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back to article JPL wants to fire a laser at MARS!

A group of JPL scientists, working on improving space-scale laser ranging, believe they could one day measure the distance from Earth to Mars with millimetre accuracy. If their scheme were adopted, it would have to wait until a new Mars mission takes place to put a laser on the red planet. That's because, unlike Earth-Moon laser …

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Anonymous Coward

An alien passing by in his space ship will seem laser fired from earth at Mars, assume we are a bunch of war mongering nutters, think we have wiped out the population of the planet and will either,

Run away never to be seen again

Or

Teach us a lesson in intergalactic diplomacy

By melting the planet.

Oops

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Joke

@AC

I find your lack of faith disturbing.

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Anonymous Coward

chchaghh...

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"An alien passing by in his space ship will seem laser fired from earth at Mars, assume we are a bunch of war mongering nutters..."

More likely, they'd say, "Oh, a laser bouncing off of a planet. How quaint."

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Alien

Or possibly "Ulla", before aiming their heat ray back towards the source.

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Anonymous Coward

"An alien passing by in his space ship will seem laser fired from earth at Mars, assume we are a bunch of war mongering nutters..

.

They then would check Earth history and find their initial thesis to be corerect.

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Holmes

More likely it's be. "hah, the laser isn't doing any damage at all. This is what a real laser can do!"

followed by the explosion of Mars.

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Joke

Bah, humbug ;-)

"A group of JPL scientists, working on improving space-scale laser ranging, believe they could one day measure the distance from Earth to Mars with millimetre accuracy."

Don't be too proud of this technological achievement you're constructing. The ability to measure the distance between planets is insignificant next to the power of the Force.

(I couldn't help myself. Darn you El Reg! ;-))

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Coffee/keyboard

Re: Bah, humbug ;-)

The monitor got showered as-well you wanker. :)

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"providing precision improvement well above three orders of magnitude over the current RF techniques"

They're suggesting that the new measurement will be millimeter accurate and three orders of magnitude better than existing methods... surely the whole thing could be thrown out by the rover standing on a rock.

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The absolute distance doesn't matter - what matters are the changes over time. So long as the unit on Mars doesn't move it doesn't matter if it is on a rock or a mountain. Mars rotates, so the transponder on its surface will be moving at quite significant rate, as is the earthbound end as the Earth rotates. Lots of fun compensating for all of that. But all manageable, and in the end you get to measure the precise orbital mechanics, and possibly a number of the relativistic influences. Which is probably the main point.

The whole shebang is not that far off how GPS works now.

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The tilt of Mars' rotational axis changes over time as well (Jupiter + no large moon), so you would probably need more than one to compensate.

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Wow.

The thing I find amazing is their ability to measure such tiny differences in the return time. Light moves VERY FAST so the time taken to travel 1mm is absolutely tiny, yet they can measure this time accurately.

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Re: Wow.

I think they measure pulses introduced into the light, rather than the light waves themselves. Thus, you can have whatever frequency and propagation rate of information that you need for the experiment.

GJC

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Re: Wow.

Light isn't really so fast. Old electronic engineering approximation is a foot per nanosecond (or 30cm). So for a 100GHz clock, that's 0.3mm per clock.

In practice with things like this you don't normally measure the exact arrival time of a pulse, you measure the phase of a modulation of a carrier wave. As someone noted above, this scheme has a lot in common with GPS and might be a very interesting way to observe and test general relativity.

BTW is Mars the best place for such an experiment? I would have thought that the (cold) dark side of Mercury might be more useful, because it's deeper in the Sun's gravity well and moving a lot faster. Maybe Mercury next?

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Re: Light isn't really so fast.

Feel free to tell us about all the things we might signal with which do go faster than light.

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Joke

Re: Light isn't really so fast.

Everyone knows bad news travels faster than everything else in the universe.

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Thumb Down

Re: Wow.

Unfortunately, Mercury doesn't have a dark side as such. It's not tidally locked, which ruins many a good sci-fi story.

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Bitchin'

Obligatory..

https://www.youtube.com/watch?v=DRmWkSbEMp4

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Re: Bitchin'

Also obligatory...

https://www.youtube.com/watch?v=KNEBLXgWhtM

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" JPL wants to fire a laser at MARS! "

Doesn't everybody? Why? Why not!

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Re: " JPL wants to fire a laser at MARS! "

Absolutely. Although I'm a little worried about their attitude:

“The lasers themselves do not need to be very powerful,” Birnbaum told Phys.org.

Yes they do, yes they do!

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Joke

Re: " JPL wants to fire a laser at MARS! "

The power of the lasers is insignificant compared to the power required to persuade the sharks they are mounted on to swim to Mars.

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Firing lasers at another planet, what couldnpossibly go wrong? :)

Just out of curiosity, why do we need to know that distance with such accuracy, especially given that it will vary anyway? I'm not trying to piss on their chips but this unlikely to be cheap. Are they going to normalise the distance, i.e. sealevel on earth to 'sealevel' on mars or core to core, and measuee asbrhe planets are closest? I'm all for science for sciences sake, just curious.

