November 12, 2002
Like any travelers worth their frequent flyer miles, the twin rovers of the Mars Exploration Rover Mission must prepare for a long journey. Unlike airline passengers, however, the rovers won't have an attentive flight crew to tend to their needs. Instead, the twins face a daunting 460 million kilometer (286 million mile) voyage to Mars. To ensure their readiness, scientists and engineers at JPL are testing the rovers by simulating conditions they'll experience en route to and upon arrival at the red planet.
Just as the twins will travel separately, they are also tested separately. Rover 1 is midway through the process affectionately known as "shake and bake." Inside the cocoon formed by the spacecraft backshell and heatshield, the rover, in its cruise stage, was placed on a vibration table and shaken intensely. Such vigorous movement mimics the conditions the rovers will face leaving Earth's atmosphere and entering the martian atmosphere. The intense sound of launch can also pose a threat to spacecraft health. Rover 1 underwent acoustic testing to test its sensitivity to sound and passed with flying colors.
JPL's Space Simulator Facility serves as an "oven" and a "freezer" for another round of the environmental testing. To reproduce conditions in space, Rover 1 will undergo solar thermal vacuum testing. In this large chamber, the spacecraft will be exposed to temperatures from -196 degrees Celsius (-320 degrees Fahrenheit) to 93 degrees Celsius (about 200 degrees Fahrenheit). The chamber's solar capabilities are known worldwide.
"The solar thermal vacuum chamber can generate sunlight at 10 times the intensity of a clear, sunny southern California day," said Robert E. Brown, JPL facility engineer.
Telecommunication equipment will also be tested for electromagnetic compatibility. Engineers must be sure that instruments onboard the rovers can freely transmit and receive data without interfering with one another.
Rover 2 is now fully assembled and in its surface configuration - the way it will look when the petals of the lander open to free it to roam the surface of Mars. Recently, engineers successfully conducted a series of mobility tests on the floor of JPL's Spacecraft Assembly Facility. Although several engineering models of the rovers had been driven, this marked the first time a flight vehicle had been tested for mobility.
While systems engineers are readying the rovers for their expedition, the operations and science teams are preparing themselves for what promises to be a demanding schedule once the science phase of the mission begins. Although long-term goals for the rovers were set in the mission planning phase, day-to-day schedules will be determined by the conditions on the planet, as well as what was accomplished the prior day.
"What makes the mission so different from anything we've done before is we're operating the rovers in a non-deterministic way," said John Callas, science manager of the Mars Exploration Rover Project. "We don't know what we'll do until we land and see what's there. Each day we'll command the rover based on what we have just learned. It's really an adventure that way."
A team of approximately 100 people will support each rover during the science phase. Teams will work in shifts that will change daily by 40 minutes to accommodate the 24 hour, 40 minute martian day. The bulk of the team's work will be done while the rovers are "sleeping" - about 14 hours a day. Data from the rovers' day must be processed and interpreted. Based on those results, the team will build new commands for the rovers to complete when they wake up.
To prepare for this, the team is participating in a series of training exercises. In thread tests, different types of software are checked for compatibility. Team members also attend "flight schools," lectures where they are instructed on specific subsystems or rover processes. The most elaborate of the exercises are the operational readiness tests, during which an exact engineering model of the rovers called the Surface System Testbed will be used in an indoor sandbox.
"These are essentially dress rehearsals," Callas said. "We'll do these tests on a flight-like timeline. If we have 14 hours, we have to get it all done in that timeframe. We'll be using flight tools and simulated data. We'll build products and commands and run them on the testbeds to make sure they work."
With the frenzy of activity that occurs before and during the mission, it is vital for scientists and engineers to remain healthy, rested and focused. The team has participated in a series of fatigue counter-measure workshops that teach how to recognize and alleviate symptoms of sleep deprivation.
"It's going to be tough because everyone's going to want to be there all the time; it's an exciting project - there are going to be new discoveries every day," said Callas. "However, some of those people need to be at home sleeping, preparing for their shift - part of my job is making sure they don't overdo it."
The Mars Exploration Rover team members are responsible for every aspect of the rovers' journey. Their reward will come when they receive digital postcards from Mars, as the rovers give scientists - and the public - new views and more detailed information about the red planet.
Contact: JPL/Colleen Sharkey (818) 354-0372