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Countries Race to Launch Moon Missions

Japan's lunar probe

When James B. Garvin, NASA’s newly appointed chief scientist, first spoke to Physics Today last month about President Bush’s space vision of returning humans to the Moon, he was caught in afternoon rush-hour traffic around Washington, DC. The Beltway traffic seemed like an apt metaphor for the surge of interest in lunar scientific and human exploration. After the initial rush of US and Soviet lunar programs in the 1960s and early 1970s, exploration was reduced to a few flybys by spacecraft on their way to the outer planets.

That changed in 1994 when a low-cost Defense Department spacecraft called Clementine reached lunar orbit and mapped the Moon. The craft measured the Moon’s shape and aspects of its mineralogy, and conducted radar observations that appeared to suggest tantalizing deposits of water ice in permanently shadowed polar craters. Lunar Prospector, a NASA spacecraft launched four years later, made detailed measurements of the Moon’s near-side gravitational field, discovered indications of hydrogen—potentially related to water ice—in the polar regions, and found indications of new crustal magnetic signatures.

Now, a new wave of research is beginning with more than seven spacecraft prepped, planned, or arriving in lunar orbit from the US, Japan, Europe, India, and China. “Clementine and Lunar Prospector were the catalysts for lunar exploration that is long overdue,” says lunar researcher Carlé Pieters of Brown University.

The global interest in the Moon can be summarized in three main points. First, “the Moon is the scientific gateway to understanding the formation and evolution of the inner solar system and the early crusts of Earth and Mars,” says NASA’s Garvin. Second, the Moon serves as a good destination for humans leaving low-Earth orbit to practice techniques that could eventually be used on Mars. Third, the Moon is also “relatively easy to get to for a nation just beginning a robotic exploration program,” says Mark Robinson of Northwestern University.

The first of the new spacecraft, Europe’s SMART-1, arrived in lunar orbit last November. It will be followed by two Japanese spacecraft, Lunar-A and Selene. In 2007, India will launch Chandrayaan-1, which will be closely followed by China’s CHANG’E-1. In 2008, the US will send the Lunar Reconnaissance Orbiter (LRO) to help scout locations for human exploration. If NASA gives the go-ahead this summer, the $700 million Moonrise mission to the South-Pole Aitken (SPA) Basin will launch in the 2009–2010 time frame and return a lunar sample to Earth.

Although the European Space Agency has talked about lunar missions for decades, the launch of SMART-1 was more associated with the results from Clementine than with any long-term lunar program. The ESA craft also acts as a technology demonstrator for a new highly efficient low-thrust ion engine.

ESA is negotiating with the European Union over a Moon–Mars program. Called Aurora, the program, which will cost €900 million (US $1.2 billion) over the next five years, will be funded by both organizations. Despite the new funding, European scientists are worried about the amount of influence the EU will have on the scientific program.

Of the two Japanese missions, Selene will be launched first in 2006, followed by Lunar-A which will hurl penetrators onto the Moon’s near and far sides. The resulting seismic shocks and heat flow measurements should help determine the size of the lunar core, and in turn the origin of the Moon, says Hitoshi Mizutani, Lunar-A project manager for the Japan Aerospace Exploration Agency (JAXA). Both missions have faced delays due to problems with Japan’s launch vehicles. Currently JAXA is reevaluating its lunar strategy and is expected to announce a series of more ambitious future Moon missions soon.

China’s CHANG’E-1 orbiter is the first of a three-stage lunar program that was announced two years ago. The 1.4 billion yuan (US$169 million) spacecraft will survey the topography, the thickness of the lunar soil, and its mineralogy, and will monitor the space environment, says CHANG’E-1’s chief payload designer Sun Hxian. The second stage will consist of a lander– rover mission. The third stage involves a sample return probe for launch before 2020. Still later, China hopes to send humans to the Moon.

In the US, the president’s speech last year focused NASA’s attention on what scientific and exploration-related measurements are needed in the near-term to implement Moon–Mars human explorations. NASA’s Moon missions are funded from two different sources: the exploration systems mission directorate and the science mission directorate. “LRO is different from the other international lunar missions, as it must fly in an extremely low lunar orbit and is extremely challenging; it’s a dual-use mission in that it’s aligned for [human] exploration needs. . . . Other missions [such as Moonrise] are purely scientific,” says Garvin. LRO is the first of many lunar missions to be funded by NASA to prepare for human exploration.

Moonrise, whose development and launch is one of several recommendations of the 2002 National Academy of Sciences decadal survey of the solar system, would be funded from the New Frontiers program in NASA’s science directorate. The SPA basin, which dominates the south-central lunar far side, is suspected to be the largest and oldest impact basin in the solar system. The kinetic energy of the impact may have thrown up material from deep within the Moon’s interior. “Dating the SPA basin impact would constrain the period of early heavy bombardment in the inner solar system,” says Brown University’s Pieters.

NASA’s long-term strategy for lunar exploration is still under development. Last month, the first steps in setting this strategy came into place when NASA held a small brainstorming workshop at the University of Maryland, College Park. “We really want the whole community involved in this,” says Garvin, “which is why, during the summer, we will be hosting a series of workshops for the public, industry, and academia to help build a roadmap for NASA. . . . Science is a key member [of the president’s space vision], but also not the only member; exploration needs to be enabled by science and to enable science.”

Many of the instruments on these spacecraft have similar capabilities. “Each mission has its own objectives and emphasis,” says Pieters. “But there is naturally some overlap, especially in imaging.” If scientists can get access to all the lunar mission data sets, then our understanding about the Moon will be stronger, she adds.

Despite having nationalistic lunar goals, nearly all the space agencies are discussing collaboration through organizations such as the International Lunar Exploration Working Group. “There are many bilateral and other negotiations going on,” says Garvin. For example, Russia is contributing a neutron detector to LRO. In turn, ESA and NASA are working with JAXA, and the US is close to completing discussions about placing up to two instruments on India’s Chandrayaan-1. Even China is considering international involvement in its lunar program. “I’m guardedly optimistic that by the end of the decade we will be sharing remarkable new data sets about the Moon,” adds Garvin.

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