The Earth Sensors on GOES-8 exhibit seasonal pointing errors in both the dual and single chord operating modes of the sensors. The errors were largely compensated for by a software patch uploaded to the satellite. The combination of detailed analyses and laboratory test results established that the observed error signatures are the result of stray solar radiation. The nature of the stray radiation paths giving rise to the seasonal errors is such that only the most significant stray path was eliminated in the GOES-9 hardware. The Earth Sensors on GOES-9 show significantly improved pointing performance over GOES-8, validating the origin of the most significant error source in the GOES-8 Earth Sensors. Low level seasonal pointing errors are observed, as expected, in the GOES-9 Earth Sensors. These errors again are effectively compensated for by an additional software patch developed to permit satisfactory single chord Earth Sensor operation. The operating principles of the Earth Sensor are described. On-orbit data of the seasonal anomalies are presented for both the uncompensated and compensated hardware and operating modes.
Some of the problems in realizing a practical optical correlator based ATR system are discussed. Two factors play a key role in the discussion: (1) the system and component issues of optical correlators, and (2) the processing potential of digital processors. The lack of an appropriate Filter SLM is identified as a major problem area for optical correlators, both now and in the future at the current rate of development and emphasis.
This paper provides an overview of the design and operation of Lockheed's portable optical correlator. The design issues for a compact correlator are given along with the performance characteristics of the Fourier transform lens. The liquid crystal spatial light modulators are described and the system level description of the optical correlator given.
Correlation provides an effective approach for recognizing targets embedded in a large field of view containing noise and clutter. Correlation is implemented either digitally or optically. When implemented digitally, correlation (consisting ofrepetitive multiply and accumulation operations) is directly realized with digital multipliers and accumulators (MAC), specialized signal processors or general computers. When the input record length is long, digital correlation is implemented in the frequency domain. Fast correlation is achieved because of the existence of the computational efficient fast Fourier transform (FFT) algorithm and specialized hardware for the discrete Fourier transform (DFT).
A parametric analysis is conducted for device and system design issues associated with the miniaturization of a hybrid optical correlator that incorporates an electronically addressed liquid-crystal spatial light modulator (SLM). Attention is given to the requirements of drive and readout electronics, as well as the associated optics. The parametrics resolve around the SLM, which is the correlator size-limiting element; emphasis is accordingly placed on the importance of small pixel pitch and minimization of ''dead space'' in order to maximize the miniaturized correlator''s performance.
Ternary Phase-amplitude Filters (TPAFs) used in a real-time hybrid (optical/electronic) correlator system coniprise a promising pattern recognition approach with potential for iiear-term j)ractical applications. Range images obtained from LADAR sensors present unique problems due to their particular signal and noise characteristics. We report computer simulation results of the application of both known and new TPAF formulations to the problem of target recognition on actu al LA DAR. images. Binary input im ages suitable for input using magneto-optic spatial light modulators were gemierated by a simple preprocessing step which seems particularly suitable for these images. Experimental results verifying the simulated smart filter performance are presented. 1.