Labrador Sea 2015 Mission Preparations

Preparations are now complete for our next VITALS glider mission. One of our deep gliders has been readied to brave the frigid waters of the Labrador Sea for our longest, most challenging mission yet. Glider 472 will overwinter in the deep waters of the central Labrador Sea from early December until spring 2016. To reach this remote location, it will first have to navigate across the shallow Labrador Shelf on the Sea's western edge, traversing the fast-flowing inner and outer branches of the Labrador current. It will also have to contend with a wide range of seawater densities in order to successfully surface and descend to depth throughout the deployment. Achieving the latter requires the glider be appropriately weighted (i.e. ballasted), while the former requires the glider's attitude sensor be well-calibrated so the glider can accurately navigate. Details of how we carried out both of these procedures are given below.

Keep tuned to this blog over the coming months for the latest developments in this exciting glider adventure.

Ballasting

Oceanographic technician Mark Downey lowers the mission glider into the MUN deep tank to begin ballasting (i.e. making it an appropriate density for the seawater it's going to operate in by altering its mass). 

Photo credit: Robin Matthews

Weighing the glider fore and aft on our hanging scales. The aim of ballasting is not only to set the glider to an appropriate overall weight but also to have its internal weight distributed evenly along and across its body such that it sits horizontal and upright.
Photo credit: Robin Matthews

Attitude sensor calibration

The glider was strung up outside away from sources of magnetic fields to calibrate its attitude sensor. This device measures magnetic heading, pitch and roll and is critical to glider navigation. Our calibration procedure involves rotating the glider across all three dimensional axes to reduce the influence of magnetic fields within the glider on this sensitive instrument. Fortunately the weather was fairly agreeable despite this being conducted in mid-November (no wind, rain or snow!). Note that normally we'd mount the glider along the central beam of this custom-designed frame for calibration, but this glider is too long for that since it has an additional battery pack for its extended deployment. Thus we hung it from the frame instead.
Photo credit: Mark Downey

Ballasted and ready-to-go our glider ponders the meaning of its existence. 

Photo credit: Mark Downey