Hazcam
Abbreviation of Hazard avoidance camera, a type of engineering camera mounted on the front and rear of certain unmanned space rovers including the Curiosity rover at Mars.
Hazcam: the rover's collision-avoidance eyes
A hazcam is a fixed wide-angle camera mounted on the front and rear bumpers of a robotic rover, designed to detect obstacles and hazards in the vehicle's path. On the Curiosity and Perseverance rovers operating on Mars, each rover carries four hazcams: two forward-facing and two rear-facing units. These cameras feed real-time imagery to the rover's autonomous navigation software, allowing the vehicle to detect rocks, slopes, sand drifts, and terrain discontinuities before driving into them.
Hazcams operate independently of the rover's primary science instruments and are active during both day and night operations. Forward hazcams help the rover identify safe driving routes and avoid tipping over ledges or becoming wedged in sand. Rear hazcams monitor the path already traveled and assist with backing maneuvers. The cameras use passive visible-light imaging; they do not emit lasers or active illumination, though the rovers carry supplementary lights for night driving scenarios.
Design and constraints
Each hazcam has a very wide field of view, approximately 120 degrees, to catch hazards near the rover's wheels and corners. This wide angle comes at the cost of geometric distortion and low resolution. The cameras must be hardened against Mars' extreme temperature swings, abrasive dust, and radiation. They are also redundant; loss of one forward or rear camera does not disable the rover, though it reduces safety margins and may slow autonomous driving speeds.
The hazcam name reflects its functional purpose: it avoids hazards rather than studying them. This distinguishes hazcams from the rover's mast cameras and arm-mounted instruments, which prioritize scientific image quality and resolution. Hazcams are essentially engineering tools for autonomous mobility, not science cameras, though their images are occasionally downlinked for mission planning and public release.
Hazcam images influence the rover's speed and trajectory decision-making. If the onboard stereo hazcam pair detects rough or uncertain terrain ahead, the rover may reduce speed, request a new route from Earth-based mission control, or stop and wait for further instruction. This real-time hazard detection adds a critical layer of protection to expensive and irreplaceable machines operating billions of kilometers away.