Archive for July 23rd, 2008

ru17 is looking good and not so good

Wednesday, July 23rd, 2008

We got back an mbd list today and some things are looking promising, while others aren't.  Earlier last week, we changed how the glider climbs and dives in an effort to save power: before, it would try to maintain a constant 26 degree pitch angle by moving its battery forward or backward to change the center of gravity and fine tune the pitch.  This causes the battery to move around a decent amount during its climbs and dives, something that we didn't think was necessary.  So, taking the average battery positions since the beginning of the atlantic mission, we commanded the glider to move the battery to one position for climbs and dives and stay there, i.e. don't move, and don't use power. We got back some rewarding data.  Still good casts and pitch very near 26 degrees!

We also got back data on the fin movement and the glider's heading.  These two don't look so good.  We're working with Webb right now to try to figure out what's wrong. There are just too many oscillations in the fin and it tries to go hard over on several occassions.  This fin movement affects the heading, which also is going pretty far beyond its commanded heading.  The team is going to look into this ASAP.

 

ru17 ballast pump analysis, something wrong with 15’s pump

Wednesday, July 23rd, 2008

This is a plot of ballast pump position for ru17 during its test deployment off NJ in August 2007.

This is a plot of ballast pump position for ru17 during its long duration test from December 2007 to January 2008.

This is a plot of ballast pump position for ru15 during its flight from NJ to Halifax. You can see that the ballast pump is way past the nominal value of +230 lots of the time. The plots of 17 look good. The plot of 15 looks bad.

Starting the turn to the east

Wednesday, July 23rd, 2008

Tropical Storm Cristobal is now forecast to stay well north of RU17.

RU17 is riding the eastern side of the cold eddy.  Heading northwest along that warm band of water.

 Intertial currents are slowly fading, and we have a current that is due north.  Something we have not seen in a couple of days.  So the current is turning, and we can start turning RU17.

 We will turn RU17 from its present NE course to a new course to the ENE.  The new waypoint will be 40.5 N 44W. We will use RU17's velocity to try to center us in that eastward flowing current we see in the altimetry below. Eric just sent RU17 on a 1 hour CTD sampling mission that he will also use to verify his tuning of its flight characteristics.  Once Eric completes his mission, he will be sending RU17 to the new waypoint.