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Unmanned Spaceflight.com _ MSL _ MSL Cruise Phase

Posted by: nprev Nov 26 2011, 03:50 PM

Okay, we're off and running! Please post all comments relating to MSL's transit to Mars here.

Posted by: Oersted Nov 26 2011, 03:52 PM



The live footage of the first couple of kilometers of the cruise looked really good... smile.gif

Posted by: climber Nov 26 2011, 04:07 PM

Oppy, here I come !
Waiting for post launch conference now!

Posted by: nprev Nov 26 2011, 04:08 PM

Yeah, that was indeed a beautiful sight to behold, all right. smile.gif

Now the waiting begins.

Posted by: vikingmars Nov 26 2011, 04:14 PM

smile.gif ... and we just had champagne at home near Paris to celebrate it, because of many known friends involved in the MSL mission... and also because, in France, we share the ChemCam experiment with the USA. Long life to MSL / Curiosity !
As we used to say in France : BRAVO to the MSL Team and CHAMPAGNE !!!


Posted by: Oersted Nov 26 2011, 04:34 PM

QUOTE (climber @ Nov 26 2011, 05:07 PM) *
Oppy, here I come !
Waiting for post launch conference now!


Waiting for that, when will it be? - Soon? - On NASATV they have a "tweetup" atm...

Posted by: climber Nov 26 2011, 04:48 PM

QUOTE (Oersted @ Nov 26 2011, 05:34 PM) *
Waiting for that, when will it be? - Soon? - On NASATV they have a "tweetup" atm...

They said 2 to 3 hours after launch!!! Guess they were much precise on MSL trajectory tongue.gif

Edited: got the answer! It'be at 18.30 eastern today in another 10 mn!

Posted by: DEChengst Nov 26 2011, 05:34 PM

They just started showing the title card for the post-launch news conference, so I'll guess it will start in a few minutes.

EDIT: Starting right now.

EDIT2: Not much news. Trajectory right on the money. Two way communications established. All temperatures and voltages where they should be.

Posted by: sgendreau Nov 26 2011, 06:01 PM

EDIT2: Not much news.


No news is good news for a long while now, I guess. Counting down till August 6!

Posted by: dmg Nov 26 2011, 07:07 PM

Anyone know why the telemetry pickup from the launch vehicle via TDRS was so spotty?

Posted by: MarsEngineer Nov 26 2011, 09:51 PM

No news is good news indeed!

We are watching cruise stage temps (most look great) - we had to turn one heater off because it was getting a tad warm. A few other things we are watching and learning about. Nothing like real telemetry. Otherwise very boring! Boring is good.

I am happy that everything is so darn nominal (knocks on wood). I am getting the "shift handover' summary from the ops flight director now. Nominal. Nominal. Nominal. (even the word makes me sleepy.) (But I am getting off-nomially sick of too many peanuts. Normally we have one jar but today there were at least three being passed around the cruise MSA. )

We will try to keep things boring until Aug. We still have oh so much to do - Test the final EDL flight software, test/finish the final surface software, there are more bugs still to uncover no doubt.

We may do the spin down to 2 rpm tomorrow (per "nominal" plan - that word again). Still talking about it. May want to wait for the temps to settle down first.We will have to do TCM-1 one of these days (first trajectory correction maneuver). We have weeks but it would be great to get it done sooner than later. Lots of cruise checkouts to do too.

Did you enjoy that launch as much as I did? It is very surreal to see stuff that you have had your hands on being pushed up and up into the sky like that, knowing it is not likely to return to Earth any time soon.

By the way, perhaps someone has mentioned this, Peter and I had your miniaturized names and signatures put on the back of the rover (next to the camera targets). If you were a Martian with very very good eyes you would be able read 12 million names and many thousands of signatures simply by leaning over the rover and reading.



-Rob

Posted by: climber Nov 26 2011, 10:11 PM

Tanks Rob, I was browsing like mad to get any news first hand... And here you are, always keen to inform us! I get very excited during final pool when I heard Peter T saying "Spacecraft's Go"! Very emotional indeed!
Thanks again...and now I know where's the best place to get those so great boring news!

Posted by: MERovingian Nov 26 2011, 10:52 PM

Bravo to all the teams involved, JPL, ULA, NASA, KSC and thanks for a beautiful day!!

From now on, I will let my nails grow in expectation of the Mars landing next August; the last EDLs I remember - close to eight years ago- I ate them all the way to the blood.

Posted by: Pando Nov 26 2011, 11:16 PM

QUOTE (MarsEngineer @ Nov 26 2011, 02:51 PM) *
No news is good news indeed!
...
Did you enjoy that launch as much as I did? It is very surreal to see stuff that you have had your hands on being pushed up and up into the sky like that, knowing it is not likely to return to Earth any time soon.
-Rob


Thanks for the insider info; it's a fantastic day to see a next gen rover being launched successfully and on its way to Mars.

Next August is going to be really exciting.

I just hope you guys removed the lens cap before launch...

Posted by: nprev Nov 27 2011, 12:01 AM

Rob, thanks very much for taking the trouble during this busy time to give us this peek! smile.gif

Go have one on me after the shift, and may the next 8.5 months be boring indeed!!!

Posted by: Explorer1 Nov 27 2011, 12:01 AM

Actually the last EDL was in 2008 with the Phoenix; though that wasn't a rover though right? wink.gif

Posted by: Oersted Nov 27 2011, 12:20 AM

QUOTE (MarsEngineer @ Nov 26 2011, 10:51 PM) *
Did you enjoy that launch as much as I did? It is very surreal to see stuff that you have had your hands on being pushed up and up into the sky like that, knowing it is not likely to return to Earth any time soon.


I sat in my apartment in Brussels, Belgium, rooting animatedly for MSL and eating too many peanuts while my pregnant wife Sandra watched TV, slightly bemused. Our girl will be born in late March next year, if all goes well, and I am hoping that she and MSL will share parallel journeys of discovery on neighbouring planets in this solar system of ours.

I cannot imagine a better example of what's best about humanity to show to her, through her childhood and hopefully adolescence. Science, cooperation, a quest for knowledge: All these good traits that can be summed up in one word, Curiosity, are what I want to hold up to my daughter as an example of what to strive for.

So, yes, you can say that emotionally I have a lot riding on Curiosity.

I feel privileged to be vicariously part of the ride and now look forward to a quiet and relaxing cruise stage while I, personally, reach other deadlines here on Earth... smile.gif

Posted by: Oersted Nov 27 2011, 12:44 AM

I uploaded footage of the launch and spacecraft separation for those who might not have been able to see it...

http://www.youtube.com/user/wwwDOTdalsgaardDOTeu#p/c/99E1D3141D8CEF84/0/qOJqDNp2afE

http://www.youtube.com/user/wwwDOTdalsgaardDOTeu#p/c/99E1D3141D8CEF84/1/k9xpePuiqA8

Posted by: Syrinx Nov 27 2011, 02:02 AM

Thank you sir for the videos. I was unable to watch this morning due to my Texas -> California launch on a Boeing first stage.

Posted by: tanjent Nov 27 2011, 03:34 AM

I'm having some trouble with "data dropouts" myself while trying to view the videos - I wanted to review the telemetry data on the evolution of perigee and apogee during the second Centaur burn, because the first time through I did not understand what I was seeing. My recollection is that after a steady increase the apogee figures dropped abruptly somewhere over Madagascar. This may have simply indicated a move to a higher power of 10 on the display but it was too blurry to be sure. The perigee seemed to be stuck somewhere in the 80's or -80's (couldn't tell if it was a negative sign or a "star" in the simulation). This I really did not understand because it persisted even after the spacecraft was well on its way to Mars. Is it just that after a certain point the perigee ceased to update? Maybe some rocket scientist here can explain how the perigee figure would be expected to evolve if we actually continued to track it as the spacecraft approaches escape velocity. Seems to me both apogee and perigee would eventually have to go to infinity at the point where the vehicle transitions to a solar orbit but when it becomes possible to view the video without a "please try again later" message I am sure it will confirm that this is not what we actually saw.

Posted by: john_s Nov 27 2011, 03:54 AM

I was watching those numbers too. The apogee should have gone infinite when MSL reached escape speed- if I recall correctly it actually went negative on the display, though the moment of reaching escape was missed in the NASA feed because of a cutaway to the launch control center. Perigee however should stay finite- after engine cutoff the the spacecraft was on a hyperbolic trajectory relative to the earth, and a hyperbola has a well-defined closest approach point to Earth (perigee). The actual value of perigee could go up or down during the burn depending on the burn direction- theoretically I suppose it could end up below the Earth's surface, though it would probably not be fuel-efficient to bend the trajectory in that direction.

John

Posted by: tanjent Nov 27 2011, 04:04 AM

OK - I bet it actually finds the perigee by looking backwards along its escape hyperbola, and naturally that would intersect the earth at some point. Got it, I think!

Posted by: MahFL Nov 27 2011, 04:49 AM

The separation video was just awesome, although I did not know the back side of the cruise stage was covered with solar panels, so I was a bit unsure of what exactly I was looking at, but it looked fantastic.

Posted by: OKB001 Nov 27 2011, 05:59 AM

QUOTE (MahFL @ Nov 26 2011, 08:49 PM) *
The separation video was just awesome, although I did not know the back side of the cruise stage was covered with solar panels, so I was a bit unsure of what exactly I was looking at, but it looked fantastic.


It sure did. Although, I was hoping for a bit more live feed from the onboard cameras during the flight ... oh well.

Posted by: kwan3217 Nov 27 2011, 02:23 PM

(Full inline quote removed- Mod)

The apogee for a perfect parabola is infinite, but if you run the formulas to find the perigee and apogee of an ellipse, on a hyperbola, you will get the correct perigee but a finite, negative apogee. Obviously a distance can never be negative (you can never be closer to me than at my same position, with zero distance) but you can run all the formulas in reverse with this negative apogee and get the correct position and velocity of the spacecraft.

Which brings me to my second point: There is in theory enough information in the elements to get the position and velocity of the spacecraft during the burns, if they are all consistent. One thing I don't know is how they handle "altitude". A really common way to do it is to take the radius distance from the center and subtract the equatorial radius of the Earth, but since the Earth is not a perfect sphere, this would result in a negative altitude at launch. So I don't know what you have to add to get back the radius vector, and it may be two different things for different altitudes. I remember seeing one of these simulations where the altitude wasn't in between periapse and apoapse.

Back to the original point: Since the apogee took one value and stuck with it after escape velocity was achieved, maybe they just put in some fill value, like -9999999 meters, and translated it to nautical miles. In which case, after escape, the orbital elements become insufficient to reconstruct position and velocity.

