Ice-penetrating radars are a valuable tool for studying subsurface processes and conditions on Earth’s ice sheets. Vast amounts of ice-penetrating radar data have been collected from coherent chirped airborne ice-penetrating radar systems. Operating these airborne radar sounders is resource intensive, requiring large teams and significant financial resources. Here, we present a coherent chirped ground-based ice-penetrating radar system that can leverage the wealth of processing methods built for coherent chirped airborne radar data at a much lower cost. Our system is based on a commercially available software-defined radio (SDR) and open-source radar code platform, enabling widespread community adoption and use of the system. Furthermore, use of the SDR platform increases flexibility of the system and allows for easy reconfiguration of specific intrinsic radar and survey parameters. We present the architecture of our system alongside data it collected on the McMurdo Ice Shelf in Antarctica and at Summit Station in Greenland. We estimate the bed echo SNR it would achieve throughout Antarctica, which can be used to guide survey design. Finally, we discuss potential future system architectures which the system can be easily adapted to.

We explore and present a range of strategies for quantifying and mitigating the effects of receiver saturation in ice-penetrating radars. Ice-penetrating radars must be able to detect very weak reflected signals while maintaining dynamic ranges greater than 120 dB or more. Historically, ice-penetrating radars have done this by increasing pulse length, increasing transmit power, and interleaving short and long pulses to improve dynamic range. In most ice-penetrating radar architectures, steps are taken to prevent receiver saturation. Here we investigate the performance trade-offs associated with receiver saturation, and explore techniques to impact the negative effects of receiver saturation.

Orbital and autonomous radar sounding platforms promise to enable widespread mapping of subglacial topography and englacial layers with greater uniformity of data and observing conditions than the current patchwork of distinct radar systems and surveys. They also have the potential to collect time-series observations of evolving subsurface conditions including ice-shelf melting, ocean access across grounding zones, 3D ice flow, and dynamic ice-sheet hydrology. Here, we investigate the impact of platform altitude and velocity on the detectability of subsurface interfaces beneath ice, sand, and permafrost in the presence of both noise and range sidelobes from surface echoes. Specifically, we evaluate the potential performance of radar sounding from orbital satellites, stratospheric UAVs, and low-altitude UAVs, relative to one another and to existing piloted platforms.

Ice-penetrating radar (IPR) instruments are a widely used tool to understand the structure and dynamics of Earth’s ice sheets and glaciers. Originally primarily designed to image the bedrock beneath ice, IPR systems are now being used for a wider range of scientific investigations. At the same time, new hardware architectures and customized radar systems are emerging. This combination of factors makes it worth re-visiting common assumptions about the noise characteristics of IPR systems and the phase coherence of measured reflections. In this work, we explore what it means for an IPR instrument to be coherent, how architectural choices in the design of software-defined radio-based instruments may impact phase coherence, and what instrument specifications should be considered for IPR applications that rely on measurements of small phase changes.

During the 1970s, the first large-scale ice-penetrating radar surveys were conducted over Antarctica and Greenland through a collaboration between the Scott Polar Research Institute at the University of Cambridge, the National Science Foundation, and the Technical University of Denmark [1]. This pioneering work represents the earliest available large-scale measurements of the sub-surface conditions of Earth’s two major ice sheets. In many cases, data collected as part of this survey pre-dates other available data in the area by decades. As we experience increasingly rapid changes in Antarctica and Greenland, understanding the historical states of these ice sheets takes on increased importance. Although 45-55 years is a short time in the evolution of continent-scale ice sheets, this dataset is unique in that it represents direct measurements over massive spatial scales. Unfortunately, integration of this data into models has proven extremely difficult due to unique challenges in how the data was collected and stored. We introduce our efforts to build digital tools for this analog dataset to bring this data into the modern era and make it accessible to researchers.

Ice-penetrating radar is the primary geophysical tool for large-scale measurements of the geometry and internal prop-erties of the Antarctic and Greenland Ice Sheets. These low-frequency radar instruments are typically mounted on crewed aircraft or towed behind snowmobiles, both of which introduce significant logistical challenges and costs. The availability of inexpensive, portable, and fully-autonomous uncrewed aerial vehicles (UAVs) promises to reduce the cost, logistical complexity, and risk of collecting ice-penetrating radar data. We introduce a chirped radar system built around a software-defined radio (SDR) that can be carried by a low-cost and easily-transportable fixed-wing UAV. The antennas for the radar are fully integrated with the wings of the UAV and have a usable frequency range from 300–450 MHz. We detail the most critical design challenges and the solutions we have chosen.

Orbital radar sounding of terrestrial ice sheets is an area of increasing research interest with mission concepts at 45 MHz, P-Band, and L-Band under development. However, large uncertainties remain in impact of glacial conditions and platform altitude on their link budgets. Here, we present a collection of empirically and glaciologically informed constraints on orbital sounder link budgets using airborne radar sounding data. We also analyze the effects of geometric spreading and englacial water. Finally, we discuss link-budget considerations for investigations beyond bed mapping including observing basal reflectivity, englacial hydrology, ice-shelf thickness, englacial layers, and estimating vertical ice velocity.

The subglacial topography of the Earth's ice sheets is a critical input to models of the evolution of ice sheets and sea level rise. Direct measurements of ice thickness, however, are sparse, necessitating techniques for interpolating these measurements. One class of interpolation methods enforces physical constraints to transform the problem into an inversion. A challenge with these approaches is that multiple unknown parameters must be solved for simultaneously. We introduce a new numerical approach to solving for mass conservation-constrained ice thickness maps. This technique, based on a physics-informed neural network, allows for the flexible incorporation of a range of soft constraints. In the future, this could enable simultaneous estimation of ice velocity, bed topography, and sliding parameters.