Detection of submarines via satellite? Experiment hidden in plain sight?

[maddbiker]

I have a question for you, and would appreciate your feedback….

 

Would a large military submarine, whilst travelling below the sea surface, affect the Earth's geoid, enabling an extremely sensitive satellite based gradiometer, to detect the anomaly caused by a submarine, in comparison to a high-resolution reference map of the geoid?

 

The submarine would most probably be at neutral buoyancy, with depth adjusted via its control surfaces.

 

Rune Floberghagen, Esa's GOCE (Gravity field and steady-state Ocean Circulation Explorer satellite) mission manager explained the sensitivity of GOCE as follows: "Imagine a snowflake, which has a fraction of a gram, slowly falling down on to the deck of a super tanker. The acceleration that the super tanker experiences from that snowflake is comparable to the sensitivity of our instrument"

 

Whilst the overall structure of the submarine would be neutral in buoyancy, there would be a large internal volume where the water will be 100% displaced by air, and thus have almost nil mass in comparison to the water surrounding it.

 

What do you think?

[D H]

Would a large military submarine, whilst travelling below the sea surface, affect the Earth's geoid, enabling an extremely sensitive satellite based gradiometer, to detect the anomaly caused by a submarine, in comparison to a high-resolution reference map of the geoid?

No, for two reasons. You gave one:

The submarine would most probably be at neutral buoyancy

 

Even more importantly, hose extremely accurate accelerometers on the GOCE cannot measure the acceleration due to gravity for the simple reason that no accelerometer can. What those accelerometers do do is measure everything but the acceleration due to gravity.

 

The GOCE ground systems propagate the vehicle's state (position and velocity) over time using those accelerometer readings and gravity models (Earth, the Sun, the Moon, and the planets). This propagated state will of course deviate from the measured state, with the errors increasing over time. These errors result from errors in the accelerometers, errors in the measured state, errors in planetary ephemerides, and errors in the gravity models -- particularly the Earth gravity model. These errors can be used to refine the Earth gravity model. To do so takes a good history of data and a *lot* of computing power.