Planetary Orbital Radar Processing and Simulation System (PORPASS)

We are developing a web-based Planetary Orbital Radar Processing and Simulation System (PORPASS), built around a new generalized radar sounder processor (GRaSP) and a new 3D orbital radar simulator (OaRS). PORPASS will access orbital radar data from the Planetary Data System or equivalent archive and use GRaSP to carry out customized processing for a chosen instrument and set of parameters. OaRS will generate simulated radar data using parameterized spacecraft orbital parameters, instrument configurations, space and planetary environments, surface topography, and subsurface attenuation and scattering effects.

Although orbital radars have added greatly to our understanding of planetary surfaces and subsurfaces, processing of raw radar data is often poorly documented and difficult to implement, leaving researchers to rely on results from standardized processing pipelines that may not be well-suited to specific scientific goals. The lack of readily available radar processors means that processing of radar data has been largely limited to instrument teams or radar scientists who are intimately familiar with orbital radar datasets, and customized processing has only ever been applied to small fractions of the available planetary radar datasets.

Geophysical data and their interpretations are intrinsically nonunique, and thus numerical models (simulators) are often used to bolster interpretations and help infer surface and subsurface properties. While various simulators are in use for planetary radar studies, they typically involve generic 1D or 2D codes that do not account for the full behavior of the spacecraft or instrument, nor do they take into account accurate 3D models of the planetary ionosphere, surface, and subsurface. Additionally, most published simulation results do not use openly available software, restricting the community’s ability to verify radar imaging and published interpretations.

The heart of PORPASS will be the development of GRaSP. Most modern sounder systems rely on synthetic-aperture radar (SAR) processing to enhance along-track resolution and boost the effective signal-to-noise ratio. Despite the similarities across radar systems, instrument teams devote a substantial amount of time and effort to designing and enhancing new SAR processing systems specific to each new instrument. We will follow a modular design for GRaSP. For the initial development of GRaSP proposed here, we will focus on the incorporation and integration of data for three radar sounders: Shallow Radar (SHARAD) on Mars Reconnaissance Orbiter, Mars Advanced Radar for Subsurface and Ionosphere Sounding (MARSIS) on Mars Express, and Lunar Radar Sounder (LRS) on Kaguya. For each instrument we will develop an independent module to preprocess the data before ingestion into GRaSP.

We will design OaRS to simulate various spacecraft and instrument configurations (e.g. SHARAD, MARSIS, LRS, and new mission concepts) as well as various space and subsurface environments. To ensure longevity and relevance, we will extend the modular design used in GRaSP to the development of OaRS, accounting for spacecraft movement and instrument parameters as well as signal propagation through space and atmosphere, surface topography, and varying subsurface electromagnetic (EM) properties. To facilitate integration with GRaSP, the simulator output will be in the format specified by each instrument’s engineering data records (i.e., raw data).