Radial velocity Radial velocity The radial velocity of an object with respect to a given point is the rate of change of the distance between the object and the point. That is, the radial velocity is the component of the object's velocity that points in the direction of the radius connecting the object and the point. In astronomy, the point is usually taken to be the observer on Earth, so the radial velocity then denotes the speed with which the object moves away from or approaches the Earth. In astronomy, radial velocity is often measured to the first order of approximation by
To be announced expected to be filled, or conversely that a particular individual will be employed in an as-yet-uncreated position. "TBA" (meaning "to be announced") is also used to describe a specific type of simple mortgage investment, the forward mortgage-backed security. This is used to indicate that the investor is acquiring some portion of a pending pool of as-yet unspecified mortgages, which will be specified at a given delivery date. This usage has existed at least since the 1980s. To be announced To be announced (TBA), to be confirmed (TBC), and to be determined or decided or declared (TBD) are placeholder terms used