Wednesday, October 14, 2009
Inside: Outside - You’re OK to Launch
Lat: 18° 24’N Long: 081° 49’W
Water depth: 2150m
In yesterday’s blog you met James, Louis and Dana: three of the core team who run Nereus’ software (hence, “brain” when it is decoupled from the ship). So now its high time I introduced you to the rest of our 8-strong team of engineers. Photo 1, here, was taken just at the moment when those working “Inside” (in the lab) had given the signal to Andy and the rest of the team “Outside” (on deck) that it was OK to go ahead and launch Nereus.
We’ve had a great day with the vehicle today which has us all set for the rest of the science program. After launching around 10:30am, Nereus descended to the seafloor (the guys don’t like it when the Captain says”sinks”!) over about 2 hours and then spent about 6-7 hours going through a series of maneuvers to test out all the different systems we might want to use for science in the next week and a half.
First it did a series of speed runs so we can calculate what its full endurance is likely to be and what will be the most efficient survey speeds for different kinds of operations. After that Nereus went through some bottom following mode operations at around 40m off the seafloor (ideal for making detailed sonar maps of areas of interest), then it ran a series of yo’yos where it will undulate up and down as it swims through the ocean – e.g. if we want to send Nereus down sniffing out new hydrothermal plumes for us. Finally, Nereus did some low-level runs, driving around just 3-3.5m above the seafloor in the mode used for taking photographs from the seafloor.
But perhaps the most interesting part of the day for me was how the mission kept getting longer! When we launched Nereus, I definitely knew that the seafloor mission was for 5.5 hours of operation on the seabed. But the little piece of masking tape across the top of the main computer that had “end of mission time” written on it kept getting updated by 20-30 minutes at a time. How do you make a mission last longer, when everything is uploaded into the vehicle’s computers before you launch it? Turns out that our engineers have found a very cool way to cheat. If they come up with better ideas while Nereus is on its way to the seafloor, or just decide they’ve seen it do enough of any one activity and want it to do something else, they just call it up and re-program it. Seriously!
They have found a new way of doing things that I have never seen done before where the vehicle can be “interrogated” via underwater acoustics and, when prompted, it sends a series of information back telling us aboard ship what is it up to: where it is, where it’s headed, how fast its moving and what its busy measuring at the moment: stuff like that. Then – and this is really VERY cool – if they have any new programs they want to send down, they can do that too! Turns out, there is only one completely untouchable “home time” sub-routine in the mission program that they can’t over-write and that cut in around 7pm. If it wasn’t for that, I think they would still have Nereus down there now. And by the twinkle in his eye, I don’t think Louis was joking when, as Nereus was finally rising back up to the seabed, he suggested that maybe they’ll be wanting to fix that, soon, too.
Tonight, our CTD system is back in action as we head further south along the ridge-crest continuing our search for stronger hydrothermal plume signals. We plan another day and a half of that so that tomorrow, while I am on CTD watch, I can also start planning our first Nereus science mission. I’m sure we haven’t even begun to think through all the ways we can make use of our acoustic communications with Nereus, but the best way to find out is to get stuck in and start working.