Wednesday, October 12, 2011

Chandrayaan


                                                      ABSTRACT
ISRO successfully launched its first unmanned moon mission, Chandrayaan-1, mounted on PSLVC11 at 0622 hrs IST on October 22, 2008. The spacecraft was placed into lunar orbit and will survey the surface of the moon in greater detail than ever before and attempt to locate resources. As per the agreement between ISRO and NASA, two NASA instruments are   also part of the Chandrayaan mission. Chandrayaan-1 is the first spacecraft mission of ISRO beyond Earth orbit. Chandrayaan-1 will be followed by Chandrayaan-2 which features a lander and a rover. India and Russia will jointly participate in this project.



INTRODUCTION:  
The Indian Space Research Organization (Bhāratīya Antariksh Anusandhān Sangaṭn) or ISROis India's national space agency. With its headquarters in Bangalore, ISRO employs approximately 20,000 people, with a budget of around Rs. 65 billion. Its mandate is the development of technologies related to space and their application to India's development. The current Chairman of ISRO is G. Madhavan Nair. In addition to domestic payloads, it offers international launch services.

Moon: Our Nearest Celestial Neighbour
Moon is the most prominent object in the night sky. From time immemorial, moon is familiar to humans. Moon is the nearest celestial body to Earth and lies at a distance of about 384,000 km from here. And, Moon is the only natural satellite of Earth. It travels round Earth once in 27.3 days and takes the same time to spin around its own axis. Thus, one hemisphere of the moon ('the farside') is not visible to us.

In terms of diameter, moon is one fourth the size of Earth and its mass is 1/81 of Earth. Gravity on the surface of the moon is only one sixth of that on Earth.
 




Parameter
Earth
Moon

Diameter
12,742km
3,474km

Mass
5.9x1024kg
7.475x1022kg

Volume
1.08 3206x1021m3
2.199X1019m3

Density
5.52g/cm3
3.34g/cm3



Surface Gravity
1g
0.166g

Like Earth, the moon too is a world with mountains, plateaus, plains, lowlands, and of course, craters. But, unlike Earth, the moon does not have an atmosphere. Thus, liquid water cannot exist on the moon. But, results from the recent unmanned spacecraft missions have raised the possibility of what appears to be the presence of water ice in the lunar polar regions. Formation and evolution of our moon are of importance in understanding the history of our solar system.


Moon: In Mythology and Literature
Similar to many other ancient civilizations, the moon finds a prominent place in Indian mythology too. In ancient Indian literature, the moon is considered to be god and is symbolised by Soma. Many poets of India, including the famous ancient Sanskrit poet Kalidasa, have chosen the moon as the subject of their poems. The moon, especially the full moon, has been treated as an object of beauty and compared with beautiful things or people. In one of his verses, Kalidasa requests his patron king Bhojaraja to provide him with a sumptuous meal that includes curds made from buffalo milk resembling moonlight during the post monsoon season.

A depiction of Indian moon god Chandra
Similarly, for over 2000 years, various science fiction writers from the second century AD Greek writer Lucien to the 19th century science fiction writer Jules Verne have treated the moon as the target of their exploring heroes.





Moon: Exploration Begins in the Space Age
   
Though the moon is familiar to humans since time immemorial, they were able to clearly see and appreciate the surface features of the moon only four centuries ago following the invention of the telescope. After the dawn of the space age in October 1957, moon became the prime target of exploration partly due to its proximity to Earth.
In September 1959, the Soviet Luna 2 hit the lunar surface while Luna 3 took the photographs of the far side of the Moon and transmitted them to Earth. In 1966, Luna 9 gently landed on the lunar surface. In the late 60s and early 70s, Soviet spacecraft brought back small soil and rock samples from the moon and landed Lunakhod-1 and 2 robotic vehicles on the lunar surface. Also during the 1960s, unmanned American Ranger, Surveyor and Lunar Orbiter spacecraft conducted detailed exploration of the moon. This was followed by successful human landing on the moon in Apollo spacecraft during 1969-72.


