Mars Rovers: FIVE YEARS And Counting...

[FSTargetDrone]

They're like Timex, or Samsonite, or something...:

MARS ROVERS HIT 5-YEAR MARK

Posted: Friday, January 02, 2009 7:48 PM by Alan Boyle



NASA / JPL-Caltech / Cornell / NMMNHS
This portion of a 360-degree mosaic known as the "Bonestell Panorama" shows
McCool Hill, named after one of the astronauts lost in the Columbia tragedy, and
some of the Spirit rover's tracks on the Martian surface.

NASA's Mars rovers were designed to last for at least 90 days on the Red Planet, and from the start, mission scientists hoped that they'd keep working well after their "warranty" expired. But few dared to predict that both Spirit and Opportunity would still be on the move five Earth years after they bounced to the surface.

To celebrate Spirit's five-year anniversary, mission managers have released a sweeping new panorama of the rover's winter refuge in Gusev Crater.

Spirit touched down early on Jan. 4, 2004 (or late Jan. 3, depending on your time zone). Since then it has traveled almost 4.7 miles (7.5 kilometers). It spent the last few months waiting out the Martian winter near an intriguing light-colored formation nicknamed Home Plate.

"This last winter was a squeaker for Spirit," John Callas, the rover mission's project manager at NASA's Jet Propulsion Laboratory, said in a news release issued Monday. "We just made it through."

Once the weather brightens up enough to boost Spirit's solar cells, the rover will resume investigating the Home Plate area. Meanwhile, on the other side of the planet, the twin Opportunity rover is making its way to 13.7-mile-wide (22-kilometer-wide) Endeavour Crater, a feature that's bigger than anything the rover has studied to date.

NASA intends to keep the rover mission funded as long as the rovers keep working, at least until the end of this year, at a minimum cost of $20 million. Over the past five years, the rovers already have turned up scads of evidence documenting the Red Planet's warmer, wetter past.



NASA's Opportunity rover looks back at its tracks on Oct. 22, during its trek toward
Endeavour Crater. This mosaic image was released on Dec. 29.

Ed Weiler, associate administrator for NASA's science mission directorate, said the mission (originally budgeted at $820 million) has proven to be one of the space agency's best deals ever.

"The American taxpayer was told three months for each rover was the prime mission plan," Weiler said. "The twins have worked almost 20 times that long. That's an extraordinary return of investment in these challenging budgetary times."

Even though the five-year mission has lasted longer than anyone ever expected, the rovers' marathon still has a way to go to match the record for surface operations on Mars. The Viking 1 lander sent data back from its touchdown site for more than six years. So Spirit and Opportunity - and the scientific teams behind them - still have something to shoot for.

I've said it before, I hope the funding is indeed maintained until they run these things into the ground. This is quite a remarkable achievement.

Interestingly, a stuck wheel on Spirit actually resulted in a new discovery in 2007:

A light-toned ring around the inside of the pit might add information about a nearby patch of bright, silica-rich soil that Squyres counts as Spirit's most important discovery so far. Spirit churned up the silica in mid-2007 with an immobile wheel that the rover has dragged like an anchor since it quit working in 2006. The silica was likely produced in an environment of hot springs or steam vents.

There is just too much information to post here in any detail, so I highly recommend the MERM site itself

[Zablorg]

This is really cool. I wonder what other things they'll find there. Even if it's more of the same stuff, a higher resolution of detail is always better.

What was Spirit doing in the last 4 years that made it so pre-occupied it only had time to trudge 7.5 kilometers? Are they trying to conserve its power supply?

[Chris OFarrell]

Um, exactly how far and fast do you think they are moving these rovers?

Answer, they take a BLOODY long time to move it even meters. They have to tell it to move a short distance, check the pictures it sends back to make sure its not going to 'trip' on anything, then send in another instruction, analyze... and so on.

It takes a while for them to go anywhere because if it gets stuck or tips over or something, well, thats game over...

[Stark]

Manipulating a drone on another planet ain't like driving a remote control car, that's for sure. I'm surprised the most serious failure they've had is a jammed wheel, given the duration and the distances covered.