Posted by: tanjent Nov 27 2011, 02:50 PM

Well, the altitude should be directly observable by the spacecraft avionics with no mathematical projection required. But you may be right, Kwan, because, as you mentioned, there were periods during the second burn when it seemed to be decreasing. I took this to mean that we were accelerating towards the Mars transfer orbit along a path that initially was sub-tangential to the curvature of the earth. Really, I wish I could see the telemetry readout again without having to watch those tiny blurry numbers in the corner of the simulation video. Dmuller should write them a little package that could run independently in its own window!

Posted by: scalbers Nov 27 2011, 04:08 PM

QUOTE (kwan3217 @ Nov 27 2011, 03:23 PM) *
Back to the original point: Since the apogee took one value and stuck with it after escape velocity was achieved, maybe they just put in some fill value, like -9999999 meters, and translated it to nautical miles. In which case, after escape, the orbital elements become insufficient to reconstruct position and velocity.

Yes those numbers were fascinating. I assumed we just had one look at the numbers after the orbit went hyperbolic (eccentricity > 1). It seemed a reasonable value of negative apogee for a hyperbolic orbit. Osculating orbital elements of course can always be converted to an instantaneous position and velocity. I wrote a FORTRAN subroutine a long time ago that does this conversion - at least for heliocentric orbits.

I wonder what the earth-relative velocity and eccentricity values were when the engines cut off? It takes about 3.2 km/sec delta-V to go from low-Earth orbit to reach escape velocity (11.3 km/sec). Another 0.6 km/sec or so is needed to get to a Mars transfer orbit, though it looks from this press-kit excerpt that the actual excess velocity is more like 3.3 km/sec.

Orbit at SC Separation
Perigee: 104.0 km
Inclination: 35.5 deg
Hyperbolic Departure
Hyperbolic Excess Velocity Squared (C3): 10.78 km2/sec2
Declination of the Launch Asymtote (DLA): -1.10 deg
Right Ascention of the Launch Asymtote (RLA): 126.6 deg

Approximate Values
Orbit parameters shown for launch on 25 Nov 2011 at 10:25 a.m. EST.

And the following velocity equation from Wikipedia can help get back the semimajor axis, and then the eccentricity:

http://en.wikipedia.org/wiki/Elliptic_orbit

Steve

Posted by: Astro0 Nov 27 2011, 10:05 PM

A little late to the party I guess. My weekend was very busy with our very first NASA-style Tweetup at the CanberraDSN.
A large group watched the launch on our big screen (at 2.02am!) and then headed out to watch our antennas acquire the spacecraft shortly after its separation and the beginning of its cruise to Mars.

A few hours later I headed back out into the light of dawn and snapped this panorama of our dishes at work.



That's DSS34 on the left tracking Curiosity; DSS43 in the middle tracking Mars Odyssey and MRO (warning them that's something is on its way); and just past the rainbow on the right is DSS45, which was the prime antenna for the acquisition and also tracking Curiosity when this photo was taken. Note: it may look as if DSS34 and DSS45 are pointing in opposite directions but wrap that panorama around and they are pointing the same way.

Posted by: Oersted Nov 27 2011, 10:30 PM

Oh, a rainbow to boot! Lovely panorama and thanks for the explanation about the various antennas.

Posted by: MarsEngineer Nov 28 2011, 12:36 AM

QUOTE (Astro0 @ Nov 27 2011, 02:05 PM) *
A little late to the party I guess. My weekend was very busy with our very first NASA-style Tweetup at the CanberraDSN.
A large group watched the launch on our big screen (at 2.02am!) and then headed out to watch our antennas acquire the spacecraft shortly after its separation and the beginning of its cruise to Mars.

A few hours later I headed back out into the light of dawn and snapped this panorama of our dishes at work.



That's DSS34 on the left tracking Curiosity; DSS43 in the middle tracking Mars Odyssey and MRO (warning them that's something is on its way); and just past the rainbow on the right is DSS45, which was the prime antenna for the acquisition and also tracking Curiosity when this photo was taken. Note: it may look as if DSS34 and DSS45 are pointing in opposite directions but wrap that panorama around and they are pointing the same way.


Hi Astro0,

Would you mind if I shared this with the MSL gang here at JPL? They would LOVE it! (I did) Who shall I give credit?

-Rob Manning (MSL chief engineer)

Posted by: MarsEngineer Nov 28 2011, 12:54 AM

Hi all,

Please take a look at the observations made by Duncan Waldron (of the Sir Thomas Brisbane Planetarium in Brisbane, Queensland, Australia).

Images and a movie of the Centaur upper stage venting and (remarkably MSL just after separation) from yesterday's launch:

http://www.facebook.com/BrisbanePlanetarium

Amazing. I shared it with our team here too.

-Rob

Posted by: nprev Nov 28 2011, 12:59 AM

ohmy.gif ...words utterly fail me. Just remarkable.

Many thanks for posting this, Rob!

Posted by: eoincampbell Nov 28 2011, 03:05 AM

WOW! Thanks for sharing another "Heimdall" moment ohmy.gif

Posted by: tanjent Nov 28 2011, 08:36 AM

Quote: http://www.facebook.com/BrisbanePlanetarium

"Other than observations by Brisbane Planetarium staff on Sunday, no other reports have been received of observations of the Mars Science Laboratory, Centaur rocket stage and plume thousands of kilometres out from Earth. Looks like only three of us saw this unique sight. Timings - Curator Mark Rigby (whose camera plays up!) first sees the plume at 2:15am and it is like a one-degree elongated cloud of VERY easy naked eye brightness. Duncan Waldron sees it about 2:30pm and begins photography as it fades. Nonetheless, he captures a unique timelapse covering 21 minutes until 3am"

Sounds familiar. I believe I saw New Horizons off from a similar vantage point. See post 460 in the NH launch thread. (That will remain forever unconfirmed, but it's still interesting to know that these things can be naked-eye visible at such distances.)

http://www.unmannedspaceflight.com/index.php?showtopic=2050&st=450

Posted by: Oersted Nov 28 2011, 01:12 PM

That is an amazing timelapse!

http://www.youtube.com/watch?v=gA9U9TZZ4nc&feature=player_embedded

Posted by: Oersted Nov 28 2011, 03:10 PM

On my youtube page of MSL launch movies I am getting some questions. I have managed to answer two of them, but I need an answer for the third, which I interpret as "cruise speed of MSL"... Could someone in here maybe help me with the answer?

http://www.youtube.com/all_comments?v=k9xpePuiqA8

"pl inside earth gravity how maney km/h speed?" - I replied 11,2 km/s, which I believe is more or less the correct the escape velocity.

"after psssing gravity how maney km/h?" - Hmmm...

"when msl will reach mars?" - I replied August 2012.

Posted by: Greg Hullender Nov 28 2011, 03:57 PM

QUOTE (Oersted @ Nov 28 2011, 07:10 AM) *
"after psssing gravity how maney km/h?" - Hmmm...

I think he wants to know the hyperbolic excess velocity.

--Greg

Posted by: kwan3217 Nov 28 2011, 08:58 PM

(Full inline quote removed- Mod)

The guys at JPL SSD (that do the Horizons ephemeris program) got the spice kernel for a projected launch at what happened to be the actual launch time, 26 Nov at start of window. Since the launch was accurate (<0.1 sigma) this is probably pretty good. You can't get the kernel from them, but you can run Horizons and get any form of vectors or elements you want, which may be even better than a kernel.

Earth departure according to the kernel:
Kernel starts at 2011-NOV-26 15:52:12.3830 CT (not UTC, about a minute difference. UTC is 2011-11-26T15:51:06.200 at kernel start)
Periapse was 798.736 seconds before this, 13m18.736 seconds, so periapse was at 2011-Nov-26 15:38:53.647 CT (15:37:47.464 UTC)
Periapse distance: 6572.438km from the center of the Earth, or about 194km altitude
Eccentricity: 1.17677
From this, velocity at periapse was 11.490km/s. This was 476m/s above escape speed at this altitude. Hyperbolic excess speed (v_inf, eventual speed of departure from Earth) is 3.274km/s, for a C3 of 10.721

Spaceflightnow reported centaur main engine start 2 at 32:40 MET (15:34:40 UTC) and cutoff at 40:30 MET(15:42:30 UTC) so theoretical periapse is during the centaur burn, which is kind of as expected.

The second burn also was used to increase the inclination, so it was not purely in plane. The parking orbit was something like 28deg inclination, while departure was at 34.5deg. This is weird, since you should be able to launch at an azimuth such that no plane change is needed in the second burn.

Posted by: Roby72 Nov 28 2011, 09:51 PM

Here you could see Curiosity 10 hours 30 minutes after launch - taken by Austrian amateur Gerhard Dangl:

http://www.dangl.at/2011/msl/msl.htm

Video here:
http://www.dangl.at/2011/msl/msl.avi

very good result in my opinion !

Robert

Posted by: Bobby Nov 29 2011, 12:40 AM

Question? Is there a site either through JPL or another place that shows where MSL is now. A tracking site showing location. I can't seem to find one.

Thanks.

Posted by: punkboi Nov 29 2011, 12:49 AM

http://space.jpl.nasa.gov/

MSL's position should eventually be posted on this page

EDIT: And this page as well:

http://mars.jpl.nasa.gov/msl/mission/whereistherovernow/

Posted by: Astro0 Nov 30 2011, 04:12 AM

As usual, Eyes on the Solar System can take us all on a ride throughout MSL's cruise phase.

From the Twitter site:
Preliminary @MarsCuriosity trajectory is in. http://1.usa.gov/tU6T8m to ride onboard looking back at Earth http://twitpic.com/7lqw60

TIP: If you haven't used Eyes on the Solar System - DO SO!
Note: You will need to download the Unity player plug-in for your browser (it'll tell you if you haven't already got it).

Posted by: Explorer1 Nov 30 2011, 05:57 AM

Is the cruise stage's spin in real-time?
Great attention to detail if so!

Posted by: MahFL Nov 30 2011, 12:08 PM

Don't forget, the whole Rover is spinning....lol. Thankfully she does not have a human "brain".

Posted by: MahFL Nov 30 2011, 12:13 PM

I am not sure how accurate the model is but it looks like there is only one thruster jet on the cruise stage for course corrections, I would have thought 2 would be more reliable.

Posted by: ilbasso Nov 30 2011, 12:18 PM

Should we bring her back for repairs? rolleyes.gif

Posted by: MahFL Nov 30 2011, 01:52 PM

I just read that the hand lens imager can take pics and movies of the rover it'self, even when driving, and can infact reach higher than the Mastcam, that will be so cool to see.

Posted by: pospa Nov 30 2011, 02:22 PM

Also VERY cool would be any MAHLI picture from inside of the spacecraft during the cruise phase ... as was done with Phoenix RAC camera.
Do we know if MSL team has intention to do such a test shot?

