About the Lazuli WCC calculator

Calculation model

Wide-field Context Camera

The WCC ETC estimates imaging sensitivity across the wide-field filter mosaic with a rendered, possibly defocused PSF and a user-selected circular photometric aperture.

GitHub -> (will be made public soon)

Reported quantity

SNR = \frac{S}{\sqrt{S + H + B + D + N_{pix} N_{read} σ_{read}^{2}}}

All electron terms are evaluated inside the selected aperture. S is source signal; H is contaminating host shot variance; B is zodiacal plus any resolved-host contribution; and D is detector dark charge. The PSF determines the enclosed source fraction and number of aperture pixels.

Model assumptions

Extraction: fixed circular aperture. The ETC does not optimize the radius and does not use a background annulus or PSF-weighted extraction.
Readout: total exposure is divided across the selected reads; read noise is incurred for each read.
Saturation: evaluated on the rendered, noiseless per-frame detector image against full well or the ADC limit. A saturated result is flagged as unreliable.
Background: one scalar surface brightness in the selected reference band, expressed in Vega mag/arcsec². It is not derived from target coordinates or observing date.

Outputs and provenance

Source and background count rates, aperture SNR, enclosed-energy and radial-profile diagnostics, and per-frame saturation.
The selected sensor/filter supplies the bandpass, detector parameters, PSF/defocus state, and current total-throughput curve.
The WCC throughput figures below are the current best estimate of total filter throughput at end of mission.

Throughput assumptions

The throughputs for the implemented filters are the current best estimate of total filter throughput at the end of life of the mission.

Site-wide notes