JPL Ephemeris Time Argument Teph
High-precision ephemerides of sun, moon and planets were developed and calculated at the Jet Propulsion Laboratory (JPL) over a long period, and the latest available were adopted for the ephemerides in the Astronomical Almanac starting in 1984. Although not an IAU standard, the ephemeris time argument Teph has been in use at that institution since the 1960s. The time scale represented by Teph has been characterized as a relativistic coordinate time that differs from Terrestrial Time only by small periodic terms with an amplitude not exceeding 2 milliseconds of time: it is linearly related to, but distinct (by an offset and constant rate which is of the order of 0.5 sec/yr) from the TCB time scale adopted in 1991 as a standard by the IAU. Thus for clocks on or near the geoid, Teph (within 2 milliseconds), but not so closely TCB, can be used as approximations to Terrestrial Time, and via the standard ephemerides Teph is in widespread use.
Read more about this topic: Ephemeris Time
Famous quotes containing the words time and/or argument:
“The Lord is thy keeper; the Lord is thy shade upon thy right hand.
The sun shall not smite thee by day, nor the moon by night.
The Lord shall preserve thee from all evil; he shall preserve thy
soul.
The Lord shall preserve thy going out and thy coming in from this time forth, and even for evermore.”
—Bible: Hebrew Psalm CXXI (l. CXXI, 58)
“There is no good in arguing with the inevitable. The only argument available with an east wind is to put on your overcoat.”
—James Russell Lowell (18191891)