Posted by: climber Nov 30 2011, 03:05 PM

You can even dream of a shot of Spacecraft separation as seen from the spacecraft tongue.gif

Posted by: ElkGroveDan Nov 30 2011, 03:46 PM

The next images we'll see from MSL will likely be from MARDI.

Posted by: eoincampbell Nov 30 2011, 04:19 PM

QUOTE (MahFL @ Nov 30 2011, 05:52 AM) *
...I just read that the hand lens imager can take pics and movies...

Could you provide a link ? I think Doug mentioned this before. I've only read that MAHLI would do time-lapse type frames...

Posted by: djellison Nov 30 2011, 04:40 PM

QUOTE (pospa @ Nov 30 2011, 06:22 AM) *
Also VERY cool would be any MAHLI picture from inside of the spacecraft during the cruise phase ... as was done with Phoenix RAC camera.
Do we know if MSL team has intention to do such a test shot?


Don't know if they plan to - but I would have thought they would... inflight-cal is a useful post-launch checkout. I wouldn't expect them to actuate the lens cover - but they could certainly power up the white-light LED's and take a picture inside the backshell. It would, I think, show the steering actuator for the front left wheel in its stowed position.

QUOTE (Explorer1 @ Nov 29 2011, 09:57 PM) *
Is the cruise stage's spin in real-time?
Great attention to detail if so!


No - it's canned at 2rpm ( the nominal cruise spin rate) Remember, 'Eyes...' uses a combination of predicted and reconstructed data. Getting 'live' data thru from a flight project in these ITAR laden times is a mountain that even I'm not even going to attempt.

QUOTE (MahFL @ Nov 30 2011, 04:13 AM) *
I am not sure how accurate the model is but it looks like there is only one thruster jet on the cruise stage for course corrections, I would have thought 2 would be more reliable.


Using this image as reference:
http://www.jpl.nasa.gov/images/msl/20111110/pia15026-43.jpg

Assuming you meant the thruster at about 5 O'clock...that's not a thruster you're looking at. That's the star-tracker.

There are 8 thrusters - two clusters of 4. In that image they are at about 1 O'clock and 7 O'clock, covered with a red remove before flight fixture. They're tiny.


QUOTE (eoincampbell @ Nov 30 2011, 08:19 AM) *
Could you provide a link ? I think Doug mentioned this before. I've only read that MAHLI would do time-lapse type frames...


If you google MAHLI. The very first link takes you to the MSSS page that includes a link to 'reference material'.
Documents like this : http://www.msss.com/msl/mahli/references/Edgett_etal_MarsMicro.pdf : and this : http://www.lpi.usra.edu/meetings/lpsc2009/pdf/1197.pdf should fill you in. I've heard annecdotal comments that using MAHLI for DD surveys is possible, as it's the widest FOV camera (apart from MARDI, which obviously isn't going to be looking for DD's) with the movie ability. Mastcam 34 is roughly Pancam FOV, and Mastcam 100 about 1/3rd of that - whereas MAHLI is, if my math is right - about 30 x 23 deg FOV. The question would be - is it worth the large energy spend to move the arm into an elevated position for such a survey. It's not something I'd expect to see happening early on, that's for sure.

D

Posted by: Deimos Nov 30 2011, 04:50 PM

http://msl-scicorner.jpl.nasa.gov/Instruments/MAHLI/

Search down to "video". The 4 cameras (2 mastcam detector+electronics assemblies + MAHLI + MARDI) have common detectors and electronics, and thus many of the same capabilities--the filters on the mastcam and the capabilities enabled by their location on the rover being the obvious exceptions.

There are a lot of ideas to take advantage of this and the general ability to focus out to infinity. We'll have to figure out which are operationally feasible given the other desires for rover activities.

Posted by: MarsEngineer Nov 30 2011, 04:57 PM

QUOTE (djellison @ Nov 30 2011, 08:40 AM) *
There are 8 thrusters - two clusters of 4. In that image they are at about 1 O'clock and 7 O'clock, covered with a red remove before flight fixture. They're tiny.

D


Doug has it right. The two thruster clusters on either side of the cruise stage used by MSL are nearly exactly the same used on Mars Pathfinder and MER.

Each thruster can provide about a pound of push when needed. This configuration is very handy (if I do say so myself wink.gif ) for doing "balanced" turns(*) that do not impart unwanted changes in the trajectory. Considering MSL is so big compared with these other mars missions, it is amazing that these little thrusters are all we need to keep the solar arrays pointed roughly to the sun and the antennas roughly toward the Earth. It is even more amazing that they can also refine MSL's flight path to stay on course (obviously MSL's TCMs take more time to accelerate the same amount as MER or MPF because MSL is several times more massive).

* we use the word "turn" to denote a rotation of the vehicle, not a left or right turn of the flight path. The latter we call TCMs - trajectory correction maneuvers.

-Rob

PS Doug, Nice tool!!!!!

Posted by: john_s Nov 30 2011, 05:21 PM

I love the idea of the rover doing an "arms-length self portrait" like we all do with our point-and-shoots. In color too! That will be something to look forward to (one of many things).

John

Posted by: djellison Nov 30 2011, 05:23 PM

It took all the way until working on the MSL animation that I learned how TCM's are done when you're still spinning at 2rpm smile.gif It's very elegant! It's like a brother on a merry-go-round trying to kick his sister each time he spins past her smile.gif

It's why I wanted to have something more than '8 months later' - we cut it down a bit for the finished thing, earlier we had a burn from each cluster, at the same point in the rotation - http://www.youtube.com/watch?feature=player_detailpage&v=P4boyXQuUIw#t=41s

Posted by: climber Nov 30 2011, 06:18 PM

I noticed on a previous video that legs extended and rétros fired BEFORE been released from the parachutte! The link you provide here is both More recent and accurate.

Posted by: djellison Nov 30 2011, 07:25 PM

Actually - the descent stage thrusters do start before sep from the backshell, but only at about 1%, so you wouldn't see anything.

The earlier animation was accurate at the time it was made. The decision to release the mobility system later in the sequence came between the old animation and the new one. (and during production of the new animation we were chasing the change from a hard drop, to a soft release and back to a hard drop..which is what we ended up with)

Posted by: john_s Nov 30 2011, 07:38 PM

That "hard drop", with the rover falling out of the backshell in free-fall before the engines kick in, is the scariest part of the animation IMHO. I assume the purpose is to get some safe distance between the rover and the backshell.

And though it's been said many times before, it bears repeating- that's a fabulous piece of movie-making.

John

Posted by: climber Nov 30 2011, 07:53 PM

I read, where?, that, as soon as released, Curiosity performs a manoeuver to put a safe distance between backshell? and parachutte? Can't really notice in the movie...or didn't look properly. Can you confirm this, Doug?

Posted by: Ron Hobbs Nov 30 2011, 08:17 PM

From what I thought was a very informative article in the January 2011 issue of Aerospace America from the AIAA:

"Things begin to happen fast at backshell and parachute separation, but the first thing the sky crane and Curiosity do is nothing." ohmy.gif "The contraption is programmed to free-fall for 1 sec to be well clear of the ... parachute canopy, risers, and backshell."

"Next (after MLE ignition) the vehicle maneuvers laterally to prevent having the backshell and parachute collide in midair or land on top of each other - the worst of luck 150 million miles from Earth."

This may have changed, although some kind of collision avoidance must still be included.

Ron

Posted by: djellison Nov 30 2011, 10:33 PM

Ron - as far as I know, that article has it about right. (Apart from semantics of MLE fire up.... they're just warming up at 1% before the drop)

http://trs-new.jpl.nasa.gov/dspace/handle/2014/41629 was our go-to document for EDL

QUOTE
At initiation of BSS, separation nuts are fired to release the PDV from the backshell. For one second, the PDV freefalls out of the backshell to provide sufficient separation to avoid inadvertent recontact when maneuvering begins. Once this one-second freefall is complete, the eight MLEs are throttled up from their 1% near-shutdown condition and the PDV begins a 2.2 second period during which any residual attitude rates from the BSS event are removed and the PDV assumes a pre-defined attitude for the beginning of powered descent...
...During Powered Approach, the PDV follows a 3-D polynomial trajectory which was computed at BSS. As the PDV follows the polynomial, horizontal velocity is smoothly brought to zero while vertical velocity is simultaneously brought to 20 m/s. The end point of the trajectory is about 100 m above the surface and 300 m perpendicular to the plane of the entry trajectory. Since the PDV is actively slowing, the parachute and backshell will actually travel past the PDV and reach the surface ahead of the PDV. The 300 m divert distance is adequate to ensure the PDV does not land on the parachute or backshell. Once the endpoint of the Powered Approach trajectory is reached, the Constant Velocity Accordion begins


So there isn't a discreet avoidance maneuver as there was with PHX ( although PHX didn't actually need it's after all ) - but avoidance is part of the mix of the trajectory design from BSS to the CVP

Enough TLA's smile.gif

Thanks John - the heavy lifting was Bohemian Grey - I just pointed them in the right direction. The BSS is the moment I'm most proud of...and showing it to the EDL team for the first time one the highlights of my short time at JPL so far. It involved a spontaneous high-five across a conference room table smile.gif

Posted by: MahFL Dec 1 2011, 12:23 AM

Well I should have known better the tragectory maneuvers would not be done with a single thruster , confidence is restored smile.gif.

Posted by: Syrinx Dec 2 2011, 07:42 AM

http://www.sciencedaily.com/releases/2011/12/111201220357.htm

Almost entirely good news. The one small bit of unexpected news (nothing to worry about):

QUOTE
The spacecraft experienced a computer reset on Tuesday apparently related to star-identifying software in the attitude control system. The reset put the spacecraft briefly into a precautionary safe mode. Engineers restored it to normal operational status for functions other than attitude control while planning resumption of star-guided attitude control.

Posted by: stevesliva Dec 2 2011, 07:56 AM

Seems to be regurgitating the same source:
http://spaceflightnow.com/atlas/av028/111201noburn.html

Posted by: MahFL Dec 2 2011, 03:10 PM

The Eyes on the Solar System make my IE 8 crash after a while, does anyone have the same problem ?, says "too many heap" entries.

Posted by: B Bernatchez Dec 2 2011, 05:42 PM

No problems for me (that wouldn't be fixed by a better video card). blink.gif

Posted by: djellison Dec 2 2011, 06:52 PM

QUOTE (MahFL @ Dec 2 2011, 07:10 AM) *
The Eyes on the Solar System make my IE 8 crash after a while, does anyone have the same problem ?, says "too many heap" entries.


Hence the Beta label. It happens. Just don't use it too look at too much stuff before restarting it ( I know, sounds lame, but it does work ) It's a Unity plugin problem that we're looking at, but is mainly outside our control.

