[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

[helvick]

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

I'm not 100% sure what you're asking but I'm assuming that you mean how can they figure out what the rovers orientation to the horizontal is?

They use both the targetted sun sightings and the images of the Sundial at the end of each traverse (well after each major traverse has finished but before moving again, and possibly only when they need to know the exact orientation). That's enough to figure out the tilt from the surface normal in the x,y and z planes. Once you have that the Navcam stereo imaging will gives you the 3D layout of the land around the rover.

[RNeuhaus]

They use both the targetted sun sightings and the images of the Sundial at the end of each traverse (well after each major traverse has finished but before moving again, and possibly only when they need to know the exact orientation). That's enough to figure out the tilt from the surface normal in the x,y and z planes. Once you have that the Navcam stereo imaging will gives you the 3D layout of the land around the rover.

Helvick

I found details about the MER' s hability to determine its referential stability position.

http://mars.jpl.nasa.gov/mer/mission/tl_su...av_balance.html

ROVER NAVIGATION DURING SURFACE OPERATIONS
Keeping the rover right side up and balanced

The rover's Inertial Measurement Unit (IMU) uses gyroscopes and accelerometers to determine the heading and tilt of the rover. The gyroscopes measure small heading changes very accurately, and the accelerometers measure where gravity is strongest, pulling down on the rover. Having knowledge of where gravity (down) is, the rover can partly assess its orientation. The rover will also use its tilt sensors to prevent rollover.

If the IMU fails or the rover is lost, the flight team can use the Pancam, which is not part of the autonomous system, to try to figure out the rover direction and position relative to the horizon (attitude).

Now, I see that procedure way by analyzing own gyroscopes and accelerometers is much better than doing by visual measurements. However, these are useful for backup purposes.

Rodolfo