SlimSat-VNIR High quality littoral ocean characterization from a CubeSat with novel Spatial Light Image Modulation (SLIM)
Abstract
(APPROVED FOR PUBLIC RELEASE) A core technology for ocean and atmospheric sensing is passive imaging of reflected solar radiation, typically detected with multispectral CCD array-based systems. General challenges in adapting such imaging technology to CubeSat platforms over the littoral environment include 1) sufficient signal-to-noise for adequate algorithm retrieval of environmental properties, 2) acceptable photon efficiency, 3) efficient information transmission to the ground station that enables the rendering of high quality images given severe data transmission limitations, and 4) saturation, blooming and edge effect problems with water adjacent to bright land and clouds. Even with current state-of-the-art satellite imagers, 5 nm resolution through the visible domain is pushing CCD array-based systems to their limit in meeting fundamental sensor specifications, particularly for ground spatial distances (GSDs) <100 m.We have developed a design for a novel optical acquisition hardware architecture for a pushbroom-type CubeSat imager based on a Digital Micromirror Device (DMD) and an improved backend compression processing scheme to optimize SNR and information transmission given data bandwidth limits. A DMD is a Spatial Light Modulator (SLM) that modulates the intensity and phase of incoming light. It consists of millions of electrostatic-actuated micro-mirrors that can be used to control light collection dynamically and adaptively from each individual pixel equivalent. DMDs have very high contrast ratios when mirrors are off vs. on and fast switching speeds, greater than 20 kHz binary patterns per second. Therefore, a DMD is ideal to implement an optical filter for imaging littoral land-ocean interfaces with substantial changes in brightness over small areas. Inserting the DMD in the opticaltrain allows optimization of information content for images requiring broad dynamic range while minimizing loading of redundant data through compressive sensing techniques.Our CubeSat mission is called SlimSat-VNIR (Spatial Line Image Modulation Satellite Visible to Near-IR). The imager will cover the spectral range 420 to 840 nm, capable of resolving a host of ocean and aerosol parameters including ocean turbidity, phytoplankton, productivity, and bathymetry from published algorithms. We currently have a detailed preliminary design for SlimSat-VNIR and are transitioning from Phase A to Phase A2 of development. Phase A2 will be comprised of our Preliminary Design Review (PDR), fabrication and testing of a fully developed prototype imaging system, continued simulations of system and compressive sensing algorithm performance, and preliminary testing with our CubeSat platform. The work plan for a subsequent Phase A2 Option will include rigorous field testing in operational modes consistent with space deployment, preliminary testing of prototype robustness to environmental conditions of launch and space, development of enhanced compressive sensing algorithms for image acquisition and processing, and preparation for our Critical Design Review (CDR).
Document Details
- Document Type
- DoD Grant Award
- Publication Date
- May 05, 2021
- Source ID
- N000142112221
Entities
People
- Mike Twardowski
Organizations
- Florida Atlantic University
- Office of Naval Research
- United States Navy