Architecture of GAIA satellite phased array antenna

GAIA is a new scientific ESA programme aimed to build a 3D map of the stars in the galaxy to unprecedented accuracy. In order to meet such requirement the GAIA satellite will be located in a Lissajous-type orbit, around the L2 point of the Sun-Earth system, which is located 1.5 million km from the Earth in the anti-Sun direction. This orbit is not impacted by Earth eclipses and shadowing from the Sun, Earth or Moon. In order to complete the required map, the spacecraft rotates on its axis at a low angular rate of about 1o/min, which permits to the scientific instrument to perform the required mapping measurements. To make the despun operation required to maintain the spacecraft-earth link, the antenna has a cone-trunk geometry which is populated by patch antenna subarrays which are electronically scanned by means of MMIC phase shifters which are commanded by a control unit which performs the required angle pointing operations.