Deceleratingly

Such a dome could then be retrorocketed to subside deceleratingly into the Earth's atmosphere, within which it will lower only slowly, due to its extremely low comprehensive specific gravity and its vast webbing surface, permitting it to be aimingly-landed slowly, very much like an air-floatable dandelion seed ball […]

It disappears between t = ±1, appears again as a spherical point at t = 1 and then, via Equation 2, it deceleratingly expands exclusively in the ±x directions as t increases in value.