deepsea metro rig vanished, page-24

Guys I don't know much about O&G but I do know a thing or two about RF and radios.

The position transponder gets its coordinates from GPS and modulates them (along with ship details) on to a VHF carrier and transmits them out in all directions through a VHF omnidirectional antenna. AIS receivers all over the world (generally shore based) pick up these signals, demodulate the data on the signals and sends the data over the internet to the marine traffic server. This collection of data is what we see when we choose a ship on Marine Traffic and view it's track or position history. A free subscription to marine traffic will tell you there are satellite position data points available, and to upgrade to a paid service to get them. These points are transmitted from the ship via a satellite phone service to the Marine Traffic server.

Now, you only get point on the radio service when the signal from the ship is strong enough to be picked up by an AIS receiver. At the distance the drill site is from shore, most likely there are very few AIS receivers that might be able to pick up the signal. A lot of the receivers are privately owned, so if there's only one receiver that can pick it up (antenna in just the right position) then if that one can't get it, it disappears from the map. VHF signal strength over that distance is very weather dependent, it may need to bounce off a cloud to get in, it may need to refract through atmospheric layers etc. So if the conditions change, signal can drop out. If the only AIS station in the fringe reception area has a power outage, or if the owner goes away for the weekend and turns off the computer, we don't get fixes. IMO at that distance offshore we're lucky to be getting any fixes at all. And from what I've heard about the reliability of Kenyan internet infrastructure it makes any AIS fix all the more amazing.

And as we know, the last AIS fix from 11/3/2014 2154 UTC had the DSM still on the drill site, and most likely it's still there.

If you ask me, the conspiracy theories about pirates and 'cone of silence' are about as crazy as the faked moon landing!