Posted by: Mars Attack Dec 4 2011, 02:57 PM

I'm a bit concerned about the reported reset of the MSL computer and safemode due to a star tracker. If this reset had happened in the middle of the upcoming trajectory correction burn, originally schedules a week or so post anomaly, wouldn't this have been disastrous? MSL is on a course to miss Mars by 38000 miles. Could it be that the delay of this course correction might have been influnenced by this potentially serioius malfunction? If I'm wrong, please write some words of assurance. Thanks

Posted by: ElkGroveDan Dec 4 2011, 03:42 PM

There is extra fuel aboard and my understanding is that due to a precise initial burn they have already delayed the first TCM by a month or so. Typically these craft are built with redundancies and contingencies built upon redundancies and contingencies. One common and predictable anomaly is not going to sink the entire mission. Chill.

Posted by: Hiwayman Dec 4 2011, 03:56 PM

Sorry for this being posted in the wrong forum, but the launch topic is closed. Did anyone notice the "umbilical" or "hose like" aperture that was still attached to the fairing during launch? It was about 10' - 15' ft from the top of the nose and protruded out about 3-4 feet? Not all cameras caught it, but it was clearly visible on the camera that showed the fairing separation, and another ground based camera. Once the fairing was ejected, the aperture went with it, so it became a mute point, but it sure looked like it was something that should have been left on the ground rather than fly with the vehicle. Did anyone see it? It obviously did not affect the trajectory as it was close to perfect.

Posted by: elakdawalla Dec 4 2011, 04:19 PM

Someone else pointed this out to me on the Atlas fairing on the Juno launch -- I think it's an Atlas V thing, and is normal.

Posted by: Hiwayman Dec 4 2011, 04:28 PM

QUOTE (elakdawalla @ Dec 4 2011, 09:19 AM) *
Someone else pointed this out to me on the Atlas fairing on the Juno launch -- I think it's an Atlas V thing, and is normal.


Thanks, Emily!

Posted by: stevesliva Dec 4 2011, 04:55 PM

QUOTE (Mars Attack @ Dec 4 2011, 10:57 AM) *
If this reset had happened in the middle of the upcoming trajectory correction burn, originally schedules a week or so post anomaly, wouldn't this have been disastrous?


Nope.

Posted by: Mars Attack Dec 4 2011, 05:20 PM

QUOTE (stevesliva @ Dec 4 2011, 04:55 PM) *
Nope.

Thanks folks for the reassurance!

Posted by: climber Dec 4 2011, 06:52 PM

QUOTE (elakdawalla @ Dec 4 2011, 05:19 PM) *
Someone else pointed this out to me on the Atlas fairing on the Juno launch -- I think it's an Atlas V thing, and is normal.

Yes, very visible indeed! Must be normal if already hapened before but quite a big device.

Posted by: Paolo Dec 4 2011, 07:04 PM

QUOTE (Mars Attack @ Dec 4 2011, 03:57 PM) *
I'm a bit concerned about the reported reset of the MSL computer and safemode due to a star tracker. If this reset had happened in the middle of the upcoming trajectory correction burn, originally schedules a week or so post anomaly, wouldn't this have been disastrous?


beside the fact that missing the first trajectory correction would still leave plenty of time to recover, I think star trackers are not used during burns in order not to mislead them into tracking particles or small debris.

Posted by: centsworth_II Dec 4 2011, 07:18 PM

QUOTE (ElkGroveDan @ Dec 4 2011, 10:42 AM) *
There is extra fuel aboard and my understanding is that due to a precise initial burn they have already delayed the first TCM by a month or so...
I saw this too, but it confuses me. As I understand it, the initial burn aimed away from Mars and the 1st TCM was to aim at Mars. How could a precise burn aiming away from Mars affect the timing of the first TCM?



Posted by: djellison Dec 4 2011, 08:23 PM


From http://trs-new.jpl.nasa.gov/dspace/handle/2014/41883


QUOTE
The first three TCMs will be jointly optimized to reduce propellant consumption and fulfill
planetary protection requirements, with TCM-3 being the first TCM that is targeted to the final
entry interface point
. TCM-4 and TCM-5 will be used to improve the delivery accuracy at the entry
interface, while TCM-6 is a contingency maneuver opportunity that is not needed to achieve the
required entry interface accuracy, but is available to correct an unplanned late anomaly


My understanding is that TCM 1 was only ever about backing out injection errors...and as they are so small, there's no need for it.

Posted by: Oersted Dec 4 2011, 08:43 PM

QUOTE (Hiwayman @ Dec 4 2011, 04:56 PM) *
Sorry for this being posted in the wrong forum, but the launch topic is closed. Did anyone notice the "umbilical" or "hose like" aperture that was still attached to the fairing during launch? It was about 10' - 15' ft from the top of the nose and protruded out about 3-4 feet? Not all cameras caught it, but it was clearly visible on the camera that showed the fairing separation, and another ground based camera. Once the fairing was ejected, the aperture went with it, so it became a mute point, but it sure looked like it was something that should have been left on the ground rather than fly with the vehicle. Did anyone see it? It obviously did not affect the trajectory as it was close to perfect.


At NASASpaceflight.com they have a drinking game going on for every time this question is being asked (ps: better to ask a question about it than just assuming it is an error):...
http://forum.nasaspaceflight.com/index.php?topic=27385.360

QUOTE
QUOTE
QUOTE
???
I was rewatching the curiosity launch and noticed a thin bent tube rocket firing on the side of the fairing right before fairing sep...what is the engineering and aerospace reasoning for this?
LH2 vent fin

Atlas V launch drinking game: when someone asks this question, drink. When someone answers accurately, drink. If Jim is first, drink again.


And as to what it actually is, it is called the LH2 vent fin.

Supremely uncatastrophical explanation here:

"Its a LH2 vent fin — a small pipe. The RL-10 engine, which powers the second stage of the rocket and is enclosed inside the fairing, uses liquid hydrogen as fuel. The LH2 is constantly boiling off producing gas, some of it is used to keep the tank pressurized, the rest must be vented overboard as a gas (it is not ignited) to avoid an explosive situation in the enclosed and confined interstage area while the RL-10 engine is inactive.
After the fairing is jettisoned, the H2 gas is simply vented directly to space causing the flare/glow that you see.
As far as any thrust is concerned resulting from the venting, it is trivial compared to the muscle of the RD-180 engine which powers the first stage — there is a lot of control authority from it."

Engineering drawings here:
http://forum.nasaspaceflight.com/index.php?topic=26327.345

Posted by: nprev Dec 4 2011, 08:49 PM

Yeah, it really was a sweet launch...and major kudos again, Doug, for the http://solarsystem.nasa.gov/eyes/ sim of the journey.

Best...Christmas...toy...EVER!!! smile.gif

Posted by: Mars Attack Dec 4 2011, 11:00 PM

Mr. Doug Djellison, any chance that you could expand your totally awesome sim of the MSL journey to include a realtime EDL phase so all of us can watch a second by second, sweat producing and heart stopping animation all the way to the touchdown. Just a suggestion. Thanks for all you do for this forum.

Posted by: djellison Dec 4 2011, 11:12 PM

We hope to - but it's entirely a matter of budgets. I can't promise anything. I will say that it is highly unlikely that such a thing would be driven by realtime telemetry during EDL for a wide range of reasons to long to discuss here. It would likely be driven by a predicted series of events, with key moments triggered manually at JPL.

Posted by: climber Dec 5 2011, 11:38 AM

QUOTE (djellison @ Dec 5 2011, 12:12 AM) *
We hope to - but it's entirely a matter of budgets. I can't promise anything. I will say that it is highly unlikely that such a thing would be driven by realtime telemetry during EDL for a wide range of reasons to long to discuss here. It would likely be driven by a predicted series of events, with key moments triggered manually at JPL.

Doug, I didn't tell you yet but yes, your "sim" is one order of magnitude better than the one we had for MER...which was already awesome.
Regarding realtime (I was about to ask actually) we have some experience there with live comments been off set with the images (like "we should be on the ground by now..."), the parachutte deployment been "decided" by the real hardware and then been informed when it actually happened "parachutte deployed xxx second later than calculated). I guess we know this but anyway.
So, if buget's ok...we'll be glad to have us the feeling of been there instead of only eating peanuts.

Posted by: punkboi Dec 7 2011, 05:57 AM

You can now view MSL's current position in space on JPL's Solar System Simulator

http://space.jpl.nasa.gov/

Posted by: Syrinx Dec 7 2011, 07:56 AM

http://space.jpl.nasa.gov/cgi-bin/wspace?tbody=1000&vbody=1001&month=12&day=6&year=2011&hour=00&minute=00&fovmul=1&rfov=2&bfov=1&porbs=1&showsc=1&showac=1

MSL and inner planets. Long journey ahead.

Posted by: Lucas Dec 7 2011, 02:56 PM

For the impatient among us... wink.gif

http://space.jpl.nasa.gov/cgi-bin/wspace?tbody=-76&vbody=1001&month=8&day=6&year=2012&hour=05&minute=15&fovmul=1&rfov=30&bfov=30&porbs=1&showsc=1&showac=1

in very good agreement with the "countdown" clock at the MSL site (obviously!)

Posted by: pospa Dec 14 2011, 02:32 PM

T +18 days - MSL has about 9% of its cruise done and starts to collect first scientific data - http://www.jpl.nasa.gov/news/news.cfm?release=2011-386.


Posted by: punkboi Dec 14 2011, 10:27 PM

Where is Curiosity now? There's now a dedicated page on its mission website

http://mars.jpl.nasa.gov/msl/mission/whereistherovernow/

Posted by: Lunik9 Dec 26 2011, 09:28 AM

New sunspot 1387 erupted during the late hours of Christmas Day, producing an M4-class flare and hurling a Coronal Mass Ejection - CME toward Earth and Mars.

The CME is expected to deliver a glancing blow to Earth's magnetic field on Dec. 28th at 1200 UT and a direct hit to the planet Mars on Dec. 30th at 1800 UT.
Using onboard radiation sensors, NASA's Curiosity rover might be able to sense the CME when it passes the rover's spacecraft en route to Mars. unsure.gif

Here on Earth, NOAA forecasters estimate a 30-to-40% chance of geomagnetic storms on Dec. 28th when the CME and an incoming solar wind stream (unrelated to the CME) could arrive in quick succession. High-latitude sky watchers should be alert for auroras on Wednesday night.


Posted by: Explorer1 Dec 26 2011, 11:40 PM

How large would an event have to be to seriously impact the electronics on-board MSL? I remember how the MERs avoided the really big ones on their cruise around Halloween 2003, with lots of relief on the ground.

