What's causing spacecraft to mysteriously accelerate? The Rosetta comet chaser's fly-by of Earth on 13 November is a perfect opportunity to get to the bottom of it.
The anomaly emerged in 1990, when NASA's Galileo spacecraft whizzed by Earth to get a boost from our planet's gravity and gained 3.9 millimetres per second more than expected. And the European Space Agency's Rosetta spacecraft had an unexpected increase of about 1.8 millimetres per second during a previous fly-by of Earth in 2005.
Scientists have ruled out various mundane explanations like atmospheric drag or the effect of deviations in Earth's shape. This has led some to propose that exotic new physics is involved, such as modifications of Einstein's general relativity, the currently accepted theory of gravity.
Comet-chaser clue
All eyes are now on Rosetta, which is set to swing by Earth again at 0745 GMT on 13 November. It is en route to a comet, and will travel around 2500 kilometres above our planet's surface at over 13 kilometres per second. If it gains an extra 1.1 millimetres per second relative to Earth, it would vindicate a formula that reproduces the anomalies seen so far.
The formula, published in 2008 by ex-NASA scientist John Anderson and his team, hints that Earth's rotation may be distorting space-time more than expected and thus influencing nearby spacecraft, though no one can explain how. General relativity predicts that spinning bodies distort the fabric of surrounding space, but the expected amount is far too small to explain the observed anomalies.
"I am definitely looking forward to this one," says Anderson, who is working with members of the Rosetta team to watch for an anomaly.
However, any anomaly will not be immediately obvious because the expected change is tiny. "I anticipate a few days or weeks before we know if an anomaly occurred," he says.
Curiously, Rosetta's 2007 flyby of Earth produced no anomaly. That might be because of its much higher altitude, about 5300 kilometres above Earth's surface, Anderson says. He suggests the effect may get weaker with distance from Earth: "There is most likely some dependence on distance – we just do not know what it is."
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Have your say
Couldn't this be the work of Dark Energy? It it does indeed exist, then would it not provide the small change in acceleration observed?
Or Dark Matter. If Earth's frame dragging is larger than expected then what effect might an entire galaxy rotating have?
It's just the mass equivalent of the kinetic energy of rotation of the Earth. Same effect supplies energy for flying saucers.
Oh dear! Maybe joke conceals truth.
It could just as easily be the effect of mundane physics in action
Not if you want an expensive research grant stretching for years it isn't.
mundane physics such as...? You think they're ignoring "mundane physics" in their models?
Solar wind, gravitational dragging, high energy particles, high speed collisions, errors in the data...
Do you really think they model the entirety of known physics?
Anomalies historically have a very very low probability of being anything out of the ordinary
Or Mudane
Wed Nov 11 09:54:41 GMT 2009 by Pete
http://www.ReallyQuick.co.uk
Or magnetic interaction between metallic spacecraft and earths magnetic fields?
While its really the asymetrical requirement thats the most intresting, meaning possibly some form of nonlinear effect, Im wondering, because its not really mentioned in simple explanations, do people who do the calculations, add in the mass equivalent gravitational field, of the energy contained in a gravitational field, to that graviational field. I thought that useing simple approximation suggests the mass equivalent of the Suns graviational field, is roughly equivalent to the Rest mass of the planet Earth?
The difference in velocity measured is fractions of parts per million, or an accuracy in the speed of light of tens of metres a second or better?
Will they be using the external measurement possibility of GPS to improve their measurements, accuracy, or is that one of the options already put forward?
Hope this has a nice measureable effect that follows predicted values. Especially if the prediction is based on methods which present thinking is uncertain with. We need new functions, its been over 50 years of stalling in solving the relationship between gravity and quantum mechanics, and others, and I hope this helps some.
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