MSL landing sites Options

[djellison]

They're all scientifically rich, they're all safe for landing.

You should start by reading the presentations to the 4th MSL Landing Site Workshop
http://marsoweb.nas.nasa.gov/landingsites/...op/program.html

[centsworth_II]

But would you say they're all equally rich, all equally safe?

[djellison]

Go and read the meeting presentations and find out for yourself.

All four are safe enough, that is for sure.

As for which is most scientifically interesting....ask four scientists and you'll get four totally different answers. There is no 'right' landing site.

[tharrison]

All four are safe enough, that is for sure.

To answer centsworth_II's question though, they are not all equally safe. They have been ranked in terms of ruggedness, as well as the risk to EDL (i.e. weather conditions during the EDL timeframe). Mawrth is considered to be the "safest" site. Holden and Eberswalde are very rugged, which makes the engineers leery. Gale has some EDL concerns, plus the landing ellipse is relatively far from the mound, and so there is a concern that the rover would never make it to the mound during the primary mission (this is also a bit of a concern for Eberswalde due to the location of the landing ellipse relative to the delta).

As for which is most scientifically interesting....ask four scientists and you'll get four totally different answers. There is no 'right' landing site.

They may all be interesting and for different reasons, but the question is which site will you gain the most from in terms of what the rover is actually capable of doing, as well as in terms of what you will learn about the history of Mars. That's the purpose of the landing site workshops.

[elakdawalla]

Holden and Eberswalde are very rugged, which makes the engineers leery.

Really? That's not what they said at the most recent landing site selection meeting. From my notes:

We can now see just about every hazard that could possibly cause Curiosity to fail during landing using actual data, not models.

There are no hazards that we can see at any of the four landing sites that make the engineers nervous. Any one of the four sites would produce the represent the safest landing site (in terms of predicted hazards) that we have ever had on Mars.

[Julius]

From what I've seen from the presentations I am inclined to favour Mawrth Vallis as my first choice for Curiosity!Eberswalde would be my second choice ..wish we had a twin rover that we could target this site as well!Mawrth being the oldest location out of the 4 landing sites makes it top choice.We should start reading a history book from the first chapter ..later chapters will make more sense if we get the the first chapter right.

[Phil Stooke]

We can only go to one of the four sites... on this mission. But don't despair if your favorite site isn't picked. The other three remain as fantastic sites, extraordinarily well documented, and it's quite possible that they will be considered again in future. Just as Meridiani was the front-runner for Mars Surveyor 2001, and Gale was a MER candidate.

My preference is for... basically any site except Mawrth. Nothing wrong with Mawrth for the primary mission, but after that I'm not sure that there is an exciting extended mission. The other sites seem to offer extensive opportunities for extended traverses. But any site will be great when we're on the ground.

Phil

[djellison]

Really? That's not what they said at the most recent landing site selection meeting. From my notes:

Seconded. I saw the presentations as well and none of the sites were marked out as making the engineers 'leery' - indeed they were described as the four safest landing sites in the history of Mars exploration.

[Holder of the Tw...]

We can only go to one of the four sites... on this mission.

Looking at the scientific targets for Eberswalde, you find good ones all over the landing ellipse. The biggest ones outside the landing area all seem to be to the west and south, toward the delta. So no matter where it lands, the goal will be to head this way. Ten, fifteen, twenty km or so.

Once you're at the delta, you are that much closer to Holden. About 150 to 180 km further down the road (as the proverbial crow flies).

Two for the price of one?

[brellis]

After spending some great quality time rereading this thread, I have a few queries:

Do weather patterns, i.e. seasonal dust storms, play into the process for choosing a location?

Has our experience landing previous rovers improved our accuracy in predicting the degree of atmospheric drag?
(As mentioned earlier in this thread, Opportunity experienced a G-force on impact on the low end of the predicted range)

Do random gusts of wind affect the incoming G-force more than general measurements of atmospheric effects?

Elevation plays a role; does the weather change falling into a large basin?

In summary, how's the weather up there? Does it matter?

Does MSL have a dust mop??

Thanks, and this is such a wonderful site! Long live UMSF!

