (October 29, 2008) morning at 07:38 am IST. During this manoeuvre, the spacecraft’s 440 Newton liquid engine was fired for about three minutes. With this, Chandrayaan-1 entered into a more elliptical orbit whose apogee (farthest point to Earth) lies at 267,000 km (two lakh sixty seven thousand km) while the perigee (nearest point to Earth) lies at 465 km. Thus, Chandrayaan-1 spacecraft’s present orbit extends more than half the way to moon. In this orbit, the spacecraft takes about six days to go round the Earth once.

The health of the spacecraft is being continuously monitored from the Spacecraft Control Centre at ISRO Telemetry, Tracking and Command Network (ISTRAC) in Bangalore with support from Indian Deep Space Network antennas at Byalalu. All systems onboard the spacecraft are performing normally. One more orbit raising manoeuvre is scheduled to send the spacecraft to the vicinity of the moon at a distance of about 384,000 km from the Earth.

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### Re: Chandrayan-1 mission launched succesfully

anupmisra
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### Re: Chandrayan-1 mission launched succesfully

Shouldn't the title of this thread be changed to "Chandrayaan's tryst with the moon" or something? The launch is over and behind us.

NRao
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### Re: Chandrayan-1 mission launched succesfully

Sigh ................

Houston, we have one very confused Tunku.

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### Re: Chandrayan-1 mission launched succesfully

Is anyone here aware that the moon's gravity is probably as high as 64% of Earth rather then 1/6th as we are taught in books? It can have implications for Chandrayaan's lunar orbital maneuver.

The neutral point of the earth-moon system is about 38,000 miles from the moon. This can be used to calculate the gravity of moon using inverse-square law.

It is probably because of this mis-information that the early mission probes of Russia and USA (Lunas and Rangers) to moon used to fail.

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### Re: Chandrayan-1 mission launched succesfully

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### Re: Chandrayan-1 mission launched succesfully

I have a question for the experts here regarding the tracking accuracy of the IDSN antenna farm.
This report lists a tracking speed of 0.01 millidegree/second. I gather this is based on the requirement to track Chandrayaan in moon orbit during its visible track.
Is there a physical limitation to the angular spread the antenna can be focussed on for future missions farther than moon orbit? Or is the angle so small (angle spread at antenna aperture subtended by spacecarft) that essentially the antenna simply needs to track the spacecraft with only the earth's rotation/motion considered and compensated for?

The more I think about this, the more amazing ISROs' (& ECIL, BARC etc.) achievement @ Byalalu seem! While the media boasts about the "indigenous 32m dish", the servo mechanisms and control behind the antenna must be truly amazing.

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### Re: Chandrayan-1 mission launched succesfully

That also answers the earlier question here about the slight increase in perigee.
“When the firing is done exactly at perigee, the velocity increases and the apogee keeps increasing. There will be no change in the perigee position,” he said.

But firing the spacecraft exactly at the perigee position is only theoretically possible. This results in a small change in the perigee altitude.

“It is not an instant firing [at the perigee]. It takes a few hundred seconds to complete the firing,” he said. But great effort is however taken to centre the firing around the perigee position.

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### Re: Chandrayan-1 mission launched succesfully

SSridhar wrote:

That also answers the earlier question here about the slight increase in perigee.
“When the firing is done exactly at perigee, the velocity increases and the apogee keeps increasing. There will be no change in the perigee position,” he said.

But firing the spacecraft exactly at the perigee position is only theoretically possible. This results in a small change in the perigee altitude.

“It is not an instant firing [at the perigee]. It takes a few hundred seconds to complete the firing,” he said. But great effort is however taken to centre the firing around the perigee position.

Excellent article. The Hindu for all its faults (and there are many many of them which we all know about) has the best science articles of all Indian (or arguably Indian) newspapers. This article appears to confirm my earlier speculation about the reason for increasing the number of intermediate orbits

But not always can one assume that the firing will happen as planned. So any change in this will in turn affect the apsidal line (imaginary line that connects the apogee and perigee). This should be corrected and maintained if the rendezvous with the moon is to happen.

