How Mars Failures Helped the Curiosity Rover Land

Mars is a graveyard; a spot where many a spacecraft slammed into the surface or perhaps, burned up in the atmosphere. This added drama to the Mars Curiosity rover landing last August.

Roger Gibbs, deputy manager for NASA’s Mars Exploration Program at the Jet Propulsion Laboratory, shared how NASA implemented “lessons learned” from Mars 6 (which died on this day in 1974) and other failed Mars missions when creating Curiosity’s game plan. We’ll get more into Curiosity in a moment, but here are the basic principles NASA uses.

Vigorous peer review. NASA wants its Mars teams to be close-knit. From working together and designing a challenging mission together, they form a common language that will serve them well during the challenging landing and mission. But that same closeness can lead to blind spots, so NASA undertakes regular peer reviews with scientists outside of the mission and sometimes even outside of the country. “The peers will come in. They are not vested in this. They haven’t become too engaged in that culture. They will ask pressing questions, and sometimes obnoxious and challenging questions,” Gibbs said.

Building for unknown dangers. Mars is an alien environment to NASA, not just because it’s outside of Earth but also because it has risks we may not know of. In the early days, some spacecraft miscalculated and grazed the atmosphere because we didn’t understand how much the thin gases expand in space, Gibbs said. So the engineers need to recalibrate the computer models with the latest information. “We model the atmosphere of Mars and say, what’s the density, what are the winds and speeds, how fast to change if a dust storm happens and the atmosphere warms up, and how much the atmosphere rises or”blooms.”

Mars Polar Lander
The Mars Polar Lander, which crashed and failed on Mars. Credit: NASA

Verifying and validating. Those words sound similar, but in NASA parlance they have entirely different meanings. Verification means they are making sure the design is meeting what they intend to meet. If NASA wants a change in velocity of 1,000 meters per second, for example, as the spacecraft inserts itself into orbit, it designs a system that can meet those specifications with fuel, thrusters and mass. The validation comes next. “It’s asking if 1,000 meters is the right number,” Gibbs said. “It’s a distinction that is sometimes lost on people, but it’s important.”

So how did this process help Curiosity? Well, this especially came to play when the team was designing the so-called “seven minutes of terror” — those final moments before the rover touched the ground. The team not only used parachutes, but also a device called a “sky crane” that used rockets and a sort of cable that lowered the rover carefully to the surface.

Imagine the measurements that must have taken, taking into account how different the Mars environment is from Earth. To gain understanding, the team reviewed again all the past mishap reports from failed Mars missions, such as the Mars Polar Lander and the European Space Agency’s Beagle 2.

Then, according to Gibbs, they spent “a lot of effort” on doing the verification and validation. Curiosity’s landing would be extremely difficult to model, but the team threw every bit of data they had in there.

The NASA team threw in every bit of data they could to model the Mars Curiosity landing. Credit: NASA
The NASA team threw in every bit of data they could to model the Mars Curiosity landing. Credit: NASA

They created an atmospheric model of Mars, modelled the trajectory of the incoming spacecraft, and tried to figure out how the various systems would respond to the environment. Next, they tried to tweak the variables to see how far they could change without posing a danger to the mission.

“There’s a paranoia where the folks will ask, did we do it to the best of our knowledge,” Gibbs acknowledged.  “What is it that we’re missing?”

If Curiosity had failed, NASA would have opened an inquiry board to figure out what had happened. These boards produce final reports that can be downloaded by anyone. Then, the agency would have tried to prevent the same situation from happening the next time a rover landed.

“It’s a lot easier to learn from someone else’s bad experience, by reading the report understanding the root cause,” Gibbs said.

New Year’s Resolution: Find the Mars Polar Lander

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Finding hidden treasure would be a great way to start the new year, don’t you think? And somewhere in this patterned landscape the remains of a missing spacecraft could be hidden, just waiting to be found. The Mars Polar Lander arrived at the Red Planet 10 years ago in December of 1999, but just before the lander entered the Martian atmosphere, MPL went silent. An immediate search began for the remains of the MPL using images from Mars Global Surveyor, and now the HiRISE camera on the Mars Reconnaissance Orbiter is continuing the search with high resolution images of the area in which MPL is most likely to have landed. The image here is another image in a series of images from HiRISE to look for MPL.

Investigations propose the most likely cause of the mission failure is that the spacecraft’s computers misinterpreted the release of the lander’s legs in preparation for descent as touch-down on the Martian surface, causing descent engines to shut off when the lander was still 40 meters (130 feet) above ground. However, no one knows for sure.

Find higher resolution images of this region here. See our previous articles about finding MPL — with additional images — here, and here.

See this page from the HiRISE site for a links to all the images. On this page, you’ll find an overview of the Mars Polar Lander, its disappearance, the search to find it, and why they want to find it. Emily also has a lengthy post with tips and instructions on how to search for particular objects in the HiRISE images. If you think you have found something of interest, post a comment on this page of the HiRISE Blog, or use this form to contact the HiRISE team. The UnmannedSpaceflight website has a thread discussing the search (serious searchers only).

Good luck!

Help Find the Mars Polar Lander!

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The Mars Polar Lander was supposed to be a mission to the Red Planet’s south polar region to study the climate, weather and the ever-changing polar cap. But the spacecraft went missing in December of 1999 after entering Mars atmosphere, and its disappearance has been a mystery. Attempts at finding the presumably crashed lander using images from the Mars Global Surveyor have been unsuccessful. But now we have the Mars Reconnaissance Orbiter and its powerful HiRISE Camera. A new campaign has begun to try and find the Mars Polar Lander, and the best thing about it is that you can help!

UPDATE: I’ve been contacted by several people wondering what they should do if they think they find something in the image. The HiRISE blog has instructions: contact the HiRISE folks with this form, or add to the comments in a previous HiRISE blog post.

HiRISE has been successful in imaging missions like the Mars Exploration Rovers and the Phoenix lander – as the location of those spacecrafts have been known. But now’s the chance to use HiRISE’s eyes to look for an object whose location is unknown.

“This HiRISE image is one of a sequence searching for either the parachute or the crumpled lander on the ground,” say the folks on the HiRISE website. “However, we expect the debris from this mission to be covered with dust and ice, making it a challenge to identify them. The more eyes that search these images the better, so try your luck!”

Click the image for a larger version, or find even larger versions on the HiRISE website.

The terrain seen here appears to be composed of alternating layers of clean and dust-laden ice. Most of the surface is covered with patches of small channels. It is thought that these have been carved by vaporized ice. On Mars, the ice goes straight to a gas (a process called “sublimation”) rather than first melting. So, as the ice heats in the spring and summer, gas is generated and flows under the remaining ice. This flowing gas can move dust and slowly carve a small channels.

The lander was to touch down on the southern polar layered terrain, between 73°S and 76°S in the region, Planum Australe less than 1,000 km from the south pole, near the edge of the carbon dioxide ice cap in Mars’ late southern spring.

So what could have happened to the spacecraft? It has been speculated that either the thrusters failed as it began to land. Or perhaps the landing sequence failed entirely, and when the legs were deployed the software accidently reported that the lander was on the ground, cutting the parachute while the lander was actually hundreds of feet in the air. Bummer.

But the only way to know for sure it to find the remains of the spacecraft. So let’s get searching! And watch for more images from HiRISE to look for the lost MPL.

Source: HiRISE