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Photon-limited synthetic-aperture imaging for planet surface studies
Robert L Lucke1, Lee J Rickard
1U.S. Naval Research Laboratory, Washington, DC 20375, USA. lucke@nrl.navy.mil
Applied Optics
|September 6, 2002
Summary
Synthetic-aperture ladar (SAL) can achieve centimeter-class resolution on Mars with a 10-microm laser. This study details carrier- and signal-to-noise ratios for photon-limited SAL imaging, considering speckle and heterodyne detection.
Area of Science:
- Optical remote sensing
- Planetary science
- Signal processing
Background:
- Photon-limited imaging presents challenges for synthetic-aperture ladar (SAL).
- Phase-sensitive heterodyne detection is crucial for signal quality in SAL systems.
- Speckle noise impacts image resolution and signal-to-noise ratio (SNR) in ladar.
Purpose of the Study:
- To develop and analyze the carrier-to-noise ratio (CNR) and SNR for photon-limited SAL.
- To provide design equations for SAL systems, particularly for orbital applications.
- To assess the feasibility of SAL at different wavelengths and its practical limitations.
Main Methods:
- Development of CNR equations for phase-sensitive heterodyne detection.
- Propagation of CNR through synthetic-aperture signal processing.
- Combination of CNR, speckle, and signal processing to determine image SNR.
- Derivation of design equations for SAL system parameters.
Main Results:
- A 10-microm SAL in orbit around Mars can achieve centimeter-class resolution with moderate laser power.
- SAL implementation is more challenging in the short-wave infrared spectrum.
- Visible wavelength SAL is likely impractical without significant image averaging.
Conclusions:
- The study provides a framework for designing and evaluating photon-limited SAL systems.
- Centimeter-class resolution is achievable with SAL on Mars, enabling detailed surface mapping.
- Wavelength selection and speckle mitigation are critical factors for SAL performance.