National Aeronautics and Space Administration

The Space Variable Objects Monitor (SVOM) will be a small X-ray astronomy mission led by the Chinese National Space Administration (CNSA; China) and National Center for Space Studies (CNES; France). It is planned for a three year duration mission with a launch data in 2023. It will be launched from the Xichang launch facility in China aboard a Long March 2C rocket.

SVOM will have a number of astrophysics instruments working in concert with each other. These include ECLAIRs, the Gamma Ray Monitor (GRM), Microchannel X-ray Telescope (MXT), and Visible Telescope (VT).

ECLAIRs is a coded mask wide Fields-of-View (FoV; 89° x 89°) X-ray/gamma-ray instrument senstive to 4–250 keV with 6400 CdTe detectors, cooled to -20°C. The detector is equipped with processing to trigger on unknown sources, such as gamma-ray bursts, rapidly slewing to bring the narrower-field MXT and VT instruments on source, as well as sending data and alert notices to the ground-based systems for co-observation.

GRM consists of three seperate gamma-ray detectors inclined at 30° from the ECLAIRs pointing direction, operating in the 15 keV–5 MeV energy range with roughly 60° wide circular FoV, giving them collectively a very similar FoV to ECLAIRs. Trianglutation with the three detectors can narrow down gamma-ray burst location to a 15° x 15° area, sufficient for training other instruments on source. Each GRM will use a NaI crystal for detection with plastic scintillation across the detector front to distinguish gamma-rays from low energy electrons.

MXT will be a soft X-ray telescope using micro-channel silicon pore focusing optics with a focal length of 1.15 m. The focal plane camera will be sensitive to 0.2–10 keV with spectral resolution of ∼75 eV at 1.5 keV. The field of view will be around 1.1° x 1.1° with 1′ spatial resolution obtained from an X-ray sensitive pnCCD array.

VT will be a a Ritchey-Christian design telescope with a 40 cm primary mirror and 26′ x 26′ FoV. The VT focal plane will be equipped with two 2048 x 2048 CCD cameras: one sensitive to blue (450–650 nm), the other red/near infrared (650–1000 nm): this is anticipated to be sensitve to objects of visual magnitude 22.5 with 300 seconds of observation: the VT thus should be able to see gamma-ray burst optical afterglow out to a redshift of 6.5, corresponding to 12 billion light years. VT is expected to about 60 gamma-ray burst sources a year, with locational accuracy of less than 1″.

While not part of the spacecraft payload, SVOM also includes a number of ground components such as co-ordinating Ground-based Wide Angle Cameras and Ground Follow-up Telescopes that scan for visual counterparts to gamma-ray bursts (and this component of SVOM is already constructed and working even as the spacecraft itself has not yet been launched), and rapid alert notices for coordination with very large ground-based instruments capable of obtaining redshifts from spectral observations smaller instruments are not able to perform for very distant sources.

SVOM is primarily designed to detect and localize gamma-ray burst sources rapidly with high accuracy.