[X] My Assistant

[RNeuhaus]

Squyres last comments on Athenas on October 4, ...Right at the dog-leg there's a pretty steep step, which we're not certain we can get down. So we're going to descend the upper portion of the ridge, right to where the step is, and assess the situation. ...

On May 6 (Sol 136), when the Oppy was on the rim of Endurance Crater:
I have cut and past a phrase from the Oppy's experience before doing down into the Endurance crater.

Brian Cooper, leader of JPL's squad of rover drivers for Spirit and Opportunity, said the initial view of the crater doesn't settle accessibility questions yet. "The slope right in front of us averages 18 to 20 degrees. Getting into the crater is no problem, but we have a lot more work to do to assess whether we could get back out. That depends on soil properties and slippage, as well as slope." The planned circuit around the rim will also require careful navigation. "If you don't go close enough to the lip, you can't look in, but if you go too far, you could fall in," he said. "We're going to have a very interesting few weeks."

http://marsrovers.jpl.nasa.gov/gallery/all...4P1214L0M1.HTML

From the above picture, ones can see the bottom of crater. However it is very hard to estimate the inclination of slope from the above perspective since the rovers' camera remains on the same horizon surface view.

How do the rovers controllers calculate the slope inclination degree on the way toward to Haskin Ridge? Does the MER have any balancing instrument: Gyroscopy?

Rodolfo

[sattrackpro]

JPL says the rovers travel at 2 inches per second. That is:

120 inches or 10 feet per minute - 600 feet per hour.

or

50.8 millimeters per second, which is:

3.048 meters per minute - 182.88 per hour.

Considering that they have to scan the road ahead, convert every inch into data, then use that data to calculate for the presence of dangerous obstacles, and make adjustments to heading that will lead to the objective location, or halt, if they can't see such a path, these things are moving at blinding speed!

[RNeuhaus]

JPL says the rovers travel at 2 inches per second.  That is:

120 inches or 10 feet per minute - 600 feet per hour.

or

50.8 millimeters per second, which is:

3.048 meters per minute - 182.88 per hour.

Considering that they have to scan the road ahead, convert every inch into data, then use that data to calculate for the presence of dangerous obstacles, and make adjustments to heading that will lead to the objective location, or halt, if they can't see such a path, these things are moving at blinding speed! 

Sattrackpro, If MER uses the facility of hazard avoidance, the girl advances only between 40-50 seconds and stops for 10 seconds for reassess the situationand compute the next move.

More detailsMore details about Rover navigation operations

Mission Timeline: Surface Operations

ROVER NAVIGATION DURING SURFACE OPERATIONS
Summary | Understand Distance | Avoid Hazards | Create Maps |
Keep Balanced | Know Direction | Traverse Far and Well

Using hazard avoidance software for a safe journey

To safeguard against the rover getting lost or inadvertently crashing into unexpected obstacles, engineers have developed software to help the rover make its own safety choices and to "think on its own." The rover hazard avoidance software stops the rover on an average of every 10 seconds, reassessing the situation and computing its next move for the next 40-50 seconds, after which it begins traveling again. With the hazard avoidance software, the rover can travel safely an average of 30 centimeters (1 foot).

The MER uses a Motorola PowerPC microprocessor (RAD6000) and 128 MB of RAM and 256 MB of Flash memory which are of old technology for today standars. Hence, MER move very slow.

Rodolfo

[MahFL]

I would not have thought the speed of the processor determins the forward speed, its how the software works. No 1 priority is not to damage, or get the rover stuck, wether its in sand or lying on its side, or upside down etc. There is absolutely no point in going fast if its the last drive you ever do.

[helvick]

I would not have thought the speed of the processor determins the forward speed, its how the software works. No 1 priority is not to damage, or get the rover stuck, wether its in sand or lying on its side, or upside down etc. There is absolutely no point in going fast if its the last drive you ever do.

It's true that the main limiting factor now is the fact that conservative parameters have been set on the drive software and the rover rivers are being quite careful these days so the rovers are only instructed to traverse relatively short distances, mostly to locatons that have already been pretty well imaged. From that point of view the limiting factor is the way the software works.

Overall though the absolute limiting factor on the distance they can travel is the speed of the processor (and the amount of storage they have). The maximum distance they can travel is limited by the speed they processor can analyse Hazcam images for autonomous navigation since manually sequenced traverses can only be carried out for the relatively short ranges that are clearly visible during a Navcam imaging sequence. That limits the speed to 30cm/min rather than the 300cm/min the drive motor system can manage.

In addition the system needs to store each hazcam drive image it takes during autonomous driving, that puts an absolute limit of somewhere between 200-300m on the distance a rover can drive on a single sol under ideal conditions (loads of sun and a perfectly hazard free flat plain).