Chandrayan-1 moon mission

SSridhar
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Re: Chandrayan-1 mission launched succesfully

Postby SSridhar » 08 Nov 2008 10:49

From the circa 2007 paper presented by ISRO, I have extracted relevant portions below. It shows the sensor evolution within various ISRO spacecraft.

In the area of platform pointing and stability, a linear array CCD-based star sensor was flown in IRS-1A/1B for measuring attitude of the satellite as a supplement to the earth sensor. Subsequently CCD-based star sensor was developed and flown in IRS-1C/1D as a full-fledged three-axis attitude sensor. Then onwards, star sensor is the main attitude sensor onboard all IRS satellites. The spacecraft pointing accuracy, which is measure of the geometrical accuracy of the imagery, has been improved from 0.4 deg in IRS-1A to 0.05 deg in Cartosat. These star sensors in conjunction with highly stable mechanical gyroscopes resulted in platform stability of about 5 × 10e–5 deg/s. Table 4 provides the different types of attitude sensors and their evolution. Development of fibre optic gyro, which will give better performance in terms of drift stability, is under way.


Code: Select all

Sensor Type                   Accuracy (degree)    No of Sensors per spacecraft

4PI Sun Sensor                       1.0                                  4
Fine Sun Sensor                      0.5                                  1
Precision Yaw Sensor                 0.2                                  2
Digital Sun Sensor                   0.125                                2
Conical Scanning Earth Sensor        0.1                                  2
Area Array CCD Star Sensor           0.01                                 2

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Re: Chandrayan-1 mission launched succesfully

Postby Arun_S » 08 Nov 2008 13:15

SriKumar wrote:Arun_S, thanks for the responses. It is interesting that modern satellites use the same reference (stars) as ancient sailors did.

A related question: How do the CY scientists know the position of a satellite in deep space. I assume that during the earth orbits, the position is a simple function of the orbit, i.e. the engineers could use the speed, time and altitude (at perigee) to calculate the position at any time in the orbit. Is there an independent way to verify position, say, by triangulating a signal from the satellite sent to the various tracking stations? Does the same approach work when CY is being injected into a lunar orbit? As it gets closer to the moon, I think it would get really tricky (and perhaps less useful) to determine its position relative to earth, and perhaps moon is a better reference point at that stage?


Indeed that is precisely the reason the Jesuit'es came to Kerela to learn the maths and geometry Indian sailors used to navigate and cut straight through oceans, where as the european sailors did not know any other means but to follow the coast line. Those Jesuit'es trips to Kerela for Indian knowledge, in a few years germinated the Renaissance.

As for deep space positioning; "ALL" deep space navigation depend on triangulation. Traingulation gives best accuracy when the reference (Datum) points are spatially as far as possible from each other. Thus when datums are located on earth as one goes above 6000 km altitude those earhly datums are located too close to each other and one starts losing precision due to DOP (Diluation of Precision). The only accurate navigational information earth bound datum can give is "distance". angular bearing by earth bound resources is too gross and give too much error. So for orientation/attitude star based datum are best. Also for triangulation based celestial naviation, star based datum happen to yield best possible DOP.

SSridhar wrote:To enable Chandrayaan-1 to be captured by the moon, its orientation will be turned around by 180 degrees with the help of on-board reaction wheels. After this , retro-rockets will be fired for about 800 seconds.
So there are rockets other than the LAM? Why not use the LAM after turning it around?

Using LAM to change attitude is like using sledge hammer to turn a car's steering wheel. Momentum wheels (based on "every rotational action has an equal and opposite rotational reaction") combined with tiny reaction thrusters give the most precise, refined and fuel efficient performance.

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Re: Chandrayan-1 mission launched succesfully

Postby SSridhar » 08 Nov 2008 15:23

More info on LOI to take place in a short while

"The lunar orbit insertion (LOI) will start around 5 p.m. and last around 800 seconds," ISRO spokesperson S Satish told PTI here.

Once the operation is completed, it will be in a 7,500 km X 500 km elliptical orbit around the moon.

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Re: Chandrayan-1 mission launched succesfully

Postby SwamyG » 08 Nov 2008 16:18

In just another hour or so.......got any nails to bite? Good luck ISRO.

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Re: Chandrayan-1 mission launched succesfully

Postby Nitesh » 08 Nov 2008 16:44

It's the time now, any updates coming in?

