Antennas and radio frequency systems for space are growing larger and more powerful, so to keep pace ESA’s ground-based test facilities are scaling up too. A construction project underway beside the dunes of the North Sea marks the expansion of the ESTEC technical centre in the Netherlands with the addition of Europe’s largest antenna and radio-frequency payload test chamber – Hertz 2.0.
An improved and expanded version of ESA’s current Hybrid European Radio Frequency and Antenna Test Range, or Hertz 1.0, Hertz 2.0 is an example of what is known as a ‘Compact Antenna Test Range’ (CATR), although that first word is misleading – it is ‘Compact’ only in the sense that it is engineered to simulate the vast distances involved in space communications within a chamber of fixed size.
Actually the Hertz 2.0 test chamber will be massive, measuring 32 by 25 m in area and standing 18 m high, able to accommodate even the largest entire satellites within an isolated ‘anechoic’ chamber, with metal walls lined with radio-absorbing foam pyramids and carefully-shaped reflectors to mimic the infinite void of space. A dedicated Microwave and Payload Laboratory will be connected to the test chamber, offering complete end-to-end radiated testing capabilities for antennas and payloads.
The Hertz 2.0 building will also be home to an expanded version of ESA’s Optics and Opto-Electronics Laboratory, allowing improved testing of laser systems, new capabilities including the calibration of small cameras, detectors and payloads, and including a transportable Optical Ground Station for ground to space laser signalling.
Supporting new generation missions
“This new Hertz 2.0 facility is designed to meet the needs of the coming generation of advanced ESA missions and other projects from our European partners,” notes Luis Rolo, project manager for the Hertz 2.0 CATR and Payload Lab. “Take the new Galileo Second Generation satellites as an example: in the case of the first generation Galileo satellites, radio frequency testing was carried out by separating the payload electronics that generates their navigation signals from the antenna that transmits these signals. But the sophisticated, integrated nature of Galileo Second Generation means that such an approach is no longer possible.
“Instead we have to test these new satellites as a whole, using a far field technique capable of handling it all without compromising accuracy. The design of Hertz 2.0 will allow just that: highly-accurate end-to-end radiated radio frequency payload performance across a very broad frequency range, to an accuracy that improves the calibration available on the ground and, ultimately, will benefit the quality of the data products and services available to Member States.”
Specially curved reflectors within the Hertz 2.0 chamber will change the shape of the signals coming to and from test antennas, as if they have travelled thousands of kilometres across space. The chamber is optimised for operation at microwave ‘L-band’ but will be able to operate from a few hundred MHz up to several hundred GHz.
The chamber will also incorporate two large pits: one to host a positioner able to move the test satellite or antenna as required, while the other can accommodate a Near Field Scanner that can in the future allow static testing of the biggest test items.
Chilled out testing
Liquid nitrogen will be available for low temperature testing – changes in temperature may alter antenna shape and performance dramatically – while gaseous nitrogen will be used to avoid humidity of sensitive test parts able to be warmed or cooled as the testing demands.
The chamber will additionally accommodate ESA’s Lorentz facility, designed to perform millimetre and sub-millimetre range testing of instruments and antennas at cryogenic temperatures.
Luis adds: “Hertz 2.0 represents a timely investment for the European space sector. As well as enhancing the testing of Galileo Second Generation and other RF-focused missions, its enlarged size will also open up testing possibilities for new developments such as large deployable reflector antennas and large active and passive arrays.”
Let there be light
The new building will also incorporate an improved and expanded version of ESA’s Optics and Opto-Electronics Laboratory OOEL, which was originally established in the 1970s, expanding steadily as demands for testing have grown.
“The new OOEL will incorporate a roughly 500 sq. m cleanroom, built to ISO 8 standards or better, able to accommodate multiple experiments and test set-ups at the same time,” explains Dana Tomuta, overseeing the Lab expansion.
“These should range from proof of concept testing for quantum and optical communications and a transportable Optical Ground Station, quantum key distribution experiments, facilities for the characterisation and calibration of lasers and detectors, spectro-radiometric test facilities for the calibration of detectors, small cameras and optical payloads, plus various measurement systems for the testing of optical components.
“Importantly this expansion will also extend the range of available light sources starting from X-rays up to longwave infrared using the latest continuous-wave optical parametric oscillator lasers.”
Test capabilities for ‘straylight’ will also be extended – unwanted light within an optical system that can reduce overall performance – using a trio of scatterometers, one of which will be able to characterise at component level the overall straylight across a large wavelength band spanning from ultraviolet to shortwave infrared.
Find out more at https://technology.esa.int/lab/optics-and-opto-electronics-laboratory
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