The Jet Propulsion Laboratory posted a video to YouTube today showing what seems to be a remarkable amount of motion out of Spirit lately, especially given that she's supposed to be a "stationary science platform" now. The video consists animations from Spirit's forward and rear Hazard Avoidance Cameras -- the belly-mounted, fish-eye cameras that help Spirit understand the terrain immediately in front of and behind it.
Drives by the Spirit rover from Jan. 14 to Feb. 4, 2010 (Sols 2145 to 2165) moved the center of the rover approximately 13.4 inches (34 centimeters) backwards. Since Jan 26 (sol 2157), drive commands have concentrated on placing Spirit into a favorable tilt toward the sun as the Martian winter approaches.
A little more context to these animations was provided by rover driver Scott Maxwell via his Twitter feed, which I've expanded on a bit in brackets:
Yaw [that is, sideways twisting to rover motion rather than forward or backward motion is] produced by three wheels driving on one side, one wheel on the other. [We are] Allowing yaw to [achieve a] configuration that reduces shadowing [presumably, by things like the mast and high-gain antenna onto the solar panels, something that can reduce available solar power substantially].
*Still* not fully clear to me why backward [driving] is so much better [i.e. more productive] than forward. But I'll take it now, and understand it later.
The HAZCAM animations [above] are ones I made this morning to better understand our #FreeSpirit progress to date.
I love 'em [the animations] -- like an old-style, choppy, black-and-white movie, but from the surface of another world.
In the animations, Spirit's center moves [about] 34cm; the [left front] wheel moves [about] 80cm. "Look at our 'stationary' rover go!" said rover driver Kevin Talley.
Note that we took more images in earlier sols, fewer in later ones, so it looks like there's an acceleration. It's actually slow & steady.
Don't get too excited -- this is either the last drive or the next-to-last drive we will see out of Spirit for the rest of the winter, due to declining power levels. But it is an awfully promising amount of motion for a stuck rover, and it gives us something besides stationary science to look forward to in the Martian spring, about an Earth year from now.