National space agencies in both countries are planning a joint mission to explore the moon’s polar regions for water that they hope could one day sustain human habitation.
The collaboration highlights the rising importance of Asia in space and the geopolitical reaction in the region to China's rise.
“Both India and Japan have demonstration landings on the moon coming up,” said Hiroki Furihata of the Japan Aerospace Exploration Agency (JAXA). “The next step for both of us is true exploration. If we combine the strengths of both sides it can be a win-win.”
Japan and India have already mounted successful lunar missions, with India’s Chandrayaan-1 impactor hitting the moon in 2008 and Japan’s Selene orbiting from 2007-09. This year, Chandrayaan-2 will deploy a rover, while Japan’s SLIM lander is scheduled to reach the moon in 2019.
But their efforts have been overshadowed by China’s ambitious 2007-14 series of Chang-e missions. Two more, intended to return lunar rocks to Earth, are scheduled for the next few years.
Exploring the moon’s south pole is one of the highest priority objectives for planetary scientists. Craters in permanent shadow at the poles may hold large reservoirs of ice, offering huge potential for scientific discovery and a resource to fuel future exploration.
But landing and operating at the lunar poles is a navigational challenge. “It’s hard to see the craters because there’s so little light,” said Takeshi Hoshino, a research and development manager for JAXA — noting wryly that “there’s no GPS on the moon”.
Initial discussions had begun on establishing common objectives and dividing up work, he said.
He noted that Japan’s H2-B rocket could deliver “several hundred kilogrammes to the surface of the moon” whereas India’s largest rocket was limited to 50kg-70kg, implying Japan would provide the launch vehicle for the planned mission.
Mr Hoshino praised the technological sophistication of the Indian Space Research Organisation, which launched the Mars Orbiter Mission in 2013: “They reached Mars on their first attempt and they’re the only people ever to do that.”
Geopolitics, however, underly the scientific goals. Japan has made a particular effort to cultivate India as it seeks democratic allies in the region to balance China. Shinzo Abe, Japan’s prime minister, has formed a close relationship with Narendra Modi, his Indian counterpart, and a memorandum on space exploration was one outcome of a 2016 summit between the two.
The proposed India-Japan space co-operation was a “byproduct of the growing convergence of their strategic interests”, said Rajeswari Pillai Rajagopalan, a senior fellow at New Delhi’s Observer Research Foundation.
“A lot of the things that India and Japan are talking about are part of this entire game of how do you mend China’s behaviour,” she said. “A lot of it is driven by the rise of China and what it means for the region and global stability.”
Their co-operation in space was driven by China’s strategic programme, which was under the supervision of the People’s Liberation Army, said Ms Rajagopalan. “The neighbours are looking at Chinese actions rather than Chinese rhetoric. That is why you see India and Japan coming together.”
For now, space collaboration was “more at the level of political interest and intent . . . which has not translated into an actionable agenda as yet”, she added.
Officials at JAXA said discussions would continue through 2018 with the intention of producing a mission proposal by March 2019 at the latest.
The US National Aeronautics and Space Administration is working on a similar mission, called Resource Prospector, which could launch early in the 2020s.
Ajey Lele, a senior fellow at New Delhi’s Institute of Defence Studies and Analysis, said that combining technical and financial resources would allow faster progress than the two countries could achieve alone.
“There is a good amount of substance in the collaboration,” he said. “When you do an independent mission, you have to do everything on your own. Instead of doing it individually, it’s better that they join hands and collaborate on a better, more productive mission . . . I would call it a natural progression of a developing relationship.”