Noun
(astronomy) a measure of time defined by Earth's orbital motion; terrestrial time is mean solar time corrected for the irregularities of the Earth's motions
Source: WordNetAlthough not an IAU standard, the ephemeris time argument T eph has been in use at that institution since the 1960s. Source: Internet
Definition of ephemeris time (1952) Ephemeris time was defined in principle by the orbital motion of the Earth around the Sun, (but its practical implementation was usually achieved in another way, see below). Source: Internet
Increasingly, after the calibration in 1958 of the cesium atomic clock by reference to ephemeris time, cesium atomic clocks running on the basis of ephemeris seconds began to be used and kept in step with ephemeris time. Source: Internet
In view of the fluctuation term, practical determination of the difference between ephemeris time and UT depended on observation. Source: Internet
Most of the following sections relate to the ephemeris time of the 1952 standard. Source: Internet
The 1961 official reference put it this way: "The origin and rate of ephemeris time are defined to make the Sun's mean longitude agree with Newcomb's expression" ESAE (1961) at p.70. Source: Internet