THESEUS

The 'Transient High Energy Sky and Early Universe Surveyor' (THESEUS) mission concept is an European Space Agency candidate in Phase A study as part of the ESA Medium class call. M7 will be the seventh, medium-sized mission of the ESA long-term science programme under the Voyage 2050 plan.

THESEUS aims to fully exploit the unique and breakthrough potentialities of Gamma-Ray Bursts (GRBs) for investigating the Early Universe and substantially advancing Multi-Messenger Astrophysics. THESEUS will discover these events, which are the most powerful explosive phenomena in the Universe over the entirety of cosmic history and allow detailed tests of fundamental physics. THESEUS will also characterise the electromagnetic counterparts to gravitational-wave events, providing unique multi-wavelength capability from gamma-rays to the near-infrared, transforming multi-messenger astronomy in the 2030s.

THESEUS will carry three instruments on a robotic, fast-response satellite, including the Soft X-ray Imager (SXI) which will be led from the UK by the University of Leicester. The SXI provides a revolutionary wide-field X-ray imaging capability, monitoring very large areas of sky simultaneously looking for X-ray transients while performing a sky survey. The SXI optics are based on technology developed at Leicester for ESA’s BepiColombo mission to Mercury and the France/China SVOM mission, while the focal plane will utilise newly developed large CMOS detectors providing fast-readout and sensitivity.

The SXI will be developed by a European consortium, including scientists from the UK, Germany, Spain, Belgium, Czech Republic, Poland and a wider international science team.

Professor Paul O’Brien from the University of Leicester, Principal Investigator for the SXI has said: “The capability of THESEUS will revolutionize time domain and multi-messenger astronomy, one of the fastest growing areas of astrophysics. The UK is a key part of the mission, providing a sensitive, wide-field X-ray telescope funded by UKSA in the UK and other European agencies.”