Chandrayaan-1, India’s lunar water finder, close to a Moon ending
India an emerging force in space exploration
Sometime in later this year it is expected that India’s first lunar spacecraft is set to crash into the Moon. Currently the 675kg spacecraft is silently orbiting the Moon. Silently as since August 29 2009 radio contact has been lost with the craft.
Now, every 2 hours or so, it complete a lunar orbit 200kms or less above the lunar surface. It has been in this orbit since May 20 2009. At 200km above the lunar surface this orbit is expected to last a 1000 days.
In reading this you may at first be surprised to know that India has a space exploration program. Perhaps even more surprised to realise that India had carried out a successful scientific probe to the Moon.
India today has one of the stronger emerging space programs with a strong remote sensing satellite capability, including a developing lunar and human space efforts. They see no ambiguity in the relevance of space activities to a developing nation. The Indian authorities are convinced that “if they are to play a meaningful role nationally, and in the comity of nations, they must be second to none in the application of advanced technologies to the real problems of man and society.”
A triumph of Newtonian mechanics and Kepler’s insight
The Indian Space Research Organisation (ISRO) successfully launched Chandrayaan-1 on the 22 October 2008 from the Satish Dhawan Space Centre in Sriharikota, southern India. After a series of orbital manoeuvres the 1380kg spacecraft entered into lunar orbit on November 8 2008.
A series of four orbit raising manoeuvres between October 23 and October 29 had bought Chandrayaan-1 half way to Moon orbit. These orbit changes were carried out via India’s Telemetry, tracking and Command network at Bangalore and the Indian Deep Space Network antennas at Byalalo.
There are a number of firsts for India in this voyage. The manoeuvre on October 25 took Chandrayaan-1 into an elliptic orbit with a perigee at 74,715km from earth. This was the first time an Indian spacecraft had gone beyond the 36,000km geostationary orbit. On October 26 the manoeuvre took Chandrayaan-1 past the iconic 150,000km from Earth point entering ‘deep space’.
The two accompanying diagrams illustrate the elegance of the manoeuvres. Beautiful examples of the utility of Newtonian mechanics. Also superb illustrations of Kepler’s elliptical-orbit theory in practice.
After a fifth manoeuvre on November 4 Chandrayaan-1 entered a lunar transfer trajectory. On November 8 Chandrayaan-1 entered into a lunar orbit. The first time an Indian spacecraft had orbited the Moon. It’s elliptical polar orbit enabled India to lay claim to being just the fifth country, after the USSR (Lunar 2, 1959), USA (Ranger 7, 1964; Apollo 8, 1968), Japan (Hiten, 1990) and China (Chang’e 1, 2007), to send a spacecraft to the Moon. In a somewhat perverse piece of country-ism the European Space Agency, which has also reached the Moon (a small, low-cost lunar orbital probe called SMART 1, 2003), as a non-sovereign 17 country consortium, is not counted in this tally.
On November 10 and 12 the orbiter two further planned manoeuvres moved Chandrayaan-1 into its operation orbit 100kms above the surface of the Moon. India’s inaugural lunar mission had taken the country, via a series of elegant orbital manoeuvres, from being an emerging technology force into a small club of countries with viable space aspirations.
Nehru’s lunar legacy
The cultural and political significance of Chandrayaan-1 was realised on November 14. This is the birthday of the late Pandit Jawaharlal Nehru, India’s 1st Prime Minister. Nehru, as Prime Minister, supported and initiated the Indian space program in 1962 and the Indian Space Research Organisation.
On this day (IST) the Moon Impact Probe became the first Indian built object to reach the surface of the Moon. The probe was a 34kg box-shaped object containing a video image system, radar altimeter, and mass spectrometer. This can be contrasted with the 899kg Martian Space Laboratory rover Curiosity, currently on its way to Mars.
Symbolically the Indian tricolour was painted on three sides of the Moon Impact Probe. This enables India to also lay claim to having the “Indian tricolour placed on the Moon”. Needless to say that “placing” in this case was a hard landing in the Moon’s south polar region.
There is water on the Moon!
The scientific payload of Chandrayaan-1 was 11 instruments. Five of these instruments, including the Moon Impact Probe, were from India, the remainder were from various countries including the UK, USA and Bulgaria. One of the great successes of this mission, from a scientific perspective, was the detection of water ice on the Moon for the first time on August 21 2009.