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Re: Chandrayan-1 mission launched succesfully

Postby jerry » 08 Nov 2008 16:50

yes its done sucessfully

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Re: Chandrayan-1 mission launched succesfully

Postby Nitesh » 08 Nov 2008 16:52

some channels reporting that the firing is successful, somebody pls confirm

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Re: Chandrayan-1 mission launched succesfully

Postby Kakarat » 08 Nov 2008 16:54

http://www.isro.org/
Chandrayaan-1 Successfully Enters Lunar Orbit

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Re: Chandrayan-1 mission launched succesfully

Postby sumishi » 08 Nov 2008 16:55

What the hell is this?
Chandrayaan enters lunar orbit
8 Nov 2008, 1715 hrs IST, SRINIVAS LAXMAN, TNN
Chandrayaan-1 has entered the lunar orbit successfully. The spacecraft will last around 800 seconds in 7,500 km X 500 km elliptical orbit around the moon.

:rotfl: :rotfl:

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Re: Chandrayan-1 mission launched succesfully

Postby rahulm » 08 Nov 2008 16:55

NDTV Breaking news reports success.
Added later: Ticker on ISRO website reports success ("Chandrayaan 1 successfully enter Lunar orbit"). Congratulations to ISRO on this milestone.
Last edited by rahulm on 08 Nov 2008 17:00, edited 2 times in total.

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Re: Chandrayan-1 mission launched succesfully

Postby sumishi » 08 Nov 2008 16:56

rahulm wrote:NDTV Breaking news reports success.

GREAT!! Way to go IISSSRROOOO!!!

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Re: Chandrayan-1 mission launched succesfully

Postby Nitesh » 08 Nov 2008 16:57

Cogrtats to everyone, MiSSION SUCCESSFULL, Chandrayan enters moon orbit..........

http://ibnlive.in.com/news/chandrayaan1 ... l?fads=ads

Chandrayaan-1 enters lunar orbit successfully

New Delhi:After two weeks of journey India's first unmanned lunar spacecraft Chandrayaan-1 entered the lunar orbit on Saturday evening. The journey so far has been 'error-free'.


Initially, Chandrayaan-1 will be circling the moon from 7,500 kilometers away. However, by Tuesday it will cruise closer to the moon early on Tuesday when it makes the transition from the earth's elliptical orbit into deeper space, a top space agency official said Monday.


"The liquid apogee motor (LAM) on board will be fired around 5.00 am on Tuesday for about five minutes to make the transition and position the spacecraft at about 500 km from the moon's surface and over 384,000 km away from the earth," Indian Space Research Organisation (ISRO) director S. Satish said.


The complex manoeuvres will be carried out from the spacecraft's control room at ISRO's telemetry, tracking and command network (Istrac) in coordination with its deep space network (DSN) at Byalalu, about 40 km from Bangalore.


"Additional velocity will be given to the spacecraft to enter the lunar orbit Saturday (November for a rendezvous with the moon. With calibrated firing of its LAMs, it will be inserted into its designated orbit, which will be about 100 km from the lunar surface," Satish said.

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Re: Chandrayan-1 mission launched succesfully

Postby thammu » 08 Nov 2008 16:58

:rotfl:
we are in the 100% Asian league compared to 30% of others !!

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Re: Chandrayan-1 mission launched succesfully

Postby sumishi » 08 Nov 2008 17:02

This calls for celebration! My "electronic" hair-ruffle to everyone here in this forum. :D :D

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Re: Chandrayan-1 mission launched succesfully

Postby rahulm » 08 Nov 2008 17:02

India is nearly there but the mission's back has been broken. Now inclination correction, Lunar orbit cirularisation should be easier.

MIP is the next psy-ops milestone.

Onward to Chandrayaan 2.

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Re: Chandrayan-1 mission launched succesfully

Postby Rahul M » 08 Nov 2008 17:10

makes my day !

now, too bad if the aam-janta doesn't get a photo of the MIP racing towards lunar surface. :(

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Re: Chandrayan-1 mission launched succesfully

Postby rahulm » 08 Nov 2008 17:13


sum
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Re: Chandrayan-1 mission launched succesfully

Postby sum » 08 Nov 2008 17:20

Hip hip hooray....
Congrts to one and all Indians(esp ISRO) for this feat...
Next stop, tiranga planting on the moon.. :twisted:
Wish we could get a video clip somehow of that goose bump raising moment!!!!
Last edited by sum on 08 Nov 2008 17:58, edited 1 time in total.

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Re: Chandrayan-1 mission launched succesfully

Postby Vipul » 08 Nov 2008 17:24

Congrats evryone.

