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MSL Landing Timeline: What To Expect Tonight
An anonymous reader writes "When the Curiosity rover lands on Mars later tonight, it'll be executing a complex series of maneuvers. JPL will be relying on the Mars Odyssey orbiter to relay telemetry back to Earth in time-delayed real-time, and if all goes well, we'll be getting confirmation on the success (or failure) of each entry, descent, and landing phase, outlined in detail here."
Telemetry will be continuously relayed back to earth, true, but with not much less than about a 15 minute latency, owing to the fact that Mars roughly a quarter of a light-hour from earth right now.
File under 'M' for 'Manic ranting'
"Time Delayed Real Time"
More like "Real Time as constrained by the Speed of Light", it's not like NASA is doing what NBC is doing with the olympics... :rolleyes:
Telemetry will be continuously relayed back to earth, true, but with not much less than about a 15 minute latency, owing to the fact that Mars roughly a quarter of a light-hour from earth right now.
That IS indeed real time. Relativity tells us nothing can have an effect here in less time. I don't know if you're trolling or just ignorant, but by your definition you can never look at the stars, galaxies or nebulae in the sky in real time either because they're all at varying distances and we're seeing light that originated anything from about 4 to several million years ago. With telescopes you can go back billions.
Don't forget the imperial to metric conversions!
As long as it doesn't require nvidia drivers for Linux, it should be ok!
see a Text Widget
I'm really excited, but I doubt the live broadcast will measure up to the bitchin' action movie NASA made of Curiosity's "Seven Minutes of Terror!"
http://www.youtube.com/watch?v=pzqdoXwLBT8 Enjoy!
Ask me about my sig!
The Viking landers were about the same size and used classic retro-rockets. Why does the Curiosity use this much more complex arrangement? I couldn't find an easy answer. Is it so the rocket blast doesn't damage the wheels? Is it so the rover doesn't lug around the dead weight of the rockets once it's landed? I really don't get it.
In a few hours from now. Roughly six hours from now as I type this.
Don't disappoint your bird dog. Go to the range.
Awesome can't wait to see how it turns out. Too bad the little ones won't be awake for it.
Chance favors the prepared mind.
Perfect is the enemy of good.
True, but for a blueworlder, the blueworld-received-time is real-time, for any definition of real-time consistent with relativity.
Speaker K'Breel knows the instant the Martian Defense Force succeeds in its mission, or fails, and either way he has enough time to throw a Junior Reporter's gelsac beneath the spot where the Skycrane will crash-land. At the moment of impact/invasion, the most recent transmissions from his spies on the Blue World will show a clock dated 10:14 PDT, but that's irrelevant. As far as the blueworlders are concerned, they find out at 10:31 PDT. Loyal Martian Citizens can start celebrating/covering their gelsacs early, but have to wait another 15 minutes (until their view of the blueworlders' clocks show 10:31) before they can enjoy true schadenfreude at the blueworlders' pain, or have hopefully protected their gelsacs in preparation for the ever-merciful Speaker for the Council's reaction to his view of the blueworlders' whoops of joy.
The single most important criteria for something to qualify as "real time" in data communications is low latency. 14 and a half minutes is not low.
Then by your definition NOTHING in space is real time. You look up into the sky and everything you're seeing is sending it's light to you from the past.
No, that's just your personal set of criteria that doesn't have anything to do with reality.
Real-Time is without artificial delay. Yes, there's 14 minutes actual delay, but it's not artificial, it is literally the fastest possible time.
If 14 minutes prevents it from being real time, then 14 seconds should too, as should 14 milliseconds, or 14 nanoseconds. All of them are arbitrary amounts of time, all of them are large amounts of latency relative to something.
...be interesting to have a "news" program that only aired news reports which were, say, a year old, that way people could look back with hindsight and see how trivial the things were that seemed so big at the time, thus hopefully giving them some perspective on the world as a whole, but I always thought it was just a pipe dream. This whole thing has me thinking that, "In other breaking news from yesterday..." might become a real catch-phrase.
Don't worry, I only used a couple of GOTO statements.
