Spirit's landing more dramatic than first thought

Spaceflight Now ^ | 1/13/04 | William Harwood

[LibWhacker]

In the end, it was probably just as well flight controllers couldn't watch the Spirit lander's hair-raising descent to the rocky floor of Gusev Crater January 3. Even a base-jumping skydiver might have experienced a jolt of fear given the last-second maneuvers required to turn a high-speed impact into a safe, if bumpy, landing.

An artist's concept of retrorockets firing
just before touchdown. Credit: NASA/JPL/

Plunging toward Mars at 920 mph, Spirit's parachute deployed at an altitude of just 4.6 miles - a mile lower than expected - and its braking rockets fired a scant 34 stories or so above the surface in a flawless, but hair-raising descent that engineers are just now coming to fully appreciate.

The parachute deployed later than predicted because of a dust storm on the other side of the planet that affected the density of the atmosphere above Spirit's landing site. Engineers had instructed the lander's computer to take that into account, but they were surprised at the magnitude of the adjustment.

"It did it just right, but because of the very interesting atmosphere at Gusev at the time we landed, as a result of the dust storm, (parachute deployment) was about a mile lower than our target altitude, which kind of, as you can imagine, makes things a little bit more exciting toward the ground," quipped Rob Manning, Spirit's entry, descent and landing director.

Coming in at an angle, the lander's actual descent velocity was 152 mph, even with its parachute fully deployed. That's somewhat slower than expected, either due to updrafts or higher-than-expected atmospheric density, but still fast enough to cause white knuckles.

"Just to remind you, at 152 miles per hour, the vehicle was going 30 percent faster than a (free-falling) skydiver," Manning said. "And this was with the parachute open. So we are going very fast. In fact, in our animations, some of the early animations we're working on, you can see the ground coming toward you and you realize robots have nerves of steel. Or copper, as the case may be. It is nerve wracking to see the ground come at you that fast. But it works fine, apparently."

As the spacecraft neared the surface, Manning said, a sudden gust of wind began pushing the lander toward a 650-foot-wide crater. But again, Spirit's computer compensated as programmed, ordering side-firing rockets to ignite, counteracting the unwanted sideways motion.

"We were surprised by the dynamics of the wind," said Manning. As a result, the airbag-enclosed lander was cut free of its support bridle at an altitude of just 28 feet above the surface, more than 10 feet lower than expected.

"Think about that. That's only one-and-a-half airbag diameters," said Manning. "Now that's pretty close."

The lander might have survived even if the side-firing rockets hadn't worked. But it would have been a close thing and the spacecraft might have ended up in the crater. But everything worked flawlessly, the lander hit the ground and bounced 28 times across a distance of nearly 1,000 feet before rolling to a stop 57 second later. Spirit ended up about 820 feet from the crater, which will be its first target once surface exploration begins.

[U S Army EOD]

Our first moon landing was a lot more exciting than that.

[RoseofTexas]

WOW! There goes the Spirit but by the grace of God!

[Howlin]

Amen!

[ummark]

Evidence of money well spent on navigation hardware and software. Compare potential residual benefit of such an exersize against the blind billions spent on social programs in just the last two decades.

[jaz.357]

Why couldn't they have a camera w/telemetry readings on during the landing?

And a microphone on the gizmo now?

[Carolinamom]

Did you see the picture yesterday of the skid marks where the parachute dragged? There was a strange colored CURVED anomaly in the middle of the scarred terrain that had all the scientists excited about it.

[boris]

As a rocket guy, I hate those cluster-of-grapes landing devices. But I gotta admit they work and are very cheap.

--Boris

[Howlin]

No, I didn't. Do you know where I might find it?

[LibWhacker]

I'll betcha space travel is going to be a real nail biter for many years to come. Hope we don't lose our nerve!

[DaGman]

"Our first moon landing was a lot more exciting than that."

When you think about it, the moon landing was literally by the seat of their pants. All they had was a joy stick and a window.

[LibWhacker]

. . . money well spent on navigation hardware and software.

I'm in awe that it works as well as it does!

[LibWhacker]

I don't think the antennae were deployed during any part of the landing. It all had to be uploaded later.

BTW, speaking of microphones, didn't the Viking spacecraft have them? I seem to remember something about that. Hope they have them this time, too.

[RightWhale]

Speaking from an Alaska-centric viewpoint: what are the bags made of that they don't just shatter at 90 below zero like everything else around here?

[ummark]

Dare to go with new stuff Boris. Dare I say "out of the box.."

[LibWhacker]

But I gotta admit they work and are very cheap.

They sure do! When NASA first proposed the idea, I thought it was kind of hare-brained, lol.

[LibWhacker]

Where are the parachutes, btw? I'd think they would be visible in that 360 degree panoramic composite they released.

[Carolinamom]

I saw it on TV last night, don't even remember what channel. It looked like another press conference so perhaps it was C-SPAN. They said that it was one of their most exciting discoveries although they didn't know quite what to make of it. It looked like a large inverted and vertical comma and was whitish and greenish in color, unlike the orange-like dirt around it. They said it did not appear to be mud but there was evidently some unknown binding agent.

[U S Army EOD]

But they weren't flying it because they couldn't see, some guy on the ground was flying it. Check it out.

