Time is ticking away to design, buildand test needed hardware for the Mars Exploration Rover (MER) missions.The project is managed for NASA by the Jet Propulsion Laboratory (JPL)in Pasadena, California.

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Double-up on Mars

NASA announced last August a go-aheadto double-up on Mars by landingdual scientific rovers on the planet, rather than an original planfor just one.

The robot land rovers are to be hurledtoward the Red Planet on individual boosters. The first rover, MER-A isto lofted May 30, 2003, with MER-B to be sent Mars-ward June 27, 2003.

Similar to the Mars Pathfinder landingin July 1997, each spacecraft will be slowed by parachute after entry intothe thin Martian atmosphere. A fast-paced sequence of mid-air events follows,leading to airbag inflation. Cocooned in a pyramid of airbags,the spacecraft tumble down onto Mars hilly, rock-strewn and crater-dottedsurface.

MER-A would bounce to a stop on MarsJanuary 4, 2004, followed on February 8, 2004 by MER-B. The mobile laboratoriesare to touch down at different locales.

After the airbags deflate and retract,a set of petals opens to reveal its rover payload. Wheeling off extendedpetals and rumpled landerairbags, each rover then begins a search for evidenceof liquid water that appears to have been present in the planets past.

Weight and see

ScottHubbard, Mars program director here at NASA Headquarters, said a reviewheld late last year did flag several issues. Specifically, how best tohandle growth in the weight of the Mars 03 MER spacecraft; the assurancethat communications with the craft through entry, descent and landing canbe maintained; and the need to add redundancy in places where a problemcould mean mission failure.

"My impressions are that the team ismaking good progress in addressing all of these," Hubbard told SPACE.com.The science team for the rovers has been asked to look at what instrumentscould be eliminated if weight-saving measures prove mandatory.

"From the point of view of the reviews, they are just making sure that the same mistakes aren"t being made. Everyone knows what the risks are."

"We know that we have a tight schedule.But weve tried to be more flexible...to make sure the project has adequatefinancial resources," Hubbard said. What constitutes the minimum successcriteria for the MER project is not completed as yet, he said.

For the twin rovers and launchers,as well as spacecraft operations on Mars the cost is in the range of $650million. "Thats really soup to nuts," Hubbard said.

Elbow room in a fishbowl

Robert Manning, JPLs Systems EngineeringIntegration and Test Manager for the Mars 03 project, said that as workprogresses "more elbow room" is being found in some problem areas.

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"Now the trick is getting all thisdone in time," Manning said. "The good news for this project is that weare building enough units to allow for a lot of parallel testing. Thatis our big mitigation strategy, quite frankly. But theres a lot to do...anenormous amount to do," he said.

While the MER team at JPL tackles myriadissues, they are also dogged by scads of advisors, independent review teamsand committees that monitor every decision. That near fishbowl-like settingis one result from the humiliating Marsfailures in late 1999 that rocked JPLs technical and managerial credibility.

Decision making on demand, a hallmarkof the MarsPathfinder project, has mutated into a sluggish process, said one observerof the MER effort. "Everybody is covering their butts. Nobody wants totake any risk," the observer said.

"Its a natural pendulum," Manningsaid. "From the point of view of the reviews, they are just making surethat the same mistakes arent being made. Everyone knows what the risksare," he said.

Manning does caution against spendingtoo much time talking about what you are doing to avoid risk, and not doingthe work to avoid the risk per se. "We have to find the sweet spot. Thisproject is the one thats got to find it," he said.

Straightforward attitude

Tests have started on the MER airbags,said Carl Knoll, program manager for space inflatables at ILC Dover, Incorporatedin Frederica, Delaware. "We do expect some design changes. But right now,it probably will look very much like a Pathfinder airbag," Knoll said.

Knoll said several drop tests of Marsairbags have been done in a unique, large chamber at the NASA Glenn ResearchCenters Plum Brook Station in Sandusky, Ohio. "Were in the evaluationphase right now," he said, "and they are kind of sneaking up on levelsthey are looking for rather than go for broke right off the bat."

BrianMuirhead, a former project manager for the highly successful Mars Pathfindermission in 1997, said the design heritage from Pathfinder is not as muchas the project team had originally planned.

A larger lander and a heftier roverhave meant changes throughout the entry, descent and landing phases ofthe MER project, contrasted to the earlier Mars Pathfinder way of doingbusiness, JPLs Muirhead said. "The original hope was just take drawingsand go build it. Well, thats not happening," he said.

Muirhead who serves on a MER reviewteam said the attitude to take at this point in time is straightforward.