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Re: Chandrayan-1 mission launched succesfully

Postby sumishi » 08 Nov 2008 17:25

sum wrote:...
Next stop, tiranga plating on the moon.. :twisted:
...


Tiranga plating!! I LIKE that!! :lol:

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Re: Chandrayan-1 mission launched succesfully

Postby SSridhar » 08 Nov 2008 17:25

All those reports posted above are dishing out confusing and some hilarious information. We have to wait for more authentic information. One report says "The spacecraft will last around 800 seconds in 7,500 km X 500 km elliptical orbit around the moon. " :lol:

Added later: ISRO has confirmed. Congratulations.

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Re: Chandrayan-1 mission launched succesfully

Postby SwamyG » 08 Nov 2008 17:32

Congratulations to ISRO, its partners and all well-wishers.

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Re: Chandrayan-1 mission launched succesfully

Postby kmanish » 08 Nov 2008 17:37


SSridhar
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Re: Chandrayan-1 mission launched succesfully

Postby SSridhar » 08 Nov 2008 17:39

Image

The Chandrayaan Logo

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Re: Chandrayan-1 mission launched succesfully

Postby SwamyG » 08 Nov 2008 17:39

It is nice that ISRO did it in phases, apart from aiming to take it step by step to achieve its goals. The yaan is in people's and media's mind for a longer time. It is a positive psy-ops :-) It is not out-of-sight, out of mind case.

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Re: Chandrayan-1 mission launched succesfully

Postby Rahul M » 08 Nov 2008 17:39

sumishi, are you convinced now that ISRO does know the mass of the moon ? :wink:

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Re: Chandrayan-1 mission launched succesfully

Postby SSridhar » 08 Nov 2008 17:43

From that ISRO press release posted above,

The spacecraft is now orbiting the moon in an elliptical orbit that passes over the polar regions of the moon. The nearest point of this orbit (periselene) lies at a distance of about 504 km from the moon’s surface while the farthest point (aposelene) lies at about 7502 km.


I think that the orbit achieved is extremely, extremely close to the one wanted by ISRO. To achieve this accuracy at the very first shot is tremendous. The future missions are going to be that much easier and accurate.

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Re: Chandrayan-1 mission launched succesfully

Postby Hariprasad » 08 Nov 2008 17:45

I'm getting bored of saying this over and over again. :wink:
A big congratulation to ISRO for its hard-work and vision.

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Re: Chandrayan-1 mission launched succesfully

Postby saip » 08 Nov 2008 17:54

rahulm wrote:India is nearly there but the mission's back has been broken. Now inclination correction, Lunar orbit cirularisation should be easier.

MIP is the next psy-ops milestone.

Onward to Chandrayaan 2.


What do you mean by that?

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Re: Chandrayan-1 mission launched succesfully

Postby sum » 08 Nov 2008 17:58

sumishi wrote:
sum wrote:...
Next stop, tiranga plating on the moon.. :twisted:
...


Tiranga plating!! I LIKE that!! :lol:

:oops:
Edited now...
not a bad idea though: plating the moon with the Tiranga. :P

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Re: Chandrayan-1 mission launched succesfully

Postby SSridhar » 08 Nov 2008 18:01

SwamyG wrote:It is nice that ISRO did it in phases, apart from aiming to take it step by step to achieve its goals.


In terms of energy budget, it is the same. ISRO has not expended extra fuel because of adding two extra orbits. With the high orbit accuracy achieved, the remaining fuel should be good enough.

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Re: Chandrayan-1 mission launched succesfully

Postby Sid » 08 Nov 2008 18:04

congrats ISRO (and BR for unconditional support to ISRO :mrgreen:).

but what is the time line for remaining actions by lunar probe?

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Re: Chandrayan-1 mission launched succesfully

Postby prashanth » 08 Nov 2008 18:14

Congratulations to ISRO and all Indians. :)

Rahul M wrote:sumishi, are you convinced now that ISRO does know the mass of the moon ? :wink:


I wonder how many sleepless nights he spent worrying about this. :wink:

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Re: Chandrayan-1 mission launched succesfully

Postby Singha » 08 Nov 2008 18:17

I will hold off on the celebrations until a circular orbit of 500km radius is achieved
and the missions payloads send back their first ouputs.

laser and radio datalink to Kayuga is reported active and the joint secret isro-jaxa
Project Dharma payload delivery can also begin next week.

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Re: Chandrayan-1 mission launched succesfully

Postby SwamyG » 08 Nov 2008 18:32

SSridhar wrote:
SwamyG wrote:It is nice that ISRO did it in phases, apart from aiming to take it step by step to achieve its goals.


