Observation opportunities missed and data left out at sea during glider missions?

Since the development of gliders, scientists have used them to collect high resolution data sets over long periods of time, weeks to months. For the majority of the time a glider is flown, scientists equip the glider with only the sensors needed to collect a limited data set specific to the scientist's research objective. Scientists can overload the glider with sensors, causing a shortening of the mission due to battery life. However, some glider missions include only the minimum of sensors, (e.g. CTD) which result in surplus battery life remaining after the mission completion. In these instances the battery life could provide additional data sets with minimal cost or interruption to the primary mission. Many opportunities for gliders to conduct multiple missions occur but decisions are required to manage the variety of sensors for optimum scientific and operational efficiency. In 2013 a joint glider mission with Shell Oil and NOAA's National Data Buoy Center was conducted in the Gulf of Mexico (GOM). This glider mission provides an example of sensors being deployed, yet data not collected. The main mission objective was to provide validation for the Ocean Heat Content being derived by satellites and augment existing in-situ data into the real time HWRF-HYCOM hurricane model. The mission was planned with coordination through the Environmental Modeling Center (EMC) to target features, such as eddies, in the GOM. The secondary objective included baseline sampling of water column dissolved oxygen and color dissolved organic matter (CDOM) in the Northern Gulf of Mexico. With the third mission objective to continually operate a glider in the GOM throughout the hurricane season, which limited sensor use in order to prolong the deployment. This creates additional and critical considerations among the piloting team to balance sampling rates of sensors with mission duration capabilities. This paper uses experiences from this 2013 glider mission, to discuss the possible gains and losses of including additional sensors on gliders for secondary mission objectives. In addition, this paper discusses the need to identify the scientific focus and sampling requirements and how to integrate the secondary requirements into flight operations.