For Linda, Pathfinder's July 4th landing is the end of a long road begun just over two years ago when she joined the Pathfinder team for the Assembly Test and Launch Operations phase of the Pathfinder mission. ATLO, as they call it, is where a spacecraft makes its last stop on Planet Earth, first at JPL's Spacecraft Assembly Facility (SAF), and finally at the test and launch facilities at Kennedy Space Center. At KSC, affectionately referred to as "the Cape," the spacecraft goes through final test and assembly, is mated to the launch vehicle for yet another round of testing, and then ultimately lifts off for the trip to Mars. It was just over a year ago that Linda helped pack up Pathfinder to begin its long road to Mars, starting with a four-month intensive effort at the Cape. But even before launch, the events of this hectic week of July 4 1997 were very much in the minds of the entire Pathfinder team.
"We were there from June through mid-December, and it was round-the-clock action the entire time." Linda was in charge of the group which assembled and tested the Pathfinder lander. It was a challenging time, since when the inevitable problems came up, Linda's team had to improvise tests and solutions on the spot, far from the support of the main JPL facility in California.
"One serious issue that came up was in how the spacecraft would respond to the venting of cooling fluid, which happens right before final approach to the planet on July 4. The concern was that the venting fluid would act as a thruster, either spinning the spacecraft or pushing it off-course. My team had to devise a way to measure the mechanical characteristics of the spacecraft there on-site at the Cape, to prove to ourselves and those back at JPL that the venting could be done without disrupting the spacecraft's motion or attitude.
"Another situation we faced, which seems kind of funny now, is when we were doing the final closing of the lander. This lander structure consists of 'petals' which fold up around the rover, electronics, and science instruments, and will be opened up again when the lander is safely on Mars. Anyway, this event turned out to be a big public spectacle; Dan Goldin (NASA Administrator) was giving a speech on the same day, and there was a huge crowd of media people and cameras around to witness our buttoning-up of the spacecraft. Well, the petals didn't close all the way. We were horrified! We could see that there was a tiny space between each of the petals, when they were supposed to be sealed tightly. None of the visiting guests could tell because the gap was small, and unless you really knew what to look for you couldn't see it. But we knew that it was supposed to fit perfectly and that something had to be wrong. We had to call off the live video feed into the press conference and send all the press home.
"Then began the frantic scrambling to find the problem. It turned out that we had never put the whole lander together before with everything on it at one time, and it was now much heavier than it used to be; parts of the lander were sagging under their own weight. The sagging made the parts not quite fit right, which forced us to really look closely at the parts, called 'latches,' that held the petals together. It turned out to be serendipitous, because when we really looked at it, we realized we needed some modifications to the latches to make darned sure the thing would work on Mars, even though Mars gravity is much lower than that on Earth. To fix the problem, we actually had people back at JPL pull parts off of an engineering model of the spacecraft, modify them slightly, and then hand-carry them out to the Cape to replace the identical parts we removed from the real spacecraft. It worked out just fine, but it was a desperate few days."
Back at JPL, Linda has taught the Pathfinder operations team everything she knows about the lander and how it was put together. She won't be actually involved in the landing activities -- unless something unexpected happens, which means the operations team might be calling her for her expert opinion.
"I'm wearing a beeper, and they know they can call me any hour of the day or night. I'll be on pins and needles the whole time, hoping they don't need to."
Linda's beeper may also go off this week for an entirely different sort of crisis -- a TV or newspaper crew needs someone to interview, right away!
"I'm on the 'Interview List,' which means I'll be available at any time to give a commentary on what's going on or to explain something in the mission or spacecraft. Over the last few weeks, they've given us training on how to deal with the media, the kinds of angles that reporters would like to know about, and even what to wear for TV! What's funny is that I've actually heard from a few high school friends of mine who are now in the news business and are calling me to use the personal touch to get the inside story.
"I'm planning to be at JPL for the whole series of events this week -- no, no Fourth of July vacation, but we'll still be celebrating. I'm going to watch the launch events with the rest of my crew from ATLO. These people include guys from the machine shop, technicians, and engineers. We've got a little conference room at the lab with a TV monitor, a microwave -- we're even getting a fire permit for a BBQ pit right outside! The first spacecraft activity I'll be watching for closely will be that coolant venting event we worried about way back during ATLO. This will happen about 9 a.m. in the morning of the 4th. Pretty soon after that, data coming back from the spacecraft will let us know whether things worked out OK. Since it was something I was personally involved in, I'll be anxious to see the results. After that, we won't be able to see much during the descent to the planet surface, so we won't know for sure everything worked until sometime later in the afternoon. We'll be biting our fingernails until then. I just know that it will be successful, though, and I'm especially excited about seeing that first picture.
"You see, I first got interested in space as a teen-ager, when I saw the pictures sent back from Mars by the Viking lander. Now, just like the first picture from Viking on Mars was of its very own foot -- you could even see a footprint in the dust where the lander had apparently bounced once! -- these first pictures from Pathfinder will be of its own open side petals. For me, it will be like coming full-circle; years after marveling at those first pictures from Mars, I'll be seeing Mars again -- but through the eye of a spacecraft that I helped build with my own hands. I can't wait."