A new probe to a Martian moon may win back respect for Russia’s unmanned space program.
- By Anatoly Zak
- Air & Space magazine, September 2008
(Page 2 of 4)
The spacecraft, which is being assembled near Moscow at NPO Lavochkin, successor to the Soviet Lavochkin Design Bureau, should reach Mars in late July or early August 2010. It will orbit the planet for almost nine months before landing on Phobos. There it will be subjected to power and communications blackouts, when Mars and Phobos block the sun and Earth.
“Phobos ends up in the shadow of Mars,” explains Aleksandr Zakharov, deputy director of IKI. “In the worst situations, this shadow lasts for almost an hour out of an eight-hour orbit.”
Immediately after the touchdown, Phobos-Grunt will load a soil sample into a return rocket. In case of a breakdown of communications with mission control, it can enter an emergency mode to collect samples and still send them home in the return rocket. Normal collection could last from two days to a week.
“There are a number of complications in taking that soil,” Zakharov says. “We are working in near-weightlessness, and to test this on Earth is practically impossible. Therefore, we go into all kinds of tricks.”
Scientists hope that Phobos-Grunt will beam to Earth a panoramic view of Phobos’ surface to help scientists select targets. For collection, engineers had hoped to use a variation of a drill the Soviet Luna probes employed to return samples of Earth’s moon in the 1970s. But in the low gravity on Phobos, which has an average diameter of less than 14 miles, the spacecraft will weigh less than a pound. The action of a drill might overturn the lander, depending on how hard a surface it encounters. So IKI developed a small robotic arm to scoop spots around the craft.
“Obviously, [the scoop] loses the ability to drill deep into the surface, as Luna did,” Zakharov says. “However—and I was personally involved in the analysis of it—the drills by Luna to the depths of more than one meter showed that there is not much difference in the chemical composition of the soil with increased depth. Therefore, it seems [drilling] is not really necessary.”
The scoop can penetrate about an inch below the surface. “What’s really critical here is to take rocks,” says Zakharov. “Because the surface regolith was reprocessed many times, it is very possible it reflects the history of something other than Phobos itself.”
The robotic arm can collect rocks up to about half an inch in diameter. It ends in a pipe-shaped tool that splits to form a claw. This encloses a piston that will push the soil sample into an artillery-shell-shaped container. A light-sensitive photo-diode in the claw will help scientists confirm that the device did scoop material. They hope also to see images of trenches the claw leaves on the surface. The manipulator should perform 15 to 20 scoops yielding a total of three to five and a half ounces of soil.