Currently two-way and three-way spacecraft Doppler tracking techniquesare widely used and play important roles in control and navigation of deep space mis-sions
The kinematics of ten superluminal components (C11- C16, C18, C20, C21 and C24) of blazar 3C 279 are studied from VLBI observations. It is shown that their init
White-light(WL) flares have been observed and studied for more than a century since their first discovery. However, some fundamental physics behind the brillian