The Space Variable Objects Monitor (SVOM) is
a small X-ray astronomy mission led by the Chinese National Space
Administration (CNSA; China) and National Center for Space Studies (CNES;
France). It has a three year planned duration mission with possible two year extension
It was succesfully launched on June 22, 2024 on from the Xichang launch facility in China aboard
a Long March 2C rocket into a low earth orbit with 625 km altitude and 30 degree inclination.
SVOM has 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° × 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 separate 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. Triangulation 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 is a soft X-ray telescope using micro-channel
silicon pore focusing optics with a focal length of 1.15 m.
The focal plane camera is
sensitive to 0.2–10 keV with spectral resolution of ∼75 eV at
1.5 keV. The field of view is roughly 1.1° x 1.1° with 1′
spatial resolution obtained from an X-ray sensitive pnCCD array.
The VT is a a Ritchey-Christian design telescope with a 40 cm primary
mirror and 26′ x 26′ FoV. The VT focal plane is 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
sensitive to objects of visual magnitude 22.5 with 300 seconds of observation:
the VT thus should 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 (GWACs) and
Ground Follow-up Telescopes (GFTs) integrated into the spaceflight mission
that scan for visual counterparts to gamma-ray bursts with rapid alert
notices. This allows very large ground-based instruments capable of
obtaining redshifts from spectral observations beyond the reach of SVOM
space-based and ground-based instruments.
SVOM is primarily designed to detect and localize gamma-ray burst sources
rapidly with high accuracy.