In terms of energy budget, it is the same. ISRO has not expended extra fuel because of adding two extra orbits. With the high orbit accuracy achieved, the remaining fuel should be good enough.

I know. I read a piece saying just that. ISRO had its own reasons for doing it in phases. Doing things in increments have their benefits, I realized that long long ago while doing a software project. I was not being critical of ISRO's phased approach. I just saw some "collateral advantage" :-) Now CNN and BBC would be forced to put a blip in a day or two.

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Re: Chandrayan-1 mission launched succesfully

Postby VRao » 08 Nov 2008 18:34

Chandrayaan-1 successfully enters moon’s orbit

Bangalore, Nov 08: India’s most ambitious moon mission, Chandrayaan-1, entered the lunar orbit at 5.04 pm on Saturday. The entry into the elliptical orbit of the moon, considered the most difficult part of the mission, was executed to perfection. Chandrayaan-1 has now been stabilised at an altitude of 504 kms from the surface of the moon.

The Chandrayaan-1’s lunar orbit insertion (LOI) started around 5.00 pm and lasted around 800 seconds. With the entry into the lunar orbit, the craft is now in the moon’s gravitational field and is in a 7,500 km X 500 km elliptical orbit around the moon and will take 10 hours to complete one revolution.

The LOI manoeuvre was tricky and involved danger because in this the craft had to traverse through an area where the earth and moon’s gravitational forces nearly cancel each other out. So, even a slight deviation could mean the end of the mission – the spacecraft could crash towards either the moon or earth, or embark on a course leading into deep space. Heaving a sigh of relief, ISRO chief G Madhavan Nair said today’s operation was the “most critical moment” in the mission.

“We ha ve done it,” a visbly happy Nair declared.

“For the last 20 minutes, almost all our hearts were at a standStill,” Nair said from a ground centre near Bangalore.

The lunar probe launch in itself will be a complex manoeuvre. Firstly, the craft will be gradually lowered to an altitude of 100 kms from the surface of the moon. The craft then will launch a probe, towards the surface of the moon, within the next 48 hours.

The last orbit-raising manoeuvres to enter the lunar transfer trajectory were completed on Tuesday by the Spacecraft Control Centre at ISRO Telemetry, Tracking and Command Network (ISTRAC) in Bangalore.

According to space experts, nearly 30% of unmanned moon missions of the US and the former USSR failed while being put into moon’s orbit.

Source: http://www.chandrayaan.bharatchronicle.com

Hurray!

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Re: Chandrayan-1 mission launched succesfully

Postby p_saggu » 08 Nov 2008 18:39

7502 Km x 504 Km orbit against a targeted 7500 x 500 Km orbit. And 400,000 Kms away :eek:
AMAZING ACCURACY
Congratulations ISRO. Every member of the team who worked on building and designing this mission and the satellite are Heroes.

Now on to orbit lowering and MIP

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Re: Chandrayan-1 mission launched succesfully

Postby RavinM » 08 Nov 2008 18:48

Great! congrats ISRO & congrats INDIA, keep shining!

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Re: Chandrayan-1 mission launched succesfully

Postby Rupesh » 08 Nov 2008 18:50

Congrats ISRO...we have done it....
Yipeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeee :lol:

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Re: Chandrayan-1 mission launched succesfully

Postby sumishi » 08 Nov 2008 18:57

prashanth wrote:Congratulations to ISRO and all Indians. :)

Rahul M wrote:sumishi, are you convinced now that ISRO does know the mass of the moon ? :wink:


I wonder how many sleepless nights he spent worrying about this. :wink:

:D Two nights, to be precise, till I came to know through this forum that they are not going for the initial mission trajectory plan (a "pot-shot" approach) but were going for a very careful multi-earth orbit tactics for calibration purposes -- basically a statistical approach to orbit determination. This gives a lot of latitude for corrections if there are gravity "discrepancies."

The neutral point, as mentioned in the Times Magazine and in von Braun's work, does not match with pre moon-probe days' figure, and even the later editions of Encyclopedia Britannica raised the neutral point value near to that quoted in von Braun's work. Maybe there is some very complicated calculation which in the final analysis keeps the moon's gravity at one-sixth. :) I would certainly like to know the gravity of the moon from ISRO's data, if it is forthcoming.

Anyways, i am GLAAAD the fears were unfounded! :D
Last edited by sumishi on 08 Nov 2008 19:34, edited 1 time in total.


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