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Two for the Mars Road
Mars Polar Lander and Mars Climate Orbiter embark to the red planet
by Michelle Evans
For those who remember the long dry spell of planetary missions of the 80s, things have definitely turned for the better in recent years. After Voyager 1 and 2 were launched in 1977, there was nothing else headed outward for more than a decade. The outlook for Mars was even bleaker. Viking touched down during bicentennial fever in 1976 and it wasn’t until more than 20 years later when the Mars Global Surveyor and Mars Pathfinder returned us to the red planet in 1997.
Now we are firmly ensconced in a 10-year-long endeavour to unlock the secrets of that planet with two missions launched, or scheduled to launch, during each biyearly Mars launch window from 1996 through 2005. Remember those first photos returned from Pathfinder when the twin hills loomed in the distance? What a difference from the bland landscape offered by Viking. Now we are on our way again to chart the weather patterns from orbit and to sample the soil from the frozen surface.
After a one-day delay, on Friday, December 11, Mars Climate Observer (MCO) rocketed aloft from Cape Canaveral in Florida. Then the launch teams took a short break for the holidays and went right back to it on Sunday, January 3 to send the Mars Polar Lander (MPL) on its way. With a one-second launch window, there isn’t much room for problems, be they mechanical or environmental. A small mechanical problem is what kept MCO earthbound the extra day. High-level winds looked like they would do the same for MPL, but as launch time neared, the constraint faded away into slightly overcast, but otherwise perfect launch weather.
A couple weeks before the Polar Lander was to launch I received a call from Melanie Knocke, a good friend of mine who also happens to be married to the Mission Engineer for both spacecraft, Phil Knocke. She and Phil had recently returned from Florida where they were able to view the MCO launch from just a couple miles from the pad. For MPL they wouldn’t be able to return to Florida, but they would have front-row seats at the Jet Propulsion Laboratory in Pasadena. Her call was to invite myself and Cherie to join them for the day and share the excitement with the people who actually designed and built these two marvelous vehicles. Needless to say, we accepted the invite, as did OCSS Secretary Jeff Howe.
On launch day, Cherie was too sick to go to JPL, so she stayed home to catch the launch coverage on CNN. Jeff and I arrived a couple hours prior to launch and were the first to receive our guest badges for the day. Launch time approached and the Von Karman auditorium filled rapidly with expectant people. As we watched the proceedings, all conversations tended to stop any time NASA gave a weather update. High-level winds could push the Boeing Delta 7425 rocket off course and could even tumble it out of control if they were fierce enough. At first there was only a 20 percent chance that these conditions would favor a launch that Sunday afternoon.
Satellite images showed a front that moved rapidly over Florida’s east coast, leaving behind a lot of clouds, and eventually, calmer conditions in the upper atmosphere. Less than ten minutes before launch, the final verdict came down that the winds were “in the green.” Mars Polar Lander would lift off less than a third of a second past the optimal time of 15:21:10 EST from Pad B of Launch Complex 17. As they say, “Close enough for government work.”
Though not in Florida to see the launch in person, our vantage point at JPL was superb. As the clock passed the last 10 seconds, all the people in the auditorium joined in with NASA’s Lisa Mallone to count down the seconds. In a brilliant flash the Delta ignited and, for a brief moment, the rocket was lost in the cloud made by it’s own exhaust. Quickly rising from the pad, it exited the cloud and streaked skyward.
Viewers at The Cape saw the Delta II head into the overcast, but for those of us watching from afar, the view was switched to a live feed from an onboard camera (aka, the “rocket-cam”) near the top of the first stage, looking directly aft. At launch the booster was covered with a thick hoar frost from the supercold of the rocket fuel. When the camera first picked up the onboard view, this frost was turning to streaking water and it took a few seconds for the camera lens to clear. But when it did, oh, such a spectacular view!
For the next several minutes we all hugged the side of the rocket and saw the Florida coast dwindle away. The solid rockets burned out at 66 seconds; we watched them jettison and tumble away to fall in the Atlantic. As we continued to rise, the curvature of the Earth became apparent, with a thin haze of atmosphere and the absolute blackness of space beyond. Four-and-a-half minutes into flight the first stage cut off and we became weightless. Particles of ice flaked off the side of the booster and tumbling into space. What a fantastic ride.
In space jargon, everything was “nominal.” All stages of the Delta burned perfectly, making the job of people like Phil that much easier. Initial thrust sent MPL away from Earth at over 37,500 mph, with a velocity relative to the Sun of 73,800 mph.
The only tense moment was when it took longer than expected to receive confirmation that the spacecraft was on its own with the solar panels fully deployed and supplying much-needed power to the MPL.
Phil does the calculations that not only determined the tight launch window, but also those that keep the spacecraft on track with trajectory-correction maneuvers during the long interplanetary coast. Four of these engine burns are planned during the yearlong flight. Come December 3rd, he’ll be right there at the Jet Propulsion Lab making sure everything is on track for the Polar Lander to separate from the cruise module and start its direct descent to the lower latitudes of Mars.
Just 18 seconds after lander detachment, two small microprobes, also known as Deep Space 2, drop away for their own appointment with Mars. They will make a fiery entry, free-falling to the surface, impacting some 60 miles from the MPL soft lander. When they hit it is estimated they will experience a force of 40,000 to 80,000 g’s, penetrating several feet below the surface to seek evidence of water, a necessary ingredient if life ever existed on Mars.
Meanwhile, over the horizon, at approximately 75° south martian latitude, the Polar Lander fires its rockets and gently touches down. An exciting addition to the mission at this point is a camera that images the landing site in great detail during descent and a microphone that gathers actual sounds of the martian environment to be heard back on Earth. This is the first time a microphone has ever been sent to another world and it promises to add a new dimension to our perceptions of Mars.
During the 90-day mission on the ground, MPL deploys a mast with a stereo camera system to take panoramic 3-D images of the landing site. A segmented robot arm swings over the side and digs trenches. Near the end of the arm another camera takes extreme close-up views of the soil and into the grooves cut by the arm. Mission scientists want to land as far south as possible (the better the chance to find water, not to mention that the instruments have been optimized for a cold environment). They have joked that if they land too far north or their target, they can use the robot arm to drag them across the rusty landscape!
In orbit above, the Mars Climate Observer will join the Mars Global Surveyor, that arrived in 1997, in gathering planet-wide data of weather patterns while taking thousands of medium-resolution photographs. Both these spacecraft can also serve as relay stations for data and photos sent back toward Earth from the Mars Polar Lander. MPL has a high-gain antenna for its Earth link and a low-gain antenna as backup to converse with MGS and MCO, which can then transmit to Earth should the high-gain system fail.
But for now, this is still in the future, even though we can predict that future much more clearly now that these two exciting missions are cruising outward from the Earth and Sun, to Mars. Phil Knocke summed it up for all of us when he told me how thrilled he was to see both missions successfully underway. The red planet awaits these spacecraft as part of the exploratory armada that will answer the questions that need to be answered before we arrive to place our dusty footprints on its surface and hopefully to settle awhile before we move even further outward.