The RAT is dead. Long live the RAT.

**01101001** · 2005-Jul-12, 06:06 AM

Spirit's RAT is used up, but there they were, wanting to look inside Independence Rock. What to do?

Meet the new RAT: the front left wheel.

SPIRIT UPDATE: Spirit Scuffs - sol 532-537, July 11, 2005

The scuff worked as follows:

1. Spirit moved into position with a turn in place.
2. Rotated only the front left wheel -- reverse 1 radian.
3. Rotated only the front left wheel -- forward 2 radians.
4. Rover used onboard visual odometry.
5. Repeated steps 2 through 4, two more times.
6. Turned in place back to the starting position in order to present the "scuff" to the robotic-arm workspace.
[...]
Sol 536: The scuff today worked nicely, except that it did not seem to remove a whole lot of material from the place Spirit scuffed. Overall, the rover only scuffed 9 radians on the rock surface, which is less than 1.5 wheel revolutions.

**Swift** · 2005-Jul-12, 01:25 PM

All I can say is "rats" :wink:

By the way, not to be too much of a leering old man, but I've been missing ToSeeks reports from NASA TV.
Mission manager

**pumpkinpie** · 2005-Jul-12, 03:32 PM

Any more details about "the RAT is dead?" From the OP link, all it said was "because the grinding teeth on the rock abrasion tool are worn..."

I learned in May of 2004 that the RATs were designed to last 3-4 grindings into hard basalt. But by that date, it had already done 5-6 and was still working. Anybody know where to go to find out how many each RAT has done?

**kucharek** · 2005-Jul-12, 03:41 PM

Originally Posted by pumpkinpie

Any more details about "the RAT is dead?"

And now, all together:

:-" :-({|= :-({|= :-"
|: The RAT is dead, the RAT is dead, :|
|: It will never grind ratati, ratata, :|
|: Ratatatatatatatati, ratata :|

:-" :-({|= :-({|= :-"

**01101001** · 2005-Jul-12, 03:42 PM

Originally Posted by pumpkinpie

Any more details about "the RAT is dead?" From the OP link, all it said was "because the grinding teeth on the rock abrasion tool are worn..."

I learned in May of 2004 that the RATs were designed to last 3-4 grindings into hard basalt. But by that date, it had already done 5-6 and was still working. Anybody know where to go to find out how many each RAT has done?

Spirit 15, Opportunity 22 (mid-May). I don't think either has RAT'd since.

From the Q&A in the Joy Crisp talk:

Q: What's the current situation with the RAT - the rock abrasion tool?

A: On Spirit, it may be at the end of its life. The last time we used it to grind into a rock, it chattered quite strongly. We've done some tests of a fairly worn down rock abrasion tool, and gotten that same kind of chatter. If it is at the end of its grinding teeth, it could hurt the arm if we continue to use it. But we can still use it to clear dust, spinning the brush around to remove dust. Spirit's RAT has done 15 grindings so far, and about 50 brushes.

Opportunity's rock abrasion tool has done 22 grindings. We ground a lot of the volcanic hard rock with Spirit, and wore the teeth down a lot faster than the sulfate rock, which is softer, that Opportunity encountered. So it has a lot more life to it.