[Neko_Oni]

What was Spirit doing in the last 4 years that made it so pre-occupied it only had time to trudge 7.5 kilometers? Are they trying to conserve its power supply?

It doesn't seem like the rovers have a destination. They just wander around looking at interesting stuff.

[GrandMasterTerwynn]

This is really cool. I wonder what other things they'll find there. Even if it's more of the same stuff, a higher resolution of detail is always better.

What was Spirit doing in the last 4 years that made it so pre-occupied it only had time to trudge 7.5 kilometers? Are they trying to conserve its power supply?

They've had it wandering in and around the hills, as they've provided a useful cross-section of the geological history of that particular region of Mars. As a result, it's not had to go far, unlike the Opportunity rover, which is sitting out, literally, in the middle of nowhere, and has to travel over miles of dull, dull sand just to get to the interesting geology tucked inside impact craters.

And Spirit does have to hole up during the Martian winters, due to being at a higher latitude (ergo, having much less sunlight for its solar panels) than Opportunity, further limiting the opportunity to travel.

[Kitsune]

Doing a bit of reading about the Rovers and found out that they have seen dust devils on Mars

[FSTargetDrone]

Doing a bit of reading about the Rovers and found out that they have seen dust devils on Mars

Since you mentioned it, here is a page packed full of animated GIFS of dust devils imaged from Spirit.

I won't link the image to display here, because it's 1024 X 256 pixels, but this is an example of one of the dust devil GIFS right here.

The importance for the need to conserve power during the Martian winters cannot be stressed enough. At times, the mission controllers wait to see just if the rovers have survived a particular night. They have to balance to energy usage of onboard heaters (to keep the rovers' systems from freezing up), communication gear, etc. Conversely, if they run the heaters too long, they can drain all the available power and the rover won't start up again the next day. It is a very delicate balance of portioning out just enough power to keep the rovers alive. Some days they just sit there and phone home because it is too dangerous to do anything else, and that is considered a success for the day.

And speaking of dust, here is a series of images (then stitched together) of Spirit taken in 2007 (by Spirit itself):

In a self-portrait, the Mars rover Spirit shows that it is covered in dust as it seeks shelter for a very long winter rest. Plus, scientists see evidence of ancient hot springs or a fumarole from earlier rover findings.

Severe Martian dust storms hit the rovers in Earth's June. Spirit's power has been severely drained by the amount of dust covering its instruments and solar panels. The other Mars rover, Opportunity, which lies near the equator, is in much better shape, having been cleaned by wind gusts.

The Mars Exploration Rover Spirit is covered with dust in this image from photos taken by its panoramic camera from Sol 1,355 through Sol 1,358 (the number of Martian days Spirit has been on Mars). This verticle view distorts the ground and antennas. The camera mast is located beneath the 8-pointed star shape.

The front of Spirit is at the bottom of the image and you can (barely) see its solar arrays on either side and also towards the top (Spirit's tail end).

[Kitsune]

I wonder if the mobile lab they are planning to send up will have some method of removing dust off of it.

Also, curious why the wheels are so small. Several times, Opportunity has almost gotten stuck in sand. Most dune buggies and combat vehicles have large wheels for just this purpose.

[FSTargetDrone]

I wonder if the mobile lab they are planning to send up will have some method of removing dust off of it.

More than once I've thought, "Why don't they have a mechanism to sweep the dust off of the solar arrays, a small brush or something?" But the Mars Science Laboratory Rover will not be solar-powered:

The rover will carry a radioisotope power system that generates electricity from the heat of plutonium's radioactive decay. This power source gives the mission an operating lifespan on Mars' surface of a full martian year (687 Earth days) or more while also providing significantly greater mobility and operational flexibility, enhanced science payload capability, and exploration of a much larger range of latitudes and altitudes than was possible on previous missions to Mars.

Here is the Mars Science Laboratory's site.

Also, curious why the wheels are so small. Several times, Opportunity has almost gotten stuck in sand. Most dune buggies and combat vehicles have large wheels for just this purpose.

