Now less than 2000km from the shores of South Africa, Challenger is continuing to inch her way across the map towards a more immediate goal: the Prime Meridian.
Last Thursday afternoon we pushed the waypoint further east in order for 29 to fly more perpendicular to the weak northward flow she had encountered. Through the weekend however, this current has picked up a bit (from .03m/s to .08m/s) and rotated to the north west, providing 29 with some more head on resistance. This change in direction of the currents is something we can see a few hundred km ahead in copernicus, but in the immediate area it almost looks like the sum of the east-west component of the copernicus model combined with the north-south component of the RTOFS model
Since the current is blowing more directly into Challenger’s nose, we moved the waypoint a little further north (to 35˚ S, 1˚ 30′ W) to try and fly a better angle against the current.
Over the weekend we also saw Challenger surface due to an abort. After looking into what happened, it was discovered that during the previous surfacing Challenger did not maintain the connection long enough to reset her timer, so then when she dove again and continued to fly she eventually hit her time limit and came to the surface with the abort for no-comms. Since this happened on Saturday afternoon she has continued to fly without any issues.
Looking ahead, over the next week 29 will continue to make her way towards the warm core eddy sitting at the Prime Meridian. From there we will likely aim for the southern edge of the two weaker warm core eddies as we ride them to the north east before making our final approach towards Cape Town.
One last note, looking at Dave’s vertical velocity plots, we are noticing a downward trend from the past few months showing that the glider has lost about 10% of its original speed, largely starting since October. This could potentially be due to biofouling especially since we have reduced our dive depth to 500m for the past 5 weeks. One suggestion so far has been to weigh the options of if we were to dive deeper again, the pump slipping vs the distance lost to being slowed down by barnacles. But for now this is just speculation and will be discussed further in the future.
Force Wind Sea & Honor