Jesus was all right but his disciples were thick and ordinary. -John Lennon
I found this link on reddit.com/r/science
God spoke to me
Not many people know this, but the Stonehenge scene in "This is Spinal Tap" was based on something that really happened to Black Sabbath. The band wanted a life-sized replica of Stonehenge for their stage show, just like in the movie. They drew up the plans, but at some point (nobody's sure where) 14 feet became 14 meters... So they wound up with this giant thing that cost way more than they planned, and worst of all, it wouldn't even fit on any of the stages they were playing. After this, and a series of similar mishaps, NASA stopped hiring members of Black Sabbath.
Just noticed a typo in the article -- it's actually PDT, not PST.
NASA has a convenient countdown timer here:
http://www.nasa.gov/mission_pages/msl/index.html
Would it really be so much to ask for a link to the Countdown?!?
A few hours from now. For a handy countdown (or to avoid trying to work out the time zone differences): http://mars.jpl.nasa.gov/msl/participate/
And that kids is how I met your mother.
. The whole thing has an amazingly sci-fi feel to it, like it's the opening scene of a sci-fi blockbuster movie. We really do live in amazing times when you think about it.
The skycrane/rover detach from the parachute at around 2:00 and you can watch as the sky crane lowers the rover at 2:48. It does seem a little too elaborate, and my gut feeling watching it is that using such a complicated landing mechanism is just asking for something to go wrong. But then again... well, think about it. Pulleys are pretty simple machines, and we've been using them for thousands of years. There are a lot of machines on this rover that are vastly more complicated than pulleys and cables- the heat shield, the parachute, the nuclear reactor, the onboard computer, the antenna, the camera that finds the landing site, the rocket motors, the software.
I sure as hell hope it all works, though. Unlike the last mission, there's just the one rover, and there's a hell of a lot riding on it. With the cuts to NASA's planetary science program, we won't be headed back to Mars for a long, long time, and it will be a lot harder to get the program started again if Curiosity fails.
Well great... publicize the time and location and you are just making the formidable Mars Homeland Security's job easy. Loose lips sinks ships.
Close(ish) to some fact. Read the real story by the singer at the time:
http://www.gillan.com/anecdotage-12.html
It all has to do with shifting the center of mass. From the official NASA press kit: http://mars.jpl.nasa.gov/msl/news/pdfs/MSLLanding.pdf
After the turn to entry, the back shell jettisons two solid tungsten weights, called the “cruise balance mass devices.”
Ejecting these devices, which weigh about 165 pounds (75 kilograms) each, shifts the center of mass of
the spacecraft. During the cruise and approach phases, the center of mass is on the axis of the spacecraft’s
stabilizing spin. Offsetting the center of mass for the period during which the spacecraft experiences dynamic
pressure from interaction with the atmosphere gives the Mars Science Laboratory the ability to generate lift,
essentially allowing it to fly through the atmosphere. The ability to generate lift during entry increases this mission’s
capability to land a heavier robot, compared to previous Mars surface missions.
The spacecraft also manipulates that lift, using a technique called “guided entry,” to steer out unpredictable
variations in the density of the Mars atmosphere, improving the precision of landing on target.
During guided entry, small thrusters on the back shell can adjust the angle and direction of lift, enabling the
spacecraft to control how far downrange it is flying. The spacecraft also performs “S” turns, called bank reversals,
to control how far to the left or right of the target it is flying. These maneuvers allow the spacecraft to
correct position errors that may be caused by atmosphere effects, such as wind, or by spacecraft modeling
errors. These guided entry maneuvers are performed autonomously, controlled by the spacecraft’s computer
in response to information that a gyroscope-containing inertial measurement unit provides about deceleration
and direction, indirect indicators of atmospheric density and winds.
After the spacecraft finishes its guided entry maneuvers, a few seconds before the parachute is deployed, the
back shell jettisons another set of tungsten weights to shift the center of mass back to the axis of symmetry.
This set of six weights, the “entry balance mass devices,” each has a mass of about 55 pounds
(25 kilograms). Shedding them re-balances the spacecraft for the parachute portion of the descent.
Not only that, but it is critical that not only can you do something like rotate the observer several different ways, but those ways are all different ways of doing it. In other words, you want redundant systems that will survive whatever tempest took out the main system.
