[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

[RNeuhaus]

What is the best way to go down? The best way is of course of minor slope, but if there is no another way, the next decision is to select the land which of the following characteristics:

1) Sandy land, a fuffly sand is even better. On rocky land or firm land with lots of pebbles are the worst ones since they make to rover to be very sleepery.
2) Go down as slow as possible, avoid in stopping during the descending until reaching the bottom flat if the slope is greater than 20 degree for a sandy land or less for another characteristics lands (slipery). Must go very down since the greater down speed, it would be harder to stop.
3) Always go down toward the gravity and not in diagonal to the gravity.
4) All wheels must be rotatting at the same time with the rotating speed to be as close as possible to the land. These offers the best bracking.
5) Never brake the front wheel instead of back wheel. The back brake helps to the rover to straight its position toward the gravity by having the effect of back wheels pull.

Hope that the Spirit rover has implemented software alogaritm to compute the percentage of slippage as a new feature of slip-detection. That will help she to have better control when she is descending on steep step.

Anyone are welcome to comment your opinions and critics to help the Rover team to be better prepared and avoid the accident that would be the first recorded in Mars

Rodolfo

P.S. Thanks to Pando, I left a link to Rover's wheels capabilities : http://marsrovers.jpl.nasa.gov/mission/spa...ver_wheels.html

This page says that the rover is designed to withstand a tilt of 45 degrees in any direction without overturning. However, the rover is programmed through its "fault protection limits" in its hazard avoidance software to avoid exceeding tilts of 30 degrees during its traverses. Its tilt capability is very similar to SUV.