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Daksha at a glance

Configuration: two identical satellites at ~650 km altitude and 6° inclination, on opposite sides of the Earth; 5-year design life, with no consumables on board.
Detectors (per satellite): 13 Low Energy Packages (5 SDDs each, 1–30 keV); 17 Medium Energy Packages (20 CZT detectors each, 20–200 keV; 13 on the dome, 4 sunward); 4 High Energy Packages (NaI(Tl) + SiPM, 0.1 to >1 MeV).
Effective area: 304 cm² on-axis per MEP; median ~1300 cm² at 100 keV over the unocculted sky (MEPs); median ~760 cm² (HEPs); median ~26 cm² (LEPs; ~32 cm² in the anti-sun direction).
Sensitivity: 4×10⁻⁸ erg cm⁻² s⁻¹ (20–200 keV, 1 s, 5σ); 5σ fluence sensitivity 7×10⁻⁸ erg cm⁻² for a 10 ms burst.
Sky coverage: each satellite sees ~71% of the sky at any instant (the Earth occults ~29%); ~86% time-averaged coverage for the pair, including South Atlantic Anomaly passages.
Localisation: ~10° for a 1 s burst of fluence 10⁻⁷ erg cm⁻²; ≈1° for 10⁻⁶ erg cm⁻² ; 1–2° with two-satellite triangulation. Coded-mask options for the LEPs are studied in Mandal et al. 2026.
Timing: photons time-tagged to ~1 µs; absolute timing better than 1 ms.
Alerts and data: on-board triggering and localisation; ~2 kB alert packets to the ground within ~1 minute for >95% of the orbit, distributed through GCN. All event data downlinked every ground-station pass and made public after a limited proprietary period, in FITS formats.
Expected yields: ~500 long and ~50 short GRBs per year; a few to ~12 neutron-star-merger counterparts per year, plus up to ~7 sub-threshold GW events; polarisation for ≥5 GRBs per year.

Full details: Bhalerao et al. 2024a (instrument, ExA 57, 24) and Bhalerao et al. 2024b (science, ExA 57, 23).

Effective area

The plot below compares the effective areas of Daksha’s detectors as a function of energy. Daksha’s LEPs are shown in blue, MEPs in purple and HEPs in green. The effective areas of Swift-BAT and of Fermi-GBM (NaI and BGO detectors) are plotted for comparison.

Daksha MEP effective area over the whole sky, in satellite coordinates.

All-sky sensitivity

The map below shows the MEP effective area as a function of direction, in satellite coordinates. The satellite X axis is at the centre of the figure and the Z axis (boresight, pointing away from the Sun) is at the top, so the Sun is always at the bottom. About 29% of the sky is occulted by the Earth at any given instant.

Each dome face carries an MEP with 20 detectors, giving 304 cm² of collecting area per face. Including projection effects, the median MEP effective area is ~1300 cm² at 100 keV over the non-occulted sky — significantly higher than the 126 cm² on-axis effective area of an individual NaI module on Fermi-GBM (Meegan et al. 2009), which has a similar orbit and also covers the whole non-occulted sky. Daksha’s effective area is comparable to that of the Burst Alert Telescope on the Neil Gehrels Swift Observatory, although BAT sees only about 11% of the sky, compared with 71% for each Daksha satellite. The effective area gradually tapers off above 100 keV.

Data, response files and software

Response files for all three detector types — can be downloaded from here
Sample data (simulated event files) — is available in this folder
Analysis notebooks, 2025 edition (from the IUCAA workshop) — can be downloaded from here
Analysis notebooks, 2024 edition (from the ASI workshop) — can be downloaded from here

If you are new to Jupyter notebooks, the Real Python introduction and the Try Jupyter page are good places to start.

Research projects and collaboration

The Daksha team welcomes participation from the community. See our Research projects page for ideas you can start on with simulated data, or write to the PI at varunb [at] iitb.ac.in to propose your own.

Citing Daksha

If you use Daksha simulations, response files or sensitivity estimates in your work, please cite Bhalerao et al. 2024, ExA, 57, 24 and Bhalerao et al. 2024, ExA, 57, 23.

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