True, there are certain phases of the mission where you can recover from a malfunction. If there's a software problem en route to Mars, or a hardware malfunction once the rover is on the ground, you can try to find a way to fix or work around the problem. The problem with the landing, obviously, is that you've just got one shot. If the pulleys jam or the cables tangle, if the explosives don't cut the skycrane free, if it selects a bad landing spot or comes in too fast... and it's all happening 15 light-minutes away, so by the time NASA figures out something is wrong, it's already too late to do anything. If something fails during that phase, that's $2.5 billion spent adding another crater to the surface of Mars.
Just give it in GMT and let us worry about daylight saving time conversions.
When our name is on the back of your car, we're behind you all the way!
You draw the line at any signal latency that is too slow to meaningfully respond to in the context that the signal was originally sent from. There's a reason why interrupt handlers in real-time OS's need to finish their job in as few computing cycles as possible.
File under 'M' for 'Manic ranting'
Well, that's a lot better than it being 20 feet from the surface and then lowering it on a tether 21 metres long.
When our name is on the back of your car, we're behind you all the way!
They have already fumbled once - the mechanism for rotating the observer failed.
That's not a fumble. That's a ten-year-old spacecraft, long past its primary mission, with a temporary problem that they were able to work around.
Owing to the fact that we will know the lander has already reached the surface (in unknown condition) by the time we get the first signal it has entered the atmosphere
Relativity says that there is a 14 minute delay in *some* frames of reference. In other frames of reference, the delay is longer. For others (those occupied by the radio signal photons, for example), the landing events and our reception of the signals happen simultaneously.
Getting hung up over what you imagine is the "time delay" between two points in spacetime that are outside of each others' light cones is kind of pointless.
Geezer Butler tells a completely different story.
It had nothing to do with me. In fact, I was the one who thought it was really corny. We had Sharon Osbourne's dad, Don Arden, managing us. He came up with the idea of having the stage set be Stonehenge. He wrote the dimensions down and gave it to our tour manager. He wrote it down in meters but he meant to write it down in feet. The people who made it saw fifteen meters in stead of fifteen feet. It was 45 feet high and it wouldn't fit on any stage anywhere so we just had to leave it the storage area. It cost a fortune to make but there was not a building on earth that you could fit it into.
I only used one...
GOTO MARS;
Happy viewing! Fingers crossed!
:)
p.s. watching the simulation while listening to the beautiful blue danube is kind of fun
while [ 1 ]; do echo -n -e "\xe2\x95\xb$((($RANDOM&1)+1))"; done
Then by your definition NOTHING in space is real time. You look up into the sky and everything you're seeing is sending it's light to you from the past.
Duh. Real time is a bit subjective, but it basically is a threshold of control over a system. The strict definition is that a system is real time, if it meets strict time constraints imposed on it (I gloss over some important nuance). So in a sense, one can have real time systems with say, years of lag, for really generous time constraints.
For me, I have an informal definition of real time, namely, a control methodology which wouldn't change, if communication lag were instantaneous.
For example, the human body wouldn't move differently even if human nerves were transmitting signals instantaneously. Walking, running, and such still are the best means for moving. You might be able to try other movement forms (such as cartwheeling), but these wouldn't give you an advantage in normal operation over the usual means of movement.
So in this sense, the human body and its normal means of moving about are "real time". Movement of the MSL and other rovers remotely controlled from Earth have less optimal movement schemes (there's a lot of need to evaluate terrain obstacles, for example, resulting in a lot of move-then-stop operation) than if someone were controlling them from nearby on the Martian surface. So these systems are not real time in my sense.
Now suppose instead of the MSL, one were piloting this fine piece of gear, one of the largest excavators in the world. Suddenly that 15 minute lag time is not so significant and the machine probably wouldn't operate all that differently, if the operator was sitting in a cockpit directly rather on distant Earth.
Since I mentioned systems with extremely long lag still qualifying as real time, consider this example. One could set up vast streams of gargantuan slow moving space vehicles carrying basic crude, bulk resources (water, organic compounds, metals, etc) between different planetary systems, say moving at the speed of the Voyager spacecraft. It might take 50,000 years to make the trip and adjustments in trajectory would be very minimal and glacial. Would it matter if one had instantaneous communication? Not really. The years of communication lag have no real effect on the system.
