NASA Ready To Cut Mars Probe Cord

NASA expects to cut a final cable Monday to free the Spirit rover from its lander a week after touchdown and allow it finally to touch the soil of Mars.

The umbilical that supplies power and communications to the rover will be severed via programmed instructions sent late Monday night or early Tuesday morning using the last of more than 120 explosive devices that began detonating Jan. 3 in a precisely scripted sequence, officials said.

Overnight Saturday, two small explosive devices detonated, cutting cables holding Spirit's two center wheels in place, reports CBS News Space Consultant Bill Harwood. The rover's robot arm also was released from its launch locks and stowed for roll off. The only physical connection remaining between the rover and its lander is a final umbilical that routes power and data to and from the lander.

"The vehicle status remains pretty darn perfect," mission manager Arthur Amador said. "Everybody's extremely pleased with the health and safety status of all the subsystems."

Meanwhile, Europe's first Mars probe remained stubbornly silent Monday when the European Space Agency's orbiter passed over its landing site, British scientists said.

Colin Pillinger, lead scientist on the Beagle 2 program, said no fresh attempts will be made to contact the probe until Jan. 22. The Beagle team hopes to force the lander into communication search mode 2, where the probe will transmit a signal throughout the Martian day.

Hopes of finding the British-built lander, which was due to touch down on the Red Planet on Christmas Day, are fading.

The actual process of having NASA's Spirit roll down a ramp onto the dusty, rock-littered terrain of Gusev Crater was pushed back a day and was expected to begin late Wednesday night or before dawn Thursday.

Cautious NASA scientists adjusted the rover's schedule based on analysis of photos and data it sent back, and said the rollout could be delayed another day if necessary.

That's not unusual given the complex nature of the three-month mission that began with Spirit's landing on Jan. 3.

"We adjust (and plan) every day to manage risks and resources," Amador said Sunday at the Jet Propulsion Laboratory.

Otherwise, Spirit was ready to go. The golfcart-sized, unmanned rover was unfolded Friday from a tight crouch and raised to its full height of 4 feet, 11 inches. Cables holding the middle set of its six wheels were cut Saturday, leaving just the umbilical attached. And in another milestone, the robotic arm was swung up to lock in front of the rover for driving position.

The arm will scrape into rocks to help determine whether water once flowed on Mars, making it conducive to life.

On Sunday, scientists used a rover mock-up to plan a dress rehearsal of the slow dance that will put the craft into position to leave the lander.

Engineers initially hoped to have Spirit roll straight off its lander, almost due south as it sits on the floor of Gusev Crater. But bunched-up airbag material poses a potential threat to the rover's solar arrays and engineers instead have decided to roll off to the northwest. That will require Spirit to rotate in place about 120 degrees to its right.

First, however, the rover will be commanded to back up eight inches. Then, the four wheels on the outer corners of Spirit's rocker-bogey suspension will be commanded to turn sharply inward. That will cause the rover to rotate about its central axis, literally turning on a dime. Once properly lined up, the rover will roll off the lander's egress aids and onto the surface.

But in keeping with their "brave, but not stupid" approach to Spirit's activation, the JPL engineering team has decided to carry out that rotation in two stages over two days.

Spirit will park for a day or two to give scientists a chance to study the chemistry and mineralogy of the area before it roams any farther. One of the first things Spirit will do is extend its robotic arm to touch the soil. It also will make measurements of any rock that happens to be in range.

John Callas, science manager for NASA's Jet Propulsion Laboratory, said things were going so well that the extra day on the lander allowed a bonus of "unplanned science." Researchers planned to take stereo, full-color panorama photographs of the area where the rover will touch down. That will become part of a 360-degree view still being assembled.

Also, a spectrometer that sees infrared radiation — heat — will take a look at three places, including intriguing feature dubbed Sleepy Hollow that lies about 40 feet away. Scientists believe the 30-foot-diameter depression is a dust-filled impact crater, one of dozens that pock an otherwise flat landscape.

The instrument, known as a miniature thermal emission spectrometer or Mini-TES, can help determine the makeup of rocks and soil. Last week it found traces of carbonate minerals in the area, which could support theories that the area once was a lake.

However, scientists caution that the carbonate dust also could have formed through interactions with the tiny amounts of water vapor found in the Martian atmosphere.

Meantime, the science team had moved into what he called the tactical phase, making decisions on the fly based on the newest data from the rover.

From now on, the team will quickly analyze photographs and will plan Spirit's day during the 17-hour period when the craft sleeps. Swiftness is important given that the rover's rolling mission will cost about $4 million a day, Callas said.

In previous exploration missions, activities were planned well in advance, Callas said.

Future destinations include a cluster of hills 330 feet tall that stand about 1.6 miles away. The golf-cart sized rover is capable of roaming dozens of yards a day.

The $820 million Mars Exploration Rover project includes a second, identical rover named Opportunity that is expected to land on the opposite side of the Red Planet on Jan. 24.

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CBS News Space Consultant William Harwood has covered America's space program full time for nearly 20 years, focusing on space shuttle operations, planetary exploration and astronomy. Based at the Kennedy Space Center in Florida, Harwood provides up-to-the-minute space reports for CBS News and regularly contributes to Spaceflight Now and The Washington Post.