Trigger System

¡¡¡¡Once installed on top of CSS, HERD is expected to work continuously until the end of its lifetime. HERD is always pointed to zenith ascribed to the TEA attitude control system of CSS. Two kinds of operation mode are planned for HERD by considering the capability of readout systems, which are:

• A NOMINAL mode acquiring data consecutively with fixed instrument configurations.

• A CALIBRATION mode designed to trigger down MIP-like penetrating charged particles to equalize the response of nearly 7500 CALO cells. A full calibration of HERD detectors, which takes within three days, will be implemented every 2 months.