P-3 Antenna Array Changes Produce Faster, Clearer Results


By Shawn Schaller
Summer 2011

Before CReSIS embarked on its 2011 field season, a few adjustments had to be made. For the P-3 aircraft, this meant major structural and electrical changes to the radar depth sounder system and the antenna arrays. In early March, the CReSIS team began field operations on the P-3: first in test flights out of NASA’s Wallops Flight Facility in Virginia and then on to Greenland and Alaska for science flights. The CReSIS team joined with four other instrument teams operating two LIDARs, a gravimeter, a magnetometer, and a cartographic camera sensor in addition to CReSIS’ four radars.

Two and a half months later, in the middle of May, the P-3 team returned to CReSIS with a bevy of positive results. Discussing the data produced by the deployment brought a smile of relief to CReSIS Deputy Director Carl Leuschen’s face, as the testing phase of new elements and upgrades can be an uncertain, stressful time. Ultimately, Leuschen said that he was pleased and that the mission was “very successful.”

In summary, the changes made to the radar system and P-3 antenna arrays allow CReSIS to receive the clearest data ever received and to produce results in a much shorter time frame than was previously possible.

According to Electrical Engineering and Computer Science professor Fernando Rodriguez-Morales, the upgrades reduced Radio Frequency Interference (RFI), optimized radar settings during sea-ice flights, and utilized new data processing software to produce ‘quick-look’ results for accelerated echogram production.

Many of the upgrades were directly connected to the physical structures and mounting systems of the antenna arrays. In order to increase sensitivity, members of the University of Kansas’ Aerospace Engineering and Electrical Engineering and Computer Science departments worked together to replace the metal elements within the antennas and mounting systems.

The changes to the antenna array on the P-3 aircraft were a completion of work that began the previous year. Fifteen total elements were installed, nearly doubling the total of eight elements previously attached to the aircraft’s belly.


New antenna arrays line the underside of the P-3 aircraft. Photo courtesy of Rick Hale.

According to Leuschen, four different instruments operated on the aircraft: the Radar Depth Sounder, the Snow Radar, the Ku Band-Altimeter, and the Accumulation Radar. Rodriguez-Morales added that the P-3 radar depth sounder also utilized the newly-developed 16-channel receiver system so that all fifteen antenna elements could be monitored simultaneously (with a spare).

Prior to the Greenland deployment, the P-3 underwent numerous simulations and tests to ensure that the improved antenna arrays could produce quality data amid the rigors of clinging to the underside of an aircraft in flight. The antennas were tested for consistency through variations in air flow, vibrations, and the force pressing upon the structures.

During the Greenland deployment, it was quickly apparent that all the hard work the P-3 team logged during the winter months paid off in full. According to Rodriguez-Morales, Operation IceBridge Project Scientist Michael Studinger said that some of the results produced directly in the field were “the coolest radar images [he’s] seen of the Greenland Ice Sheet.”

As for his own opinion, Rodriguez-Morales was also pleased with the results, saying that they were certainly as good as expected. However, he was even happier with the work of the P-3 team throughout the mission.

“This mission was a success,” Rodriguez-Morales said, “thanks to the excellent work effort from our technical team.”