SOHO
SOHO was almost lost in 1998 and was saved.
In a halo orbit, at L1, SOHO has been studying the SUn and has discovered comets after comets, right before they most of the time, vanish into our star. Since 1995, it has marveled the science community and the world. But it can't last forever and a successor should be planned. Not only to go on studying the Sun, but also to have a permanent view of our own planet, 1,000,000 miles away.
Raoul