The Telescope Resolution Mission Requirements Estimator determines the aperture needed to reach a target diffraction-limited angular resolution at a selected wavelength. It uses the Rayleigh criterion for a circular aperture, giving optical and mission teams a direct way to connect science resolution goals with a first-order telescope diameter requirement.
The calculator is useful for early feasibility studies of imaging systems, astronomical observatories, remote sensing payloads, and other diffraction-limited concepts. A margin can be added so the displayed aperture requirement is larger than the ideal theoretical minimum.
1. Enter the observation wavelength
Use the wavelength at which the stated resolution requirement must be achieved.
2. Enter angular resolution
Use the smallest angular separation you need the diffraction-limited system to resolve.
3. Set aperture margin
Add a percentage allowance above the ideal Rayleigh diameter.
4. Review required aperture
Use the result as a first-order optical requirement, then account for real optical quality, obscuration, sampling, jitter, and atmosphere as applicable.
The calculation assumes a circular, diffraction-limited aperture and uses the Rayleigh criterion. Real systems may require a larger aperture or tighter system performance because of wavefront error, central obscuration, detector sampling, pointing jitter, atmosphere, contrast requirements, or image-processing goals.
The result is the clear-aperture diameter required by the Rayleigh diffraction criterion, increased by the selected aperture margin.
Actual telescope diameter may need to be larger after optical quality, sampling, jitter, obscuration, and environmental effects are included.
Given
Calculation
λ = 5.50×10⁻⁷ m. θ = 0.10/206,265 = 4.848×10⁻⁷ rad. Ideal D = 1.22×λ/θ = 1.384 m. With 10% margin, D = 1.522 m.
Result
Required clear aperture ≈ 1.52 m.
A diffraction-limited circular aperture of roughly this size is the theoretical starting point for the stated wavelength and resolution.
For a fixed aperture, the diffraction angle is proportional to wavelength. Shorter wavelengths therefore produce a smaller diffraction-limited angle.
No. Diffraction sets an optical limit, while pixel scale describes detector sampling on the sky. A camera typically needs sufficient sampling in addition to adequate optical resolution.
It can change the point-spread function and contrast response. This simple Rayleigh estimate treats the aperture as unobstructed and circular.
You can use it for the diffraction component, but atmospheric seeing may dominate unless adaptive optics or other correction is available. In that case the practical resolution can be much worse than the diffraction limit.
The margin lets the mission requirement exceed the ideal theoretical minimum before detailed optical error budgets are available. It should not be treated as a substitute for those error budgets.