[X] My Assistant

[vikingmars]

With a little image processing, one can easily see the final descent trajectory of the Phoenix Lander with its plumes disturbing the top layer of the Martian surface. After the release of the lander from the backshell, the effect is barely seen first, but is becoming more obvious, until the final strong pulses before landing. Any better estimates ? Enjoy !

[kwan3217]

Actually this is about what I expect. The powered descent is not random. The lander specifically looked at its radar to see which way it was travelling across the surface. From how the parachute is blown, I would say that it is basically from due north. Having measured that, after it separated, it purposely flew upwind (to the north) a ways as parachute avoidance, then tipped back over the other way to slow down its horizontal velocity and land. It flew straight upwind because it was supposed to.

There is a PDF slide presentation posted here which shows the details of this "backshell avoidance maneuver".

I guess what I'm saying is that I think your interpretation is plausible.

[dmuller]

There is a PDF slide presentation posted here which shows the details of this "backshell avoidance maneuver".

As a non-engineer, I just love the engineering English [engenglish???] (from above document):

... there is an increased probability the backshell/parachute will recontact the lander ...

Mmm yeah, recontact

I was actually hoping to include more of these events (BAM. gravity turn, alignment etc) into my real-time simulation but could not get the necessary information. Maybe next time.

[Greg Hullender]

As a non-engineer, I just love the engineering English [engenglish???]

As an engineer and a linguist, I'd call that jargon, and what I find cool is that it follows its own domain-dependent rules. Consider how NASA uses the word "nominal." I like this one because I'm still puzzling over how they got "nominal" to mean "good," when it usually means "in name only." So if I said, "the orbiter is nominally functioning," that means that despite appearances to the contrary, I don't think it's working correctly, BUT, if I say "the orbiter is functioning nominally," that means there are no known problems, and I think it's working fine. Only the second is the "correct" way to use "nominal" when talking about space probes, and if you misuse it, you identify yourself as an outsider.

As for "recontact," I'd guess that arises from the fact that you can't say "contact," since these things are in contact to begin with. It crisply captures the idea of "to collide with, at any speed, but after separation." Standard English lacks such a term, since the circumstance is uncommon in daily life. (We'll ignore the fact that lots of people still think it's a solecism to use "contact" as a verb.) :-)

--Greg

[dmuller]

As for "recontact," ... It crisply captures the idea of "to collide with, at any speed, but after separation."

No doubt it is very precise language. Just imagine the press conference if the backshell did actually "recontact" with the lander on the ground!
Official: Ahm we've had an anomaly during landing as the backshell deviated from its nominal trajectory and recontacted the lander on the ground. We're currently working on the issue
Bewildered reporter: Huh, you mean the backshell crashed into the lander on the ground?
Official: It seems that an unplanned recontact was made and we're working the problem. We will update you during the next press conference (which I hope I wont have to attend ...)