Today’s front page story on Spirit arriving at Mars provide for a welcome afternoon chuckle.
After an entirely correct, and likely regurgitated explaination of the mission:
“Spirit is one of two $410 million U.S. robotic spacecraft on the way, equipped with cameras and instruments to search for evidence that cold, arid Mars may once have been wet and warm enough for some form of life.”
Then later on in the article they discuss plunging through the thin atmosphere and ludicrously add:
“Spirit still will be moving at 1,000 mph, leaving a long contrail in its wake.”
For those unfamiliar with the atmospheric physics, a contrail (a condensation trail) is caused by airplanes (or anything else hurling through the atmosphere) causing high pressure on their leading edge which causes evaporated water vapor to be forced to condensate into tiny liquid water molecules, also well known for making clouds.
Apparently Mark Carreau didn’t get that far in high school science.
Jan. 3, 2004, 2:01PM
NASA holding breath as Spirit nears Mars
By MARK CARREAU
Copyright 2004 Houston Chronicle
PASADENA, Calif. — All of the pre-set commands from Earth have been double-checked and transmitted.
Locked on autopilot, NASA’s Mars-bound robotic rover, Spirit, is flying straight and true on the homestretch of a seven-month journey from Earth.
If all goes well, the golf-cart-size spacecraft will plunge into the thin Martian atmosphere late tonight, deploy a parachute and inflate two dozen airbags moments before it bounces onto the rock-strewn terrain.
Separated from their spacecraft by more than 100 million miles, flight controllers assembled at NASA’s Jet Propulsion Laboratory must wait 10 minutes, or until 10:35 p.m. CST, at the earliest, for signals revealing Spirit’s fate.
If ever it was appropriate to experience a case of the cosmic jitters, that time is now.
“Everyone will be anxious to see what Mars has in store for us, in spite of our best efforts,” said NASA’s Ed Weiler, the agency’s space science chief. “One gust of wind or a rock in the wrong place and it would be over.”
Spirit is one of two $410 million U.S. robotic spacecraft on the way, equipped with cameras and instruments to search for evidence that cold, arid Mars may once have been wet and warm enough for some form of life.
Spirit’s twin, Opportunity, is on course to reach the Martian surface late on Jan. 24.
On Friday, Spirit moved within 250,000 miles of Mars and began to accelerate as the planet’s gravitational forces pulled it closer.
“All the required commands are on board,” said NASA’s Peter Theisinger, the Spirit project manager. Two more opportunities to issue course corrections remained. “We will if we have to, but (we) are good to go, right now,” he said.
The final hours of the journey will be perilous.
Great Britain’s tiny Beagle 2 Mars lander has not been heard from since its attempted landing Christmas Eve.
Three of a dozen previous U.S. and Russian spacecraft dispatched to the planet’s surface have succeeded in completing the difficult journey. The latest was NASA’s 1997 Mars Pathfinder mission, which like Spirit pierced the atmosphere at more than 12,000 mph before slowing enough to deploy a parachute and airbags to cushion the impact with the surface.
“This is very difficult,” said Donna Shirley, now a Seattle-based consultant who served as NASA’s Mars program manager during the Pathfinder mission. “There are so many things that have to be dealt with, and the landing is really the tricky part.”
Her list includes faultless navigation and carefully conceived equipment of a robust design.
“You have to know where you are so you don’t make another crater in the ground. You have to make sure all of your systems work reliably, which means you have to test and test and test before you launch,” said Shirley. “People wonder why these missions are so expensive. It’s because it take a lot of people being fantastically dedicated and working hard for a lot of years to make things happen.”
Spirit’s destination is Gusev Crater, a 100-mile-wide blemish caused by an impact from a comet or asteroid. Imagery gathered by NASA spacecraft suggests the crater was once filled with water fed by a long channel that intersects the southern rim.
Before it can investigate the rocks and soil for more evidence, the 1,819-pound spacecraft must overcome risks not faced since its June 10 launching: atmospheric heating, high winds, cliffs and boulders.
The drama builds a half-dozen minutes before touchdown, when the protective capsule surrounding Spirit pierces the thin Martian atmosphere.
Within four minutes, the craft slows dramatically and the temperature rises to 2,600 degrees from atmospheric friction.
Spirit still will be moving at 1,000 mph, leaving a long contrail in its wake.
One hundred seconds from touchdown and at an altitude of 30,000 feet, a rugged parachute emerges, slowing the plummeting spacecraft to 200 mph, about the velocity of a dragster. Six seconds before the landing, small retro rockets will fire, suspending the probe momentarily at a height of 40 to 60 feet.
At that moment, spacecraft commands will trigger the inflation of airbags, forming a protective cocoon around Spirit as the probe begins the final descent. Seconds later the parachute will be cut away.
The airbags should strike the surface at 48 mph, sending Spirit on a bouncing roll. Thirty bounces are anticipated, as Spirit rolls to a stop a half-mile to two miles from first impact.
As Spirit and Opportunity descend, they will transmit tones back to Earth using a special radio that can broadcast in 256 frequencies. The tones should broadcast every 10 seconds, revealing the success of each landing milestone.
The transmissions will be disrupted by the rough landing, but once at rest, Spirit will broadcast a sequence of five tones every 30 seconds.
The spacecraft’s descent also will be monitored over a radio receiver aboard NASA’s Mars Global Surveyor, which has been circling Mars since 1997.
Even if there is no word then, space agency experts will wait through the night and into Sunday.
If Spirit still is silent late Sunday, though, NASA will acknowledge a problem.
“If we have not heard from Spirit by late Sunday night, we have a very low probability of success,” said Weiler.