Having said that, you pointing out the mechanism for rotating the observer. Understand this, in projects like this there is NEVER EVER ANYTHING THAT CAN ONLY BE DONE A SINGLE WAY.
Not only that, but it is critical that not only can you do something like rotate the observer several different ways, but those ways are all different ways of doing it. In other words, you want redundant systems that will survive whatever tempest took out the main system.
Absolutely, but that doesn't mean it's not a failure. If your main parachute doesn't deploy, it's good if your spare deploys, but that doesn't mean whoever packed or produced your parachute didn't screw up.
And, as others have said, for the descent tonight, they only have ONE chance, no backup systems, and a boatload of things that can go wrong. We just have to keep our fingers crossed.
I saw the "story" and all the ridiculous spin when it came out this week. All he said is the US won't be the leader in every endeavor; other nations will do things too. And he said NASA isn't planning to go it alone to Mars. Neither of these means NASA won't be the leader in space exploration.
You're both rude and wrong. GP is correct.
"Relativity tells us nothing can have an effect here in less time." True, but that doesn't mean that it's real time. Here are a few examples that show that it's completely ridiculous to call it real time:
The cosmic microwave background is the glow of the hot early universe, from shortly after the Big Bang. No cosmologist would refer to this as seeing the Big Bang "in real time."
It's possible for a ray of light to travel in a circular orbit around a black hole. That means that it would theoretically be possible for me to face in a certain direction, stick out my tongue, and then turn around 180 degrees, look through a telescope, and, some time later, see myself sticking my tongue out at myself. I'm obviously not seeing myself "in real time."
As a third example, there are distant galaxies whose light hasn't gotten to us yet. I don't think anyone would argue that we are seeing them "in real time" -- we haven't even seen them yet.
It sounds like you're misinterpreting something you heard about the nature of simultaneity in relativity. You can define simultaneity in relativity. You simply have to keep in mind that it's relative, not absolute.
In special relativity, the standard way to do this is Einstein synchronization. The relative motions of the bodies in the solar system, as well as all space probes launched so far, is at velocities much less than c, so it doesn't even matter very much whether you talk about doing your Einstein synchronization in the frame of the earth, of mars, or whatever. This is the sense in which the information from Mars is 15 minutes behind "real time." (There are also gravitational time dilations, and they're also quite small.)
Since you brought up astronomy and cosmological look-back times, it's worth addressing that as well. To describe cosmological scales, you need general relativity, and in general relativity Einstein synchronization doesn't work. However, there is a natural notion of clock synchronization in cosmology that is defined as follows. At any spot in the universe, define a frame of reference that is at rest with respect to the cosmic microwave background (or the local flow of galaxies, which amounts to the same thing). Define a time coordinate as measured by a clock that is at rest in that frame. This is what cosmologists mean when they state the age of the universe as so many billions of years. This time coordinate is also the only reasonable definition of "in real time" for use in cosmology.
Next time, please try being more polite and/or getting your facts right.
Find free books.
And why tungsten anyway?
Because its the densest material around that isn't also absurdly expensive (Platinum, Iridium, Osmium, or Gold), or radioactive (Plutonium), so they can use smaller weights.
upon the advice of my lawyer, i have no sig at this time
Has anyone collected all these dispatches from the Martian Council over the years? Every time the Earthlings throw a probe at the homeworld, there'll be an update from the Speaker regarding the success or failure of the defences. I've actually come to anticipate the next entry - they're generally quite funny.
Any reason not to try to embed little experiments in the weights though?
My guess is density - it's the densest common metal (1.7 times the density of lead), so it takes up less much space than an experiment pod would use. Plus the center of gravity of the tungsten weight is easy to calculate, while an experiment pod's center of gravity could shift if the materials inside move around. 150kg of Tungsten takes up the space of a cube of around 20cm on each side. Even if the experiment pod was a block of solid aluminum, each side of the cube would need to be around 40cm, so would be much bigger.