orbiter (Viking)
Part of the probe that flies over a celestial body before placing itself in orbit around the latter and studying it; the two Viking orbiters were launched in 1975.
thruster engine 
Machine that burns a liquid fuel mixture, thereby providing thrust.
star tracker 
Instrument that serves to direct the probe, in Viking’s case pointing it toward the star Canopus.
solar panel 
Power supply device that converts solar energy into immediately usable electrical energy.
infrared thermal mapper 
Instrument used to analyze the surface and atmosphere of a celestial body by measuring its temperature variations.
camera 
Captures thousands of images, thereby providing an overall view of the celestial body.
attitude control thruster 
Small rocket engine that directs the orbiter to the desired position.
low gain antenna 
Secondary antenna used to communicate with Earth when the high gain antenna cannot be used.
high gain antenna 
Principal antenna pointed toward Earth to transmit large quantities of scientific data as well as photographs.