It was great to see the SIERRA head off over the horizon yesterday, on its first science mission. This first science flight targeted a range of sea ice conditions to the north of Ny-Alesund by flying a box pattern with a short “mapping” segment (flight tracks closely aligned to provide full coverage with camera and radar imagery). The flight length and location was designed to provide good science return while keeping the aircraft within relatively close range for this first flight. The total pattern covered about 500 km, with about 160 km flown over the ice (the ice edge is present about 170 km from Ny-Alesund).
From the science team’s perspective, today was a successful flight in terms of UAS and sensor performance, demonstrating that the plane can handle adverse conditions (moisture and winds), and also achieve the desired range that should permit flights of 8 to 10 hours. The digital cameras and initial examination of SAR imagery showed the hoped-for variety of ice conditions. The data show the ice pack in this location to consist of a variety of floe sizes, nearly all of which appeared to be multiyear ice, with its characteristic blue-colored melt ponds. Some floes were quite rounded, as is typical of multiyear ice, while other multiyear floes had sharper angles and edges. This suggests possible differences in overall ice age – a situation that we are hoping to observe and study as one of the main goals of the project.
One of the questions I had regarding operations was the degree to which we could revise flight plans during flight to accommodate changing conditions as observed by the aircraft on its way out to the study location. We tested this by shifting the flight pattern to take into account changes in wind direction. The ground operator was able to revise the plan quickly once I supplied the revised latitude/longitude waypoints. I did this simply by changing the flight plan in Google Earth and then e-mailing the revised pattern to the ground operator.
This first science flight also demonstrated successful operation of all of the primary sensors (data from the other sensors has not been checked yet). As it turned out, the aircraft ended up flying in thin cloud or mist conditions nearly the entire time while over the sea ice. This meant that the PLAS LIDAR did not collect useful data of the surface since the laser beams are obscured by liquid moisture in the air. However, PLAS data were collected over the open-water segment of the flight, before entering cloud and mist. Also, the camera photos and video can see through some thin cloud, so nearly all of the imagery is of value.
The imaging radar system is not affected by clouds. Initial processing of the SAR data show that it collected data successfully, but not with full coverage across the entire image swath. This is being investigated, but may be due to cross winds that caused the aircraft to point in a direction not aligned directly with the intended flight track (in other words, the plane is “crabbing” into the wind while moving along the flight track), or to variations in flight speed when the plane was flying upwind (producing a slower ground speed) or downwind (faster ground speed).
The next mission plan will include 800 km of flying, and based on current ice conditions, will map the ice cover further to the west, crossing over much of Fram Strait.
Posted by CASIE Principal Investigator, Dr. James Maslanik (CU-Boulder)