  

                                            
            Ranger                                             Surveyor                                 Man on the moon  

                                      
            Luna 2                                              Luna 9                                           Lunar Orbiter 

                 
            Luna 16                                        Lunakhod 1     
        
Moon: Still Unanswered Questions


Moon is the only celestial body towards which dozens of manned and unmanned spacecraft have been launched. Moreover, moon is the only world other than Earth on which humans have set foot. The unmanned and manned spacecraft sent to the moon have provided plenty of information of scientific value.
But this does not mean that every important aspect of the moon is known to humans. On the contrary, there are many secrets which the moon is yet to reveal.
For example, there is no unanimous agreement in the scientific community about the origin and evolution of the moon. Additionally, mineralogy of the moon is yet to be understood in much finer detail. Similarly, the presence of Helium-3, said to be a relatively clean fuel for the future nuclear fusion reactors, is yet to be quantified on the Moon. And, the debate over the presence of water in the permanently shadowed regions of the moon's polar areas is not yet settled.
                                    
    Moon’s Origin                                      Mineralogy                                         Helium-3
 
     Moon’s Polar
         region
 



Thus, from the point of view of human intellectual quest as well as in the context of the future of humanity, exploration of the moon is very important.
In the past few years, there has been a renaissance with regard to lunar exploration. Many countries and international space agencies, including the European Space Agency (ESA), Japan, China, the US and Russia have undertaken or in the process of undertaking unmanned exploratory missions to the moon. These missions intend to seek answers to some of the fundamental questions that concern the moon. India's Chandrayaan-1 is an integral part of that renewed interest of the international scientific community about the moon.





          India in Space
Today, India is one of the very few countries that have significant achievements to their credit in the arena of space. The Indian Space Research Organisation (ISRO) has designed, developed and built a variety of satellites. And, it has successfully launched many of them into their intended orbits. More importantly, the country has used its satellites for the rapid expansion of its national infrastructure including telecommunications, TV broadcasting, weather monitoring, education, public health, agriculture and rural development. More recently, India has provided many space-based services including launch services to foreign customers on a competitive basis. With ample experience and many successes in Earth orbit, ISRO has now taken up Chandrayaan-1, its first bold step beyond Earth orbit into deep space.



                                                                 
Chandrayaan-1: The Goals
   
The primary objectives of Chandrayaan-1 are:
1. To expand scientific knowledge about the moon
2. To upgrade India's technological capability
3. To provide challenging opportunities for planetary
research to the younger generation of Indian scientists
Chandrayaan-1 aims to achieve these well defined objectives through high resolution remote sensing of the moon in the visible, near infrared, microwave and X-ray regions of the electromagnetic spectrum. With this, preparation of a 3-dimensional atlas of the lunar surface and chemical mapping of entire lunar surface is envisaged.
               Readying the spacecraft for
                          Thermo-vacuum test
Chandrayaan-1: The Payloads

   
There are 11 payloads (scientific instruments) through which Chandrayaan-1 intends to achieve its objectives. The instruments were carefully chosen on the basis of many scientific and technical considerations as well as their complementary /supplementary nature.

They include five instruments entirely designed and developed in India, three instruments from European Space Agency (one of which is developed jointly with India and the other with Indian contribution), one from Bulgaria and two from the United States. Thus, Chandrayaan-1 is a classic example of international cooperation that has characterised the global space exploration programmes of the post
cold war era.




The Indian payloads are:
1. Terrain Mapping Camera (TMC): The aim of this instrument is to completely map the topography of the moon. The camera works in the visible region of the electromagnetic spectrum and captures black and white stereo images. It can image a strip of lunar surface which is 20 km wide and resolution of this CCD camera is 5 m. Such high resolution imaging helps in better understanding of the lunar evolution process as well as in the detailed study of the regions of scientific interest. When used in conjunction with data from Lunar Laser Ranging Instrument (LLRI), it can help in better understanding of the lunar gravitational field as well. TMC is built by ISRO's Space Applications Centre (SAC) of Ahmedabad.
 
