Geometric stitching of a HaiYang-1C ultra violet imager with a distorted virtual camera.

The HaiYang-1C (HY-1C) ultra violet imager (UVI) consists of five independent cameras with a designed total image swath of approximately 3000 km. In order to obtain a complete seamless image formed by the five sub-images, a feasible geometric stitching method for the HY-1C UVI with a distorted virtual camera is proposed. First, we perform the absolute geometric calibration of camera 3 and the relative geometric calibration of cameras 1, 2, 4, and 5. Then, a distorted virtual camera is assigned. Finally, the five sub-images are stitched together with the distorted virtual camera. Three HY-1C UVI images were tested. The experimental results showed that the georeferencing accuracy of the stitched images was better than 1 pixel. Compared with the conventional stitching method with an undistorted virtual camera, the ground sampling distance differences of the five cameras obtained by the proposed method were reduced from 23%, 37%, 53%, 37%, and 25% to 6%, 6%, 1%, 7%, and 8%, respectively.

Attitude computation algorithm for star camera based on combining calibration and attitude determination processes.

In this paper, a new approach for calculating star camera attitudes, which can calculate calibration parameters and attitude information simultaneously, in situations where precise camera calibration results are unknown, is proposed. This algorithm combines the calibration and attitude determination processes, achieving significantly improved performance as a result. Experiments using 1500 star images from different sky regions show that, compared with the traditional method that separates calibration and attitude determination, the proposed algorithm not only exhibits more precise and stable results, but also shows improved tolerance for the star mismatching which is inevitable in star sensor data process technology.

New on-orbit geometric interior parameters self-calibration approach based on three-view stereoscopic images from high-resolution multi-TDI-CCD optical satellites.

To increase the field of view (FOV), combining multiple time-delayed and integrated charge-coupled devices (TDI-CCD) into the camera and the pushbroom imaging modality are traditionally used with high-resolution optical satellites. It is becoming increasingly labor- and cost-intensive to build and maintain a calibration field with high resolution and broad coverage. This paper introduces a simple and feasible on-orbit geometric self-calibration approach for high-resolution multi-TDI-CCD optical satellites based on three-view stereoscopic images. With the aid of the a priori geometric constraint of tie points in the triple-overlap regions of stereoscopic images, as well as tie points between adjacent single TDI-CCD images (STIs), high accuracy calibration of all TDI-CCD detectors can be achieved using a small number of absolute ground control points (GCPs) covering the selected primary STI. This method greatly reduces the demand on the calibration field and thus is more time-, effort- and cost-effective. Experimental results indicated that the proposed self-calibration approach is effective for increasing the relative internal accuracy without the limitations associated with using a traditional reference calibration field, which could have great significance for future super-high-resolution optical satellites.

Image Mosaicking Approach for a Double-Camera System in the GaoFen2 Optical Remote Sensing Satellite Based on the Big Virtual Camera.

The linear array push broom imaging mode is widely used for high resolution optical satellites (HROS). Using double-cameras attached by a high-rigidity support along with push broom imaging is one method to enlarge the field of view while ensuring high resolution. High accuracy image mosaicking is the key factor of the geometrical quality of complete stitched satellite imagery. This paper proposes a high accuracy image mosaicking approach based on the big virtual camera (BVC) in the double-camera system on the GaoFen2 optical remote sensing satellite (GF2). A big virtual camera can be built according to the rigorous imaging model of a single camera; then, each single image strip obtained by each TDI-CCD detector can be re-projected to the virtual detector of the big virtual camera coordinate system using forward-projection and backward-projection to obtain the corresponding single virtual image. After an on-orbit calibration and relative orientation, the complete final virtual image can be obtained by stitching the single virtual images together based on their coordinate information on the big virtual detector image plane. The paper subtly uses the concept of the big virtual camera to obtain a stitched image and the corresponding high accuracy rational function model (RFM) for concurrent post processing. Experiments verified that the proposed method can achieve seamless mosaicking while maintaining the geometric accuracy.

On-orbit calibration approach for optical navigation camera in deep space exploration.

