Aeronautics | 02. June 2015

ARCTIC15 - Airborne SAR acquisitions up and running

Credit: DLR / Martin Keller (CC-BY 3.0)
A first SAR data quicklook of the Kangerlussuaq calibration test site. The colours represent the intensity in different polarisations (Red: VV, Green: HV, Blue: HH). The airport is clearly visible in black. From the centre of the image, the fjord extents in a south-west direction, where skidoo-tracks to the next village can be seen.

Three calibration flights, 10 flights to test sites, and over 100 radar data sets resulting in 4.8 Terabyte of SAR data. These are the numbers behind the work our F-SAR team conducted within the last two weeks – including even the alteration from the X-C-S-L to the P-band antenna configuration and fortunately only one bad weather day.

DLR's Do-228 airplane, with the F-SAR system on board arrived on Friday, 24 May, in Kangerlussuaq. On the following Monday, the team consisting of two pilots, one flight engineer and two radar operators took off for the first calibration flight. In the first two weeks, the antenna configuration for the X-, C-, S- and L-band frequencies was installed on the plane. This range of different frequencies will allow us to compare radar acquisitions with different penetration depths into the snow and ice. The team acquired SAR data over all the test sites where we had installed corner reflectors. Additionally, the area around the airport and town of Kangerlussuaq is overflown for calibration purposes and is well equipped with seven reflectors. It seems like the locals got used to these strange metallic artefacts in their town pretty fast.

Credit: DLR / Ralf Horn (CC-BY 3.0)
DLR's Do-228 with the F-SAR radar system on board after refuelling at the airport of Ilulissat, Greenland. The X-C-S-L antenna mount is visible on the rear of the plane.

Eventually, during the first days after the calibration flight, we had to face exactly those smaller and bigger problems – those that one must always expect during a campaign, as mentioned in the previous post. But the F-SAR team proved their problem-solving skills and campaign experience. From non-matching connections of the local oxygen supply to unstable electronic parts, they were able to fix everything without causing any delay to the campaign plan. I have to admit that I was already worried about losing one test site due to the technical difficulties, but the team was able to acquire almost all the data we had planned for. For now, we can say that the X-C-S-L phase was successful, giving us plenty of scientific data.

Credit: DLR / Georg Fischer (CC-BY 3.0)
The F-SAR team preparing to remove the X-C-S-L antenna from the side of the Do-228 airplane.

The change to the P-band antenna configuration was completed successfully. The P-band wavelength is the longest we will use during this campaign and penetrates several tens of metres into the ice. We are already curious about what kind of subsurface features we will see in the data.

Today, while I'm writing, the F-SAR team is flying over the K-transect to conduct the first P-band acquisitions. Currently, we are all very optimistic about the upcoming part of the campaign.