Posted by: centsworth_II Dec 27 2011, 08:05 AM

According to http://www.nasa.gov/mission_pages/sunearth/news/curiosity-cme_prt.htm CMEs present no threat to MSL.

"With solar activity on the upswing it's only a matter of time before a CME engulfs the Mars-bound rover. That suits some researchers just fine. As Don Hassler of the Southwest Research Institute (SWRI) in Boulder, Colorado, explains, 'We look forward to such encounters because Curiosity is equipped to study solar storms.'

Encounters with CMEs pose little danger to Curiosity. By the time a CME reaches the Earth-Mars expanse, it is spread so thin that it cannot truly buffet the spacecraft."



Posted by: pospa Jan 6 2012, 11:03 PM

TCM-1 scheduled for Jan 11th, dv 5,5 m/s.
Then equipment tests for one week, starting from Jan 15th.
Let's see if we'll get some picture(s) from interior.

http://www.jpl.nasa.gov/news/news.cfm?release=2012-004

Posted by: pospa Jan 13 2012, 10:01 AM

TCM-1 completed successfully.
Rob Manning http://youtu.be/MDD9pAkMqR8 while almost whispering in mission control room. Nice smile.gif

Posted by: Phil Stooke Jan 13 2012, 12:12 PM

"By the time a CME reaches the Earth-Mars expanse, it is spread so thin that it cannot truly buffet the spacecraft"

I hope this also applies to MESSENGER!

Phil


Posted by: climber Jan 31 2012, 06:53 PM

According to AW&ST next trajectory correction is scheduled on March 26th

Posted by: pospa Feb 6 2012, 09:53 AM

Not sure if mentioned here before, but radio amateurs from Germany, Bochum have received signals (X-band telemetry) from MSL last year.
It should be the first reception of the MSL outside the official NASA DSN and USN tracking station at Dongara, Australia.

http://www.uk.amsat.org/2578

Posted by: MahFL Feb 10 2012, 01:37 PM

Software fix for Star Tracker problem. smile.gif

http://www.theregister.co.uk/2012/02/10/msl_computer_issue_resolved/

Posted by: Mars Attack Mar 1 2012, 03:36 PM

The computer that received the software fix, is it the sole computer for MSL or was it located on the cruise stage, decent stage, or the lander? If there are separate computers, will they also need a software fix for the same type of problem?

Posted by: MahFL Mar 2 2012, 12:20 AM

QUOTE (Mars Attack @ Mar 1 2012, 03:36 PM) *
... will they also need a software fix for the same type of problem?


MSL has 2 identical main computers which control all aspects of flight, EDL and the surface operations, one is a backup. There is also a fly away controller on the decent stage which enables the descent stage to keep flying away.

So no other computers need updating.

http://en.wikipedia.org/wiki/Mars_Science_Laboratory

Posted by: stevesliva Mar 13 2012, 02:46 AM

I found this article interesting:
http://spaceflightnow.com/news/n1203/06marsorbiters/

QUOTE
Engineers are shifting the orbits of the Mars Reconnaissance Orbiter and Odyssey probes, ensuring they have line-of-sight communications with Curiosity as it lands at Gale crater

Posted by: DLM Mar 19 2012, 02:04 AM

Forgive me if this has already been answered, but I submitted my name many months ago for the chip on the MSL, I was wondering if there is a site where I can confirm that it's there.

Posted by: Astro0 Mar 19 2012, 11:46 AM

A quick search of the Forum revealed this http://www.unmannedspaceflight.com/index.php?showtopic=5911&view=findpost&p=167391

The MSL website only carries participation maps:
http://www.unmannedspaceflight.com/index.php?showtopic=5911&view=findpost&p=167391
http://marsparticipate.jpl.nasa.gov/msl/participate/sendyourname/worldmap/

Looks like you'll have to trust that your name went in.
Hopefully you made a copy of your certificate.

Posted by: Explorer1 Mar 27 2012, 05:45 AM

TCM #2 complete...

http://www.jpl.nasa.gov/news/news.cfm?release=2012-088

Halfway there on April 1st!

Posted by: MahFL Mar 27 2012, 10:06 AM

I like the way they are a slightly cautious, saying if the landing is sucesssfull, etc.

Posted by: ElkGroveDan Mar 27 2012, 06:06 PM

QUOTE (MahFL @ Mar 27 2012, 02:06 AM) *
I like the way they are a slightly cautious, saying if the landing is sucesssfull, etc.

Of course it will be successful. I've run the simulation created by Doug and his team over and over again. I can report that it results in a successful landing every single time.

Posted by: tedstryk Mar 27 2012, 08:08 PM

QUOTE (ElkGroveDan @ Mar 27 2012, 07:06 PM) *
Of course it will be successful. I've run the simulation created by Doug and his team over and over again. I can report that it results in a successful landing every single time.


Wow, good, now the team doesn't have to be nervous on landing day.

Posted by: climber Mar 27 2012, 08:57 PM

QUOTE (tedstryk @ Mar 27 2012, 09:08 PM) *
Wow, good, now the team doesn't have to be nervous on landing day.

Doug and team will have to... laugh.gif

Posted by: MahFL Mar 31 2012, 02:36 PM

Talking of landing day, I took the Monday off from work so I can watch the landing and the first pictures coming back. That's if we don't have a hurricane bearing down on us......

Posted by: centsworth_II Mar 31 2012, 06:27 PM

QUOTE (MahFL @ Mar 31 2012, 10:36 AM) *
...I took the Monday off from work....
laugh.gif
I took the whole week off!

Posted by: charborob Mar 31 2012, 08:44 PM

I will be on vacation also during that crucial week, in a remote location. Don't know if I'll be able to get news about MSL. I'll try not to worry too much and enjoy my time with the family.

Posted by: Oersted Mar 31 2012, 11:04 PM

As long as you eat peanuts at the appointed time that's ok... wink.gif

Posted by: Paolo Apr 2 2012, 12:56 PM

QUOTE (charborob @ Mar 31 2012, 10:44 PM) *
I will be on vacation also during that crucial week, in a remote location.


the same for me. if all goes as planned, I should be enjoying my second trip to a remote, barren, Mars-like country: Mongolia!

Posted by: Phil Stooke Apr 2 2012, 06:49 PM

I'll be in transit between a week in Tofino and a return to Ontario... the hardest part will be convincing my fellow travellers that checking up on the latest from Mars is OK for vacation because it's not work! (since normally I would excuse looking at Mars stuff all day by saying - I'm not goofing off, this is my work!)

Phil


Posted by: Hungry4info May 4 2012, 10:29 PM

Curiosity's Hand Lens Imager (MAHLI) Acquires Test Image En Route to Mars
http://www.msss.com/science-images/mahli-acquires-test-image-en-route-to-mars.php

Posted by: Oersted May 5 2012, 12:08 AM

I'm sure our image wizards can coax some more detail out of that picture, maybe with a super-sampling-stacking algorithm and boosting the red channel, or - ehh, actions to that effect, ...ahem... wink.gif

Posted by: walfy May 10 2012, 04:44 AM

There doesn't seem to be any detail hidden in the shadows, except in the lower right-hand side there's something more there than all that random noise – probably something else reflecting its blurry self. Considering how cold the CCD must be, I'm surprised there's some noise. Or maybe the spacecraft is warm in its shell, from the RTG?

The highlights don't seem to be hiding much either.

The image is nearly twice the size as those from Spirit and Opportunity rovers! And in color!

Here's a version with shadows boosted way up bringing out the noise, and highlights trimmed down bringing out more blur patterns:


Posted by: djellison May 10 2012, 04:39 PM

You can see some of the carbon figre textures to the right of the LED reflections on the inside of the backshell as a slightly lineated checker like pattern
http://mars.jpl.nasa.gov/msl/images/msl20110607_2011-4314-full.jpg

The actual spot we're looking at is not visible in that picture - but it's basically the same all the way around.

It's pretty warm in the backshell - typically room temperature. The CCD will be much happier once it's on Mars. Moreover - it will have been quite a long exposure to get that image, an order of magnitude or longer that will be done on Mars. We're talking a range of 20cm+, rather than the 2cm the LED's will typically be illuminating.

Posted by: PDP8E May 11 2012, 03:44 AM

Here is my take on the 'forward mobility cable bracket' in approximately the MSSS orientation.
Do we have a JPL image (close up) of this bracket?



Posted by: djellison May 11 2012, 06:11 AM

I've looked at most of the publicly available MSL images and there isn't a close up of it - and certainly not when stowed.

It's visible here - http://photojournal.jpl.nasa.gov/jpeg/PIA14256.jpg

This is a poor image, from above, but you can see stowed MAHLI and stowed mobility and the bracket in question

http://photojournal.jpl.nasa.gov/jpeg/PIA15021.jpg


it's just behind the callout graphics in this one
http://photojournal.jpl.nasa.gov/jpeg/PIA15289.jpg

It's also on these...
http://photojournal.jpl.nasa.gov/jpeg/PIA14252.jpg
http://photojournal.jpl.nasa.gov/jpeg/PIA13980.jpg
http://photojournal.jpl.nasa.gov/jpeg/PIA13981.jpg
http://photojournal.jpl.nasa.gov/jpeg/PIA13808.jpg




Posted by: PDP8E May 11 2012, 11:54 PM

Doug,
Thanks for digging those images out !
As I looked over each image I was thunder struck <again> by how intricate and large MSL really is.
The hand lacing on the cables is exquisite work. I'll look at the bracket and see if I can come up with something in few days (there seems to be four of them, one on each corner-wheel 'mobility' arm).

thanks!




Posted by: atomoid May 12 2012, 12:25 AM

yes amazing.. and fun little 'easter eggs' like:

"http://photojournal.jpl.nasa.gov/jpeg/PIA13808.jpg" hiding in plain sight back there. And is that a http://photojournal.jpl.nasa.gov/jpeg/PIA15289.jpg? ..signifficance..?

Posted by: djellison May 12 2012, 12:30 AM

It's a 1909 penny. Had MSL launch in 2009 - it would have been 100 years old at the time.

Posted by: nprev May 12 2012, 12:48 AM

QUOTE (atomoid @ May 11 2012, 05:25 PM) *
"Bender" hiding in plain sight back there.



Yeah, unfortunately they discovered me before I could swipe any swag... tongue.gif

Posted by: ustrax Jun 6 2012, 04:40 PM

t-minus 60 days.
...and counting.

Posted by: fredk Jun 9 2012, 02:20 PM

http://www.nasa.gov/news/media/newsaudio/index.html
Noon EDT, Monday, June 11

Posted by: djellison Jun 9 2012, 02:47 PM

Look out for some landing ellipse news.