Can't say for sure, but I'm guessing it was an issue of saving space/weight. Remember, the Mars Rovers were sent to Mars in a folded-up state. Halfway into this video you can see how it was done (watch the whole video, it's cool!).

[Kitsune]

This is the best of the animated ones I have been able to find:

http://www.lpl.arizona.edu/~lemmon/mer_ ... d_486a.gif

[CaptJodan]

More than once I've thought, "Why don't they have a mechanism to sweep the dust off of the solar arrays, a small brush or something?" But the Mars Science Laboratory Rover will not be solar-powered:

Thanks for posting that. I was just about to say that the next rover should be independently powered, given the problems involved with solar. Though a simple arm with a brush attached couldn't hurt if they decided to do solar again.

[FSTargetDrone]

This is the best of the animated ones I have been able to find:

http://www.lpl.arizona.edu/~lemmon/mer_ ... d_486a.gif

That's a really nice one! I'm not sure if any of those GIFS are in color, but even in B&W it's still interesting to look at.

Thanks for posting that. I was just about to say that the next rover should be independently powered, given the problems involved with solar. Though a simple arm with a brush attached couldn't hurt if they decided to do solar again.

I have no doubt people at NASA/JPL have given thought about possibly clearing off dusty solar panels, but another thing to keep in mind is that the rovers were only intended to be used for a few months. Every day after that has been a bonus, so when the original plans were drawn up, perhaps not much thought was given to worrying about potentially dusty solar arrays because for all they knew, the rovers would have been silent long before now.

Also, again, weight may be an issue. Who knows what some sort of brush device and its associated motors, controllers and other necessary equipment might have weighed. You would need at least one brush per separate array. The solar arrays also partially unfolded when the Rovers became active on Mars, so maybe having yet another moving part on the vehicle, this time sliding across the panels and potentially getting hung up on something might also not be worth the trouble.

It's amazing how the dust has built up, yet these things are still able to soak up enough power. The occasional gust of wind clearing them off helps too!

[The Spartan]

Something that might save weight, if it works, would be to put a little vibrating motor on each of the solar panels that periodically kicks on and gets the dust to slide down (just design them to angle a little when they unfold) so that enough clears off to pull some charge out of them.

Not necessary this time around, but on a different mission it could come in handy.

[Darth Ruinus]

Funny, since I just saw an old NOVA video on TV talking about these very same rovers. "Is There Life on Mars" I think it was called, it seemed to be just another rerurn, since at the end they go on a sad note about how Spirit and Oppurtunity won't work again, due to the winter on Mars. That show was pretty damn good, I never knew all that stuff about Mars' weak magnetic field, how an asteroid may have acted as a dynamo to kick start its magnetic field only to crash into it and wipe out any chance of life.

Also, this is pretty great news. I hope those things bring back even more good information.

[Kitsune]

Looking at failed missions and I don't think the Russians / Soviets have ever truly succeeded at a Mars mission.

[RedImperator]

Looking at failed missions and I don't think the Russians / Soviets have ever truly succeeded at a Mars mission.

Mars kicked their ass. Which is odd, because they successfully pulled off multiple Venus landings, which is far more difficult.

[Kitsune]

Could it have to do partially with orbital dynamics of getting to Mars as compared to Venus. Maybe combined with simple bad luck. Venus is dropping into the gravity well after all.

[phongn]

Manipulating a drone on another planet ain't like driving a remote control car, that's for sure. I'm surprised the most serious failure they've had is a jammed wheel, given the duration and the distances covered.

I have no idea how accurate this anecdote is, but my AI/Robotics professor noted that they did have a remote control interface set up, and once someone used it without realizing the horrendous roundtrip latency and ran right into a rock, even though the rover's AI knew it was going to hit something and wanted to avoid it.

Looking at failed missions and I don't think the Russians / Soviets have ever truly succeeded at a Mars mission.

Mars kicked their ass. Which is odd, because they successfully pulled off multiple Venus landings, which is far more difficult.

It's a pity, because a lot of the later Soviet missions to Mars were really ambitious in scope.

