The IXO telescope optics is located in the mirror assembly, rigidly connected to the fixed metering structure and the service module. The mirror assembly is designed as a separate spacecraft module, given the specific constraints applicable to its manufacturing, assembly and alignment.

In the launch configuration the mirror assembly is located close to the launch adaptor and protected via dedicated contamination covers. The mirror assembly includes a primary support structure to carry the launch loads associated with the optics elements, the actual X-ray mirror modules with their secondary structure, the thermal control hardware and the contamination protection elements.

The mirror assembly design is based on a highly modular approach, starting at the level of the individual mirror modules and including 8 petals which populate the complete mirror area. Such a modular approach is required in order to be able to cope with the specific assembly, alignment and calibration requirements of X-ray optics.

Above: Mirror assembly with 8 petals and areas allocated to the spectrometer gratings. Top right: A CAD drawing of a single mirror petal (grey) populated with mirror miodules (blue). Bottom right: Accomodation of individual mirror modules into the telescope petals. Credit: ESA

As mentioned above, the optics module will have an inner and an outer cover to preserve the cleanliness of the mirror during ground handling, launch and spacecraft out-gassing. The outer cover will be ejected in orbit. The inner cover could either be a retractable membrane or a panel that folds as it is retracted out of the path of the X-ray beam.

To prevent illumination of the front of the mirror assembly by the Sun, particularly when the spacecraft performs pitch manoeuvres to access off-axis targets, the optics module will be equipped with a deployable sunshade.

	Introduction
	Fixed telescope structure