 
2. Hyperspectral Imager (HySI): This CCD camera is designed to obtain the spectroscopic data for mapping of minerals on the surface of the moon as well as for understanding the mineralogical composition of the moon's interior. Operating in the visible and near infrared region of the electromagnetic spectrum, it will image a strip of lunar surface which is 20 km wide with a resolution of 80 m. It will split the incident radiation into 64 contiguous bands of 15 nanometer (nm) width. HySI will help in improving the already available information on mineral composition of the lunar surface. HySI is also built by SAC.
 
 
3. Lunar Laser Ranging Instrument (LLRI): This instrument aims to provide necessary data for determining the accurate altitude of Chandrayaan-1 spacecraft above the lunar surface.It also helps in determining the global topographical field of the Moon as well as in generating an improved model for the lunar gravity field. Data from LLRI will enable understanding of the internal structure of the moon and the way large surface features of the moon have changed with time. The infrared laser source used for LLRI is Nd-YAG laser wherein Neodimium atoms are doped into a Yittrium Aluminium Garnet crystal. The wavelength of the light emitted by LLRI is 1064 nm. LLRI is built by ISRO's Laboratory for Electro Optic Systems (LEOS) of Bangalore.
 
4. High Energy X-ray Spectrometer (HEX): This is the first planetary experiment to carry out spectral studies at 'hard' X-ray energies using good energy resolution detectors. HEX is designed to help explore the possibility of identifying polar regions covered by thick water-ice deposits as well as in identifying regions of high Uranium and Thorium concentrations. Knowledge of the chemical composition of the various solar system objects such as planets, satellites and asteroids provides important clues towards understanding their origin and evolution. HEX uses Cadmium Zinc Telluride (CZT) detectors and is designed to detect hard X-rays in the energy range of 20 kilo electron Volts (keV) to about 250 keV. HEX is built jointly by Physical Research Laboratory (PRL) of Ahmedabad and ISRO Satellite Centre of Bangalore.
 
 
5. Moon Impact Probe (MIP): The primary objective of MIP is to demonstrate the technologies required for landing a probe at the desired location on the moon. Through this probe, it is also intended to qualify some of the technologies related to future soft landing missions. This apart, scientific exploration of the moon at close distance is also intended using MIP.
The 29 kg Moon Impact Probe consists of a C-band Radar Altimeter for continuous measurement of altitude of the Probe above lunar surface and to qualify technologies for future landing missions, a Video Imaging System for acquiring images of the surface of moon from the descending probe and a Mass Spectrometer for measuring the constituents of extremely thin lunar atmosphere during its 20 minute descent to the lunar surface. MIP is developed by Vikram Sarabhai Space Centre of Thiruvananthapuram.
     
Of the six payloads from abroad in Chandrayaan-1, three are from the European Space Agency (ESA). They are:
 



1. Chandrayaan-1 Imaging X-ray Spectrometer (C1XS): This instrument intends to carry out high quality mapping of the moon using X-ray fluorescence technique for measuring elemental abundance of Magnesium, Aluminium, Silicon, Iron and Titanium distributed over the surface of the moon. This will help in finding answers to key questions about the origin and evolution of the moon. The instrument is sensitive to X-rays in the energy range of 0.5—10 keV. C1XS is jointly developed by Rutherford Appleton Laboratory of England and ISRO Satellite Centre, Bangalore.
 
 
2. Smart Near Infrared Spectrometer (SIR-2): This instrument aims to study the lunar surface to explore the mineral resources, the formation of its surface features, the way different layers of the moon's crust lie over one another and the way materials are altered in space. It has the ability to detect and record near Infrared radiation coming from the moon. Since this is the radiation band through which various minerals and ices reveal their existence, SIR-2 is well suited for making an inventory of various minerals on the lunar surface. It can detect the radiation in the range of 0.93-2.4 micron. SIR-2 is developed by Max Plank Institute of Germany.
 
