Chandrayaan-1 (2008): India's Historic First Mission to the Moon

On October 22, 2008, the Indian Space Research Organisation (ISRO) etched its name in history with the successful launch of Chandrayaan-1, India's first unmanned lunar probe. This ambitious mission was not just a demonstration of India's technological prowess but also a scientific endeavor of global significance, designed to orbit the Moon and conduct a comprehensive survey of its surface. Chandrayaan-1 marked a major milestone, making India the sixth nation or entity to send a mission to the Moon.

The Journey Begins: A Perfect Launch

The mission began at the Satish Dhawan Space Centre in Sriharikota, Andhra Pradesh. The spacecraft was launched atop a Polar Satellite Launch Vehicle (PSLV-C11), one of ISRO's most reliable workhorses. The launch was a textbook success, injecting the spacecraft into an initial elliptical transfer orbit around Earth.

Following the launch, the spacecraft performed a series of complex orbital maneuvers, gradually raising its orbit over a period of about two weeks. On November 8, 2008, a crucial Lunar Orbit Insertion (LOI) maneuver was successfully carried out, capturing the spacecraft into a polar orbit around the Moon. It was subsequently lowered to its final 100 km circular operational orbit.

The Spacecraft and its Scientific Arsenal

The Chandrayaan-1 spacecraft was a 1,380 kg cube-shaped satellite. Its primary mission was to orbit the Moon for two years, conducting high-resolution remote sensing of the lunar surface in visible, near-infrared, low-energy X-ray, and high-energy X-ray regions.

The orbiter carried a total of 11 scientific instruments, a remarkable mix of indigenous and international payloads. Five were designed and developed by ISRO, while the remaining six were from NASA, ESA, and the Bulgarian Academy of Sciences. These instruments were designed to create a 3D atlas of both the near and far sides of the Moon, and to map the distribution of chemical elements and minerals.

Some of the key instruments included:

• Terrain Mapping Camera (TMC): An ISRO payload that provided high-resolution, 3D maps of the lunar surface.

• Moon Mineralogy Mapper (M3): A NASA imaging spectrometer that became the mission's most famous payload.

• Moon Impact Probe (MIP): An ISRO-developed impactor that we will discuss in the next section.

The Moon Impact Probe (MIP): Touching the Lunar Surface

A highly symbolic and scientifically important part of the mission was the Moon Impact Probe (MIP). This 35 kg probe was carried by the Chandrayaan-1 orbiter. On November 14, 2008, the birthday of India's first Prime Minister, Jawaharlal Nehru, the MIP was released from the orbiter.

As it descended towards the Moon's south pole, the MIP's instruments—a video imaging system, a radar altimeter, and a mass spectrometer—were active, sending back valuable data about the lunar atmosphere and surface. The probe successfully crashed into the lunar surface near the Shackleton Crater, making India the fourth country to place a flag on the Moon.

A Major Discovery: Water on the Moon

The most significant and path-breaking discovery of the Chandrayaan-1 mission was the confirmation of water molecules (H2O) and hydroxyl ions (OH) on the lunar surface. This discovery was made possible by the data collected by the Moon Mineralogy Mapper (M3), a NASA instrument on board.

The M3 detected absorption features near 2.8-3.0 micrometers in the reflected sunlight from the Moon, which is a characteristic signature of water and hydroxyl. This finding challenged the long-held belief that the Moon was a completely dry and desolate body. The data indicated that the water was present in very small quantities in the lunar soil, but its presence was widespread, with higher concentrations towards the poles. This discovery has had profound implications for our understanding of the Moon's history and its potential for future human exploration.

Other Key Achievements

Besides the discovery of water, Chandrayaan-1 achieved several other significant milestones:

• High-Resolution Mapping: The TMC provided some of the most detailed 3D maps of the lunar surface ever obtained, covering over 70,000 images.

• Mineral Mapping: The M3 instrument created the first comprehensive mineralogical map of the lunar surface.

• X-ray Fluorescence: The X-ray instruments on board detected signals of elements like magnesium, aluminum, silicon, calcium, and iron on the lunar surface.

• Radiation Environment: The Radiation Dose Monitor (RADOM) payload provided valuable data on the radiation environment around the Moon.

Mission End and Legacy

The Chandrayaan-1 mission was planned for a two-year operational life. However, after about 10 months in orbit, the spacecraft began to experience technical issues, including the failure of its star sensors and thermal management system. On August 29, 2009, ISRO officially declared the mission over after losing radio contact with the spacecraft.

Despite its premature end, Chandrayaan-1 was an overwhelming success. It had completed over 3,400 orbits around the Moon and had achieved more than 95% of its primary scientific objectives. The data collected by the mission continues to be analyzed by scientists around the world.

Chandrayaan-1 was a watershed moment for India's space program. It demonstrated the country's ability to design, build, launch, and operate a complex interplanetary mission. It laid the foundation for future ambitious projects, including the Mars Orbiter Mission (Mangalyaan) and the subsequent Chandrayaan-2 and Chandrayaan-3 missions. The discovery of water on the Moon will forever be its most enduring legacy, a testament to the mission's scientific triumph.