A novel effectiveness evaluation method was proposed based on the Johnson criteria and minimum resolvable contrast to evaluate effectiveness. In this process， target and background contrast， atmospheric transmission， detectors， and human eyes， are considered comprehensively. The noise equivalent contrast is introduced to measure the noise level of the detector， and the detection efficiency is measured by the joint probability of contrast and resolution， which can quantitatively and intuitively evaluate the detection ability of space-based optical imaging system. Verification experiments are carried out based on aerial and GF-2 satellite images. In aerial images， the recognition probability of car is 46%， the identification probability of aircraft is 73%， and the NIIRS level is 4.23； in GF-2 satellite images， the recognition probability of truck is 67%， the detection probability of small ship is 63%， and the NIIRS level is 4.53. The results show that the probability calculated by our method is basically consistent with the subjective judgment of human eyes， which is basically consistent with the NIIRS. The results prove the effectiveness of the method. Our method is of great significance to the design of space-based imaging systems and the evaluation of the on-orbit satellite detection capability.
Optical remote sensing is extensively used in military［1］， ecological［2］， agriculture［3］， aerospace［4］， disaster reduction［5］， and daily life applications［6］. The overall design of the optical remote sensing system is the most important task according to application requirements （field-of-view， meteorological and environmental conditions， characteristics of target and background， effective distance， etc.）. For land-based low-light-level and infrared detection systems， there are effectiveness evaluation methods based on Minimum Resolvable Contrast（MRC）［7-8］ and MRTD［8-9］. However， there is still a lack of effective means for the evaluation of the effectiveness of optical remote sensing systems. Ground Resolution Distance （GSD）， Modulation Transfer Function （MTF）， and the Signal-to-Noise Ratio （SNR）， cannot evaluate the detection effectiveness scientifically and/or intuitively that is not conducive to system design and user use. At present， image interpretation is commonly used to evaluate the effectiveness of the detection system. The United States has studied the National Imagery Interpretability Rating Scale （NIIRS）［10］ since the early 1970s. Based on these studies， the image quality can be described quantitatively. According to the interpretation task， it can be divided into different levels （0~9）， and can be used as a reference to evaluate the ability of detection of different targets. However， the calculation of the NIIRS level needs an image acquired by the system for evaluation. NIIRS is the post-evaluation method and cannot provide reference for the system demonstration and design. Moreover， the NIIRS level is not specific， and the quantification is not adequately precise. The Johnson criteria is a method used for the prediction of the probability of target discrimination. When the human eye searches for the target in a certain background or on the display， the continuous response of the eye can be divided into three stages： detection， recognition， and identification. The different stages correspond to different discrimination measures. Discrimination measures combine the effectiveness of system with human vision. Discrimination measures need to be quantified using visual psychological experiments. Johnson combined target detection with equivalent bar detection based on experiments［11-12］. It is possible to evaluate the detection ability of the imaging system with target equivalent bar resolution without considerations of the nature of the target and image defects. Johnson validated the fact that the equivalent bar resolution can be used to predict the probability of target discrimination， and determined the criteria pertaining to the cycles of the equivalent bar for different discrimination measures. Johnson criteria has been extensively used worldwide.