The Soviet Union and the US raced through the sixties and seventies to conquer the Moon, but the Soviets only managed to deliver some automated sample return spacecrafts instead of cosmonauts strolling on the surface. Then the exploration of the Moon ended, somewhat abruptly, with the Luna-24 mission and priorities were shifted towards Mars and even farther planets in the next decade. After the decade of the Viking, Voyager or Phobos missions, the Moon started to slowly gain interest once again in the nineties in Russia, just as in the rest of the world. After the failed Mars-'96 mission in 1996, the new goal was to search for affordable resources in the Solar System and pave the way towards the industrial exploitation of the Moon and near-Earth asteroids in the middle of the 21^st century. Although money was virtually absent, such planning only required pen and paper. So the Russian planetary exploration plans were set to explore the Moon and Mars' moon Phobos (as a stand-in for an asteroid) once again through the Luna-27 and Phobos-Grunt missions in the early 2000s. The former would have send an orbiter, lander and penetrators (spear-like probes that impact into the surface) to the Moon while the latter should have make up for the two failed Phobos missions by bringing back samples from the tiny body. But the grave financial state of Russia and the international pressure to save the prospective Spektr-RG space telescope meant that one of the missions had to be chosen over the other to have at least some chance to be ready in the decade. Decision was finally made to carry on with the Phobos-Grunt which was considered more ambitious and sophisticated while the Luna program was put on hold, waiting for better economic times.

The Lunokhod-2 examines it's own tracks in this raw, scanned image. Detailed surface imagery hasn't been collected on the Moon since the (quite overlooked) missions of the Soviet rovers in 1970-74. (Courtesy of the Laboratory of Comparative Planetology, Vernadsky Institute, Russia. You can browse the Lunokhod archives here.)

Big plans, little money

Then, after only two years later in '99, the redesigned Moon program returned with a multi-phased plan, to be executed in the 2000s, starting with an orbiter called Luna-Glob (as Globe), followed by the Luna-Resurs (Resource) lander and finally the Luna-Grunt (Ground, Soil) mission that included two landers, a sample-collecting rover and another vehicle to return the samples to the Earth. Plans were made plentiful – unlike actual money to build the spacecraft: the Luna-Glob mission has been redesigned a number of times in the last one and a half decade. After the original plan that included penetrators and a small lander to one of the poles came the idea of fusion with the Japanese Lunar-A mission. The Lunar-A consisted of two penetrators that would have impacted into the lunar soil but the two cooperation of the two nations were unsuccessful. Japan canceled the project in 2007 and soon the Russian partners abandoned the idea as well. In the second half of the 2000s the probe was redesigned once again but this time without penetrators, the previous trademarks of the mission, since the engineers struggled to develop of either instruments that would survive an impact at 2,5 km/s, or retrorockets that would slow this neck-breaking speed to a semi-hard landing – and at least one the solutions was required for the mission.

Artists' impression of the cancelled Japanese Lunar-A project (Credit: JAXA)

The soap-opera-like story of Luna-Glob took another turn when her almost forgotten sister stepped in and claimed her love (the Moon). Starting with 2007, plans of a Russian-Indian joint mission started to take shape through the fusion of the Chandrayaan-2 and the resurrected Luna-Resurs programs. The cooperation was initiated basically on political grounds, without real consultations with scientists. As a consequence, scientific goals had to be determined after the mission decision, another round of endless redesigns ensued, including various plans from Russian rovers to Indian orbiters. The Indian partner finally weighed in as the Chinese seemed to be on the fast lane in the Asian space race. Launch was set to 2013 while the Russians pushed the once primary Luna-Glob mission back to 2014-15.

While the landers of the two missions will be almost identical, other hardware components will have completely different origins. Luna-Glob will be launched by a Russian rocket and will carry a Russian orbiter to the Moon, but both the launcher and the orbiter will be Indian for Luna-Resurs/Chandrayaan-2. An Indian rover will ride along the latter mission as well. Let's get through the details of these two missions.

