After lift-off on September 7th 2023, the X-ray space telescope XRISM goes through various tests to check whether all parts have survived the launch. All detector elements of the Resolve instrument, which SRON has contributed to, have now picked up X-rays from the calibration source. They achieve an energy resolution better than 5 eV.
ultimate vibration test
As with any launch, XRISM underwent the ultimate vibration test on September 7th by blasting into space aboard a Japanese H-IIA rocket. And as is customary after any launch, the telescope undergoes a series of measurements in the following weeks. In the week of October 16th, it was the Resolve instrument’s turn to test its detector. After the temperature was reduced to 0.05 Kelvin—or -273.10 °C—all 36 pixels managed to detect X-rays from the calibration source. They produce a uniform graph with a resolution better than 5 eV at an energy around 5.9 keV.
filter wheel including calibration source
SRON Netherlands Institute for Space Research, together with the University of Geneva, has developed the filter wheel including calibration source for the Resolve spectrometer. Astronomers will use Resolve to unravel the spectra of high-energy processes in the universe, such as supernovae and supermassive black holes that emit powerful jets. Resolve determines the energy of X-rays so accurately (5-7 eV at 0.3-12 keV) that astronomers can calculate the conditions in the jets with unprecedented accuracy, such as the velocities of ejected matter. They also gain a unique insight into the flow of gases throughout galaxies, in between galaxies, and back again. The gas between galaxies, within galaxy clusters, is so hot that it mainly emits X-rays.
iron-55 source
The now successfully completed test was carried out with a slightly radioactive iron-55 source within the filter wheel. This source is also used for calibration during regular astronomical observations. Iron-55 emits a known X-ray spectrum to serve as a reference point. The filter wheel also puts various filters in front of Resolve’s camera, so astronomers can filter out the brightness and wavelength of the cosmic X-rays as desired. For example, they will use the Molybdenum gray filter if a star or black hole emits more X-rays than the detector can readout, and they will choose the Beryllium or Polyimide aluminum filter to block certain wavelengths.