International Atomic Time ( TAI, from the French name Temps atomique international ) is a high-precision atomic coordinate time standard based on the notional passage of proper time on Earth's geoid.

Time coordinates on the TAI scales are conventionally specified using traditional means of specifying days, carried over from non-uniform time standards based on the rotation of the Earth.

The participating institutions each broadcast, in real time, a frequency signal with time codes, which is their estimate of TAI.

The latter is not to be confused with TA ( NPL ), which denotes an independent atomic time scale, not synchronised to TAI or to anything else.

This combined time scale is published monthly in Circular T, and is the canonical TAI.

In hindsight it is possible to discover errors in TAI, and to make better estimates of the true proper time scale.

In the 1970s, it became clear that the clocks participating in TAI were ticking at different rates due to gravitational time dilation, and the combined TAI scale therefore corresponded to an average of the altitudes of the various clocks.

Starting from Julian Date 2443144. 5 ( 1 January 1977 00: 00: 00 ), corrections were applied to the output of all participating clocks, so that TAI would correspond to proper time at mean sea level ( the geoid ).

Its successor time scales, such as TDT, as well as the atomic time scale IAT ( TAI ), were designed with a relationship that " provides continuity with ephemeris time ".

This is also the instant at which TAI introduced corrections for gravitational time dilation.

The TAI service, running since 1958, attempts to match the rate of proper time on the geoid, using an ensemble of atomic clocks spread over the surface and low orbital space of the Earth.

TAI is canonically defined retrospectively, in monthly bulletins, in relation to the readings that particular groups of atomic clocks showed at the time.

Estimates of TAI are also provided in real time by the institutions that operate the participating clocks.

This new pulsar time scale will serve as an independent means of computing TT, and it may eventually be useful to identify defects in TAI.

International Atomic Time ( TAI ) is the primary international time standard from which other time standards, including UTC, are calculated.

Thus, civil broadcast standards for time and frequency usually follow TAI closely, but occasionally change discontinuously ( or " leap ") in order to prevent them from drifting too far from mean solar time.

Errors in publication may be corrected by issuing a revision of the faulty Circular T or by errata in a subsequent Circular T. Aside from this, once published in Circular T the TAI scale is not revised.

Doing so does not create another version of TAI ; it is instead considered to be creating a better realisation of Terrestrial Time ( TT ).

While TT is strictly uniform ( being based on the SI second, every second is the same as every other second ), it is in practice realised by International Atomic Time ( TAI ) with an accuracy of about 1: 10 < small >< sup > 14 </ sup ></ small >.

TT is ahead of TAI, and can be approximated as TT ~= TAI + 32. 184 seconds.

The main realization of TT is supplied by TAI.

Because of the historical difference between TAI and ET when TT was introduced, the TAI realization of TT is defined thus:

Because TAI is never revised once published, it is possible for errors in it to become known and remain uncorrected.

It is thus possible to produce a better realization of TT based on reanalysis of historical TAI data.

TDT is tied in its rate to the SI second, as is International Atomic Time ( TAI ), but because TAI was somewhat arbitrarily defined at its inception in 1958 to be initially equal to a refined version of UT, TT is offset from TAI, by a constant 32. 184 seconds.

Because the clocks had been on average well above sea level, this meant that TAI slowed down, by about 10 < sup >− 12 </ sup >.

TAI is kept by the BIPM ( International Bureau of Weights and Measures ), and is based on the combined input of many atomic clocks around the world, each corrected for environmental and relativistic effects.

Time codes are usually published in the form of UTC, which differs from TAI by a well-known integer number of seconds.

* To millisecond accuracy, TT runs parallel to the atomic timescale ( International Atomic Time, TAI ) maintained by the BIPM.

UTC differs from TAI by an integral number of seconds.

Nowadays, UT in relation to International Atomic Time ( TAI ) is determined by Very Long Baseline Interferometry ( VLBI ) observations of distant quasars, a method which has an accuracy of microseconds.

where L = 1. 550519768, TDB = − 6. 55 s, T = 2443144. 5003725, and JD is the TCB Julian date ( that is, a quantity which was equal to T on 1977 January 1 00: 00: 00 TAI at the geocenter and which increases by one every 86400 seconds of TCB ).

Air Madagascar was formed in March 1947 by Transports Aériens Intercontinentaux in order to feed into flights by TAI and Air France.

It is the new name for the former TAI – Transporti Aerei Italiani and the former Air Columbia and was operating two Fairchild Metro aircraft from Pescara to Milan and Rome in April 2004 ( replaced by a Dornier 328Jet in January 2005 and a second one in August 2005 ).

Founded in 1989 by former naval officer and military expert John L. Petersen in Arlington, Virginia, TAI ( TAI ) is a futurist think tank.

Since 30 June 2012 when the last leap second was added, TAI has been exactly 35 seconds ahead of UTC.

TAI in this form was synchronised with Universal Time at the beginning of 1958, and the two have drifted apart ever since, due to the changing motion of the Earth.

The continued existence of TAI was questioned in a 2007 letter from the BIPM to the ITU-R which stated " In the case of a redefinition of UTC without leap seconds, the CCTF would consider discussing the possibility of suppressing TAI, as it would remain parallel to the continuous UTC.

International Atomic Time ( TAI ) was set equal to UT2 at 1 January 1958 0: 00: 00.

This difference may be assumed constant — the rates of TT and TAI are designed to be identical.

MKEK, TAI, Aselsan, Roketsan, FNSS, Nurol, Otokar, and Havelsan are major manufacturers.

TAI builds various aircraft types and models, such as the F-16 Fighting Falcon for the Turkish Air Force.

Other important products include the Altay main battle tank, TF-2000 class AAW frigate, Milgem class corvette, TAI Anka UAV, Aselsan İzci UGV, T-155 Fırtına self-propelled howitzer, J-600T missile, T-129 attack helicopter, Roketsan UMTAS anti-tank missile, Roketsan Cirit laser-guided rocket, Panter Howitzer, ACV-300, Otokar Cobra and Akrep, FNSS Pars 6x6 and 8x8 APC, Nurol Ejder 6x6 APC, TOROS artillery rocket system, Bayraktar Mini UAV, ASELPOD, and SOM cruise missile.