Peak power is max power that appears during the transmissions period.
Pulse power is power that is transmitted during transmission period.
Average power is power that is calculated when pulse power is divided by sum of transmission period and pause period (usually T0 is much greater then t0, and t0 may be removed from equation - see attachment).
This suits for pulse radars.
Best regards.
Dejan
PS: Radar transmission pulse is simplified with rectangular pulse.