 
3. Sub keV Atom Reflecting Analyser (SARA): The aim of this instrument is to study the surface composition of the moon, the way in which moon's surface reacts with solar wind, the way in which surface materials on the surface of the moon change and the magnetic anomalies associated with the surface of the moon. SARA will be sensitive to neutral atoms that have escaped from the surface of the moon and having energy in the range of 10 eV—2 keV (kilo-electron-Volt). The instrument has been developed by the Swedish Institute of Space Physics and Space Physics Laboratory (SPL) of ISRO's Vikram Sarabhai Space Centre built its processing electronics.
 
 
The Bulgarian Payload onboard Chandrayaan-1 is:
4. Radiation Dose Monitor (RADOM): This instrument aims to qualitatively and quantitatively characterise the radiation environment in space around the moon’s vicinity. It will help study the radiation dose map of space near the moon at various latitudes and altitudes. Besides, the instrument helps in investigating whether the space near the moon shields it from cosmic rays coming from distant cosmic sources as well as those from the sun. Such studies and investigations will be helpful in the important task of finding out the shielding requirements of future manned missions to the moon. RADOM is developed by the Bulgarian Academy of Sciences.
 
 
The NASA instruments carried by Chandrayaan-1 are:
5. Mini Syntheic Aperture Radar (MiniSAR): This is one of the two scientific instruments of the United States flown in Chandrayaan-1 mission. MiniSAR is from Johns Hopkins University's Applied Physics Laboratory and Naval Air Warfare Centre, USA through NASA. Working in S-band, MiniSAR is mainly intended for the important task of detecting water ice in the permanently shadowed regions of the Lunar poles up to a depth of a few meters. It can optimally distinguish water ice from the dry lunar surface. MiniSAR has a spatial resolution of about 75 metres.

 
6. Moon Mineralogy Mapper (M3): This is an imaging spectrometer which is intended to assess and map lunar mineral resources at high spatial and spectral resolution to support planning for future targeted missions. It will help in characterising and mapping lunar minerals in the context of the moon's early geological evolution. M3 is from Brown University and Jet Propulsion Laboratory through NASA. M3 may also help in identifying water ice in the lunar polar areas. Its operating range is 0.7 to 3 micrometre. The instrument has a spatial resolution of 70 m.
   

The Chandrayaan-1: The Spacecraft

 

Loading Chandrayaan-1 spacecarft
into Thermo-vacuum Chamber

The fully integrated
Chandrayaan-1 spacecraft

Chandrayaan-1 spacecraft carrying 11 scientific instruments weighs about 1400 kg at the time of its launch and is shaped like a cuboid with a solar panel projecting from one of its sides. The state of the art subsystems of the spacecraft, some of them miniaturised, facilitate the safe and efficient functioning of its 11 scientific instruments.
The spacecraft structure has been mainly built using composites and Aluminium honeycomb material. The Thermal subsystem consisting of paints, tapes, multi layer insulation blanket, optical solar reflectors, heat pipes, heaters and temperature controllers, ensures the proper functioning of the spacecraft by keeping its temperature within acceptable limits. The Mechanisms subsystem of Chandrayaan-1 spacecraft takes care of the deployment of its solar panel and the steering of the dual gimballed antenna.
The spacecraft is powered by a single solar panel generating a maximum of 700 W. A 36 Ampere-Hour (Ah) Lithium ion battery supplies power when the solar panel is not illuminated by the sun. The Telemetry, Tracking and Command subsystem of Chandrayaan-1 working in S-band takes care of radioing the detailed spacecraft health information, facilitating the knowledge about spacecraft's position in space and allows the reception and execution of commands coming from earth by the spacecraft.
Sun and star sensors as well as gyroscopes provide the orientation reference for spacecraft in space. The Attitude and Orbit Control subsystem, essentially the brain of Chandrayaan-1, consisting of a Bus Management Unit (BMU), reaction wheels and thrusters, ensures the proper orientation and stability of the spacecraft as well as in changing its orbit during different phases of its flight.
To make Chandrayaan-1 spacecraft to escape from orbiting Earth and to travel towards the moon, its liquid apogee motor (LAM) is used. Liquid propellants needed for LAM as well as thrusters are stored onboard the spacecraft.
Chandrayaan-1 spacecraft's Communications subsystem transmits the precious information gathered by its eleven scientific instruments to Earth in 'X-band' through its Dual Gimballed Antenna.
Chandrayaan-1 spacecraft is built at ISRO Satellite Centre, Bangalore with contributions from ISRO/Department of Space (DOS) establishments like Vikram Sarabhai Space Centre (VSSC), Liquid Propulsion Systems Centre (LPSC) and ISRO Inertial Systems Unit (IISU) of Tiruvananthapuram, Space Applications Centre (SAC) and Physical Research Laboratory (PRL) of Ahmedabad and Laboratory forElectro-optic Systems (LEOS) of Bangalore.