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Shields up!

Maybe I'll use one of these in my DIY projects at home. I struggle to achieve millimetre accuracy just cutting a piece of wood

Yes, I have two of those. ===>

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Holmes

It'll never work

How are they going to get the shark to Mars?

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Re: It'll never work

In a tornado.

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Coat

Re: It'll never work

How are they going to get the shark to Mars?

It's dead easy! First mount your laser on your shark. Then as your shark can't walk on the surface of Mars,, mount it on a donkey. Then you simply:

Get your ass to Mars.

Coat? You think I ought to? OK, getting it now...

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Happy

Re: It'll never work

Dr. Evil will find a way, he'll get those frickin' laser beams there one way or another ;)

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Boffin

Re: It'll never work

Use a sharkapult of course ... the 21st century's deadliest weapon.

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why and how.

Why. Better distance measurement --> better values for anything that changes with distance. So tighter distance measurement (and presumably tighter range rate measurement) means having to carry less reserves for spacecraft going there. Obviously this would count for more if going to Saturn and Jupiter but that's not going to happen anytime soon.

How. The article points out they can use COTS lasers for this. It's the receivers that have to work hard. I'll take a wake and filter spec will be very tight to ignore most ambient light and they will use some kind of lockin detection to.

There's lots of subtle problems here. Constant offsets can be cancelled out but things like the Earths atmosphere are constantly changing (the biggest correction in GPS is for pulse delay through the ionosphere. The civilian code uses a model, the military system uses 2 frequencies to give something like 10x the accuracy).

Thumbs up for this. I suspect this will enable a whole lot of stuff to be improved.

Pity about the shark though....

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Meh

Re: why and how.

So they're going to spend £all_the_money in an attempt to save a much smaller amount of money on petrol next time we drive to Mars.

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Anonymous Coward

Dantooine.

They're on Dantooine.

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Painting

Well a laser firing outwards from Mars certainly simplifies navigation for the incoming ... oops ....

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Alien

No! Mars is peaceful. We have no weapons. You can't possibly...

I can't believe that El Reg are peddling this blatant propaganda!. Why even now, as reported and photographed in several of your own articles no less, there is a laser armed robot tank roaming round the surface of Mars!

Clearly these people are dangerous and must be dealt with forthwith! I say that lasers are too good for them. We should nuke them from orbit! it's the only way to be sure.

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jai
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You'd prefer another target? A military target? Then name the system!!

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Mushroom

BBC Headline: British space penetrator passes icy test

Well, the UK seems to have its eye set on shelling Europa:

http://www.bbc.co.uk/news/science-environment-23281423

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jai
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The Tick

Can we write our name on the surface with it?

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Re: The Tick

You mean something like

Humanz woz 'ere

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Does Martian 'elf and safety know about this? It's bad enough skangers pointing 'em at planes here, let alone flicking 'em at flying saucers. I'd love to see their risk assessment, especially if they haven't included tracking for those iridium satellites.

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Turn off the shields!

They know about the lasers! Butlers serve unto no one!

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Mushroom

I see...

Americans, not content with starting pointless conflicts on other continents, now plan to do the same with other PLANETS?!?!

Oh, yes, they say it is weak, they say it is for measuring distance, but just wait until the targeting had the bugs ironed out - it'll be easy to ramp up the power until it is a Weapon Of Friggin' Unbelievable Destruction (WOFUD)...

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lolz on the WOFUD

It is a typical american approach to life ...

Lets test this harmless thing (or so we will have people believe).

I still think it's funny that Americans can somehow take ownership of parts of the moon ... wtf?

Someone needs to step in and tell the american gov to go F*** themselves (NSA anyone?).

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Where's the *KABOOM* ..?

There's supposed to be an Earth shattering *KABOOM*

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Re: Where's the *KABOOM* ..?

I always wondered who put the Vogons up to it, now I know. It was Marvin the Martian.

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Coffee/keyboard

But... What if they MISS ?

You know... the Planet. Mars.

What if they miss? What will they hit next? Beetlejuice ?

I guess firing a LAzer at the trafficlights on the roundabout at Bernards Star is going to bugger the traffic in a spectecular way! Imagine all them starcruisers and heavy haulers slamming on the retrorockets.

We'll have to wait some time but what a fireworks show that'll be !

I got my finger on the button -->>

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Headmaster

Re: But... What if they MISS ?

*cough* Betelgeuse *cough*

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"The chances of anything coming from Mars are a million to one," he said.

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Anonymous Coward

Gravity, blocking matter, and relativity could mess up this idea.

I wonder if JPL can compensate for variably bending of laser light, by a far more complex gravity field, over such a large distance; this could require precise dynamic aiming of both lasers and compensation for skewed time delays in both directions i.e. tricky. It could also be fun if the light beams don't line up in both directions or are blocked by matter, so miss a light sensor at one end. If the Mars laser has an earth synchronized clock, it probably won't be in-sync when it gets there, because of relativity.

Radio waves may prove more practical i.e. space radar. It may even be possible to use ambient radiation from behind Mars somehow.

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