Daksha utilizes three types of detectors, grouped in detector packages mounted on the satellite, to obtain the broadband spectral coverage:
1. Low energy (LE; 1–30 keV): 13 packages, each containing 5 Silicon Drift Detectors (SDDs)
2. Medium energy band (ME; 20–200 keV): 17 packages, each containing 20 Cadmium Zinc Telluride (CZT) detectors
3. High energy band (HE; 100–1000+ keV): 4 packages, each containing position sensitive NaI Scintillator with Silicon Photomultipliers (NaI + SiPM).
The workhorses for Daksha are the Medium Energy (ME) detectors. The 17 ME packages together give nearly uniform all-sky coverage, with a median effective area of ~1300 cm2. The sensitivity in the 20-200 keV range is 4 × 10-8 erg cm-2 s-1 – similar to that of Swift-BAT when correcting for the energy range.
The Daksha satellites will be in a 650 km near-equatorial orbit. Individual photon data will be downlinked in every satellite pass. On-board software will be used to detect transients, and the detection will be relayed to the ground within a minute for broadcast to the community.
Individual Daksha satellites will GRBs localize transients in-orbit based on relative counts in different detectors. The resolution for GRBs with fluence 10-7 erg cm-2 will be about 10°, with resolution improving for brighter bursts. On-ground processing, including joint processing of bursts detected by both instruments, will provide better localization. The Medium and High Energy detectors can also jointly function as a Compton Imager.
Daksha uses the same Cadmium Zinc Telluride detectors as the CZT Imager instrument on AstroSat, where we have demonstrated polarization measurements by using double-photon measurements in the detector. Daksha will have excellent polarization abilities for transients thanks to its large area (300 cm2 for each ME package). The varied incidence angles on the different surfaces will provide a check against systematic errors.