To measure the ionization of gases in the atmosphere of a planet or a moon, a satellite will often use an ionosonde. Ionosondes were used aboard Canada's first satellite, Alouette. Alouette was an atmospheric studies satellite that studied the aurora borealis, the northern lights. It was important to Canadians scientists and to Canadian industry to study this phenomenon because the ionized gases in the atmosphere that caused the northern lights also have an effect on communications signals.