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Radiometry for X-ray Astronomy

Quantitative X-ray astronomy with space born observatories relies on accurate radiometric calibrations provided by PTB’s synchrotron radiation laboratory.

The space observatories Chandra of the US National Aeronautics and Space Administration (NASA) and X-ray Multi Mirror Mission (XMMNewton) of the European Space Agency (ESA), successfully launched last year, are expected to lead to new scientific insights from the detection of cosmic X-rays. One project, for example, aims at the determination of the age of the universe by a measurementof the X-ray emission from distant objects.

In PTB’s laboratory at the Berlin Electron storage ring for Synchrotron radiation (BESSY), methods and instrumentation for the determination of the spectral responsivity of detectors and for the characterisation of X-ray optical components and modules were developed. The detector calibrations are based on the utilisation of the electron storage ring as a primary source standard for the spectral range from the visible to the X-ray region and cryogenic radiometers as primary detector standards.

In dieser Darstellung von XMM in der Umlaufbahn sind die Öffnungen der drei Teleskope (vorn) und die Plattform für die Fokalinstrumente (hinten) klar erkennbar.

One of the three focal-plane instruments of XMM, the flight module of the pn-CCD camera from the Max-Planck-Institute for Extraterrestrial Physics, was calibrated directly at PTB. The prelaunch calibration of the telescope for Chandra has been performed at NASA’s X-ray calibration facility at the Marshall space flight center by comparison with transfer detector standards calibrated with a relative uncertainty of 1 % in PTB’s laboratory at BESSY. Therefore, the measurement of cosmic X-rays can be traced back to the radiometric scales of PTB.

Contact at PTB:

Phone: +49-531-592-0