NA62 is a fixed-target experiment at the CERN SPS designed to measure the branching ratio of the very rare kaon decay $K^{+} \rightarrow \pi^{+}\nu \bar{\nu}$ with 10% precision. Measurements of time, momentum and direction of incoming beam particles are provided by a beam spectrometer called GigaTracker. The GigaTracker is made of three stations of hybrid silicon pixel detector installed in vacuum ($\sim10^{-6}$ mbar). Each station consists of 18000 pixels of $300\times300\mu m^{2}$ area each, arranged in a matrix of $200\times90$ elements corresponding to a total area of $62.8\times27mm^{2}$. The beam particles, flowing at 750 MHz, are tracked in 4-dimensions by means of time-stamping pixels with the single hit time resolution reaching 115 ps. This performance has to be maintained despite the beam irradiation amounting to a yearly fluence of $4.5\times 10^{14} 1MeV n_{eq}/cm^{2}/200\ days$. In order to limit multiple scattering and beam hadronic interactions, the station material budget is reduced to $0.5\%X_{0}$ by using micro channel cooling (first application in HEP). We will present the detector design and performances during the NA62 data taking periods.