Hazard Detection & Avoidance

NGC’s Hazard Detection & Avoidance software system enables terrain mapping, hazards detection and safe sites designation in real-time during landing manoeuvres.

NGC is recognised internationally for its autonomous Hazard Detection & Avoidance (HDA) software system for planetary landers. This system makes use of Lidar and camera sensor measurements to detect and identify surface hazards in real-time during the descent.

Based on Lidar range measurements, camera images and knowledge of lander motion, this system computes various hazard properties of the terrain, such as surface local slope, roughness, illumination and propellant cost of reaching the site. This information is combined into a single hazard map which provides an overall safety assessment of each candidate landing area. The safest landing site, based on the fusion of all these criteria, is proposed by the HDA system. This assessment is done in real-time, a few hundreds of meters above the surface, while the lander is making its final approach.

One of the key features of NGC’s HDA system is its motion compensation function. The system can handle inputs from a scanning Lidar, which takes a few seconds to scan a complete frame. Since the lander is moving during the scanning process, the raw output of the sensor is distorted. However, based on the estimated lander motion during the scan, NGC’s software compensates for the motion and removes the distortions from the sensor measurement. This prevents imposing tight immobility constraints during the scanning process and improves overall propellant-efficiency of the mission.

The system was demonstrated in 2010 and 2011 with a full-scale helicopter flight demonstration. This experiment, called the Autonomous Landing Flight Experiment (ALFIE) conducted the first ever real-time full scale demonstration of a Lidar-based Hazard Detection and Avoidance system. It successfully demonstrated the real-time motion compensation and safe site determination capability of the system in a very challenging dynamic environment.

ALFIE

ALFIE Experiment Package Mounted on Helicopter

CSA Mars Yard
CSA Mars Yard

Test Site at the Canadian Space Agency

Safe Site Detection

NGC’s software quantifies candidate landing sites safety in real-time during the descent. In this picture, landing sites exceeding system constraints in slope, roughness or shadows are not color-coded and kept in grey. The remaining landing sites meeting these constraints are color-coded between red (unsafe) and green (safe). The safest landing sites are therefore the ones shown in green.

Fusion of hazard maps into combined safety map

Fusion of hazard maps into combined safety map

Lidar

Lidar-Based Safe Site Identification with Real-Time Motion Compensation