Monitoring and Early Warning of NEOs
Theme Keywords： optical observationimage processingNEOsspace-based observation
- The Paper
Dim moving target detection based on fluctuation analysis
Abstract：To detect moving targets with very low SNRs for monitoring small objects near the ground and providing early warnings regarding such objects, a dim moving target detection method based on fluctuation analysis was proposed. Furthermore, the principle of a correlation feature extraction method based on the fluctuation analysis of a light field in a time interval was expounded. Strong background signals were distributed and changed steadily in the time dimension. Transient fluctuation in the time dimension, caused by the movement of a target, reflected the existence of a weak moving target. First, a one-dimensional signal model based on single pixel gray-scale time series was established. Then, the time window was divided in the time domain, and fluctuation analysis was used to extract related features. Finally, the target signal was detected based on changes in the correlation feature. The method was applied to one-dimensional time-series signal simulation, dim moving target simulation, and a near-Earth asteroid detection experiment. The experimental results show that the detection rate and false alarm rate of the proposed method are significantly better than those of several other commonly used methods. This method provides good detection using simulated and real data.Keywords：image sequence;fluctuation analysis;High frame rate;dim moving target;near earth asteroids560|983|4
<HTML><L-PDF><Meta-XML>Updated：2020-12-09A method of real-time data reduction of asteroid optical observation image based on GPU
Abstract：Ground-based optical observation is an important means of asteroid detection and property research. In recent years, asteroid survey projects have developed toward larger apertures and larger fields of view. While the detection capability has increased, the amount of data has also increased greatly. To improve the speed of asteroid data reduction, a graphics-processing-unit-based real-time processing method for asteroid optical observation images was proposed. Based on a previous target extraction algorithm, we realized the parallelization of target extraction, researched the Source Extractor algorithm, simplified and parallelized the Source Extractor code, and improved the Match algorithm to improve both applicability and accuracy. The experimental results show that the simplified, parallelized algorithm implemented in an experimental platform built based on the NVIDA GeForce GTX 2080Ti graphics card offers an increase in speed by a factor of up to 17 (with the signal-to-noise threshold set to 3) compared with that of a serial algorithm running on only a central processing unit. With the further development of high-performance graphics cards, there is room for improvement in speedup ratio, and this method is also suitable for the processing of other optical survey observations.Keywords：asteroid optical observation;target extraction;GPU;code parallelization655|1408|3<HTML><L-PDF><Meta-XML>Updated：2020-12-09Trajectory detection of small targets based on convolutional long short-term memory with attention mechanisms
Abstract：Trajectory detection of small infrared targets is important for infrared guidance and is widely used in aerospace for functions such as detection of small celestial bodies, missile guidance, and battlefield reconnaissance. Aiming at the traditional trajectory-detection algorithm based on track-before-detect technology, which requires prior knowledge of the target, such as the gray distribution or target speed, this paper proposes a convolutional long short-term memory method based on the attention mechanism in neural networks to detect weak target trajectories. This method involves the use of 3D convolutional kernels to extract short-term temporal and spatial information and combines the convolutional long short-term memory network to extract long-term spatial-temporal information of 15 consecutive infrared image sequences. It also uses the attention mechanism to focus on the key information related to the trajectory and discard irrelevant background information. This method enables the network to realize end-to-end prediction. Four objective indicators such as root mean square error, mean absolute error, peak signal-to-noise ratio, and structural similarity index were applied to three infrared sequences for an experimental evaluation. The experimental results indicated that, compared with 3DCNN, 3D-ConvLSTM, and 3D-AIConvLSTM, 3D-AOConvLSTM achieved an average reduction of 32.8% and 46.3% in the root mean square error and average absolute error, respectively, and an average increase of 18.3% and 4.3% in peak signal-to-noise and structural similarity, respectively. It can detect the trajectory of an infrared target with fewer than six pixels. The predicted trajectory is highly consistent with the actual trajectory. The proposed method provides the least background clutter and the best detection result.Keywords：trajectory detection of small target;infrared multiframe image;convolutional long short-term memory;deep learning;attention mechanisms536|1322|8<HTML><L-PDF><Meta-XML>Updated：2020-12-09Photometry studies of physical properties for Near-Earth asteroids
Abstract：Near-Earth asteroids (NEAs), orbiting around the sun in the proximal space of the Earth, and they have become crucial for two reasons.Some of them, identified as potentially hazardous asteroids, pose the danger of collision with the Earth.They are adopted as the targets for investigating the origin of the planets and small bodies of the solar system, and for sampling and mining in future space missions.However, we couldnot "see" them in detail directly, even with the aid of the largest ground-based telescopes, owing to their small size.Hence, it is difficult to determine the size and shape of NEAs and more challenge to determine their mass and internal structure.Currently, some inversion techniques are applied to determine the basic physical properties (spin parameters, size, shape, scattering parameters, and composition) of asteroids.Among these techniques, the photometry inversion method is widespread used, by which the spin parameters, shape, and scattering parameters of asteroids are subtracted from the photometric data of asteroids.Assuming cartain an experimental scattering law and certain a shape model a series of brightness models of asteroids, and the models were used to inverse the spin parameters, shape, and scattering parameters of asteroids using the least-square and/or Markov chain Monte Carlo approaches.We used the Lommel-Seeliger ellipsoid model to estimate the physical parameters of the near-Earth asteroid (155140)2005 UD based on its photometric data.Further, the photometric data of (106) Dione were analyzed using the Cellinoid shape model.Based on the convex shape model, we analyzed the photometric data of (103) Hera and (346) Hermentaria.Furthermore, a hierarchical analysis platform was built to determine the basic physical parameters of near-Earth asteroids efficiently, which contained a series of brightness models developed based on an assumed scattering law and a selected shape model.For the targets with sufficient data (photometric data obtained for at least four apparitions), the best values of the parameters involved in the convex inversion and their uncertainties can be estimated using a Monte Carlo simulation procedure.Keywords：Near-Earth asteroids;brightness models;shape;spin parameters;photometric phase function670|818|3<HTML><L-PDF><Meta-XML>Updated：2020-12-09Study on observation simulation for space-based potentially hazardous asteroids warning mission on Earth trailing heliocentric orbit
Abstract：Monitoring and early warning of asteroids are the premise of planetary defense. To monitor and provide early warning of asteroids from the Sun direction, an Earth trailing heliocentric orbiting optical telescope mission was proposed. Furthermore, considering the third-body gravitational perturbation of the Earth, an orbit maintenance model was established for the telescope. Considering apparent visual magnitude constraints of asteroids and field of view constraints of the telescope, an observation model for potentially hazardous asteroids was established. The observation and early warning efficiency of the telescope were evaluated. Simulation results showed that with delta-v of approximately 580 m/s, the orbit drift distance of the telescope did not exceed the initial state by 6% within 6 years. The telescope, under the condition of limited apparent visual magnitude of 24, could observe 84.5% of potentially hazardous asteroids with a diameter of more than 140 m. It could also provide effective early warning for potentially hazardous asteroids from the Sun direction. Thus, the optical telescope on an Earth trailing heliocentric orbit exhibited good observation and early warning performance.Keywords：planetary defense;potentially hazardous asteroids;space-based optical monitoring;Earth trailing heliocentric orbit;orbit maintenance604|1458|11<HTML><L-PDF><Meta-XML>Updated：2020-12-09
