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Chandrayaan-1: The Remarkable Story of India's Maiden Moon Shot
Embark on the journey of India's Maiden Moon Shot: Chandrayaan-1, right from how the mission was conceived to finding water on the lunar surface.
Vikram Sarabhai’s vision to start the Indian Space Programme involved building satellites and rockets for the betterment of the everyday life of the citizens of independent India. On 18th April 2001, ISRO’s Geosynchronous Satellite Launch Vehicle (GSLV) successfully launched. And thus, ISRO achieved all goals set forth by Dr Sarabhai. It was, therefore, a suitable time for India to seek new avenues and explore planetary missions. This called for India’s very own moon shot: Chandrayaan-1.
The Genesis of Indian Lunar Mission – Chandrayaan-1
In the year 1998, India carried out the Pokhran nuclear tests in the month of May. The tests were a technological and strategic feat, for that they were done hidden from the whole world. To commemorate this accomplishment, PM Atal Bihari Vajpayee, declared 11th May as the National Technology Day. You may be wondering how some nuclear tests done by the military and DRDO are relevant to the non-military Indian Space agency. You’ll know in a minute.
On 11th May 1999, the first Technology Day was celebrated. At a function in New Delhi, Dr K Kasturirangan indicated the possibility of India undertaking a lunar mission using the PSLV. This was the first mention of an Indian Lunar Mission. He even said that such a mission could take time and ‘if all goes well, it could be a reality by 2008.’ I wonder if he knew how he had just predicted the future!
Soon after, in 2000, a National Lunar Mission Task Force was set up with an aim to prepare a report and submit for parliamentary approval. In 2003, the report was unanimously recommended to the government by a pool of hundred scientists. The idea of a lunar mission picked up parliamentary support and the Prime Minister mentioned, “… now I think there is a political interest in this; there is a general societal interest in this. I would certainly make an announcement.” On 15th August 2003, he declared the Chandrayaan-1 mission. There is an interesting story behind the announcement.
ISRO had recommended Mr Bajpayee to call the mission Somayaan, but he announced it as Chandrayaan-1. When asked later, he replied that he consulted some Sanskrit scholars and Chandrayaan was a better name. He also added that he put it as Chandrayaan-1 because India is not going for one mission; we need to have a long-term planetary exploration programme. Perhaps, this is the kind of attitude that a nation requires from its Political leaders. Finally, in November 2003, Chandrayaan-1 got parliamentary approval.
The mission is Approved! What to pack for the Journey?
Parliament approved Chandrayaan-1. The budget was allotted. We were ready to go to the Moon, but what to take along? To understand the science (payloads) chosen for Chandrayaan, let’s look at the history of Lunar Exploration.
A brief history of Lunar Exploration
The Soviets and Americans utilized every trick in the book to explore the lunar surface back in the cold war era. With the advent of space-age by Sputnik-1 launch, both the nations were engaged in a space war. The Soviets reached the Moon first with their Luna satellites and even landed rovers called ‘Lunakhods’ to explore the surface. To top it all off, the USA sent humans to the Moon. Apollo was a huge success. We not only did experiments on the Moon, but the astronauts also brought lunar regolith (soil) samples back to the Earth. Even, India got some of these samples (thanks to Dr Sarabhai’s connections) to undertake experiments.
But after Luna and Apollo, the Moon got sidelined. There was no dedicated mission to Moon for the next 14 years. Finally, with the advent of Asian space nations like Japan, China, and India came the Renaissance of Lunar Exploration. Clementine, a NASA spacecraft, detected the presence of water ice in the south polar region of Moon in 1994. This renewed interest about the Moon and 21st Century saw a burst of missions. ESA launched SMART-1 in 2003, Japan Kaguya in Sept 2007, China Chang’e-1 in Oct 2007 and finally, India Chandrayaan-1 in October 2008.
The Search for Payloads for Chandrayaan-1
After the parliamentary approval in 2003, a Science Advisory Board (SAB) was established by ISRO. They took the National Lunar Mission Task Report as a starting point while comparing the planned missions by ESA, Japan, China, and the USA. Finally, they decided on five Indian payloads. The spacecraft configuration zeroed in on a model with had some margins in mass, power and space. ISRO, therefore, decided to accommodate another payload of maximum 10 Kgs and 10 W power consumption. SAB then called an Announcement of Opportunity for any lab outside ISRO.
The Indian Space Agency received a whopping 26 number of proposals from across continents. The SAB liked two of NASA’s instruments, but they both together exceeded the 10 Kg requirement. After some discussions and deliberations, ISRO optimized Chandrayaan-1 to accommodate 25 Kg. NASA and ISRO optimized the two instruments, and suddenly, Chandrayaan-1 had a total of extra six science payloads.
In 2004, a scaled model of Chandrayaan-1 with four Indian and six foreign payloads was presented at ‘Sixth International Conference on the Exploration and Utilization of the Moon’. The conference was held in Udaipur, Rajasthan, in November 2004. But a veteran space scientist’s suggestion added a vital payload to the spacecraft.