Description: Spacecraft for lunar mission is :

· 
Cuboid in shape of approximately 1.5 m side.
· 
Weighing 1380 kg at launch and 675 kg at lunar orbit.
· 
Accommodates eleven science payloads.
· 
3-axis stabilized spacecraft using two star sensors, gyros and four reaction wheels.
· 
The power generation would be through a canted single-sided solar array   to provide required power during all phases of the mission. This deployable solar array consisting of a single panel generates 750W of peak power. Solar array along with yoke would be stowed on the south deck of the spacecraft in the launch phase. During eclipse, spacecraft will be powered by Lithium ion (Li-Ion) batteries.
· 
After deployment, the solar panel plane is canted by 30º to the spacecraft pitch axis.
· 
The spacecraft employs a X-band, 0.7m diameter parabolic antenna for payload data transmission. The antenna employs a dual gimbal mechanism to track the earth station when the spacecraft is in lunar orbit.


· 
The spacecraft uses a bipropellant integrated propulsion system to reach lunar orbit as well as orbit and attitude maintenance while orbiting the Moon.
· 
The propulsion system carries required propellant for a mission life of 2 years, with adequate margin.
· 
The Telemetry, Tracking & Command (TTC) communication is in S-band frequency.
· 
The scientific payload data transmission is in X-band frequency.
· 
The spacecraft has three Solid State Recorders (SSRs) Onboard to record data from various payloads.
· 
SSR-1 will store science payload data and has capability of storing 32Gb data.
· 
SSR-2 will store science payload data along with spacecraft attitude information (gyro and star sensor), satellite house keeping and other auxiliary data. The storing capacity of SSR-2 is 8Gb.
· 
M3 (Moon Mineralogy Mapper) payload has an independent SSR with 10Gb capacity.




Chandrayaan-1: The Journey


 
The launch of Chandrayaan-1 takes place from the Second Launch Pad at Satish Dhawan Space Centre, SHAR, Sriharikota in the Nellore district of Andhra Pradesh state. Sriharikota is situated at a distance of about 80 km to the North of Chennai.
Chandrayaan-1 spacecraft begins its journey from earth onboard India's Polar Satellite Launch Vehicle (PSLV-C11) and first will reach a highly elliptical Initial Orbit (IO). In the Initial Orbit, the perigee (nearest point to earth) is about 250 km and apogee (farthest point from the earth) is about 23,000 km.
After circling the Earth in its Initial Orbit for a while, Chandrayaan-1 spacecraft is taken into two more elliptical orbits whose apogees lie still higher at 37,000 km and 73,000 km respectively. This is done at opportune moments by firing the spacecraft's Liquid Apogee Motor (LAM) when the spacecraft is near perigee.
Subsequently, LAM is fired again to take Chandrayaan-1 spacecraft to an extremely high elliptical orbit whose apogee lies at about 387,000 km.
In this orbit, the spacecraft makes one complete revolution around the Earth in about 11 days. During its second revolution around the Earth in this orbit, the spacecraft will approach the Moon's North pole at a safe distance of about a few hundred kilometers since the Moon would have arrived there in its journey round the Earth.
Once the Chandrayaan-1 reaches the vicinity of the Moon, the spacecraft is oriented in a particular way and its LAM is again fired. This slows down the spacecraft sufficiently to enable the gravity of the moon to capture it into an elliptical orbit.
Following this, the height of the spacecraft's orbit around the moon is reduced in steps. After a careful and detailed observation of perturbations in its intermediate orbits around the moon, the height of Chandrayaan-1 spacecraft's orbit will be finally lowered to its intended 100 km height from the lunar surface.
Later, the Moon Impact Probe will be ejected from Chandrayaan-1 spacecraft at the earliest opportunity to hit the lunar surface in a chosen area. Following this, cameras and other scientific instruments are turned ON and thoroughly tested. This leads to the operational phase of the mission. This phase lasts about two years during which Chandrayaan-1 spacecraft explores the lunar surface with its array of instruments that includes cameras, spectrometers and SAR.

