According to the marinetraffic web site the PMS Burullus spent a day moving at a snail's speed in a classic zig zag course coverign an area about 1Km by 1Km. Its position has not been updated for nearly 24 hours - at least on the "free" version of the tracker I have used.
The lack of an update is most likely due to the Burullus being in exactly the same area of poor radio coverage, with the added problem of its antenna for the tracking system it uses, AIS, being just a few metres above sea level. In fact there was a loss of coverage for a hour or so yesterday. Some vessels use a satcom version of AIS, but you have to have a rather expensive subscription to see that data. Anyone have access to the Satcom version? I do not know if the PMS Burullus is using satcom to broadcast its position though.
It could be that the "authorities" do not want the vessel's movements to be tracked of course, and the vessel has simply turned its AIS transmitter off.
There is no suggestion that the vessel is stationary - the last update is time stamped nearly 24 hours ago, so it is simply the data is not available.
It is also notable that there seems to be a big empty space around the Burullus clear of other shipping, though that may just be coincidence, or a consequence of the particular location.
What was interesting is two days ago the Burullus moved on a relatively long "base line" (my interpretation) NE to SW many Km long at quite some speed, before retracing its steps to roughly halfway along that line, then moving very slowly 2Km SW, perpendicular to that line and then starting this 1Km by 200 odd metres zig zag back and forth (see posts 784 & 785).
Could the base line be the "pinger" being heard and triangulated, approximately, and then the fine zig zag be a sonar scan? Post 808 gives some very helpful information about sonar, but makes the point the Burullus was moving rather slowly for a sonar fish. My logic would say the pattern was more closely spaced than you would need to home in on a pinger, which I understand has a range of several Km not the hundred or so metres the pattern suggests. Would you not "just" make one pass in an arbitrary direction, looking for the peak sound level, then pass through that peak point at right angles looking for a peak again, and thus, with a bit of trigonometry, home in on the source?
But the fact that a vessel has swept an area just 1Km by 1Km (2 square Km or so if it has kept going at the same rate for the past 24 hours while its position has not been updated) may suggest they are hunting something down. The press "noise" would seem to support this.
We will know in due course.