Time and Frequency
The Time and Frequency Metrology Department carries out research activities in the following fields:
1) Space applications
1. Satellite synchronisation systems
INRIM sent regularly to BIPM the GPS-P3 synchronization data supplied by an Ashtech Z-XII3T
geodetic GPS receiver, obtained from the output RINEX files, contributing to a
TAI computation
performed by BIPM using this kind of data. The RINEX files, supplied by the same receiver,
using UTC(IT) as a reference, have been sent regularly to the GeoDAF data centre of the
Italian Space Agency (ASI), to be used by the EUREF Permanent Network, and subsequently
by the International GPS Service (IGS).
INRIM regularly contributed to the "real-time network prototype" developed and
operated by the IGS Real Time Working Group. With this architecture, the real time GPS
data provided by the receiver is routed to the Canada Natural Resources archive. Near
real-time estimates of the UTC(IT) time scale are expected as a regular product supplied
by the IGS Real Time Project.
2. Satellite Navigation System GALILEO
The Time and Frequency Metrology Department was deeply involved in the development of the
Galileo System, for which a Precise Timing Facility is foreseen in order to generate the
Galileo System Time. In addition, the support of an external Time Service Provider is
expected to maintain Galileo time in agreement with the international standard Universal
Coordinated Time (UTC).
The main INRIM experimental activity was carried out in the framework of the Galileo
System Test Bed (GSTB) V1 supported by the
European Space Agency (ESA).
2) Time and frequency
1. Models, methods, and mathematical algorithms for time scales
The main research activities are currently devoted to:
- Clock error modelling and uncertainty evaluations
- Optimal and robust time scale algorithms
2. 3. 4. Atomic frequency standards
Atomic frequency standard research at INRIM covers the fields of primary and compact gas cell
frequency standards.
Using laser cooling facilities a caesium fountain frequency standard was developed. This
primary standard promises a realization of SI second with a relative accuracy at 10-15
level. Semiconductor laser assisted, gas cell frequency standards provide a good compromise
between performances and compactness.
A new kind of standard, based on maser emission without population inversion in alkali gas
cells was constructed and it shows a good short time stability.
5. 6. National time scale generation and dissemination
The activities concern the realization of the Italian reference time scale UTC(IT) from an ensemble of
commercial cesium beam frequency standards and hydrogen maser, and the participation to the
international timekeeping activities, coordinated by BIPM, such as the TAI and UTC international
time scales realization and in the experimentation of satellite based synchronization techniques.
Moreover, the dissemination of the national time and frequency standard is ensured providing
the traceability to the SI second to scientific institutions, calibration laboratories, and
to industrial and commercial users, by means of the distribution of coded date and time signals
(RAI and CTD) and in-house and remote calibration of frequency and time standards.
INRIM takes part to EURAMET activities related to the Time and Frequency field.
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