Goce satellite shows new data on earths gravity

[Eric Mc]

To quote Neil fromn "The Young Ones" -

That's heavy man!

[D-Angle]

The womenfolk are going to get very excited by this news, "lose weight just by going on holiday to Portugal"...

[The Wookie]

I genuinely have no understanding, so I ask what are the zig zags all about, and why isn't the gravity of the Andes and such reflected on the other side of the planet?

[jmorgan]

Interesting. You can see where plates collide and where volcano chains live. Wonder if the atlantic rift is not showing due to the ocean?

[Graham E]

I think that plot has a large amount of error there.You can clearly see the path of the saelite in both "red" and "blue" lines. Could this be bad calculation from the relative positions of sun, earth and moon?

[Eric Mc]

The Wookie said:

I genuinely have no understanding, so I ask what are the zig zags all about, and why isn't the gravity of the Andes and such reflected on the other side of the planet?

All planets, moons and stars exert a gravitational pull. The strength of that "pull" is based on the mass of the planet, moon or star. On rocky planets and moons, this mass is not uniformly distributed throughout the body. Some parts of the planet/moon will be denser than others. Therefore, the gravitational pull exerted by the moon or planet will vary if you are passing over a dense part of the planet or a less dense part of the planet.

These variations in gravitational strength weere first discovered on the moon in the mid 1960s. The first unmanned orbiting missions (NASA's Lunar Orbiter spacecraft) all experienced variations in their orbital speeds which had not been predicted. This was found to be due to concentrations of material under the Lunar Mare. They were officially christened Mass Concentrations but this was quickly shortened to MASCONS.

It looks like the earth's crust is denser where the continental plates are colliding with each other - either at subduction zones or where mountain ranges are being pushed up.

Edited by Eric Mc on Thursday 24th December 14:11

[poo at Paul's]

Notice UK is jus about the only country with nothing on it!!

Maybe Gordo comlained it was all blue so the beeeb doctored it!!?

[nonegreen]

Guam said:

Being a fat bd I need to relocate to a blue area I guess

bugger off I am having the blue areas. I am fatter than you

[Marf]

Eric Mc said:

To quote Neil fromn "The Young Ones" -

That's heavy man!

The satellite itself is pretty interesting

http://www.esa.int/esaLP/ESA1MK1VMOC_LPgoce_0.html

[esselte]

Eric Mc said:

The Wookie said:

I genuinely have no understanding, so I ask what are the zig zags all about, and why isn't the gravity of the Andes and such reflected on the other side of the planet?

All planets, moons and stars exert a gravitational pull. The strength of that "pull" is based on the mass of the planet, moon or star. On rocky planets and moons, this mass is not uniformly distributed throughout the body. Some parts of the planet/moon will be denser than others. Therefore, the gravitational pull exerted by the moon or planet will vary if you are passing over a dense part of the planet or a less dense part of the planet.

These variations in gravitational strength weere first discovered on the moon in the mid 1960s. The first unmanned orbiting missions (NASA's Lunar Orbiter spacecraft) all experienced variations in their orbital speeds which had not been predicted. This was found to be due to concentrations of material under the Lunar Mare. They were officially christened Mass Concentrations but this was quickly shortened to MASCONS.

It looks like the earth's crust is denser where the continental plates are colliding with each other - either at subduction zones or where mountain ranges are being pushed up.

Edited by Eric Mc on Thursday 24th December 14:11

How does that account for the symetrical "zig-zag" pattern we can see on the picture...?

[TomE]

esselte said:

How does that account for the symetrical "zig-zag" pattern we can see on the picture...?

Is that not just due to the path the satellite has taken?

[Eric Mc]

TomE said:

esselte said:

How does that account for the symetrical "zig-zag" pattern we can see on the picture...?

Is that not just due to the path the satellite has taken?

Looks like it to me.

As the mission progresses and the number of orbital passes increases, this zig-zag pattern will fade out.

[FourWheelDrift]

So will the save the earth MMGW brigade look at that and blame us for it, starting a new Save The Gravity campaign? Trying to make up some more lies about how the gravitational fields are creating changes in the environment killing fluffy animals and it's all our fault.


I bet you someone is thinking about it. If there is money to be made you know they will.

Edited by FourWheelDrift on Thursday 24th December 17:37

[turbobloke]

The presence of a signal along the satellite's path is almost inevitable. As mentioned in the article the very sensitive gradiometer - possibly consisting of gravimeters / accelerometers and a means of detecting differences between them - can pick up changes of one tenth of a millionth of a millionth of g. This is sensitive (!) and will see any slight deviation in readings between the accelerometers as equivalent to a change in gravitational field. If the satellite pivots even the slightest amount while orbiting then there will be an output signal. The smallest of collisions with microscopic space debris could do this. Undoubtedly the very sophisticated gradiometer design and data processing will have taken this into account but at such high levels of sensitivity it seems almost unavoidable that various minuscule motions of the satellite will be picked up. If everything at that scale was screened out then the sensitivity would be compromised. There must be something very special about the design, if full details are available it would be fascinating to see how the designers are handling extraneous signals.

[turbobloke]

PS
If anybody on here knows what the gradiometer design is and knowing PH there may well be somebody in the design team or with insider info, please do post up as there are other possibilities than the one I suggested and it'd be a good read.

[dilbert]

turbobloke said:

PS
If anybody on here knows what the gradiometer design is and knowing PH there may well be somebody in the design team or with insider info, please do post up as there are other possibilities than the one I suggested and it'd be a good read.

I'm not an insider, but reading the description it sounds like they have three instruments, presumably each measuring gravity on a different axis. To calibrate they shake the satellite in a known way and are able to compute the errors in each sensor by comparing it with the others.

By this means it is possible to null out gravitational influences from the sun, moon and any other source and measure only the gravitational influence along the line that intersects the centre of the overall instrument and the centre of the earth.

The gradiometers individually are known suspended masses, that presumably are only able to move in one axis. It sounds like there is an electronic control system that can move the mass, by means of magnetism. The control system is designed to keep the mass in a precise location, probably measured optically. The error force exerted by the electromagnets to correct the position of the mass, is a measure of the gravitational force exerted on that axis.

An object hitting the satellite would certainly affect the measurement process, but I would imagine that it would be easy to identify as erroneous.

More difficult to remove would be effects due to variations in density of the upper atmosphere, and also variations in temperature.

Edited by dilbert on Thursday 24th December 23:29

[turbobloke]

Clever stuff.