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:
“Anybody who knows the difference between the kind of conversation you have walking in the woods and the kind of conversation you have between the segments of a show on Nickelodeon can tell you that quality time exists. Quality time is when you and your child are together and keenly aware of each other. You are enjoying the same thing at the same time, even if it is just being in a room or going for a drive in the car. You are somehow in tune, even while daring to be silent together.”
—Louise Lague (20th century)
“A striking feature of moral and political argument in the modern world is the extent to which it is innovators, radicals, and revolutionaries who revive old doctrines, while their conservative and reactionary opponents are the inventors of new ones.”
—Alasdair Chalmers MacIntyre (b. 1929)