Posted by: RoverDriver Jun 9 2012, 03:53 PM

QUOTE (djellison @ Jun 9 2012, 07:47 AM) *
Look out for some landing ellipse news.


Old news to me ;-) When is the announcement be made? I hope they will include my traversability map.

Paolo

Posted by: djellison Jun 10 2012, 12:17 AM

Monday - 9am Pacific.

Posted by: DEChengst Jun 11 2012, 04:06 PM

New landing elipse:

http://www.nasa.gov/mission_pages/msl/multimedia/pia15685.html


Seems there's a problem with the drill as it contaminates the samples with teflon. They're investigating how to handle this and are confident that in the end they should be able to handle this problem.

Posted by: nprev Jun 12 2012, 01:08 AM

Do you have a link for this teflon problem, or was this a comment from a press conference?

Posted by: SFJCody Jun 12 2012, 02:10 AM

I guess this makes things a little more even in the Opportunity vs. Curiosity race-for-the-clays. wheel.gif wheel.gif wheel.gif

Posted by: Phil Stooke Jun 12 2012, 02:23 AM

The teflon thing was in the telecon... I can't imagine it being a huge problem personally. Should be able to model its effects and subtract it.

Phil


Posted by: SteveM Jun 12 2012, 03:00 AM

QUOTE (DEChengst @ Jun 11 2012, 11:06 AM) *
New landing elipse:

http://www.nasa.gov/mission_pages/msl/multimedia/pia15685.html

Does anyone plan to put the landing ellipse on a .kmz file for Google Earth (and perhaps an appropriate base map plleease)?

Steve M

Posted by: Astro0 Jun 12 2012, 03:20 AM

nprev and others...
The teflon issue is mentioned in the press release.
http://www.jpl.nasa.gov/news/news.cfm?release=2012-168

Posted by: brellis Jun 12 2012, 05:32 AM

What are the numbers on "chance of failure" during the procedures of the 7 minute plunge from outer space to Gale crater? I'm really scared about this.

Is the scariest part getting into the atmosphere at the correct angle?

Does the sky crane have a failure potential based on the fact that it's never been tried on Mars?

Narrowing the landing ellipse eases my fears about the early parts of this process. The sky crane part has me all twisted up in concern!

Posted by: djellison Jun 12 2012, 06:52 AM

QUOTE (brellis @ Jun 11 2012, 09:32 PM) *
Is the scariest part getting into the atmosphere at the correct angle?


That's something we've done many times

QUOTE
Does the sky crane have a failure potential based on the fact that it's never been tried on Mars?


Yup. As has every landing system sent to Mars. When Viking went, it hadn't been tried on Mars. Nor had Pathfinder. Nor had MER ( which was similar to, but far from identical to Pathfinder ) And Phoenix's only previous test was a failure. There are many many ways in which MSL could fail during EDL.

QUOTE
Narrowing the landing ellipse eases my fears about the early parts of this process. The sky crane part has me all twisted up in concern!


Many many people seem to point at the Sky Crane and express concern, but no one's ever pointed out to me what it is that has them all concerned. Why does it make you any more or less concerned than Viking, Pathfinder, MER or Phoenix?

It's worth noting that the very same team that put Spirit and Opportunity on the surface of Mars - is the team responsible for MSL EDL.




Posted by: Paolo Jun 12 2012, 08:17 AM

QUOTE (nprev @ Jun 12 2012, 03:08 AM) *
Do you have a link for this teflon problem, or was this a comment from a press conference?


see also the Science blog
http://news.sciencemag.org/scienceinsider/2012/06/nasa-rover-will-contaminate-its.html

Posted by: brellis Jun 12 2012, 01:41 PM

"Why does it make you any more or less concerned than Viking, Pathfinder, MER or Phoenix?"

Lack of redundancy makes this trip scarier to me. There was some comfort on the Viking and MER missions because we had two shots at everything. It took ten years for the Polar Lander mission to rise again as Phoenix.

Regarding feeling 'scared' about the Sky Crane: it just seems that there are so many more phases to the procedure that have to be executed perfectly as compared to MER. I do take comfort from the success of the Phoenix landing. In the case of the Sky Crane, a thousand things can go perfectly but if the 'umbilical cord' stage of the landing fails, this giant SUV might clunk down to the Martian surface, or get dragged away if the cord doesn't detach, or...or...or smile.gif

Posted by: djellison Jun 12 2012, 02:51 PM

QUOTE (brellis @ Jun 12 2012, 06:41 AM) *
it just seems that there are so many more phases to the procedure that have to be executed perfectly as compared to MER.


Really?

Put it this way....think of MER.

Now take off the solid rocket RAD motors over which there is no control authority once ignited. Replace them with throttlable liquid engines. How different are they, really?

There was an umbilical cord between an the MER airbags and backshell. That had to be cut at the exact right moment or lander would have been dragged away by residual RAD motor thrust or have the backshell collapse ontop of the airbags.

Take the EDL timelines and put it side by side with previous ones...honestly - there are not any more phases to MSL.

Cruise stage sep. (same)
MSL has a phase here - ballast jettison.
Entry. (difference here - MSL's is guided using a lifting body design, but Vikings was 3-axis RCS as well, just without the nav algo)
MSL has another here - more ballast jettison.
Chute Deployment (same)
Heat shield sep (same)
Radar lock on the ground (same)
Backshell Sep (difference here - backshell sep on MSL is like PHX/Viking. MER's was more like the skycrane phase of MSL)
Powered decent (same as PHX and Viking. MER was very susceptible to cross winds at this phase. PHX, VIking, MSL are not. MSL, PHX and Viking can control this phase. MER's RAD motors, fired later in EDL, are solids with no adjustments once fired)
Constant velocity phase ( same as PHX and Viking)
At this moment - MER had to do DIMES imaging and airbag inflation. MSL doesn't.
Spacecraft separation ( like the MER rappelling down it's bridle from the back shell)
Mobility deploy (like deploying Viking of PHX's landing legs - at this moment in the MER timeline, it's firing the RAD motors and TIRS motors. Once fired, zero control authority on the spacecraft attitude etc)
Touchdown detection (far easier on MSL. Viking and PHX had touchdown sensors on the legs - potentially the cause of the failure of MPL. MSL just waits for the throttle to decrease on its engines to maintain constant velocity as the rover is offloaded onto the ground)
Bridle cut ( MER had this as well. It had to be timed perfectly. There is several seconds of margin for MSL here)

From this point on - VIking and PHX are safely on the ground and finished.

MER and MSL have more work to do.

MSL's Descent stage turns up the descent engines to full throttle for 4 seconds and it flys away at 45 degrees to get away from the rover.
MSL is now safely on the ground on its wheels, on the dirt. The only critical deployment left is the camera mast, probably done 2 days later which all these vehicles ( apart from Viking ) had to do.

MER however - has to conduct all of its bounces safely. Once the bounces have stopped...
Deflate the airbags
Retract the airbags
Identify which petal is face down, and begin to open the lander, righting itself if necessary.
Deploy the solar arrays.
Standup the rover using the lift mechanism.
Unfold the front wheels and lock in place. Drive the rear wheels out and lock in place.
Cut bridle to the lander
Drive off the lander (Spirit of course, had to turn around on the lander to do this)
NOW you've got the rover safely on the ground on its wheels in the dirt.

MSL has none of that to do.

Honestly - I look at the two side by side and I see MORE steps of complexity for MER. MER was far less robust, those spacecraft took massive impact G's on those bounces. A big nasty rock on any of them and it could have been game over. MSL will be the most gentle touchdown on any planetary surface in history - including Apollo. Once that touchdown is over, we're done. With MER, that just began another final phase to landing... impact to egress.

Moreover - the MSL landing ellipse has been entirely mapped, at 25cm/pixel, with 1m/pixel DTMs. MER was not. HiRISE and CRISM were not available when MER's landing sites were picked. Gale is the safest landing site we've sent a vehicle to.

I know that there's a gut reaction to the skycrane phase of MSL that make it look scary.

So was MER. We just forget how scary it was because it worked twice.

As for redundency....it's worth noting there is almost zero redundancy within each MER itself. The redundancy was two vehicles. MSL has two flight computers etc etc. There is system redundancy within it.

I worked on this : http://www.youtube.com/watch?v=P4boyXQuUIw&feature=relmfu : as technical director for about a year. Lots of meetings with the MSL EDL team. The breadth and depth to the testing, the fidelity of simulations, the options and trade spaces they've looks at, the way they've gone about designing building and testing this system....it gives me far more confidence than I ever had for MER.

I really want to understand why people think MSL is worse than MER. So - after me saying all that - what is it that still stands out? Sorry if this comes across as bit agressively - but I really want to understand why people seem to be more scared by this than MER. It doesn't make sense to me at this point.

Posted by: brellis Jun 12 2012, 03:15 PM

Doug, thanks for the detailed reply. I'll downgrade my current emotion from "scared" to "encouraged, but still a bit worried". smile.gif

Great vid -- you helped design/produce that? Very impressive!

QUOTE
I really want to understand why people think MSL is worse than MER. So - after me saying all that - what is it that still stands out?


I don't think MSL is worse, it's a wonderful upgrade. It's also bigger, which had me worried for a while, but now I feel better, thanks to your response. I'm still gonna save some munchies for the nervous nellie moments when the Curiosity SUV arrives!

Posted by: elakdawalla Jun 12 2012, 03:41 PM

During my research for my Sky & Tel article on MSL, I was surprised to discover that of all the problems facing MSL that caused its launch delay, the EDL system was not one of them. EDL was ready two years before they launched. In the unexpected extra two years, they've had time to simulate all kinds of bad situations during landing -- unexpectedly high winds, low/high air density, landing on steep slopes, on big rocks, and all of these at once; and they've found that the EDL system not only meets its engineering requirements, it copes with really terrible situations. They told the landing site selection committee that they could land this rover practically anywhere. This is not to say that nothing bad can happen -- it surely can -- but there's nothing specific for us to fear; the engineers really have built a system that should be robust to even serious problems. I'm going to be having an anxiety attack on landing day, but not about any specific issue, and frankly, I'm very glad to be moving away from a landing system that intentionally bounces a half-billion-dollar spacecraft several times.

Posted by: Tesheiner Jun 12 2012, 03:44 PM

QUOTE
I really want to understand why people think MSL is worse than MER.

My impression is that this ("MSL is more dangerous") is a subjective conclusion because MSL EDL ***looks*** much more dynamic than MER. Someone really have to go into the details of each EDL sequence to make an objective assessment.

Posted by: algorimancer Jun 12 2012, 04:43 PM

My only real concern with MSL's EDL is the deployment on that cable. I've seen too many cases of variants of snagging occur during that sort of scenario -- case in point being the Shuttle-deployed tethered-satellite-system. I'm hoping no spool is involved in MSL, I'm envisioning something more like the stowed loops of tether as used in parachutes, designed to smoothly deploy without any intrinsic mechanism for snagging. Probably this mechanism has been well-tested, and won't be a problem.

