The Challenges of Getting to Mars - Cruise Phase

Lynn Craig
The Mars Phoenix Lander is headed for the north polar region of Mars and its goal will be to search for habitable regions -- places where life may have existed in the past.

(Mark Garcia)
The phase that we're in now is called "Cruise"...

(Lynn Craig)
...which sounds really easy and laid back, although it's actually a very busy time for the spacecraft teams

(Brian Portock)
We're busy making sure the systems of the spacecraft are working as they should...
(Mark Garcia)
The teams are busily preparing for the science that's going to occur after landing...

(Lynn Craig)
And the navigation team is getting ready to make sure that the spacecraft actually gets to its target on Mars

(Brian Portock)
It's very similar to the sport of archery. In archery, you have the archer, who's standing some distance away from the target, and that person's job is to make sure that the arrow hits the target.

(Lynn Craig)
An archer will have to draw back the bow with a certain amount of force... secondly, the archer has to make sure that he aims the arrow at a certain angle... and then that arrow has to traverse the correct amount of distance so that it hits the target. These three things have to come together just right.

(sound of arrow hitting target)

(Mark Garcia)
With launching a spacecraft to Mars, it's a little different. The bow, in this case, is a 250-ton rocket.

(Lynn Craig)
Our arrow is the Phoenix spacecraft...

(Mark Garcia)
...that has to travel over 420 million miles to its target...

(Lynn Craig)
...that's 70 miles long by 15 miles wide.

(Mark Garcia)
This is like trying to shoot your arrow from Dodger Stadium and hitting home plate at Wrigley Field in Chicago.

(high speed whooshing sound)

(Lynn Craig)
So this seems like almost an impossible shot to take just in one single shot. So we actually make it a little more fair by having six opportunities to correct that trajectory along the way.

(music, heart pounding)

Imagine if you could shoot an arrow...

(whoosh, arrow shooting, rocket rumble)

...stop it in its path...

(whoosh)

...check to make sure if it's on course for the target, and if not, be able to nudge it back to its target so that it's headed for the right place.

(music, whoosh)

Now of course, our spacecraft is moving at about 60,000 miles per hour. It never stops.

(whoosh)

So the corrections have to be performed along the way while the spacecraft is still in motion.

(Mark Garcia)
We track the spacecraft using the Deep Space Network of antennas, and we figure out exactly where the spacecraft is, where it's heading, and then compute where it actually needs to be. We develop commands to fire the trusters onboard the spacecraft to make any corrections that we need to make. Twenty-two hours prior to entry, we have one last chance to make a fine-tuning of where we're going to land

(whoosh, mechanical release sound)

(Lynn Craig)
The arrow hitting a target is a decent analogy for what the navigation team does...

(Mark Garcia)
...but in reality, it's a lot more complicated than that.

(Lynn Craig)
Earth and Mars are rotating around the sun at various speeds, in constant motion.

(high speed whooshing)

(Mark Garcia)
The spacecraft itself is moving very fast across the solar system. It's trying to hit a moving target, and that target is also spinning on its axis. And we have to keep all of these things in mind while we're attempting to hit this target. It's pretty challenging -- all these things that you have to take into account and actually get done during this so-called "Cruise" phase, where it's not laid back at all, by any means.

(music)