A proposed architecture of the Luna-Resurs lander, carrying the Chandrayaan-2 minirover. (Credit: IKI - Space Research Institute, Russia)

Chandrayaan-2/Luna-Resurs

India intends to take the lead in the Asian space race from the Chinese after the success of Chandrayaan-1. Both nations plan their respective first lunar landings to 2013 (although China have suggested the end of 2012 recently). The Russian-Indian dual mission will be launched atop a GSLV MkII rocket that picked up the annoying habit of blowing up recently, but will be hopefully fixed. After the trans-lunar injection maneuver will have been executed by the orbiter's own thrusters, the lander will separate and the two will continue the journey on their own. The lander will touch down at the south polar region where subsurface ice is expected. There are complications of course: ice can only exist in places protected from direct sunlight, primarily in permanently shadowed craters around the poles but, to a lesser extent, buried under the surface as well. Because of direct and indirect (through the weight of the spacecraft) financial reasons, the lander has to generate power with solar arrays. Besides these two conflicting requirements, the landing zone has to be considered safe: a 30x15 km ellipse, devoid of steep hills and deep craters, where the lander can have direct radio contact with the Earth. There are two preliminary sites selected, a region between Shoemaker and Faustini craters and another next to de Gerlache crater. But this is still subject to change, for example if engineers can narrow down the size of the landing ellipse, allowing smaller patches of safe places to be considered.

Selected preliminary landing sites of the Luna-Resurs mission. (Source: Slyuta et al., LPSC2010 - pdf)

Whichever site will finally be selected, there is no guarantee of course that Luna-Resurs will land atop a patch of ice (as Phoenix did it on Mars) since ice-indicating measurements only have a resolution of several kms and it is unclear how even or patchy the distribution of ice is on smaller scales. Anyhow, the lander will operate as a well-equipped research station, using, among other instruments, various cameras, a remote manipulator arm, multiple mass spectrometers and a radio detector capable of penetrate the regolith two meters deep. Its manipulator arm will take soil samples to determine its volatile content. The tiny (about 15 kg) Indian rover will crawl around for only a few days, carrying two mass spectrometers to analyze nearby rocks in detail – let's not forget though that its equally important mission is to represent a rolling saffron-white-green flag in front of the cameras, ideally before the landing of the Chinese Chang'e-3.

In the meantime the Chandrayaan-2 orbiter will map the Moon from low polar orbit in great detail. Aside from “simple” photographing, it will examine the chemical composition of the surface and will search for subsurface ice patches with a synthetic aperture radar capable to probe the first few ten meters below the surface. Unlike Chandrayaan-1 however, all instruments will be developed domestically and there will be no place left for foreign detectors left either. (The miniSAR radar of the first probe was developed by NASA for example.)

Luna-Glob

The sister mission will execute a very similar scenario. The two units will detach after the trans-lunar injection and will reach the Moon separately. The orbiter will enter a 700 km initial orbit while the lander will slowly descend to the surface. To where exactly is not yet determined: either at the south polar region to aid the Luna-Resurs mission or to the north polar region to find out if there is any ice hidden as well. Since this lander will not carry a rover, the available space will most likely be filled with a drilling unit to examine the subsurface layers. In the meantime the orbiter will not only map the surface and determine its mineral composition and ice content but it will study the plasma environment of the Moon and carry out astrophysical measurements, such as detection of cosmic rays.

Bold plans, big hopes

The Luna-Grunt landers, both atop their Fregat lunar cruise stages. (Credit: NPO Lavochkin, Russia)

The proposals clearly show that if anything, ambition is overabundant in the Russian space program as instead of simpler, easier and faster achievable programs, they want to return into planetary exploration through the immensely complex Phobos-Grunt mission. There will be benefits for the Moon program because many devices will be almost identical in all landers and will have gone through some deep space testing before departing to the Moon. On the other hand, any trouble with Phobos-Grunt would trigger another wave of checks, reviews and delays. But if the planetary space program will finally be set in motion (let's hope it will be), other spacecrafts may follow. The Luna-Grunt mission will send a large rover to the surface of the Moon in the second half or more likely at the end of this decade. It will then explore its surroundings and collect carefully selected soil samples. That's where the other lander, the return stage steps in: descending close to the rover, it would store the collected samples, up to 1 kg, and return it to the Earth. (NASA plans a similar, multi-stage sample return for Mars as well.) That would be a great improvement compared to the previous Russian attempts where samples were collected from a single and largely random location. And let's draw a line here because that may be the limit of what can be achieved during the decade. There are of course some fancy ideas of a lunar grid of spacecrafts from telescopes, rovers and sample collecting robots to a fully automated base but this is rather a dream than a possible reality. For now, let's hope that Phobos-Grunt will be launched safely and even more that it will carry out its mission successfully, pawing the way before our return to the surface Moon. Unless a GLXP team gets there first!

László Molnár