MSL FAQ - The pool of questions Options

[climber]

Question for both Phoenix and MSL : what kind of colour-target / sundial will we have ?

As it's gona be the most targeted target....

[mcaplinger]

Question for both Phoenix and MSL : what kind of colour-target / sundial will we have ?

Phoenix cal target: http://www.lpi.usra.edu/meetings/lpsc2006/pdf/1149.pdf

MSL cal target is still being designed.

[monitorlizard]

Given the power output of MSL's RTG and the best model you have of rate of power output decline due to plutonium decay, how long could the RTG provide enough power to keep MSL roving (assuming nothing else failed)? Thanks.

[Thu]

I have some questions:

1. What is the ratio of final mass delivered (the rover) and entry mass at Martian atmosphere for the two methods: SkyCrane and airbag delivery method on Mars?
I'm expecting SkyCrane to have better efficiency than using airbag but could anybody give me some specific numbers for comparison?

2. I remember reading somewhere that MSL will be equipped with a flashlight that will allow it to move or perform some science observations at night. Is this true and what's the advantages for observing in the dark on Mars?

3. Another question, maybe a stupid one: Did engineers find out what went wrong with Spirit's right front wheel and come up with an upgrade for MSL's wheels? Or should we let it happens because who knows a dragging wheel may lead to an unexpected discovery

4. Thinking of the 3rd question, I come up with this last one: if something bad forces MSL to move backward just as Spirit is doing now, I think it'll be more difficult for MSL's computer to navigate because her camera mast is not at the center as her sister's. How do you think about this?

Thanks,

[mcaplinger]

2. I remember reading somewhere that MSL will be equipped with a flashlight that will allow it to move or perform some science observations at night. Is this true and what's the advantages for observing in the dark on Mars?

http://www.msss.com/msl/mahli/MAHLI_description.html

"MAHLI has a suite of white light LEDs and a suite of ultraviolet LEDs to provide illumination of the targets it is imaging. The white light LEDs permit the instrument to operate at night and allows the science team to avoid problems of shadowing during daytime imaging. The ultraviolet LEDs provide an opportunity to look for minerals that fluoresce."

[remcook]

If you've got an RTG you might as well do nighttime observations. So, I guess science of MSL is limited by data rates, not power?

[centsworth_II]

MSL operates off the batteries and the MMRTG recharges them. It will operate about 7 hours per sol

How fixed is this seven hour figure? Is it a maximum? An average? And what does "operate" mean?
The MERs routinely "operate" their spectrometers for 12, 24 or more hours at a time.

[elakdawalla]

Here's a few that I've received by email. The first two are variations on a theme:

What kind of AI, if any, is built into the descent stage in terms of selecting an exact point to set the rover down? In other words, does the sky crane "look around" for a suitable spot as it descends, or does it just go straight down regardless?

Is it the rover or the descent stage that decides when the rover is safe on the ground? I'm guessing they both need to know when touch-down occurs because, from the video, it looks like the rover releases the cables and the descent stage flies clear of the rover. So do they both detect it? Or does one detect it and communicate to the other? How is detection done? Radar? Touch sensor?

Why is the "skycrane" concept better than just lowering the rover to the ground with retrorockets (as if using zero-length cables)? Are the cables used for cushioning? Wouldn't it be better for the "skycrane" to hover in one place and lower the rover by unwinding the cables very slowly till the rover touches down, rather than descending with the cables fully extended, as in the video?

[Jim from NSF.com]

How fixed is this seven hour figure? Is it a maximum? An average? And what does "operate" mean?
The MERs routinely "operate" their spectrometers for 12, 24 or more hours at a time.

Operate = rove

If you've got an RTG you might as well do nighttime observations. So, I guess science of MSL is limited by data rates, not power?

limited by power

[Jim from NSF.com]

1. Why is the "skycrane" concept better than just lowering the rover to the ground with retrorockets (as if using zero-length cables)? Are the cables used for cushioning? Wouldn't it be better for the "skycrane" to hover in one place and lower the rover by unwinding the cables very slowly till the rover touches down, rather than descending with the cables fully extended, as in the video?

Skycrane concept eliminates thruster plumes and dust on the rover

The mobility system (wheels etc) absorb the shock

no, extended hover is harder to maintain

[Alex Chapman]

I know it’s a little off topic but I have a quick question about something I saw on the animation post EDL. The animation shows a sample being loaded into, what I asume is, one of the sample holders in the Chemistry & Mineralogy X-Ray Diffraction (Chemin) instrument. From what I can see it looks like there is 24 or so separate sample holders and I was wondering if each holder only be used once and so limiting the number of samples analysed by Chemin.

Do the instruments within the Sample Analysis at Mars Instrument Suite (SAM) have similar limitations on the number of samples that can be studied? Just one last thing, why does Sam have two sample entry ports on the rover’s deck?

Thanks

[Jim from NSF.com]

SAM is being redesigned at the moment

[Cugel]

Skycrane concept eliminates thruster plumes and dust on the rover

Would that be a problem when there is no solar panel up there?
I believe the big advantage of the skycrane is that it minimizes the mass that actually lands.
And by doing so it reduces the stress and loads caused by touchdown.

The mobility system (wheels etc) absorb the shock

I don't think a rocker-bogie system does much shock absorbing as it is completely rigid.
This simply means the vertical speed at touch down must be very small.

BTW, I'm much more concerned about horizontal speed at landing than about vertical speed, which is much more easy to control. I'm afraid the suspension system will not have much tolerance for horizontal speed at touchdown and any swinging motion of the rover must be dampened by the skycrane. Or does the rover have any reaction control system of its own? (I don't think so, as it doesn't carry any fuel tanks).
This will be a pretty tough control job in the windy Martian atmosphere and coming from a huge horizontal entry speed.

[centsworth_II]

Hold a Yo Yo by the string. With a few cm of string, the Yo Yo swings wildly
when the string is shaken back and forth. As the string is lengthened, the
swinging becomes less. When the string is sufficiently long, it can be moved
back and forth quite a bit with little or no motion of the Yo Yo.

[tty]

Would that be a problem when there is no solar panel up there?

Rocket plumes are always a problem close to the ground and they start impinging on it. Not only do they raise dust, but if the ground is uneven you can get quite difficult control problems. Back in the forties they experimented a great deal with using retrorockets to airland loads without parachutes. It worked quite well right until the rockets started impinging on the ground. Then the load invariably turned over.