Calibration of the flight model lobster eye optic for SVOM

Abstract

The space-based multi-band astronomical variable objects monitor (SVOM) is a Chinese–French mission due to be launched in 2023. It is composed of four space borne instruments: ECLAIRs, for detecting x-ray and gamma-ray transients; GRM, a gamma-ray spectrometer; VT, a visible telescope and the Microchannel X-ray Telescope (MXT). The MXT’s main goal is to precisely localize, and spectrally characterize x-ray afterglows of gamma-ray bursts. The MXT is a narrow-field-optimised lobster eye x-ray focusing telescope comprising an array of 25 square micro pore optics (MPOs), with a detector-limited field of view of ∼1 square degree, working in the energy band 0.2-10 keV. The SVOM flight model (FM) MXT optic (MOP) was designed, built and initially tested at the University of Leicester and a full calibration of the MOP was completed at the PANTER facility (MPE). It was then integrated in to the full proto flight model (PFM) MXT instrument before it returned to PANTER for the PFM MXT’s full calibration. We present the optic performance as part of the full FM MXT instrument calibration. The response of the telescope was studied at 11 energies from C-K (0.28 keV) to Ge-K (9.89 keV), including measurements of the effective area and the PSF size and shape. The focal length of the instrument was determined and details of the modelling and analysis used to predict the performance are presented. The measurements demonstrate that the actual effective area and PSF are in good agreement with the modelling.