Ultra-Wideband Radars for Measurements over Land and Sea Ice

• Main Authors: Hale, Richard, Miller, Heinrich, Gogineni, S., Yan, J.-B., Rodriguez-Morales, F., Leuschen, C., Wang, Z., Paden, John, Gomez-Garcia, D, Binder, Tobias, Steinhage, Daniel, Gehrmann, Martin, Braaten, David
• Format: Conference Object
• Language: unknown
• Published: 2015
• Subjects: Greenland; West Antarctica; Antarc*; Antarctica; Ice Sheet; Sea ice
• Online Access: https://epic.awi.de/id/eprint/39610/; https://epic.awi.de/id/eprint/39610/3/AGU-Gogineni-2015_1.pdf; https://hdl.handle.net/10013/epic.46814; https://hdl.handle.net/10013/epic.46814.d003

We developed two ultra-wideband (UWB) radars for measurements over ice sheets in Greenland and Antarctica, and sea ice. One of the UWB radars operates over the frequency range of 150-600 MHz with a large cross-track 24-element array. It is designed to sound ice, image ice-bed interface and map internal layers with fine resolution. The 24-element-array consists of three 8-element sub-arrays. One of these sub-arrays is mounted under the fuselage and the other two are mounted under the wings of BT-67 aircraft. The measured inflight VSWR is less than 2 over the entire operating range. The fuselage sub- array is used both for transmission and reception, and wing-mounted sub-arrays are used for reception. The transmitter consists of 8-channel digital waveform generator to synthesize chirped pulses of selectable pulse width and duration. It also consists of driver and power amplifiers to increase the power level to about 1 kW and a fast transmit/receive switch that can handle more than 1 kW of peak power. Each receiver consists of a limiter, switches, low-noise and driver amplifiers, and filters to shape and amplify received signals to the level required for digitization. The digital sub-section consists of timing and control sub-system, and 24-A/D converters to digitize received signals at a rate of 1.6 GHz. The radar performance is evaluated using a delay line to simulate returns from about 2 km thick ice and the loop sensitivity is more than 215 dB. The other UWB microwave radar operates over the frequency range of 2-18 GHz in the Frequency-modulated Continuous Wave (FM-CW) mode. It is designed to sound more than 100 cm snow over sea ice and map internal layers to a depth about 25-40 m in polar firn and ice. We operated the microwave radar over snow-covered sea ice and mapped snow as thin as 5 cm and as thick as 60 cm. With an early version of the radar we mapped internal layers to a depth of 45 m with fine resolution in West Antarctica. We will discuss design considerations and present laboratory results to document radars performance including their impulse response functions. We will show the results from a field campaign over the Greenland ice sheet.