Posted by: elakdawalla Jun 12 2012, 05:06 PM

QUOTE (algorimancer @ Jun 12 2012, 09:43 AM) *
Probably this mechanism has been well-tested, and won't be a problem.
That is what I would call a safe assumption.
QUOTE (Tesheiner @ Jun 12 2012, 08:44 AM) *
My impression is that this ("MSL is more dangerous") is a subjective conclusion because MSL EDL ***looks*** much more dynamic than MER. Someone really have to go into the details of each EDL sequence to make an objective assessment.
I think it's also a basic fear of change.

Posted by: ElkGroveDan Jun 12 2012, 05:20 PM

I'm going to guess that because the MERs have the appearance of a ballistic delivery (dropping a beach ball from high up) they intuitively seem simpler to someone not taking into account the complexities and timing of RAD firings, bag inflation, ground lock radar, bridle cut, airbag deflation, etc.

Posted by: Explorer1 Jun 12 2012, 05:26 PM

We could easily extrapolate and say any moving part is a point of failure, right? Galileo's HGA, Mars Express' radar (which was solved eventually), Odyssey (and Hayabusa's) reaction wheels, Genesis, whatever happened to Mars 3, Phoenix's oven doors, etc, etc.
But of course no one launches a solid block of metal that can't do anything. The entire point is to have scientific instruments, spacecraft control, and yes, complex but well-test EDL methods. They are a necessity, so cheer up doubters!

Posted by: elakdawalla Jun 12 2012, 05:34 PM

Amen, Explorer1!

Let me add a general comment on responding to MSL EDL fear. For those of us who have actually been paying attention, repeated questions like "are they crazy?" and "how can that possibly work?" and "have they tested that?" drive us batty. I urge people (and sometimes need to remind myself) to respond to questions like these with firmness but also patience both at UMSF and elsewhere. Probably every person just waking up to MSL will ask these questions. We will do a greater service to Mars exploration by not treating EDL worries as being ridiculous but instead by calmly responding to it with answers rooted in facts. It's a tightrope to walk; the message is that landing on Mars is hard and failure can happen, but also that the engineers really have thought this through and the landing mechanism is a robust and well-tested one.

XKCD had a relevant cartoon about this recently: http://xkcd.com/1053/

If you're not familiar with XKCD, note that mousing over the cartoon will produce more text. In this case it's:

QUOTE
Saying "what kind of an idiot doesn't know about the Yellowstone supervolcano?" is so much more boring than telling someone about the Yellowstone supervolcano for the first time.

Posted by: djellison Jun 12 2012, 08:48 PM

QUOTE (brellis @ Jun 12 2012, 08:15 AM) *
Great vid -- you helped design/produce that? Very impressive!


Yup - I was the technical director, the interface between JPL and the animation team. We didn't quite nail everything, but given the schedule and budget, we got pretty damn close.

Posted by: Gsnorgathon Jun 12 2012, 09:58 PM

I think part of the unease with MSL EDL - especially the "L" part of EDL - is that the rover is *naked*. Everything else that's landed on Mars had legs or airbags. It's not that either of those are any guarantee of safe landing (e.g. all the Soviet landers, Beagle 2, MPL), it's just that they *look* safer. Curiosity is just out there hanging by what looks like a thread, as part of a landing that looks right out of a Gerry and Sylvia Anderson production. It just seems so improbable.

Posted by: brellis Jun 12 2012, 10:20 PM

hi Emily

algorimancer pinpoints my concern -- we're landing six wheels on Mars! Hanging from a Skycrane! As you wisely http://www.unmannedspaceflight.com/index.php?s=&showtopic=7318&view=findpost&p=184931, after all the complexity of these fantastic machines why do we have problems with the WHEEL?

QUOTE (elakdawalla @ Jun 12 2012, 08:41 AM) *
During my research for my Sky & Tel article on MSL, I was surprised to discover that of all the problems facing MSL that caused its launch delay, the EDL system was not one of them. EDL was ready two years before they launched. In the unexpected extra two years, they've had time to simulate all kinds of bad situations during landing -- unexpectedly high winds, low/high air density, landing on steep slopes, on big rocks, and all of these at once; and they've found that the EDL system not only meets its engineering requirements, it copes with really terrible situations. They told the landing site selection committee that they could land this rover practically anywhere. This is not to say that nothing bad can happen -- it surely can -- but there's nothing specific for us to fear; the engineers really have built a system that should be robust to even serious problems. I'm going to be having an anxiety attack on landing day, but not about any specific issue, and frankly, I'm very glad to be moving away from a landing system that intentionally bounces a half-billion-dollar spacecraft several times.


I'm glad that my favorite informed reporter is nervous about EDL! What did cause the launch delay? My 'outsider' internet search only speaks of 'inadequate test time'.

Thanks to you and Doug for answering my questions. I really do poke around the webz before daring to ask!

Posted by: elakdawalla Jun 12 2012, 11:02 PM

I hope you will not be surprised to learn that that was discussed in depth on this forum. There is, in fact, http://www.unmannedspaceflight.com/index.php?showtopic=5871.

Posted by: brellis Jun 12 2012, 11:39 PM

Emily, I am happy to tell you that I am not surprised to learn of this, but I couldn't find it on my searches. The http://www.thespacereview.com/article/1319/1 cited in that thread answers my question. I'll try to keep quiet now!

Posted by: siravan Jun 12 2012, 11:47 PM

QUOTE
I really want to understand why people think MSL is worse than MER.


I guess it is just simple psychology. We are not comparing MER before landing to MSL before landing; we are actually comparing our feeling about MER after couple of successful landings to our risk assessment about MSL EDL.

Posted by: centsworth_II Jun 13 2012, 12:05 AM

QUOTE (brellis @ Jun 12 2012, 05:20 PM) *
algorimancer pinpoints my concern -- we're landing six wheels on Mars!
Thus eliminating potential problems that could occur driving off a platform down a ramp.

Posted by: centsworth_II Jun 13 2012, 12:14 AM

QUOTE (algorimancer @ Jun 12 2012, 11:43 AM) *
My only real concern with MSL's EDL is the deployment on that cable....
MER was deployed on a cable. See beginning at 2:30.
http://www.youtube.com/watch?v=tZRXwRybb1I

Posted by: djellison Jun 13 2012, 12:24 AM

QUOTE (Gsnorgathon @ Jun 12 2012, 02:58 PM) *
Curiosity is just out there hanging by what looks like a thread,


Just like Pathfinder, Spirit and Opportunity. Actually - they were hanging by a single thread...Curiosity will be hanging by three.

For those wondering - yes - there were tests of that deployment for MSL - here's a video of just one of them : http://www.youtube.com/watch?v=YasCQRAWRwU

A bit more video of other tests here - http://www.youtube.com/watch?feature=player_detailpage&v=aU_Z-6snF0Q#t=147s

Posted by: elakdawalla Jun 13 2012, 12:37 AM

I'll admit to having a brief "oh my god what were they thinking" moment a few weeks ago. Someone from JPL's outreach office did a presentation about MSL at my daughter's school. She had brought a box of goodies that she had convinced engineers to part with -- bits of spent test hardware. One of these was a sample of the cable on which MSL is descending. In my mind, I'd imagined steel cable. It is not steel. It is braided nylon. It looks a hell of a lot like clothesline. I was, briefly, aghast. Then she handed me another piece of hardware: a spent pyro cutter device, one of the things that will cut that nylon cable when it's time for the descent stage to break away. I almost dropped it, it was so unexpectedly heavy: solid steel, or maybe even something heavier. This is a spacecraft; mass is important. Nylon is clearly strong enough (and reliable enough) for the purpose, while being very very light. That guillotine of a cable cutter is made of what it needs to be made of. You can be quite sure that every material in this rover has been carefully thought through and optimized for mass, strength, and whatever other properties it needs.

brellis: Google has made us all very lazy. I don't always find what I'm looking for on UMSF with Google. But we admins work very hard to keep this forum well-organized. I found that thread by clicking on the http://www.unmannedspaceflight.com/index.php?showforum=59 and browsing backward in time.

Posted by: MahFL Jun 13 2012, 02:11 AM

I love these insights to MSL. Sometimes we followers of MSL fret that the thing won't work. In reality though many talented people designed and tested MSL to work, not fail smile.gif.

Posted by: climber Jun 13 2012, 09:55 AM

I think Doug wrote it, we know MER worked and we have fear what is "unknown".
Anyway, I'm also very confident in the system for several reasons.
This technique has been developped for landing larger masses than previously so it's a stepping stone for the future.
When I "accidently" met the EDL team (see here: http://www.unmannedspaceflight.com/index.php?showtopic=3765) it was in early 2007 and they were already working on it for several years. I've seen with my eyes how much those guys are dedicated to their job.
I certainly will be bitting my nails at EDL but well, these tense moments are what keep our passion for Space alive.

Posted by: Oersted Jun 14 2012, 12:30 AM

My fear with regard to the landing would stem from the fact that we have a dynamic two-body system, where the lower body has to arrive at a certain position with quite a low tolerance for accelerations on arrival. The MER airbag clusters had to arrive at an altitude whose precision was measured in meters, and with rather forgiving tolerances for arrival accelerations, compared to MSL.
There was an ancient computer game twenty-odd years ago in which you had to control a two-body system where the jet pack was on one of the two bodies only. It was fiendishly difficult. Two bodies connected by a three-stringed non-rigid bridle arrangement sounds even more challenging. However, I have great confidence in the engineers at JPL and their expertise easily cancels out my gut instincts and fears.

Posted by: nprev Jun 14 2012, 03:01 AM

Yes, I believe that it's quite safe indeed to assume that the MSL landing system is not based on 20-yo gaming technology. ph34r.gif

Posted by: elakdawalla Jun 14 2012, 03:56 AM

John Grotzinger told me that at the outset the engineers had some concern about the three-bodies-connected-by-strings problem but after poking at the situation in all kinds of ways, both simulated and empirical, they found it to be remarkably (to them) stable. I'm afraid I didn't follow his explanation at any level of detail deeper than that, but it's not a concern.

Posted by: djellison Jun 14 2012, 05:01 AM

The sky crane phase is also very brief, just a few seconds. We intentionally made it longer in the project animation to give editors etc plenty of B-roll to use at a later date.

Posted by: Stu Jun 14 2012, 05:25 AM

Bottom line: the guys behind this are almost supernaturally clever and have almost magical levels of technology. If they weren't sure this would work they wouldn't be *doing* it. Let's all trust them, ok?

