1. ETC Block Diagram

2. Source Spectrum is derived from: Spectra Type –Stellar (50 stellar types) –Galaxies (elliptical, spiral) –QSO Luminosity Profile –point source –extended (uniform, gaussian, elliptical, exponential) Redshift

3. Sky Background Spectrum based on specified observing parameters Lunar Phase Moon-target separation Airmass Solar cycle (min, max, average)

4. System Throughput derived from LSST system specifications Telescope Aperture Optics (Lenses and Mirrors) Filter Transmission – U G R I Z Y Detector Sensitivity

5. Atmospheric Transmission Model Base Sky Transmission Curve Clouds Humidity Airmass

6. Signal-to-noise Analysis Select optimal aperture Sum weighted source count Sum weighted sky background count Add sources of noise: –Poisson noise (source and background) –Sky Estimation Noise –Readout Noise –Dark Current Noise

7. Sources of Noise Weighted source noise Weighted background noise Dark current noise Readout noise Sky subtraction noise Poisson 0.0015 e - /s/pixel 5 e - /pixel 1/sky aperture