  The Joint European Telesscope (JET-X) is one of the core scientific
instruments of the SPECTRUM-X-Gamma mission. JET-X was designed to study X-ray
emissions in the band 0.3-10 KeV. Its angular resolution is better than 20
arcsec; the values of the effective areas are 161 cm2 at 1.5 KeV and 69 cm2 at
8 Kev (for one telescope). The value of the HEW circle in function of the
off-axis angle is presented; it is found to be below 20 arcsec at 1.5 Kev and
around 23 arcsec at 8 KeV up to an off-axis angle of 12 arcmin.