     


PSLV-C11: The Launcher
 


PSOM-XLs surrounding
the first stage

Nozzle End segment
of the first stage


   Second Stage 
with its Vikas engine  
  
PSLV-C11, chosen to launch Chandrayaan-1 spacecraft, is an uprated version of ISRO's Polar Satellite Launch Vehicle standard configuration. Weighing 316 tonnes at lift-off, the vehicle uses larger strap-on motors (PSOM-XL) to achieve higher payload capability.
PSLV is the trusted workhorse launch Vehicle of ISRO. During 1993-2008 period, PSLV had twelve consecutively successful launches carrying satellites to Sun Synchronous, Low Earth and Geosynchronous Transfer Orbits. Now, its fourteenth flight is being used for launching Chandrayaan-1 to moon.
PSLV has repeatedly proved its reliability and versatility by launching 29 satellites into a variety of orbits. Of these, ten remote sensing satellites of India, an Indian satellite for amateur radio communications, a recoverable Space Capsule (SRE-1) and fourteen satellites from abroad were put into polar Sun Synchronous Orbits  (SSO) of 550-820 km heights.
   Hoisting the
third & fourth stages
Besides, PSLV has launched two satellites from abroad into Low Earth Orbits of low or medium inclinations. This apart, PSLV has launched KALPANA-1, a weather satellite of India, into Geosynchronous Transfer Orbit (GTO).

PSLV-C11vehicle assembled upto
fourth stage at
Vehicle Assembly Building

      Chandrayaan-1
in PSLV-C11envelope                                                                                                                                                                    







PSLV-C11 Flight Profile


 
                   



PSLV was initially designed by ISRO to place 1,000 kg class Indian Remote Sensing (IRS) satellites into 900 km polar SunSynchronous Orbits. Since the first successful flight in October 1994, the capability of PSLV was successively enhanced from 850 kg to 1,600 kg. In its ninth flight on May 5, 2005 from the Second Launch Pad (SLP), PSLV launched ISRO's remote sensing satellite,1,560 kg CARTOSAT-1 and the 42 kg Amateur Radio satellite, HAMSAT, into a 620 km polar Sun Synchronous Orbit. The improvement in the capability over successive flights has been achieved through several means. They include increased propellant loading in the stage motors, employing composite material for the satellite mounting structure and changing the sequence of firing of the strap-on motors.
PSLV-C11 is 44.4 metre tall and has four stages using solid and liquid propulsion systems alternately. The first stage, carrying 138 tonne of propellant, is one of the largest solid propellant boosters in the world. Six solid propellant strap-on motors (PSOM-XL), each carrying twelve tonne of solid propellant, are strapped on to the first stage. The second stage




carries 41.5 tonne of liquid propellant. The third stage uses 7.6 tonne of solid propellant and the fourth has a twin engine configuration with 2.5 tonne of liquid propellant.
The 3.2 metre diameter metallic bulbous payload fairing protects the satellites and it is discarded after the vehicle has cleared dense atmosphere. PSLV employs a large number of auxiliary systems for stage separation, payload fairing separation and so on. It has sophisticated systems to control the vehicle and guide it through the predetermined trajectory. The vehicle performance is monitored through telemetry and tracking. The main modification in PSLV-C11 compared to its standard configuration is the use of larger strap-on motors (PSOM-XL) containing more propellants.
Vikram Sarabhai Space Centre (VSSC), Thiruvananthapuram, designed and developed PSLV-C11. ISRO Inertial Systems Unit (IISU) at Thiruvananthapuram developed the inertial systems for the vehicle. Liquid Propulsion Systems Centre (LPSC), also at Thiruvananthapuram, developed the liquid propulsion stages for the second and fourth stages of PSLV-C11 as well as reaction control systems. SDSC SHAR processed the solid motors and carries out launch operations. ISRO Telemetry, Tracking and Command Network (ISTRAC) provides telemetry, tracking and command support during PSLV-C11's flight.