Dr APJ Abdul Kalam, the then President of India, suggested adding a lander/ impactor to Chandrayaan-1. And hence, an 11th payload, Moon Impact Probe was added.
Overview of the Spacecraft
To further enhance the already acquired knowledge about the Moon.
To achieve further progress in India’s capacity to build more efficient rockets and satellites, especially through miniaturization.
To provide challenging opportunities for young scientists of India to do research in new and exciting areas like the study of planets.
To photograph the surface of the Moon in such a way that length, breadth, and height of the surface features of the Moon can be found out accurately. This is called 3D imaging and can lead to the preparation of a more accurate map of the Moon.
To prepare a map of the Moon accurately showing the way in which various elements and minerals are distributed over its surface.
To prepare a map of the Moon that shows different geological areas there clearly
Size and Shape: 1.5 m cuboid with 600 Kg mass in the Lunar Orbit
Control: 3-axis stabilized using reaction wheels and attitude control thrusters;
sun sensors, star sensors, and miniaturized DTGs for orientation reference.
Power: 700 W Solar Panel with 36Ah Li-Ion Battery
Propulsion: Bi-propellant Liquid Apogee Motor
Communication: S-band for Telemetry and X-band for Payload data transmission
PSLV’s new variant (launching for the first time) PSLV-XL launched Chandrayaan-1 on 22nd October 2008. The launch vehicle placed the spacecraft in a 250 km X 23,000 km initial Earth Parking Orbit. This was followed by a series of perigee manoeuvres to raise the apogee to 380,000 km in 17 days. Finally, Chandrayaan-1 was placed in 100 km circular orbit around Moon on 12th November 2008.
The trajectory to reach Moon was a special one. It took a long time but less fuel. A whole different article is planned on understanding this trajectory.
Chandrayaan-1 was India’s first mission above the 36,000 km Geosynchronous range. This required better and more efficient ground segments to be built. After surveying several possible sites, ISRO finalized to set up two large dish antennas at Byalalu, about 40 km from Bangalore. This established the Indian Deep Space Network. L&T was one of the industrial partners involved in setting up this facility.
Along with IDSN, Indian Space Science Data Centre was established. It aims to store, retrieve and distribute scientific data from Indian Space Science Missions.
Finding Water on the Moon
Over its short mission life, Chandrayaan-1 achieved some great science. Listing all the achievements of scientific data in a single article may not be even possible because scientists are conducting research based on the data even today. But one discovery by India’s maiden lunar mission deserves its story to be told. The discovery of water molecules on the Moon!
NASA’s Moon Mineral Mapper (M3) could detect the presence of H2O molecule and OH by looking at the absorption spectrum of the lunar surface. This meant M3 could look for water in the sunlit areas of the Moon. But it was earlier conjectured that if there is water on the Moon, it’ll be in the dark areas. Therefore, when M3 found traces of hydroxyl in the reflected sunlight, it was a happy surprise for the whole team.
When M3 continued to find traces for months, the team decided it was indeed a breakthrough in lunar science. They decided to try and validate their discovery by using some other spacecraft which had the same capability. NASA’s Deep Impact mission on its return journey from the Comet 9P/Tempel was perfect for this validation. After some discussion and a few months, the team was able to get Deep Impact to look at Moon and there it was. Same features were present in Deep Impact data as well.
To add to all these scientific data, some scientists of M3 team, remembered that Cassini, NASA’s Saturn Exploration Spacecraft, had calibrated its instruments by looking at Moon. They got hold of the Cassini archived data and indeed, the hydroxyl and water signatures were present there as well. Chandrayaan-1 had indeed discovered water on the Moon, and it was published in the Science journal along with Cassini and Deep Impact data.
Other instruments onboard Chandrayaan-1 like the Chandrayaan-1 Altitude Compositional Experiment (ChACE), a part of the Moon Impact Probe (MIP), revealed signals of water (H2O) and carbon dioxide (CO2) molecules as it descended to the lunar surface. Even NASA’s mini-SAR found the presence of sub-surface ice in permanently shadowed areas of the lunar south pole. NASA confirmed this discovery with its LCROSS and LRO missions.
India’s maiden moon shot became the beacon for the discovery of water on the Moon!
End of the Mission
Chandrayaan-1 was overall a highly successful mission. But undertaking a maiden planetary mission with no surprises would be impossible. For us, the DC/DC converters onboard the spacecraft failed earlier in the mission. These failures disabled the spacecraft to utilize the star sensor for orientation referencing. The spacecraft team came up with a unique process of operating the spacecraft using the data from all the science payloads. Therefore Chandrayaan-1 was able to achieve great science, including finding water on the Moon. Finally, on 29th August 2009, all contact was lost subsequent to the failure of redundant DC/DC converters.
Chandrayaan-1: India’s Giant Leap to Moon by B R Guruprasad