The Space Variable Objects Monitor is a planned small X-ray telescope satellite under development by China National Space Administration and the French Space Agency, to be launched in 2021. SVOM will study the explosions of massive stars by analysing the resulting gamma-ray bursts. The light-weight X-ray mirror for SVOM weighs just. SVOM will add new capabilities to the work of finding gamma-ray bursts currently being done by the multinational satellite Swift. Its anti-solar pointing strategy makes the Earth cross the field of view of its payload every orbit.
Objectives
Using synergy between space and ground instruments, the mission has these scientific objectives:
Measure the temporal properties of the prompt emission
Quickly identify the afterglows of detected GRBs at X-ray and optical wavelengths, including those which are highly redshifted
Measure the broadband spectral shape of the early and late afterglow
Measure the temporal evolution of the early and late afterglow
Scientific payload
The selected orbit is circular with an altitude of and an inclination angle of 30° with a precession period of 60 days. The payload is composed of the following four main instruments: ; ECLAIRs ; Gamma-ray Burst Monitor ; Microchannel X-ray Telescope ; Visible Telescope
Ground segment
The ground segment includes a set of three ground-based dedicated instruments – two robotic Ground Follow-up Telescopes and an optical monitor, Ground Wide Angle Camera – which will complement the space borne instruments. A large fraction of GRB will have redshift determinations, an observing strategy optimized to facilitate follow-up observations by large ground-based spectroscopic telescopes. A key elements of the SVOM mission are the Ground Wide Angle Cameras and the Ground Follow-up Telescopes. The GWACs, an array of wide FoV optical cameras operating in the optical domain, will permit a systematic study of the visible emission during and before the prompt high-energy emission. It will cover a field of view of about 8000 deg^2, with a sensitivity of about 15 magnitudes at 5 s, in the V band and with a 15 s exposure time. It will monitor continuously the field covered by ECLAIRs in order to observe the visible emissions of more than 20% of the events, at least 5 minutes before and 15 minutes after the GRB trigger. The GFTs, two robotic 1-meter class telescopes, will point automatically their field-of view towards the space-given error box within tens of seconds after the alert reception and will provide panchromatic follow-up. They will contribute to the improvement of the link between the scientific payload and the largest telescopes by measuring the celestial coordinates with an accuracy better than 0.5'', and by providing an estimate of its photometric redshift in less than 5 minutes after the beginning of the observations. This data will be available to the scientific community through an alert message. Evenly placed on the Earth, they will be in a position to start the research of the GRB optical emission immediately after the alert reception in more than 40% of the cases.
