Research activities are carried on in the following fields:

• Generation of the Italian time scale, time and frequency comparison and dissemination;
• Atomic frequency standards and frequency synthesis;
• Algorithm and mathematical methods for metrology and time scales.

The national time scale UTC(IT), based on five caesium beam clocks and two hydrogen masers, since June 2006 has been generated directly by a hydrogen maser plus an AOG (Auxiliary Offset Generator), improving the short and medium term instability of the time scale, at the level of 4×10^-13 (τ = 1 s) and 1×10^-14 (τ = 1 d) respectively in terms of Allan deviation.
The time offset of UTC(IT) versus UTC has been maintained within ± 30 ns for 97% of the time. The maximum frequency departure (over 5 days) of the time scale was 3×10^-14 (3σ).
The UTC(IT) time scale is compared every two hours with remote time scales generated at ten European and two American laboratories, by the Two Way Satellite Time and Frequency Transfer (TWSTFT) method. The TWSTFT link between INRIM and PTB was calibrated with an accuracy of 1.3 ns (1s) and is routinely used by BIPM to link INRIM clocks to TAI. Apart from contributing to the BIPM computation of the International Atomic Time scale with its clocks ensemble, INRIM has also sent the GPS, TWSTFT and GPS-P3 synchronization data regularly to BIPM. The last ones, supplied by an Ashtech Z-XII3T geodetic receiver, obtained from the output RINEX files, were also supplied to the GeoDAF data centre of the Italian Space Agency (ASI), to be used by the EUREF Permanent Network, and by the International GNSS Service (IGS).
INRIM has contributed regularly to the "real-time network prototype" operated by the IGS Real Time Working Group, and has pursued the investigations in order to have a real time tool to estimate UTC(IT) time scale performances versus other international references.
The dissemination of the UTC(IT) time scale in real time has been provided by the SRC (RAI Coded Signal) and CTD (Telephone Data Code) services, and by two NTP (Network Time Protocol) time servers (ntp1.inrim.it, ntp2.inrim.it).

During 2006 INRIM Cs fountain primary frequency standard was operated three times to calibrate TAI (circular T 218, 224 and 228). The final uncertainty of the calibrations, including the link to TAI, ranged from 1.4×10^-15 to 1.8×10^-15.
In collaboration with the Geodesy department of the Politecnico di Torino, the INRIM elevation upon the Geoid was re-evaluated, giving a total uncertainty of 10 cm. This measurement is important to allow the realization of the SI time unit, defined on the Geoid, at the 1×10^-17 uncertainty level as can be approached in the near future by the next generation of the primary frequency standards.
The realization of the INRIM second fountain proceeded with the realization of the optical system, and with the design of the physical structure that is currently being realized.
The work towards the realization of a Yb optical clock proceeded with the realization of the vacuum structure and the realization of the light frequency duplication cavity to achieve the cooling transition at 399 nm.
With respect to vapor cell frequency standards, the characterization of the Pulsed Optically Pumped Maser prototype was completed indicating outstanding performances for short and medium term stability. The Allan deviation of the prototype was measured at 1×10^-12 at 1 s, and a white frequency noise was observed up to several days of operation (4×10^-15 relative stability at two days).

The Time and Frequency Section participated in the development of the Galileo System in collaboration with European space industries and the European Space Agency (ESA).
In early 2006, an experimental phase called "Galileo System Test Bed V2 (GSTBV2)" was launched and INRIM is taking part in it hosting a Galileo prototype receiver, generating the "reference signals" for the Test Bed experiments, and analyzing the data coming from the first experimental Galileo satellite, in order to characterize its on board clock. In the following figures, the Galileo prototype receiver and a diagram of the installation at INRIM are shown.
INRIM is also involved in two additional projects:

• Galileo development(phase CDE1) supported by ESA, with INRIM contributing to the development of the Galileo time laboratory named Precise Time Facility by designing the time scale algorithm;
• Galileo Time Service Provider (TSP) Prototype, supported by the European Union, with INRIM contributing as UTC(k) laboratory providing clock and comparison measures, and taking care of the relationship of the TSP with BIPM and the main standardisation organizations.