If it does, is there a functional seismometer on Mars?

http://neo.jpl.nasa.gov/news/news151.html

"Designated 2007 WD5, the asteroid was discovered on Nov. 20, 2007 by the
NASA-funded Catalina Sky Survey using a 1.5m telescope on Mt. Lemmon, near
Tucson. The object had already passed within 7.5 million km (5 million
miles) of the Earth on Nov. 1, before it was discovered. Based on its
magnitude, we estimate the asteroid to be about 50 meters (160 feet) across.
As the accompanying diagram shows, it has already reached the halfway point
between Earth and Mars. When it closes in on Mars, it will approach from the
day side, and would then be very difficult to observe from any of the
spacecraft on or around Mars. Our current best estimate predicts the
asteroid will miss Mars by 50,000 km, but the miss distance is highly
uncertain because the asteroid's path is not known with sufficient accuracy.
The uncertainty region during the Mars encounter currently extends over a
million kilometers (700,000 miles) along a very slender ellipsoid only 1200
km (700 miles) wide, but the ellipsoid does intersect Mars. The zone of
potential impact on the surface of Mars is approximately 800 km wide, and
sweeps across the Martian equator from southwest to northeast, crossing the
equator at roughly 30 deg W longitude. The MER Opportunity rover is close to
the southern edge of this possible impact zone but clearly outside it."

--
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electronic repair etc
http://home.graffiti.net/diverse:graffiti.net/

Is there a corner-cube prism array reflector placed on Mars , like the one
placed on the moon ?

"N Cook"  wrote
> Is there a corner-cube prism array reflector placed on Mars , like the one
> placed on the moon ?

Almost certanly not, for practical reasons. Even when they bounce off
the one on the Moon, apparently they get (or got) <1 photon returned per
outgoing pulse. So they have to send lots of pulses and extract the signal
from noise. I think they were going to upgrade the laser at some point,
but even still, if they have, they're probably getting just a few photons
back per shot.

How much further away is Mars? They'd so seldom get a photon back,
it probably wouldn't be worth it. BICBW.


Martin
-- 
M.A.Poyser                                                  Tel.: 07967 110890
Manchester, U.K.          http://www.livejournal.com/userinfo.bml?user=fleetie

Wasn't it N Cook who wrote:
>Is there a corner-cube prism array reflector placed on Mars , like the one
>placed on the moon ?

I don't think there'd be much point. The 1 Gigawatt laser that is used 
with the lunar rangefinder is pretty close to the maximum that would be 
feasible for firing through the Earth's atmosphere. At closest approach, 
Mars is 153 times further away than the Moon, so you'd probably need a 
laser that's 23409 times brighter to get an equivalent result (the 
brightness falls off with the square of the distance).

-- 
Mike Williams
Gentleman of Leisure

Fleetie  wrote in message
news:o6adnY4f-dgpn-DanZ2dnUVZ8uOdnZ2d@bt.com...
> "N Cook"  wrote
> > Is there a corner-cube prism array reflector placed on Mars , like the
one
> > placed on the moon ?
>
> Almost certanly not, for practical reasons. Even when they bounce off
> the one on the Moon, apparently they get (or got) <1 photon returned per
> outgoing pulse. So they have to send lots of pulses and extract the signal
> from noise. I think they were going to upgrade the laser at some point,
> but even still, if they have, they're probably getting just a few photons
> back per shot.
>
> How much further away is Mars? They'd so seldom get a photon back,
> it probably wouldn't be worth it. BICBW.
>
>
> Martin
> --
> M.A.Poyser                                                  Tel.: 07967
110890
> Manchester, U.K.
http://www.livejournal.com/userinfo.bml?user=fleetie
>
>

Just found
http://www.bautforum.com/questions-answers/37716-question-laser-reflectors-m
ars.html
and a handful of reasons why there is not one on Mars

On or about 2008-01-03,
Mike Williams  illuminated us with:
> Wasn't it N Cook who wrote:
>>Is there a corner-cube prism array reflector placed on Mars , like the one
>>placed on the moon ?
>
> I don't think there'd be much point. The 1 Gigawatt laser that is used 
> with the lunar rangefinder is pretty close to the maximum that would be 
> feasible for firing through the Earth's atmosphere. At closest approach, 
> Mars is 153 times further away than the Moon, so you'd probably need a 
> laser that's 23409 times brighter to get an equivalent result (the 
> brightness falls off with the square of the distance).

Plus Mars has an atmosphere with rather a lot of dust in it to
contaminate the reflector surface and it doesn't generally keep the
same bit facing Earth like the Moon does.

-- 
Mark
      Real email address     |      Sign seen in our veterinarian's office:
          is mark at         |         "All children left unattended will
        ayliffe dot org      |              be given a free kitten."

In uk.sci.astronomy message , Thu,
3 Jan 2008 15:46:55, Mike Williams  posted:
>Wasn't it N Cook who wrote:
>>Is there a corner-cube prism array reflector placed on Mars , like the one
>>placed on the moon ?
>
>I don't think there'd be much point. The 1 Gigawatt laser that is used
>with the lunar rangefinder is pretty close to the maximum that would be
>feasible for firing through the Earth's atmosphere. At closest
>approach, Mars is 153 times further away than the Moon, so you'd
>probably need a laser that's 23409 times brighter to get an equivalent
>result (the brightness falls off with the square of the distance).


True, but unless the corner cube is so large that diffraction can be
ignored (in which case it needs also to be very cubical), the return
signal also falls off as the square, so that the received signal is
proportional to the inverse fourth power of the distance.


To avoid diffraction, I believe that the square of the cube size must
exceed the product of wavelength and distance (approximately) -

sqrt (600E-9 * 153*384E6), for closest Mars approach, is somewhere
between the sizes of Jodrell Bank and Arecibo.


The only hope would be to send a radio signal directly from Earth to a
lander, and get an immediate response back.  But, if that could be done,
I suspect the bandwidth would be too low for usefully accurate timing in
the Subject context.

ICBW, IANAE; but I once knew a bit about bouncing random numbers off the
Moon.

-- 
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