Archive for December, 2009

Over the Hills and through the Sand: Six Years of Driving on Mars

Thursday, December 31st, 2009
John Wright
John Wright

I almost didn’t get to drive the rovers.

As one of the five developers of the software used to build the command sequences and rehearse and visualize the rover activities, I really wanted to be one of the people using it in flight. Unfortunately, only three members of the team were selected to be Rover Planners (a job title we believe was chosen in place of Rover Drivers to make the job sound very boring and reduce competition for it). I was not one of them.

I was originally slated to be a downlink analyst looking at the telemetry from the rover to assess the driving and arm operations. This entailed months of training to learn how to run somebody else’s software, a much more difficult task than using your own. Fortunately for me, and unfortunately for someone else, a position opened up on the Rover Planner team and I was transferred over. This entailed more months of training to learn the procedures, but the fuse was very short since Spirit was careening towards its landing. The fact that I knew the software tools already was the saving grace that allowed me to be ready to go on landing day.

Looking back on these six years, I’m tired, but amazed, when I think about how much we’ve accomplished and continue to accomplish. During the prime mission, I remember hearing Steve Squyres say how much we would like Spirit to go explore the hills in the distance but that we would never get there. Well, we have driven to the top of those hills and down the other side.

I remember when Opportunity drove into Purgatory and the Rover Planners immediately said that we needed to back out of the sand dune. After months of testbed activities and review, the decision was made to back out of the sand dune. I can remember looking over at Scott Maxwell, another Rover Planner, and saying to each other “This is so cool!!” (We still say that).

Some of my favorite memories are of giving talks to school kids about what I do, though one of my saddest was being asked by one of the kids, an honor student, if the moon landings were faked. I especially enjoyed calling up Car Talk and asking the guys how to keep our electric vehicle running through the winter on Mars. I laugh when I think about a recent talk I had with Scott when the right front wheel of Spirit seemed to work again after four years of being dragged around. Scott said he didn’t know if we were driving with six wheels or only five. Immediately I jumped in, Dirty Harry-style, with, “I know what you’re thinking punk. Are we driving with six wheels or only five? To tell the truth, I don’t know myself. The question you have to ask yourself is, ‘Do I feel lucky?’ Well, do ya’, punk?”

As we work on getting Spirit out of the current sand trap, I feel manic-depressive about our chances. One day I am sure we will have no problem but the next day I am equally convinced that all is lost. This is about the toughest situation we have ever had to get out of. When we are stuck, it seems as if we are always running out of daylight, which translates to power. It happened at Tyrone, it happened at Tartarus, and it has happened at Troy.

Hmmm, maybe we should stop giving names to locations that start with T.

Rocks and Stars with Amy: It’s Time to Go

Friday, December 11th, 2009

By Amy Mainzer

Rocks and Stars with Amy

Now that we are just days from launch (wow!), the team is making final decisions and preparations. We’ve just held our Flight Readiness Review, at which the final commitment to launch was made by NASA, the United Launch Alliance (the rocket folks) and the WISE project. It turns out that fueling our Delta II rocket’s second stage engine is an irreversible process — once we fuel the second stage, we have 34 days to launch the rocket. If we don’t launch within 34 days of fueling it, we have to replace the second stage completely — and that would mean taking WISE off the rocket. So we needed to be really sure that we were “go for launch” before we decided to fuel up the second stage. That is now done, and we are in the process of putting the final finishing touches on cooling down our solid hydrogen tanks.

These last few weeks and days before launch require a lot of flexibility of the team, since the schedule can change on a dime. There are about a million things having nothing to do with the launch vehicle or the spacecraft that can delay a launch — winds, too much fog, too many clouds, lightning and even something as mundane as a fishing boat or aircraft straying into the “keepout” zone that’s established around the launch site. You would think that the prospect of running into a giant, 330,000-pound rocket loaded with fuel would be enough to make people move out of the way, but sometimes they don’t seem to get the message! Any of these items is enough to scrub a launch attempt.

But that’s why we’ve built in the ability to make two consecutive launch attempts with WISE, separated by 24 hours. We get two tries. After that, our tank full of frozen hydrogen starts to warm up too much, and it takes two days for us to cool it back down. To keep the tank of frozen hydrogen a frosty 7 degrees above absolute zero (minus 447 Fahrenheit), we circulate an even colder refrigerant, liquid helium, around the outside of the tank. But the process of re-cooling takes two days; we have to hook all the hoses back up, cool everything down, then disconnect the hoses again before the next launch attempt.

So we have to be flexible. We’ve all put our lives on hold for the duration, since we have to be ready for anything that happens. Meanwhile, I’ve frantically tried to take care of stuff like cleaning the house and laying in supplies, because once WISE launches, things will go into overdrive. Needless to say, our families have all been very patient with us!