Over the past month, there has been a prototype glider roaming the waters off of the Middle Atlantic Bight; Darwin.
Darwin over the years has been a in a way TWR's test glider, and this summer he continued this legacy as Webb outfitted it with a prototype fluorescence puck to compare with the standard florescence puck, and a prototype thruster.
The first test being done, is the puck comparison, where the prototype C3 puck is being compared to the Wetlabs ECO Puck which has been used regularly in the Slocum Gliders. In the past, the Wetlabs ECO Puck has provided a reliable source of collecting data on Chlorophyll, Color Disolved Organic Matter (CDOM) and Back Scatter. The new Turner C3 Puck has similar sensors including Chlorophyll, Phycoerythrin, CDOM, Turbidity (back scatter), temperature, and depth.
Left: Turner C3 Puck, Right: Wetlabs ECO Puck
The first two preliminary plots I have created, are a subplot comparing the Chlorophyll sensors on each of the pucks and then a concentration plot of the same goal.
Both sensors seem to collect the bulk of the data to the same extent, however there are some minor differences, such as picking up data in different areas of the water column in different intensities.
I made a similar plot of Turbidity from the Turner C3 Puck against the Wetlabs ECO Puck's Back Scatter. This plot again shows that there is a lot of consistency in the bulk of the data, but they also seem to pick up some differences as well.
There will be more of an analysis to come!
Darwin is also equipped with a prototype thruster that can be programmed to turn on and off in different intensities throughout the mission. This can be incredibly useful in piloting when it comes to getting out of sticky situations such as eddies or unfavorable currents, reaching an ideal area of sampling quicker, or flying more exact lines when sampling an area for a successful mowing-the-lawn pattern.
As the design of the glider does not leave much room for exterior modifications, the ejection weight had to be moved during installation from its standard orientation. Below are two images showing the new orientation along with the thruster relaxed and set.
The thruster was tested on two occasions in which 'Bath Tub' profiles were attempted. An ideal bath tub profile consists of the glider diving to a pre-set depth (in this case 10 m) and the thruster then kicking in causing the glider to cruise, level at depth for a period of time before returning to the surface creating a path that looks like a bath tub. This was attempted on September 14th and 17th and the results are below:
As we can see, the thruster worked, however Darwin was not able to maintain depth as planned. After recovery, there is some hardware maintenance that must be done to the thruster, and there will also be a software upgrade that will allow the gliders brain to use logic that will help it maintain depth by adjusting pitch.
As Darwin has now been running tests off of the coast of southern NJ for a couple weeks now, Darwin has been making its way back up the coast towards Belmar, NJ where a recovery will take place early this week depending on the weather. After recovery, the adjustments to the thruster listed above will be made, along with changes to the science payload bay. After the upgrades are completed, Darwin will be redeployed off of New Jersey and fly the reverse of the track previously flown on its way back up to Teledyne Webb Research's facility in Massachusetts.