[GrandMasterTerwynn]

I wonder if the mobile lab they are planning to send up will have some method of removing dust off of it.

More than once I've thought, "Why don't they have a mechanism to sweep the dust off of the solar arrays, a small brush or something?"

To put a solar panel cleaning mechanism aboard a rover would involve adding a complex and heavy mechanical system to the spacecraft. This is mass which would otherwise be used for another scientific instrument, or an especially good version of a scientific instrument already on the vehicle. This device would have to work reliably for years with only intermittent operation (lest you scratch the solar cells into uselessness with repeated brushing with grit.)

Furthermore, as has been mentioned, the rovers were designed for 90 day missions, and it is highly likely that the rovers will be killed by some other electronic or mechanical failure, or be blanketed in a large regional or global dust storm severe enough to drain them of power regardless of any solar panel sweeping mechanism used . . . long before regular dust buildup becomes an insurmountable problem.

Also, curious why the wheels are so small. Several times, Opportunity has almost gotten stuck in sand. Most dune buggies and combat vehicles have large wheels for just this purpose.

Can't say for sure, but I'm guessing it was an issue of saving space/weight. Remember, the Mars Rovers were sent to Mars in a folded-up state. Halfway into this video you can see how it was done (watch the whole video, it's cool!).

That's precisely it. Not only were they sent to Mars in a folded-up state, but the volume they occupied in that configuration could not exceed the volume occupied by Mars Pathfinder, as they used the same Delta II launch vehicle as Pathfinder did and had to fit inside that vehicle's nose.

[tim31]

I have no idea how accurate this anecdote is, but my AI/Robotics professor noted that they did have a remote control interface set up, and once someone used it without realizing the horrendous roundtrip latency and ran right into a rock, even though the rover's AI knew it was going to hit something and wanted to avoid it.

Was that Sojourner or Spirit?

[Turin]

Manipulating a drone on another planet ain't like driving a remote control car, that's for sure. I'm surprised the most serious failure they've had is a jammed wheel, given the duration and the distances covered.

I have no idea how accurate this anecdote is, but my AI/Robotics professor noted that they did have a remote control interface set up, and once someone used it without realizing the horrendous roundtrip latency and ran right into a rock, even though the rover's AI knew it was going to hit something and wanted to avoid it.

I'm fairly certain that's apocryphal. I heard a similar story once about a remote control rover that ran over a rock due to lag on Mars (or on the Moon, and in one version it was an alien they ran over!), but that was when I was in high school when the current Mars rovers hadn't even been conceived.

[FSTargetDrone]

To put a solar panel cleaning mechanism aboard a rover would involve adding a complex and heavy mechanical system to the spacecraft. This is mass which would otherwise be used for another scientific instrument, or an especially good version of a scientific instrument already on the vehicle. This device would have to work reliably for years with only intermittent operation (lest you scratch the solar cells into uselessness with repeated brushing with grit.)

Furthermore, as has been mentioned, the rovers were designed for 90 day missions, and it is highly likely that the rovers will be killed by some other electronic or mechanical failure, or be blanketed in a large regional or global dust storm severe enough to drain them of power regardless of any solar panel sweeping mechanism used . . . long before regular dust buildup becomes an insurmountable problem.

Yes, just as I surmised in my last post, however, I hadn't thought of the solar arrays becoming scratched. But in any case, the solar array dust problem-solving for future rovers is moot, given the intended plutonium power source.

Incidentally, with respect to the remote-control/driving off of a cliff stories, both Spirit and Opportunity, as well as Sojourner before them are not mere drones. They all feature some rudimentary self-navigation ability to help avoid getting into the sort of trouble described several posts above:

For Sojourner:

