As a leading system developer and integrator, we applied our extensive RF experience to provide the European Space Agency (ESA) with two of the world’s largest and most technically advanced TT&C antenna systems, one in Australia, the second in Spain.
Forming the backbone of ESA’s Deep Space Network, these 35 metre systems are used for flagship science and exploration missions led by ESA for deep space and high-elliptical-orbit missions. The system in Australia is being used primarily for the Rosetta mission, launched in early 2004. In this case, the spacecraft will rendezvous with a comet and orbit it while performing remote sensing investigations. The system in Spain focuses on ESA’s Venus Express mission, launched in 2005. In each case, the antenna system communicates with the spacecraft, sending commands and receiving health, status, and scientific data.
As prime contractor, SED was responsible to ESA for the program management, system design, final installation and commissioning, and overall technical performance. SED placed and managed major subcontracts with companies in Germany, France, Australia and Spain.
Operating at S-, X- and Ka-band, the systems employ cryogenic liquid helium-cooled amplifiers and 20 kilowatt water-cooled amplifiers. A beam waveguide system uses shaped metal reflecting plates to direct and focus RF signals between the parabolic reflector to the stationary RF feeds mounted in the antenna base. The servo/tracking subsystem is capable of 26 milli-degrees accuracy at S-band, 11 milli-degrees at X-band, and 5 milli-degrees at Ka-band, meeting these requirements in constant winds of up to 45 km/h with gusts to 60 km/h. The system can survive 180 km/h winds.
To improve pointing accuracy at Ka-band, SED also developed an antenna pointing calibration system (PCS). The PCS automates measurement of, and provides compensation for pointing errors due to thermal distortion of the reflector and subreflector struts, as well as systematic errors caused by tower tilt, encoder offsets, feed and beam waveguide mirror alignment errors, az/el axis orthogonality errors, collimation error, and gravity flexure. The PCS also compensates for frequency and polarization dependent beam squint caused by curved beam waveguide reflectors or phase shifts in the antenna’s optical/RF system. PCS tools automate and speed up routine pointing accuracy and system noise temperature measurements, the latter being made by using the SED-developed radiometer that is integrated into the PCS.