Ancient Indian astronomers knew the real scientific causes of the eclipses. Even before Aryabhata (AD 476), the celestial phenomena were explained correctly without any traditional myths, as evident from the extant Panca Sidhantas. India’s Chandrayaan-1 continues this tradition of scientific observation and understanding of the natural phenomena.
The best view of the Moon was available only after Galileo saw it through his telescope. Even the first picture of the crescent Moon he drew with its craters along the line of lunar sunrise matched well with a photograph taken 350 years later. His telescope demolished the traditional idea of the Moon as a smooth celestial body and incurred the wrath of the Church, even as it quietly triggered a scientific revolution in our understanding of the cosmos. Science fiction seems to have revived people’s interest in the study of the Moon and other celestial objects without reference to myths. Jules Verne (1828-1905), a founder of modern science fiction, inspired the founders of astronautics like Tsiolkovsky, Goddard and Oberath. Verne’s classic novels, A Trip to the Moon (1865) and its sequel, Around the Moon (1870), triggered serious studies on real journeys into space.
Despite all the modern telescopes and lunar mission, the Moon has yet to yield much of its secrets. India’s first unmanned lunar mission, Chandrayaan-1, joins the worldwide exploratory journey to the Moon in the International Lunar Decade, which began in 2007.
Chandrayaan’s scientific payloads (525 kg in 100 km lunar orbit) are designed for simultaneous photo, geological and chemical mapping of the lunar surface (Box 20.1). The data will test the early evolutionary history of the Moon and help in determining the nature of the lunar crust.
The Mission Sequence
Chandrayaan-1 was launched on October 22, 2008 from Sriharikota on the east coast, initially into a highly oval-shaped Earth orbit. In order to get the speed and the angle of the final orbit correctly, the spacecraft’s onboard liquid rocket was fired five times on different days, raising the
On November 8, 2008, it entered into the lunar orbit Earlier, at about 500 km from the Moon, the velocity of the spacecraft was reduced so that the Moon’s gravity would capture it. The elliptical lunar orbit was later made circular at 100 km from the surface of the Moon. The experiments have since been switched on and the data are being received and processed by the Deep Space Network. En route, the Terrain Mapping Camera took pictures of Earth and the Moon.
The satellite weighed 1,304 kg at launch and 590 kg in lunar orbit. It is three-axis stabilized to keep itself in correct position with the help of star sensors, four reaction wheels, attitude control thrusters inertial reference unit, accelerometers. The spacecraft has bipropellant propulsion system for use in maintaining its altitude. The propellant is designed for a mission of two years but it can last for some more time. Its deployable solar array has a single panel that generates 700 W of peak power. When the spacecraft does not get sunlight, it is powered by lithium ion batteries. Its parabolic antenna (0.7 m in diameter) transmits data to the Earth station. The satellite has three solid state recorders on board to store data from various payloads. The recorder can store 32 giga bits. Another recorder has 8 giga bits of capacity, mostly for attitude information and “house-keeping”. The Moon Mineralogy Mapper on board the satellite has an independent recorder with 10 giga bit capacity.
A Deep Space Network has been set up to communicate with the satellite. A fully steerable 18-m and a 32-m antenna (for both up and down links) function at Byalalu near Bangalore. The Deep Space Network will support the spacecraft at a slant range of upto 4,00,000 km.
The existing ISTRAC network (8 in S-band) stations that support other missions of ISRO, were used during launch and early orbit phase. The network has been strengthened with stations in Bearslake (Russia), and Jet Propulsion Laboratory (USA) and other stations so that the satellite’s “visibility” lasts longer. Dedicated communications links connect the ground stations and the antennae. A National Science Data Centre to process the data into user friendly format will be set up.
The design, development and fabrication as well as installation of the 32-m antenna constitute a totally indigenous effort.