[Carolinamom]

I don't know. Only saw the skid mark of the parachute that they had a photograph of and were so excited about. No mention that I heard as to the location of the parachute.

[Spunky]

Press Release Images

The third and fourth picture down in this link show the Airbag Trails.

[Howlin]

Well, what is that? Is that part of the airbag (it sure looks like some kind of foreign material to me) or is it where the surface was disturbed?

That is very interesting.

[Spunky]

"Is that part of the airbag"

I was wondering the same thing.

[ChadGore]

I sure would like to see a REAL animation of the landing useing the data aquired.

[blam]

"what are the bags made of that they don't just shatter at 90 below zero like everything else around here?"

Technology company ILC Dover, Inc., based in Frederica, Delaware, is up to their pressure gauges building Mars-bound airbags. ILC created the Mars Pathfinder inflatable-airbag landing system. The firm has now been tasked by the Jet Propulsion Laboratory (JPL) in Pasadena, California to work on airbags for the possible 2003 Mars lander mission, said Mark Grahne, business development manager for the company.

May try tracking down these guys for your answer.

[Howlin]

I'm not very good at reading those photos, but in a way it looks like a shredded bag, but in another way (wishful thinking?) it looks like a completely different kind of terrain/surface, doesn't it?

(It doesn't seem to have as much of a well defined edge, if you will, for what I would think an airbag would look like though.)

[RightWhale]

It's part of the soil surface, which appears to have formed a kind of skin over the years. Strictly a geological process?

[Carolinamom]

Those were not the photos I saw projected on their screen. Theirs were terrifically magnified and 3-D. Just amazing.

[Howlin]

The part we "see" is the skin, or this new looking thing <-----all technical words.

[ChadGore]

Re: I don't think the antennae were deployed during any part of the landing.

You're correct the high gain wasn't aligned during decent, but the low gain was indeed working during EDL.

From what I understand, they made it a design and mission planning priority to have an orbiter over head while the lander was decending, so that they could learn things from real data instead of conjecture.

They got a tone at the moment of parachute deployment and another while bouncing. That same low gain sent back these pics of what the decent camera saw during 3 different points during decent.

The first of these 3 images were not sent back live, but were made a high prioity for the low gain when it later linked up with earth.

The later 3 images were sent back at a later time, but once they got all 3, they layed them over existing MAPS like this one, to match up the crater pattern.

An interesting aside, the first 3 EDL pictures, in order to compress data as much as posible, are 4x smaller in the y axis in the first 3 images, if you extend the Y axis 4x, you get a crater pattern that matches the map very well.

If you look at the 3rd EDL picture, the first crater they'll be driving to is the largest one in the picture, 1/3 the way over from the right.

[LibWhacker]

Me, too! The only thing like that that I've seen was prepared before Spirit actually landed. I hope they do another one using actual landing data.

[Spunky]

My husband just came in so I had him take a look. He thinks what we are seeing in that picture are the shields the Spirit Rover.

Here is a picture of it on Mars and I would say those square lines are what we saw. If you look again at the other picture you can see a line in it.

[LibWhacker]

Thanks for the pics and your very informative comments!

[nightdriver]

"Why couldn't they have a camera w/telemetry readings on during the landing?"

Sounds like a good idea. Then we could watch what was happening some four minutes previously. That's about as close as we can get to "real time" with the distance between Earth and Mars.

[spodefly]

The parachutes are released when the airbag drop, so they would be around 1000 feet away from the lander.

[ChadGore]

Re:Thanks

My pleasure!

Here's a better version of how the craters match up:

[Quix]

I love seeing this title remain in the News forum.

Thanks for the post.

[brazucausa]

As the spacecraft neared the surface, Manning said, a sudden gust of wind began pushing the lander toward a 650-foot-wide crater. Maybe that would explain why british had failed, maybe just maybe they did not counted for that kind of reaction.

[chimera]

BTW, speaking of microphones, didn't the Viking spacecraft have them? I seem to remember something about that. Hope they have them this time, too.

The only microphones I know of were on the Polar Lander, and they bounced that one. It's Martian rat bait. Neither Viking nor Pathfinder have them. I don't think Spirit or Opportunity have them, either. Too bad. It'd be neat to hear that whisper-whistle of thin atmosphere, especially if a dust storm or dust devil blew by.

[Doc On The Bay]

.."All they had was a Joy Stick & a Window!!"..

AND THEY DID IT!!!

REMEMBER THAT!

Doc

[Huck]

I watched a show on tv that explained how this landing system works. It showed them testing it and developing it, and showed cool animations of the landing. Very nifty.

[LibWhacker]

Yes! The Polar Lander. My mistake. I guess the next microphone to go to Mars is on the NetLander, scheduled to arrive at Mars in 2008, is that right? BTW, for some fun, check out the Marsinator, the Martian sound simulator. :-)

[LibWhacker]

Check out the link to the NASA animation I posted in #31. I was surprised to learn that if our lander had hit a sharp rock or boulder on the first bounce, a bag could've deflated, and that in turn, possibly could've ended Spirit's mission right then and there. I was unaware that so much had been left to chance! :-(

[Ernest_at_the_Beach]

Good discussion, thanks for the ping!