The Ground Segment
 
32m DSN Antenna

                            18m Antenna


During the various phases of its flight, Chandrayaan-1 spacecraft will send detailed information about its health to Earth through its transmitter. At the same time, the spacecraft will be ready to receive radio commands sent from Chandrayaan-1Spacecraft Control Centre instructing it to perform various tasks. Besides, the spacecraft receives, modifies and retransmits the radio waves sent by ground antennas in a precise way. This plays a crucial role in knowing its position and orbit at a particular instant of time. All these happen at 'S-band' frequencies in the microwave region of the electromagnetic spectrum.
Additionally, as it orbits the Moon, the spacecraft sends valuable imagery and other scientific information to Earth through X-band (at a higher frequency compared to S-band), which also lies in the microwave region.
But, such information is transmitted through radio at a very low power of a few watts. Thus, radio signals carrying that precious information become extremely feeble by the time they travel 400,000 km from the Moon and reach the earth.
The Ground Segment of Chandrayaan-1 performs the crucial task of receiving the radio signals sent by spacecraft. It also transmits the radio commands to be sent to the spacecraft during different phases of its mission. Besides, it processes and safe keeps the scientific information sent by Chandrayaan-1 spacecraft.
ISRO Telemetry, Tracking and Command Network (ISTRAC) had a lead role in establishing the Ground Segment facility of Chandrayaan-1 along with ISRO Satellite Centre (ISAC) and Space Applications Centre (SAC). The Ground Segment of Chandrayaan-1 consists of:
1. Indian Deep Space Network (IDSN)
2. Spacecraft Control Centre (SCC)
3. Indian Space Science Data Centre (ISSDC)





The Indian Deep Space Network performs the important task of receiving the radio signals transmitted by Chandrayaan-1 spacecraft that become incredibly feeble by the time they reach the earth. Besides, it can send commands to the spacecraft at a power level of up to 20 kilowatts. IDSN consists of two large parabolic antennas, one with 18 m and the other 32 m diameter at Byalalu, situated at a distance of about 35 km from Bangalore. Of these, the 32 m antenna with its 'seven mirror beam waveguide system' is indigenously designed, developed, built, installed, tested and qualified. The 18 m antenna can support Chandrayaan-1 mission, but the 32m antenna can support Chandrayaan-1 and any spacecraft mission further deep into space.
During the initial phase of the mission, besides these two antennas, other ground stations of ISTRAC Network at Lucknow, Sriharikota, Bangalore, Thiruvananthapuram, Port Blair, Mauritius, Brunei, Biak (Indonesia) and Bearslake (Russia) as well as external network stations at Goldstone, Applied Physics Laboratory in Maryland, Hawaii (all three in USA), Brazil and Russia support the mission.
The Spacecraft Control Centre, located near ISTRAC campus at Peenya, North of Bangalore, is the focal point of all the operational activities of Chandrayaan-1 during all the phases of the mission. Commands to be transmitted to Chandrayaan-1 spacecraft to maintain its health as well as to make it perform various tasks originate from here. Experts specialising in various spacecraft subsystems as well as spacecraft mission operations personnel will be available at SCC.
The Indian Space Science Data Centre forms the third element of the Chandrayaan-1 ground segment. ISSDC receives (from IDSN as well as other external stations that support Chandrayaan-1), stores, processes, systematically archieves, retrieves and distributes the precious scientific information sent by Chandrayaan-1 cameras, spectrometers and other scientific instruments from the lunar orbit. It has state-of -the- art computers and data storage devices. ISSDC is also located at Byalalu.