Posted by: pospa Jun 14 2012, 07:19 AM

For those who still doubt about skycrane system robustness http://www.planetaryprobe.eu/IPPW7/proceedings/IPPW7%20Proceedings/Presentations/Session5/pr478.pdf might help a bit. smile.gif

Some terminal descent challenges and strategy is described http://www.planetaryprobe.eu/IPPW7/proceedings/IPPW7%20Proceedings/Presentations/Session3/pr508.pdf.

Posted by: djellison Jun 14 2012, 10:41 PM

Someone was asking about the actual mechanism that lowers the rover under the descent stage...

http://photojournal.jpl.nasa.gov/catalog/PIA11428
http://photojournal.jpl.nasa.gov/catalog/PIA11426

On the second image the S/N001

I love the optimism that there might be cause to make as many as 999 of them smile.gif

Not as optimistic as MSSS who use S/N00001 smile.gif
http://www.msss.com/images/science/MAHLI_PP0121_wb_cb.jpg

Posted by: elakdawalla Jun 15 2012, 12:04 AM

Oy. I was on the Google+ Space Hangout this morning and another space blogger was giving an account of the story of the landing ellipse being moved. They said that the reduction in ellipse size meant that the rover was more likely to crash into the mountain on descent. The amount of wrongness in that summary was hard to bear. I corrected the statement, but clearly it's an uphill battle to explain how landing on Mars actually works.

Thanks, Doug, for that photo; I hadn't seen it before. And pospa, those links are very useful.


Posted by: SFJCody Jun 15 2012, 02:01 AM

People were skeptical of airbags before Pathfinder landed. Novelty is often treated with suspicion.

http://groups.google.com/group/sci.space.tech/browse_thread/thread/ab2f31b1de87c62a/ca9634a1c05618ae?hl=en-GB&q=pathfinder+airbags#

Posted by: Oersted Jun 16 2012, 10:40 AM

QUOTE (elakdawalla @ Jun 14 2012, 05:56 AM) *
John Grotzinger told me that at the outset the engineers had some concern about the three-bodies-connected-by-strings problem but after poking at the situation in all kinds of ways, both simulated and empirical, they found it to be remarkably (to them) stable. I'm afraid I didn't follow his explanation at any level of detail deeper than that, but it's not a concern.


Glad that my posting elicited this interesting tidbit of information. It doesn't surprise me that the JPL engineers "had some concern" at the outset. But, if the right attenuation and active dampening mechanisms are built into the system, then of course the "dynamic-bodies-connected-by-string" problem can be solved. A lot of systems - at least since the F-16 - have been inherently unstable, but work just fine with high-speed computers in the drivers' seat (F-16 "negative stability" described here: http://www.fas.org/programs/ssp/man/uswpns/air/fighter/f16.html).

Didn't know that the skycrane phase is much shorter than indicated in the movie, thanks for explaining that Doug! - So, how short would it nominally be then?

Posted by: Oersted Jun 16 2012, 10:43 AM

QUOTE (elakdawalla @ Jun 15 2012, 02:04 AM) *
Oy. I was on the Google+ Space Hangout this morning and another space blogger was giving an account of the story of the landing ellipse being moved. They said that the reduction in ellipse size meant that the rover was more likely to crash into the mountain on descent. The amount of wrongness in that summary was hard to bear. I corrected the statement, but clearly it's an uphill battle to explain how landing on Mars actually works.


Just like Phoenix that almost crashed into Heimdall crater... - wasn't that what the MRO/HiRISE shot showed? rolleyes.gif

http://dalsgaard.eu/Pics/2008-06.Phoenix-over-Heimdall-Crater/Phoenix-over-Heimdall-Crater-by-Soeren-Dalsgaard.jpg

Posted by: pospa Jun 16 2012, 12:52 PM

QUOTE (Oersted @ Jun 16 2012, 12:40 PM) *
Didn't know that the skycrane phase is much shorter than indicated in the movie - So, how short would it nominally be then?

See my previous post with link to presentation, page 10.
The Sky Crane maneuver / rover deployment starts about 19 m above the ground and 14-15 sec before touchdown.

Posted by: Oersted Jun 16 2012, 06:01 PM

Thanks!

Posted by: DavidVicari Jun 18 2012, 07:47 AM

Does the decent stage have its own computer? I figure it must at least have something simple to perform the fly-away maneuver. Do the rovers redundant computers control most of the decent? If not, does the decent stage have redundant computers like the rover?


Posted by: pospa Jun 18 2012, 10:06 AM

The spacecraft’s main computer inside the rover controls all activities during EDL.

Regarding DS fly-away the http://trs-new.jpl.nasa.gov/dspace/bitstream/2014/41629/1/10-1775.pdf can explain all details of this maneuver:

"Once touchdown is declared, the DS halts vertical motion and the triple bridles are cut. The BUD has built-in retraction springs to retract the now free bridles away from the Rover top deck. At this point, control is transferred to the Flyaway Controller on the DS and the command to cut the umbilical is issued. Once the flyaway controller on the DS assumes control, it first holds the current altitude for 187 msec to allow sufficient time for the umbilical to be cut. After the
requisite hold time, the MLEs throttle up and the DS ascends vertically for a predetermined amount of time. Then, the DS begins to execute a turn to approximately 45° pitch. The DS holds this attitude with the MLEs at 100% until the fuel depletes. The hold, ascent, and turn take place within 2 seconds, and the remaining time is variable depending on the amount of fuel remaining. The DS will then ballistically fall to the surface at a distance of at least 150 m from the Rover."

Posted by: djellison Jun 18 2012, 01:38 PM

Only change to that I know of is that the flyaway has been changed from until-depletion, to a 4 second burn. There is sufficient fuel margin to allow that to happen, and it's preferable to get that burn in, than a potential explosion in a depletion event after a burn that might be even longer.

Posted by: pospa Jun 18 2012, 02:07 PM

Thanks for the update, good to know. smile.gif
So, if flyaway burn will be fixed time now then the distance of DS wreck from just landed Curiosity should be clear as well (not only "at least 150 m from the rover").
Doug, do you know that more accurate value?
Thx

Posted by: djellison Jun 18 2012, 03:29 PM

Several hundred meters. It depends exactly how much fuel is left at that moment, how it tumbles at burnout etc etc. There's a fairly large dispersion to it I'd expect.

With no rover to carry, and almost all its fuel exhausted - even just using 4 of its 8 engines, that descent stage is going to haul out of there.

VERY crude approximation....4 x 3060N of thrust on about 800kg of descent stage with maybe 100kg of fuel remaining.... 13.6m/s/s - so after 4 seconds it'll be at about 54.4 m/sec.

http://www.calctool.org/CALC/phys/newtonian/projectile

45 degrees, 54m/sec, gravity of 3.711. Max height is 343m, distance is 785m and it'll take 20.6 seconds ( that's assuming no drag etc)

I'd put error bars of 50% on that..but it'll be something like that.




Posted by: ElkGroveDan Jun 18 2012, 04:01 PM

Is there any return of telemetry from the descent stage after the bridle is cut? I would imagine that data on low-altitude flight performance would certainly be valuable -- even chaotic flight.


Posted by: djellison Jun 18 2012, 04:18 PM

Nope - that would invoke a bunch of engineering requirements on the vehicle it just doesn't need. All we actually care about is the rover. The redundent UHF radios are in the rover itself, and the three UHF antennae used during EDL ( Parachute cone, Descent Stage and Rover ) are all driven by the rover UHF radios. The descent stage doesn't have UHF transmitters of its own

This is the MSL telecom bible - it's amazing! http://descanso.jpl.nasa.gov/DPSummary/Descanso14_MSL_Telecom.pdf

Block diagram on Pg 44. Timeline on Pg 25

The descent stage does have X-Band transmitters - but that's simply to transmit the tones we're used to seing a-la MPF/MER. It's transmitter is 100 watts to try and hammer thru the plasma and it does so via two LGAs on the backshell (one at 17.5 degrees to account for the pitch of the capsule during entry) and the LGA on the descent stage. The rover can pick up and transmit as well, but its X-Band is only 15 watts


Posted by: elakdawalla Jun 19 2012, 12:16 AM

Folks, I will be hosting a "Cosmoquest Science Hangout" Wednesday at 1600 PDT/2300 UTC, with guest Ravi Prakash of the MSL EDL team. I'll ask him to explain EDL in detail with particular emphasis on the parts that are different from MER (and why they're different from MER). The Hangout will go straight to Youtube so if you can't watch live you'll be able to watch the recording right away. Post here if you have any burning questions you'd like me to ask him. My hope for this Hangout is to produce a video that we can point people to if they have lots of questions about EDL and why they're doing this crazy Skycrane thing.

http://www.planetary.org/blogs/emily-lakdawalla/2012/06201600-science-hangout-ravi-prakash.html

Posted by: brellis Jun 19 2012, 01:05 AM

The 'presentation' in pospa's http://www.unmannedspaceflight.com/index.php?s=&showtopic=7138&view=findpost&p=185002 has an excellent graph on page 4 comparing the vertical+horizontal velocities of various spacecraft that made it successfully to the surface of Mars. Wow! In comparison, Beagle and the MERs look like they're bouncing a very long way!

Question: in case something goes even slightly awry during the SkyCrane phase of landing, how much more velocity can MSL take than the 0.75 vertical or 0.5 horizontal 'requirements' referred to in the presentation? Can it take a Viking level of velocity in the drop to the surface? btw, the more time I spend rereading this thread, the less worried I become! smile.gif

Posted by: ElkGroveDan Jun 19 2012, 01:52 AM

Emily you might ask him to also compare and contrast Viking and MPL/Phoenix as well since they have the powered final descent in common.

Posted by: djellison Jun 19 2012, 04:56 AM

The MSL descent stage MLE's are infact derived from Viking engines, but with a monolithic single large nozzle rather than a cluster of many smaller nozzles.

The Phoenix descent engines were derived from large RCS thrusters I believe (hence the pulse, not throttle) and were stolen from the '01 lander to be the orbit insertion engines for MRO and had to be replaced on PHX.


Posted by: Astro0 Jun 23 2012, 10:45 AM

Not only http://www.jpl.nasa.gov/video/index.cfm?id=1090 but another 13 minutes and 48 seconds until the signal gets back to Earth ( to CanberraDSN btw) and we know that the terror is over.

Posted by: SteveM Jun 23 2012, 05:10 PM

About 20 seconds in as the narrator discusses how everything has to go perfectly, the image displays the text: "500,000 LINES OF COD3". Beautiful. laugh.gif

Posted by: nprev Jun 23 2012, 05:35 PM

Well, it's been a great cruise phase! The approach phase begins on 23 June; please post all relevant comments http://www.unmannedspaceflight.com/index.php?showtopic=7347&hl=.

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