SSridhar
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### Re: Chandrayan-1 mission launched succesfully

prao wrote:So any change in this will in turn affect the apsidal line (imaginary line that connects the apogee and perigee). This should be corrected and maintained if the rendezvous with the moon is to happen.

A perfectly tangential point impulse given to the spacecraft at perigee will alter the apogee without changing the apsidal line (i.e the orbital plane or the inclination). Similarly, a perfectly radial point impulse at the perigee (or the apogee) will only alter the inclination without altering the apogee (or the perigee). Since it is not possible to have a point firing and since the firing takes place around the perigee, the inclination will also be altered. The inclination will have to be precise so that the moon and the spacecraft will be at the right place and time for the moon's gravitational force to capture the spacecraft.

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### Re: Chandrayan-1 mission launched succesfully

Sid wrote:Got this observation from another forum. As per this live tracking site Chandrayaan still have 300 KM * 37800 KM earth orbit.
Is it supposed to be like this or this site is crap?? Any gurus on this?
http://n2yo.com/?s=33405

The site deal with old data points, in my opinion. It is for satellite tracking, not spacecraft. For tracking satellites, once the orbital data points are fed in, the program can go on "tracking" it ad nauseam. Chandrayaan's orbits are being changed frequently, and the site is not updating the new orbits

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### Re: Chandrayan-1 mission launched succesfully

sumishi wrote:Is anyone here aware that the moon's gravity is probably as high as 64% of Earth rather then 1/6th as we are taught in books? It can have implications for Chandrayaan's lunar orbital maneuver.

The neutral point of the earth-moon system is about 38,000 miles from the moon. This can be used to calculate the gravity of moon using inverse-square law.

It is probably because of this mis-information that the early mission probes of Russia and USA (Lunas and Rangers) to moon used to fail.

Sorry, I meant 43,495 miles, not 38,000, to arrive at the 64% figure . This value for the "Neutral Point" was published in Times Magazine (July 25, 1969) in reference to Apollo 11 landing. The same value is quoted in the 1969 edition of History of Rocketry & Space Travel by Wernher von Braun and Frederick I. Ordway III

If you consider other reputed information sources, the neutral point is variously mentioned from 38,000 to 43,495 miles. It is actually NOWHERE close to the 20,000 to 25,000 miles data that calculation were based on in days prior to moon probes from Russia and US.

The important point is: Does ISRO know about this Neutral Point discrepancy vis-a-vis common official knowledge in textbooks?

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### Re: Chandrayan-1 mission launched succesfully

On a related note, seems like there is progress on Chandrayaan-2:

India, Russia giving final shape to Chandrayaan-2

http://www.hindustantimes.com/redir.asp ... 1c19bebd24

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### Re: Chandrayan-1 mission launched succesfully

This co-operation with russia with lander being russian is denying a crucial opportunity to develop soft landing capability.... we should suspend this idea of "Vasudeva Kutumbakam" for a while...

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### Re: Chandrayan-1 mission launched succesfully

Why waste time in re-inventing the wheel when we're almost on a race?

UPrabhu
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### Re: Chandrayan-1 mission launched succesfully

Anabhaya wrote:Why waste time in re-inventing the wheel when we're almost on a race?

In that case why even have a space program when others can build and launch satellites for us... we can just apply our paint to it..like the porkis

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### Re: Chandrayan-1 mission launched succesfully

yes.. though the rover is from India, the lander is planned to be russkie!.. soft landing on moon, and further to which a similar launch off the moon, and soft land back to earth is very important technology to bring back the h3 at moon. now, if that is not in the strategy, why spend billions when we can feed the deserving mouth here.

good points here.

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### Re: Chandrayan-1 mission launched succesfully

edited.
Last edited by vishwakarmaa on 30 Oct 2008 17:02, edited 1 time in total.