Which of the following is a use of the STELLA program?

The STELLA program is primarily used for celestial navigation calculations, including the determination of sunrise and twilight times. This is especially useful for navigators who need to plan their activities based on daylight conditions. In maritime settings, knowing the exact times of sunrise and sunset can significantly impact safety and navigation decisions, allowing mariners to avoid operating in low-light conditions and to maximize daylight for their voyages.

While the program focuses on celestial phenomena, the other choices listed involve different types of navigational data or calculations that are not the primary focus of STELLA. For instance, calculating vessel weight relates to stability and load management, determining ocean currents pertains to hydrodynamics and navigation strategies, and calculating wind speed and direction is often associated with weather reporting and sail planning. These functions may be addressed by other specialized tools or software tailored more closely to those specific navigational aspects.