Phoenix Mission Lander on Mars, artist’s concept.

A computer program called "phxlrsim" simulates the behavior of the radar system used as an altimeter and velocimeter during the entry, descent, and landing phases of the Phoenix lander spacecraft. The simulation includes modeling of internal functions of the radar system, the spacecraft trajectory, and the terrain. The computational models incorporate representations of nonideal hardware effects in the radar system and effects of radar speckle (coherent scatter of radar signals from terrain).

This program was written by Curtis W. Chen of Caltech for NASA's Jet Propulsion Laboratory.

This software is available for commercial licensing. Please contact Karina Edmonds of the California Institute of Technology at (626) 395-2322. Refer to NPO-44431.

Topics:
Aerospace Aircraft instruments Altimeters Avionics Computer simulation Computer software and hardware Electronic equipment Entry, descent and landing Entry, descent, and landing Radar Simulation Software Simulation and modeling Software Spacecraft Vehicles
This Brief includes a Technical Support Package (TSP).
Document cover
Simulating the Phoenix Landing Radar System

(reference NPO-44431) is currently available for download from the TSP library.

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    Overview

    The document is a Technical Support Package from NASA's Jet Propulsion Laboratory (JPL) detailing the simulation of the Phoenix Landing Radar System. It is part of the NASA Tech Briefs and aims to disseminate information on aerospace-related developments with broader technological, scientific, or commercial applications.

    The document outlines various simulation approximations and modeling considerations relevant to the Phoenix Landing Radar System. It highlights several key assumptions and limitations in the simulation process. For instance, the Intermediate Frequency (IF) filter is assumed to have an infinitely sharp cutoff and zero group delay, which may not accurately reflect real-world conditions. Additionally, the correlation of the IF filter across samples could have a minor impact on tracking points.

    The document notes that the surface cell spacing is computed based on true altitude radar parameters, but when searching through short-range gate positions at high altitudes, the probability of false lock due to range ambiguity may be underestimated. It also mentions that sources of internal offsets affecting biases are not fully understood, and the gain linearization is assumed to be perfect, although the total gain minus loss is unknown.

    Further approximations include the absence of temperature variations in noise or gain, and the spread in range over a single surface cell due to topography is not modeled. The simulation does not account for geometry-dependent polarization in antenna patterns, sigma0, or speckle, nor does it include variations in antenna pattern phase. The document also points out limitations in backtracking the platform along its trajectory, which may affect scene consistency.

    The modeling of the scene representation includes various parameters and arrays, such as sigma0 arrays and a Digital Elevation Model (DEM) array, which are essential for simulating the radar's performance in different environmental conditions.

    Overall, the document serves as a comprehensive overview of the methodologies and challenges associated with simulating the Phoenix Landing Radar System, providing insights into the complexities of radar technology and its applications in space exploration. It emphasizes the importance of understanding these approximations to improve the accuracy and reliability of radar simulations in future missions.