On May 20 the orbit was raised to 200km. With the Indian Space Research Organisation declaring that “all major objectives achieved” in their press release.
This aside the detection of hydroxyl and water were tremendous finds and also demonstrate the value of joint missions. Amongst the instruments on Chandrayaan-1 were the Moon Mineralogy Mapper (M3) and Miniature Synthetic Aperture Radar (Mini-SAR) from NASA. The Moon Mineralogy Mapper has covered nearly 97% of the lunar surface, some of the other instruments have covered more than 90%.
A detailed analysis of the data obtained from Moon Mineralogy Mapper, has clearly indicated the presence of water molecules on the lunar surface extending from the lunar poles to about 60 deg. latitude. Hydroxyl, a molecule consisting of one oxygen atom and one hydrogen atom, was also found in the lunar soil. The confirmation of water molecules and hydroxyl molecule in the moon’s polar regions raises new questions about its origin and its effect on the mineralogy of the moon.
The Moon Mineralogy Mapper measures the intensity of reflected sunlight from the lunar surface at infrared wavelengths, splitting the spectral colours of the lunar surface into small enough bits revealing finer details of the lunar surface composition. This enabled identification of the presence of various minerals on the lunar surface that have characteristic spectral signature at specific wavelengths. Since reflection of sunlight occurs near the moon’s surface, such studies provide information on the mineral composition of the top crust of a few millimeters of the lunar surface.
The findings from Moon Mineralogy Mapper clearly showed a marked signature in the infrared region of 2.7 to 3.2 micron in the absorption spectrum, which provided a clear indication of the presence of hydroxyl (OH) and water (H2O) molecules on the surface of the moon closer to the polar region. It was also concluded that they are in the form of a thin layer embedded in rocks and chemical compounds on the surface of the moon and the quantity is also extremely small of the order of about 700 ppm.
These molecules could have come from the impact of comets or radiation from the sun. But most probable source could be low energy hydrogen carried by solar wind impacting on the minerals on lunar surface. This in turn forms OH or H2O molecules by deriving the oxygen from metal oxide.
Following these findings, the scientific team revisited the data from NASA’s Deep Impact Mission launched in 2005 which carried an instrument similar to Moon Mineralogy Mapper. Deep Impact Probe observed the moon during the period June 2 and 9, 2009. This, along with some laboratory tests carried out from samples brought from Apollo missions, has confirmed that the signature is genuine and there is a thin layer of surface mineral which contains traces of hydroxyl and water molecules.
The Moon Mineralogy Mapper observations are further strengthened by results obtained from the analysis of archived data of lunar observation in 1999 by another NASA Mission, Cassini, on its way to Saturn. This data set also revealed clear signatures of both OH and H2O absorption features on the lunar surface.
Further to these findings, ice was detected in small polar craters (2-15km in diameter) that are not visible from the Earth. These North polar craters have sub-surface water ice located at their base. The interior of these craters is in permanent shadow from the Sun. Although the total amount of ice depends on its thickness in each crater, it’s estimated there could be at least 600 million metric tons of water ice.
This water was detected using the mini-SAR instrument. Mini-SAR is a lightweight (less than 10 kg) synthetic aperture imaging radar. It uses the polarization properties of reflected radio waves to characterize surface properties. This instrument could detect new craters by their internal roughness. As well it could find craters that gave anomalous signals, that were consistent with them having water in their base.
Manned lunar exploration
Chandrayaan-1 show cased India’s ability to plan and deploy a lunar exploration. It will be interesting to see whether they can realise their Space Vision 2025. The major objective of a 2016 manned mission program is to develop the fully autonomous three-ton ISRO Orbital Vehicle spaceship to carry a 2 member crew to low Earth orbit and safe return to the Earth after a mission duration of few orbits to two days. The extendable version of the spaceship will allow flights up to seven days, rendezvous and docking capability with space stations or orbital platform.
Milestones along the way include a second unmanned Chandrayaan-2 mission to the Moon, for launch in 2012. The creation of an astronaut training programme in 2012. The launch of a manned lunar orbital mission sometime after 2020 and manned expedition to the Moon by 2025. Although these are all near impossible to verify, at present. India’s space aspirations are without doubt real, just like the existence of Chandrayaan-1. Their immediate future is not quite predictable – just as is Chandrayaan-1’s.