1.The platform and its specification

The Structure Model of EP

EP mission will develop a astronomic satellite which has wide field-of-view and high sensitivity to carry out all-sky survey in soft X-ray band for discovery of transient sources and variable sources.

The EP satellite equips advanced Lobster-eye-type MPO X-ray imagers with much better capability to GRASP X-ray transients in the universe than all the other instruments flight before.

The EP is able to downlink alarm information quickly after detecting transients and guide the other astronomic instruments for the follow up observations. And also has the ability of receiving upload alarming information from the ground station and guide EP to carry out follow-up observation for transients.

• satellite:lifetime of satellite not less than 3 years and the design of life time is not less than five years
• orbital altitude : > 650 km
• orbital inclination: < 30°
• scientific data reception: Sanya scientific data receiving station, HBK and Maspaloms scientific data receiving station(coordinate with ESA), the X-band data rate not less than 80 Mbps

2.Scientific Instruments

The scientific instruments of EP satellite is composed of Wide-field X-ray Telescope (WXT, for X-ray all-sky monitoring) and Follow-up X-ray Telescope (FXT, for transient sources and variable sources observations)

（1）Wide field-of-view X-ray Telescope (WXT)

WXT

• the total field of view: ≥3600 square degrees
• Detection energy range: 0.5～4.0 keV;
• Energy resolution: ≤170 eV@ 1.25 keV(FWHM);
• Effective area( parallel x-rays incidence) ≥2cm2@1 keV;
• space resolution: ≤5′(FWHM);
• Precision of source location: 1′(confidence>90%,  number of photo larger than 200 in the center of focal spot)
• Triger threshold: ≥10mCrab transient(the integration time is 10 minutes)

(2)Follow-up X-ray Telescope (FXT)

FXT

• field of view: diameter≥38′;
• Detection energy range: 0.5～8.0 keV (the X-ray effective area in the detection energy range is greater than 10cm2)
• Energy resolution: ≤170 eV@ 1.25 keV;
• Effective area( arallel x-rays direction), ≥100 cm2@1.25 keV，on axis;
• spatial resolution: ≤2′(FWHM);
• Object localization: Better than 20 arcsec