[centsworth_II]

Does MSL have a dust mop??

Of course MSL does not have solar arrays to be concerned about dust buildup on. But I wonder if some other components on the deck, or the heat-radiator, might be affected by dust buildup.

[nprev]

To be honest, I've had concerns in that vein regarding the steering differential lever (?) on the top deck; seems like a prime region for foreign material intrusion, and I wouldn't be too surprised if martian dust has abrasive properties.

[djellison]

No more worrying than, say, the rocker bogie of MER. Passive mechanical linkages are probably not at significant risk. Motors / Flex-Cables etc...those are the troublesome parts.

[helvick]

Do weather patterns, i.e. seasonal dust storms, play into the process for choosing a location?

Yes they do but the current sites in the selection list have been chosen, in part, because the probability of large scale storms affecting the atmospheric region important for EDL is low. If you dig into the documentation I'm sure you'll find a lot about this. Global and large scale weather is most important but some locations will have been excluded purely because the local weather has a high probability of causing unpredictable wind conditions at precisely the wrong time (just before landing).

There's a nice summary of some of the modelling work here.

Has our experience landing previous rovers improved our accuracy in predicting the degree of atmospheric drag?
(As mentioned earlier in this thread, Opportunity experienced a G-force on impact on the low end of the predicted range)

A lot of work has gone into improving the atmospheric models but most of that has come from ongoing atmospheric science activities than the relatively small sample size that has come from previous landers' EDL experiences. The important point you made there is that Opportunity was still within the predicted range at the time so it's experience can't really be used to dramatically refine those models. 7 (earth) years of coordinated atmospheric science data from the ground and the various orbiters provides a lot of really useful data for modelling. That's not to say that nothing was learned from the MER EDL data but I think it's less useful than the ongoing science.

Do random gusts of wind affect the incoming G-force more than general measurements of atmospheric effects?

No. The most important factor will be the broader effects that result in the raising (or lowering) of the atmosphere, changing the density profile and high altitude winds (in the 30km to 2km altitude range) during the descent. A bad atmospheric model would have the descent stage hitting critical points at velocities that were a couple of orders of magnitude out of line with reality or many km's off track, a bad wind gust\downdraft at lower altitudes would have effects that are serious but a lot less dramatic. That still has to be considered and dealt with but it's not the same magnitude of problem.
Edited to add some facts to my speculation
Apparently the EDL data from the six successful landers is critical because it provides higher resolution data than any other mechanisms for critical parts of the modelling problem so I'm wrong there - see this for some more detail.
End Edit.

Elevation plays a role; does the weather change falling into a large basin?

Yes it does, just as it does here on earth but again it's the broad characteristics (bulk density\temperature) rather than small scale effects like wind gusts and direction that are most important. It's a lot easier to land at very low elevations because there is a lot more atmosphere to make use of on the way down both in terms of simple distance and atmospheric mass that can be used for braking.

Does MSL have a dust mop??

I'm not even going to go there, we've thrashed that to death far to often in the past.

[tharrison]

Seconded. I saw the presentations as well and none of the sites were marked out as making the engineers 'leery' - indeed they were described as the four safest landing sites in the history of Mars exploration.

I was at the landing site workshop as well, but that statement doesn't match what I'm hearing behind the scenes as a member of the operations team. Yes, they have all been dubbed as "safe" for landing, but they've still been ranked in terms of relative safeness. Eberswalde was very near the cutoff for being dubbed "safe" (there is basically a percentage of risk assigned to any landing site and to make the cut the risk has to be below a certain percentage), and Mawrth is considered to be the safest. The rover *should* be fine at any of the four sites, but with the cost being as high as it is, I can see them wanting to take as few risks as possible to make sure the mission lands successfully. Again, it's all relative.

7 (earth) years of coordinated atmospheric science data from the ground and the various orbiters provides a lot of really useful data for modelling.

We actually have nearly 12 Earth years of continuous weather data from Mars between the MGS MOC (wide angle) and the MRO MARCI. Daily color global mosaics of the entire planet were started in mid-March of 1999 by the MGS MOC. Pretty darn cool.