Spacecraft Control Centre (SCC)

A view of Indian Space Science Data Centre (ISSDC)



Mission Sequence:


· 
Chandrayaan-1 spacecraft was launched from the Satish Dhawan Space Centre, SHAR, Sriharikota by PSLV-XL (PSLV-C11) on 22 October 2008 at 06:22 hrs IST in an highly elliptical initial orbit (IO) with perigee (nearest point to the Earth) of 255 km and an apogee (farthest point from the Earth) of 22,860 km, inclined at an angle of 17.9 deg to the equator. In this initial orbit, Chandrayaan orbited the Earth once in about six and a half hours.
· 
Subsequently, the spacecraft's Liquid Apogee Motor (LAM) firing was done on 23 October at 09:00 hrs IST, when the spacecraft was near perigee, to raise the apogee to 37,900 km while the perigee to 305 km. The spacecraft took eleven hours to go round the Earth once.
· 
The orbit was further raised to 336 km x 74,715 km on 25 October at 05:48 hrs IST. In this orbit, spacecraft took about twenty-five and a half hours to orbit the Earth once.
· 
The LAM was fired again on 26 October at 07:08 hrs IST to take the Chandrayaan-1 spacecraft to extremely high elliptical orbit with apogee 164,600 km and perigee at 348 km. Chandrayaan-1 took about 73 hours to go round the Earth once.
· 
On 29 October, orbit raising was carried out at 07:38 hrs IST to raise the apogee to 267,000 km and perigee to 465 km. Chandrayaan’s present orbit extends more than half the way to moon and takes about six days to orbit the Earth.
· 
On 4 November at 04:56 hrs IST, Chandrayaan entered the Lunar Transfer Trajectory with an apogee of 380,000 km.
· 
On 8 November at 16:51 hrs IST, the spacecraft’s Liquid engine was fired to reduce its velocity to insert the spacecraft in the lunar orbit (LOI) and enable lunar gravity to capture it. As a result, the spacecraft was in an elliptical orbit with periselene (nearest point to the moon) of 504 km and aposelene (farthest point from the moon) of 7,502 km.
· 
The first orbit reduction manoeuvre was carried out successfully on 9 November at 20:03 hrs IST. Thus the spacecraft was in lunar orbit with 200 km periselene. The aposelene remains unchanged (i.e 7,502 km).
· 
After careful and detailed observation, a series of three orbit reduction manoeuvres were successfully carried out and the spacecraft’s orbit was reduced to its intended operational 100 km circular polar orbit on November 12.
· 
On 14 November at 20:06 hrs IST, the Moon Impact Probe (MIP) was ejected from the Chandrayaan-1 spacecraft and hard landed on the lunar surface near the South Polar Region at 20:31 hrs IST after 25 minutes journey. It placed the Indian tricolour, which was pasted on the sides of MIP on the Moon.
· 
Currently, the scientific instruments/payloads are being commissioned sequentially and exploration of Moon with the array of onboard instruments have begun.






The Future
 


Chandrayaan-1 is the first spacecraft mission of ISRO beyond Earth orbit. Chandrayaan-1 will be followed by Chandrayaan-2 which features a lander and a rover. India and Russia will jointly participate in this project. However, there may be a provision to accommodate payloads from other space agencies as happened in Chandrayaan-1. This apart, studies are being conducted by ISRO on sending unmanned spacecraft to planet Mars as well as to asteroids and comets. Through such programmes, ISRO intends to undertake the exploration of space besides its primary mission of developing and utilising space technology for the overall development of the country.
                                                                                                             



REFERENCES 
1. www.google.com
2. www.isro.org/chandrayaan/htmls/home.htm
3. www.isro.org/chandrayaan/htmls/mission_sequence.htm
4. www.isro.gov.in         17 nov. 2008
6. www.isro.org/pslv-c11/brochure/page(1-12).htm
7.  en.wikipedia.org/wiki/Indian_ Space_Research_organisation       23 nov. 2008