Measurement of the cosmological constant

The type Ia Supernovae (SN Ia) provided the first direct indication of a non zero cosmological constant (Λ). After an introduction of the scientific context, the status of the cosmological constant measurement will be reviewed. The usage of SN Ia to probe the vacuum energy and more generally to study the dark energy seems quite promising. In a close future SN Ia should provide precise and well controlled measurements. The program 'nearby SuperNova Factory' (SNFactory), centered on detailed studies of ∼400 nearby SN Ia, and the proposal 'SuperNova Accelerating Probe satellite' (SNAP), which should be a break through in the study of the acceleration of the Universe expansion, will be introduced