Opportunity Sol 507 (Spirit Sol 528)

Ah, that feels better. The drive went just exactly as planned; the old track, tailings, and wide swaths of undisturbed soil are within the IDD work volume. I've never been so excited about an 80cm drive.

Nor has most of the rest of the team. I forget, they actually started their approach to this spot well before I got here -- it took something like a week to do the drive away, turn-in-place, and drive back -- and today was the last chance to get it. But we got it. Brenda says Steve is "happy as a clam," and he is. "Take your time getting SAP set up, Brenda," he says. "I'm just gonna sit here and gaze in wonder at this reachability map -- nice job, Rover Planners!"

I feel a little silly about taking a bow (figuratively!). It's just 80cm; I'm supposed to be able to do this with my eyes closed. Well, whatever.

I take a moment to look at the drive telemetry. After all that time we spent worrying about what to set them to, I'm curious about what the bogie angles were during this drive. The left bogie started at 14 degrees -- the value that aborted our previous drive -- and we knew it was going to increase as we finished climbing North Ripple, but how much did it increase?

It went to 15 degrees. That's it. All that time we spent quibbling about the drive, arguing over whether 20 degrees was enough headroom, and so on ... and we needed about one extra degree.

Well, at least it worked. It did execute nicely, and now we're ready to swing the IDD out and attack the soil. We'll start with a 2x2 MI mosaic around a patch of undisturbed soil near the RF wheel, then do another such mosaic, followed by an APXS placement, in the track.

This is fairly straightforward IDD work, though it's making Jeng nervous. Maybe it's that he doesn't yet trust his ability to sequence the IDD, or maybe it's the early deadline -- this is what we call a "tight" sol, with uplink in just a few hours, leaving little room for error. But it's an undramatic day; with me looking over his shoulder, Jeng cranks out the IDD sequence in plenty of time.

At the Activity Plan Approval Meeting, Paolo points out that the near side of the track, the spot we've picked as our representative undisturbed-soil location, is darker than the far side. This means that the far side has lighter-colored dust, which generally means smaller, finer dust particles. This is the stuff we sometimes call "foo-foo dust," and there's a going hypothesis that that's what Purgatory Ripple is made of. So, Paolo suggests, maybe we should be IDDing there instead?[1]

Rob Sullivan answers the question. "What we think we're seeing there is the result of a recent wind event -- in the last few sols, a gust of wind came through here and blew away a lot of the material we dredged up when we exited Purgatory Ripple. So a lot of that dust probably blew in from that event. The nearby patch is more likely to be the native material of Purgatory Ripple."

"So your interpretation is right," Steve Squyres chimes in. "That lighter-colored stuff probably is foo-foo dust -- but in this case, that's a bad thing. But keep makin' suggestions!"

The rest of the day goes ahead pretty nominally. At the CAM, Dan resurrects the Picture-of-the-Day tradition to show a true-color PANCAM image of the trench we (inadvertently) made in Purgatory Ripple. It's enormous, as wide as a wheel and at least that deep.

"How did we ever get outta that?" he wonders aloud.

"We have really good rover drivers," Wendy Calvin says.

"And a whole lotta patience," adds Steve.

Courtesy NASA/JPL-Caltech. At last. That's what we've been trying to do.


[1] A characteristically brilliant observation. At this point, Paolo had been on the project for only a few weeks -- a couple of months, at most -- but he was already showing the keen insights and attention to detail that would later make him a top-notch rover driver.

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