|A Vemco VR4 Global buoy floats at the surface, uplinking|
to Iridium satellites through the dome at the top.
Ensuring that each step in the chain, from detection to sending the signal to the surface unit to transmitting the signal to the satellite, is working perfectly requires patience and a lot of testing – after all it will be twelve months before we have a chance to service this equipment again.
Dr Taylor Chapple is our team’s expert on working with the ‘Globals’, and he has had a busy couple of days. Despite having no apparent issues with replacing batteries, cleaning, and reinstalling both our units earlier in the expedition, we had been getting no data sent through, despite everything apparently working perfectly. Taylor, supported remotely by the Vemco team, worked to eliminate all the possible causes by testing each link in the chain. He concluded that it might be the hydrophone – the listening tip of the system – or its connection that was causing the problems.
With spare hydrophones carefully swaddled in bubble-wrap we set out to our the first of our Global receivers again, this time with a battery of additional testing equipment. Two divers detached the hydrophone from the mooring cable and passed it up to Taylor, who carefully changed the hydrophone and checked the connections, before placing it back in the water with some test transmitters. Connecting wirelessly to the surface part of the system, he is able to see what the system sees, and he was quickly able to confirm that it was now detecting the tags. Hot on the heels of this a radio call from Robbie Schallert, back on board the ship, confirmed that the system was also sending the data back to Vemco. We were back on line! Carefully reattaching the hydrophone back to its anchor, the system was ready to go for another year of work in Chagos.
Dealing with problems like this in the field requires patience and resourcefulness, and the support of a good team at home as well!