Optics Playground — Alper Şanlı

GSD Explorer

Estimate ground sampling distance and swath from basic payload/orbit parameters.

Altitude (km) Focal length (mm) Pixel size (µm) Sensor width (px) Sensor height (px)

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GSD (m/pixel):–

Along-track swath (km):–

Cross-track swath (km):–

Horizontal FOV (deg):–

Vertical FOV (deg):–

Formulae

GSD ≈ H × (p / f), where H is altitude (m), p is pixel size (m), f is focal length (m). FOV ≈ 2·atan( (N·p/2) / f ). Swath ≈ 2·H·tan(FOV/2).

Diffraction & PSF/MTF (Aperture + Spiders)

Adjust central obscuration and spider geometry; compute PSF (|FFT{pupil}|²) and MTF (|FFT{PSF}|).

Resolution (N×N) Obscuration ratio ε (0–0.6) 0.30 Spider arms (0–6) 4 Spider width (as radius %) 1.6% Spider rotation (deg) 0°

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PSF (log scale)

MTF (radial)

Misalignment (Zernike phase)

Apply low-order Zernikes (waves): tilt, defocus, astigmatism, coma. See PSF impact instantly.

Resolution (N×N) Obscuration ratio ε 0.30 Tilt X (waves) 0.00 Tilt Y (waves) 0.00 Defocus (waves) 0.10 Astig 0° (waves) 0.00 Astig 45° (waves) 0.00 Coma X (waves) 0.15 Coma Y (waves) 0.00

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PSF (log scale)

Wavefront (phase, ±π)

Notes

We use standard low-order Zernike modes (Noll indexing): Z2/Z3 (tilts), Z4 (defocus), Z5/Z6 (astigs), Z7/Z8 (coma). Coefficients are entered in waves (λ); phase = 2π·Σ a_iZ_i.