The primary function of Sojourner is to demonstrate that small rovers can actually operate on Mars. The Russians placed a remote control vehicle on the moon called Lunakhod 1 (Luna 16). It landed on November 11, 1970 and drove a total of 10.5 Km and covered a visual area of 80,000 square meters during which it took more than 20,000 images. Even though there was only a 3 second signal delay, that rover proved very difficult to drive. Sojourner will be humanities first attempt to operate a remote control vehicle on another planet. After landing, Sojourner will stand up and drive down one of the two ramps mounted to the lander petal. A lander IMP (IMager for Pathfinder) camera mission panoramic image as well as images taken on either side of the rover petal will assist the mission operations engineers in deciding which ramp is safest to drive down. After a successful ramp egress we will begin a nominal 7 sol (1 sol = 1 Martian day) mission to conduct science and technology experiments. This mission is conducted under the constraint of a once-per-sol opportunity for command and telemetry transmissions between the lander and earth operators. Communications with the rover is not done in real-time because of the approximately 11 minute light-time delay in receiving the signals. Sojourner must be able to carry out her mission with a form of supervised autonomous control. This means that goal locations (called waypoints) or move commands must be sent to the rover ahead of time and Sojourner then navigates and safely traverses to these locations on her own.

And Spirit and Opportunity:

Having more physical capability than 1997's Sojourner rover, Spirit and Opportunity also needed more autonomy. Engineers improved the auto-navigational driving software to give the golf cart-sized explorers more freedom.

When the rovers are navigating themselves, they get a command telling them where to end up, and then evaluate the terrain with stereo imaging to choose the best way to get there. They must avoid any obstacles they identify. This capability has enabled longer daily drives than would have been possible by simply depending on step-by-step navigation commands from Earth. As of mid-August, 2004, Opportunity has used auto-navigation to drive for 230 meters (about 755 feet, or one-third the distance between Eagle and Endurance craters), and Spirit for over 1250 meters (about 8 tenths of a mile), mostly during the nearly 3000-meter (nearly 2 miles) drive to the Columbia Hills.

The auto-navigation system takes pictures of the nearby terrain using one of the Mars Exploration Rover stereo camera pairs (body-mounted hazard-avoidance cameras on Spirit, mast-mounted navigation cameras on Opportunity). After stereo images are taken, 3-D terrain maps are generated automatically by the rover software. Traversability and safety is then determined from the height and density of rocks or steps, excessive tilts and roughness of the terrain. Dozens of possible paths are considered before the rover chooses the shortest, safest path toward the programmed geographical goal. The rover then drives between 0.5 and 2 meters (1.6 and 6.6 feet) closer to its goal, depending on how many obstacles are nearby. The whole process repeats until it either reaches its goal, or is commanded to stop.

The Mars Exploration Rover autonomous driving software is more advanced than Sojourner's in several ways. Sojourner's onboard safety system also looked for obstacles, but could only measure 20 points at each step; Spirit and Opportunity typically measure more than 16,000 points from each pair of images. The average Mars Exploration Rover obstacle-avoidance driving speed of nearly 34 meters (about 112 feet) per hour is ten times faster than Sojourner's. During its entire three-month mission, Sojourner drove just a little more than 100 meters (328 feet) total. Spirit and Opportunity each broke that record in a single day; Spirit drove 124 meters (407 feet) during sol 125, and Opportunity 141 meters (about 463 feet) during sol 82.

Another improvement over Sojourner is the Mars Exploration Rover Visual Odometry software system. As the rovers drive over sandy and rocky terrains, they can slip by unpredictable amounts - even backwards when driving up very steep slopes. But the Visual Odometry system helps by giving the rover a much better notion of how far it has actually traveled. It works by comparing pictures taken before and after a short drive, automatically finding dozens of features in the terrain ( for example: rocks, rover tracks and sand dunes), and tracking their motion between images. Combining that with the 3-D terrain shape is more than enough information to let the rover figure how it really moved, much more precisely than simply counting how much its wheels have turned.

As we can see, it's a bit more sophisticated than simple remote control.

[phongn]

Oh, I'm quite aware of the trip-planning system for the rovers.

I'm fairly certain that's apocryphal. I heard a similar story once about a remote control rover that ran over a rock due to lag on Mars (or on the Moon, and in one version it was an alien they ran over!), but that was when I was in high school when the current Mars rovers hadn't even been conceived.

It could've been, though this particular professor did do quite a bit of work for various government agencies, and it was used as an example of how sometimes humans really don't know better than an AI.