….. back to base.
The long haul of the Congo team – their 56 day round trip UK to UK is over and saw an occasionally eventual time during the 3 week run back to the UK.
A few hundred miles north of the Canaries well out into the Atlantic we came across a fishing boat adrift.
A very small boat a very long way out, and no-one in sight, and certainly not something you want to hit in the dark.
Running up the English Channel we were buzzed by the French Fisheries Protection.
Came in for a very close overhead look.
Past the Victorian forts in the Solent – currently up for sale, with one being a boutique hotel – a retirement project perhaps?
And then into the dock in front of the National Oceanography Centre in Southampton – 56 days port-to-port.
The weather had certainly changed significantly in between.
Along side the first job is to offload our container with all of the recovered instrument platforms securely stowed inside ready to shipment back to the lab in the NE of England.
This container will not arrive for a week or so.
But in a van we also brought back the more urgently needed equipment, and some equipment belonging to another group in the Congo project that had been attached to the moorings that had been released from the seabed by the large avalanche of sediment in January that broke several telecoms cables.
These moorings had been recovered by a passing cable laying vessel that just happened to spot them during a transit, and took them to South Africa.
They had recently been shipped back to Southampton and arrived the week before the RRS James Cook did.
We offered to download recorded data for the owning group as part of the return process.
However, taking it out of its box revealed a problem ………..
……. with seabed or water column instrumentation you don’t expect to see water come out of the pressure tube that’s designed to keep water out when deployed.
Opening ….. carefully ….. revealed ……
……. that water had got in at some point and all the electronics is corroded well beyond repair ……. and …..
….. so were the batteries.
This level of electronics corrosion suggests the boards were still powered when the water got in.
The hard disk on which the data is stored was in a similarly badly corroded condition.
This kind of leak often happens when pressure vessels coming up from the deep ocean reach the surface rapidly when their seals do not have time to adjust to the change in pressure – they are known as shallow water leaks.
And if they float around at the surface for a while, water often gets in.
This is why we always try to pick our instruments out of the water as soon as they surface.
If this is a case of a shallow water leak once the mooring surfaced, it means there is a good chance that there is data on the hard drive ….. but the electronics in this system is beyond salvaging to enable access to it on the disk if it is there, and even if it is there the disk itself may be too badly damaged to be able to read it.
This is a job for a specialist and so it was dried out and duly dispatched to a specialist data retrieval company …… and so we wait to see.
Back in the lab during the 56 day Congo recovery, the development work continued with the datalogger, and we have reached a fully constructed board test point.
So put in the test rig, known signals are applied to each channel, and the test is, in simple terms, what comes out must be the same as what goes in.
This board was made in our printed circuit board facility in the lab.
So we always test with known and easily recognisable signals, like simple square wave pulses every second – and shown below is that recording on each of the three channels being tested.
With some confidence we then test all 12 channels, and instead of 1 pulse per second on all, we get a little adventurous and try one one second long pulse every 25 seconds and an even longer 12 second square wave.
A wide variety of tests is the key as we need to be sure that it will handle all of the signals that it is likely to record, not just specific types.
So having proved that the hardware works, it now has to be made intelligent by giving it a software brain!