India's Chandrayaan programme is "ambitious"
Till 1999, India's space programme was focussed on application-driven projects. Sending satellites to space with an eye to immediate benefits. But that didn't mean that space scientists weren't nursing the desire to explore space from more of a pure science perspective.
At an annual meeting of the Indian Academy of Sciences (ias) in October 1999, a symposium was organised to discuss moon exploration, says V Adimurthy, whose team is designing the rocket for India's proposed lunar orbiter, Chandrayaan-1, slated to take off by 2008, at the Vikram Sarabhai Space Centre, Thiruvananthapuram. There was widespread support from the scientific community, despite the popular belief that the Apollo and Luna missions of the 1960s and early 1970s had gathered whatever information about the moon was needed. It was felt that an Indian mission would only "reinvent the wheel". "This was a misconception, which got cleared because we could explain the gaps in the knowledge about the moon," says Adimurthy.
Three missions in the 1990s -- two sent by the us and one by Japan -- substantiated this. Subsequently, the Indian Space Research Organisation (isro) set up a task force headed by George Joseph, former director of the Space Applications Centre, Ahmedabad. It was asked to prepare a moon mission plan, work out cost estimates, and suggest scientific experiments, taking into account technical resources available within and outside isro .
Its report came out in 2001 and two years later the Union government cleared the mission. It is now expected to cost Rs 380 crore (us $88.6 million), the cheapest-ever lunar mission. In comparison, China's Chang'e-1 mission has an estimated cost of us $170 million.
The Indian mission got a fillip in May 2006, when it signed a formal agreement with nasa to carry two scientific instruments on the Chandrayaan-1 mission. More significant, was an understanding between the two space agencies on broader collaboration on space exploration, which was being hammered out from June 2004 (see box: Moon men).
Cost and benefit
India's moon mission might be the cheapest ever, but many question whether even this expenditure is justified, especially when existing satellite programmes may need more funds and work to fulfil their potential. isro officials say that one reason for backing the lunar mission is that talented young scientists who join the organisation do not find building and launching rockets and satellites challenging because the template is now in place. To retain them requires offering more challenging tasks. "We can't offer them big money as private sector firms do, but we can certainly offer exciting opportunities," says M Annadurai, project director for Chandrayaan. Planetary sciences have always been a stimulating subject. Venturing into this arena will also attract more bright students, Adimurthy says.
G Madhavan Nair, isro chairperson, says the space organisation is not spending much on the lunar mission. "The total money being spent on Chandrayaan-1 is around 2 per cent of the isro budget in the 10th five-year plan."
Experts, however, say the problem with these missions is they never stop at one. For making such research missions successful, isro may have to launch several probes, ranging from orbiters to landers, which is going to cost huge sums.
But isro officials argue that such cutting-edge scientific endeavours can generate a number of spin-off technologies that can be applied in other areas. For example, a satellite launch requires reliable information about the weather around the launching station. isro has developed automatic weather stations around its launch pad in Sriharikota. This weather station, which automatically downloads and relays data to a central location, can be used for meteorological forecasting. While an imported station costs anything between Rs 10-20 lakh, the one developed by isro is available for Rs 3 lakh. If India were to modernise its weather data collection comprehensively, it might require more than 2,000 such stations, which translates into huge savings, the officials say. Annadurai says path-breaking ventures such as the lunar mission always yield several offshoot products.
|Path to the moon
How Chandrayaan-1 will reach lunar orbit
|After launch, Chandrayaan-1 will go around the earth twice, before being fired towards the moon. The entire journey of 386,000 km will take
There are purely scientific issues as well. The two us missions that rekindled interest in lunar exploration were Pentagon's Clementine launched in 1994 and nasa's Lunar Prospector in 1998. They returned with lunar images, which suggested that the polar regions of the moon could have water, a possibility that had remained unexplored during the moon race between the us and the Soviet Union. Photographs also revealed that the earlier understanding of the earth's only natural satellite was limited because almost all landing missions (both the us's Apollo missions and the Soviet Union's Luna exploration) landed closer to the lunar equator region on the near side. Other regions of the moon, particularly the polar regions and those on the far side, seemed to have different chemical and material composition.
The possibility of finding water (in the form of ice) in the polar regions has been the trigger for the current rush in lunar exploration, says Annadurai. The presence of water could possibly help colonise the moon, an idea dropped like a hot brick in 1974 as it was found to be an exorbitant proposition. Apart from being available for drinking, water in any form can be split into oxygen for breathing and hydrogen as fuel for rockets as well as land rovers. It can result in substantial cost saving, if permanent human residence is planned. Carrying a litre of water from earth could cost a whopping us $67,000 (about Rs 30 lakh).
As a result of the past missions, including several Apollo and Luna landers, a huge amount of data, covering chemical, geophysical and geochronological aspects have been collected. The Apollo and Luna missions had also brought back nearly 380 kg of moon rock and dust, collected from nine different locations in the equatorial regions of the near side of the moon. However, scientists found the data wanting for accurate modelling of the chemical and physical evolution of the moon. The details of these chemical and physical processes, their time scales and the extent to which the moon was subjected to them have not been fully understood.
According to Clive R Neal, a geologist at the University of Notre Dame, usa, knowledge about the lunar interior is also close to zero. "This is the biggest gap, in my opinion. We need a long-lived geophysical network (seismometer, heat flow, magnetometer) to better understand the lunar interior," he told Down To Earth .
These critical gaps in information spurred several countries to return to the moon. Among the countries that are readying the lunar probes apart from India are China, Japan, the us and the European Union (eu). If schedules hold, spacecraft from India, China and Japan will be moon-bound before nasa 's Lunar Reconnaissance Orbiter swings into action in 2008. Already on duty, the esa's smart -1 is wrapping up survey work.
