Estimate telescope detection signal-to-noise ratio from source photon rate, background rate, detector throughput, exposure time, and read noise. This simplified photon-counting budget helps compare filters, exposure lengths, and detector settings while keeping the noise contributors visible.
Detected source = source rate × throughput × time. Detected background = background rate × throughput × time. SNR = source counts ÷ √(source counts + background counts + read noise²).
Treat the main result as an engineering estimate based on the stated inputs. Compare it with the applicable mission requirement and retain enough traceability to update the result when assumptions change.
This calculator supports early trade studies and does not replace mission-specific simulation, environmental analysis, or professional engineering review.
With 120 source photons/s, 35 background photons/s, 65% throughput, 300 seconds, and 6 electrons read noise, the detected source is 23,400 photons and SNR is about 134.52.
It uses the values shown in the input panel and the formula stated on this page. It does not add hidden operational or environmental allowances.
Yes. Decimal values are accepted within each field’s displayed range, and calculations retain precision until the result is formatted.
Use a value justified by your project’s maturity, uncertainty policy, and verification plan rather than treating the default as a universal recommendation.
No. It is a first-pass estimate for trade studies. Verify the design with subsystem models, test data, and mission-specific constraints.
Zero is accepted where it represents a physically meaningful absence of load, loss, background, duty, or maneuver demand. Inputs used as divisors must remain above zero.
| Item | Use |
|---|---|
| Primary inputs | Enter values in the units printed beside each field. |
| Margin or reserve | Applied only where stated in the formula. |
| Displayed result | Rounded for readability; internal math keeps full precision. |