According to Nair, isro has always pursued space science-related activities. The first space launch undertaken by isro was a sounding rocket meant for studying the equatorial electrojet (the large eastward flow of electrical current in the ionosphere that occurs around noon within 5 latitude of both sides of the magnetic equator) and ionosphere. "Besides, the scientific community in India is very enthusiastic about gathering information about the lunar features, particularly the terrain and mineral composition on its own," he added.
Nair says the Chandrayaan-1 project offers two challenges. One is technological: designing the mission without outside support. "The farthest we have gone in space is 36,000 km (the Indian communication satellites of the insat family are parked at geosynchronous orbits 36,000 km away). Chandrayaan-1 has to travel 384,000 km," he says. isro also needs to have control over the spacecraft during its planned life of two years. This means further work on orbital control and manoeuvring the probe. isro is currently setting up a deep-space tracking network closer to Bangalore at a cost of Rs 100 crore for command, control and tracking operations for Chandrayaan-1 and other spacecraft India may decide to launch later.
Indian scientists have also designed and are building all scientific instruments needed by Chandrayaan-1. "It's a great challenge to build specialised cameras and gauges like spectrometers and altimeters at a scale that is suitable to the moon probe," says Annadurai. He adds that these sophisticated gadgets have to be at least one-tenth the size used in normal satellites because of the much larger distances involved in a lunar mission and the larger costs involved. Besides, the instruments on the orbiter have to be more reliable than those on board remote-sensing satellites, because Chandrayaan-1 won't have any back-up.
Though India usually cites scientific curiosity for launching missions to the moon, there are other reasons. Principal among them is competing for lunar resources, which could turn out to be considerable
Chandrayaan-1, which will have a mass of 590 kg when it reaches its destined orbit 100 km above the moon, will carry scientific payloads for chemical, mineralogical and topographic studies of the lunar surface weighing 90 kg. While Indian scientists have designed all the equipment required for meeting the goals of the Indian lunar mission, some is also being acquired from the us
, the esa
, Germany and Belgium.
The main questions that Indian scientists will seek to answer concern the origin and evolution of the moon and whether the polar regions of the moon actually contain water. Scientists have been wondering for long, how the earth acquired such a large satellite, which resembles the composition of the earth's mantle? In the pre-Apollo days, scientists had come up with three principal theories. The theory of co-accretion says the moon and the earth were formed at the same time from the solar nebula (just like some satellites of Jupiter, Saturn and Uranus); fission theory holds that the moon split off from the earth; and the capture hypothesis says the moon formed elsewhere and was subsequently captured by the earth (similar examples are Phobos and Deimos, recently discovered satellites of Mars). Today, analysis of rock samples has ruled out all three. Co-accretion, for instance, was ruled out, says Narendra Bhandari of the Ahmedabad-based Physical Research Laboratory (prl), because the earth and the moon do not have the same bulk composition. Also, a large number of elements found on the surface of both planetary bodies were the same, discounting the possibility that the earth captured the moon.
The hypothesis that became widely acceptable was proposed by A G W Cameron, a Harvard astronomer, in 1984. He postulated that there was a collision, or a series of collisions, between the earth and another planetary body about 4.6 billion years ago, leading to the formation of the moon. "The hypothesis resolved the problems of the low density of the moon, the lunar orbit and the high angular momentum of the earth-moon system," says S R Taylor of the Canberra-based Australian National University, the first scientist in the world to analyse the rock samples brought back by the Apollo ii mission. The material in the moon was mostly derived from the mantle of the other planetary body, not from the earth, accounting for compositional differences.
Hope of finding water in the polar regions of the moon has been the trigger for the rush in lunar exploration because it has raised expectations that colonisation of the satellite will be possible in the not-too-distant future
According to Bhandari, water can be expected on the moon in spite of its weak gravity, because comets and meteorites containing water have been hitting the moon all through its history. In addition, some juvenile water existing since its formation may still be preserved. Also, solar-wind protons impinging on the moon can reduce the presence of oxides present on the surface of the moon and produce some water molecules.
However, even trace amounts of water were not found in lunar rocks and soils. Since the lunar surface has high temperatures (approximately 130C) on the sunlit face and low temperatures on the dark hemisphere (-170C), water and other volatiles are deposited in the cooler hemisphere, the permanently shadowed polar regions. The Lunar Prospector carrying a neutron spectrometer (a sophisticated instrument that detects water even if it constitutes only 0.5 per cent of surface material, by tracking hydrogen atoms in water molecules) found a reduction of warm neutrons around the north and south poles of the moon, which shed a significant part of their thermal energy when they collide with particles of similar size. This could be because of the presence of hydrogen particles in the polar regions. Whether this hydrogen is from water has not been ascertained. Assuming the signal to be entirely due to water, it is estimated that approximately 2x10 9 tonnes of water is spread over 2.2x10 3 sq km and 103 sq km of the south and north poles respectively. This would translate into two trillion litres.
According to Annadurai, another objective of Chandrayaan-1 will be to produce a gravity map of the moon. It is known that the moon has one-sixth of the gravity of the earth. Scientists also know that it is not uniformly distributed because it does not have a core with a strong enough gravitational pull and the lunar surface has mounds of iron-rich minerals distorting the magnetic force. "If we have to plan a landing mission or fly closer to the lunar surface in future, we need to have a precise gravity map of the moon worked out," Annadurai says.
When Chandrayaan-1 leaves for its lunar orbit, however, it will have company. A moon rush is threatening to seriously crowd lunar space.