A spacecraft-borne optical navigation camera is one of the key instruments for optical autonomous navigation, and the line of sight (LOS) of the camera directly affects the accuracy of navigation. We developed an on-orbit calibration approach for a navigation camera to ensure the accuracy, in which a stepwise calibration is performed, external parameters estimated, and internal parameters estimated in a generalized camera frame determined by external parameters. In addition, we proposed a batch and sequential on-orbit estimation method to save on-orbit computing power, and established a strategy to reject misidentified reference stars while keeping consistency in on-orbit parameters estimation. After the calibration, the accuracy of LOS in inertial frame satisfied the need in optical autonomous navigation. The results have been proven precise and robust in three experiments.

On-Ground Processing of Yaogan-24 Remote Sensing Satellite Attitude Data and Verification Using Geometric Field Calibration.

Satellite attitude accuracy is an important factor affecting the geometric processing accuracy of high-resolution optical satellite imagery. To address the problem whereby the accuracy of the Yaogan-24 remote sensing satellite's on-board attitude data processing is not high enough and thus cannot meet its image geometry processing requirements, we developed an approach involving on-ground attitude data processing and digital orthophoto (DOM) and the digital elevation model (DEM) verification of a geometric calibration field. The approach focuses on three modules: on-ground processing based on bidirectional filter, overall weighted smoothing and fitting, and evaluation in the geometric calibration field. Our experimental results demonstrate that the proposed on-ground processing method is both robust and feasible, which ensures the reliability of the observation data quality, convergence and stability of the parameter estimation model. In addition, both the Euler angle and quaternion could be used to build a mathematical fitting model, while the orthogonal polynomial fitting model is more suitable for modeling the attitude parameter. Furthermore, compared to the image geometric processing results based on on-board attitude data, the image uncontrolled and relative geometric positioning result accuracy can be increased by about 50%.

[Acupuncture Alleviated Depressive-like Behavior by Down-regulating NF-κB, iNOS and NO Levels in Prefrontal Cortex of Depression Rats].

OBJECTIVE: To observe the effect of acupuncture intervention on depressive-like behavior and nuclear factor-κB (NF-κB), inducible nitric oxide synthase (iNOS) and nitric oxide (NO) levels in the prefrontal cortex in chronic stress induced depression rats, so as to explore its mechanism underlying antidepressant effect. METHODS: SD rats were randomly divided into control, model, acupuncture and medication (Fluoxetine) groups (8 rats/group). The depression model was established by chro-nic unpredictable stress stimulation (fasting, water deprivation, cold water swimming, tail clamping, constraining, etc., and solitary raising) for 28 days. Acupuncture treatment was applied to "Baihui" (GV 20) and unilateral "Neiguan"(PC 6) once every other day for 14 days. Fluoxetine (10 mg/kg) was given to rats of the medication group by gavage (p.o.) before every stress stimulation, once every day for 28 days. The animals' behavior was tested by using sucrose intake and open field tests (number of crossings and rearings in 5 min). The expression of NF-κB in the prefrontal cortex was detected by Western blot, and the contents of prefrontal iNOS and NO were detected by ELISA and nitric reductases, respectively. RESULTS: After modeling, the sucrose intake and the numbers of crossing and rearing times were significantly decreased (P<0.01), and the expression of NF-κB protein and the contents of iNOS and NO in the prefrontal cortex were significantly increased in the model group compared with the control group (P<0.01). Following the treatment, the sucrose intake and the numbers of crossing and rearing times were significantly increased in both acupuncture and medication groups compared with the model group (P<0.05, P<0.01), and the expression level of NF-κB, and iNOS and NO contents in the prefrontal cortex were significantly lower in both acupuncture and medication groups than in the model group (P<0.01). There were no significant differences between the acupuncture and medication groups in the crossing number and rearing times, NF-κB expression, and iNOS and NO levels (P>0.05). CONCLUSION: Acupuncture treatment can improve the depressive-like behavior of depression rats, which is closely related to its effects in down-regulating the levels of NF-κB protein, iNOS and NO in the prefrontal cortex to reduce brain inflammatory damage.

Acupuncture ameliorates inflammatory response in a chronic unpredictable stress rat model of depression.

Depression is one of the most common psychiatric disorders. Chronic inflammatory response has been viewed as a key factor in depression. Acupuncture in Chinese medicine has been shown to be an effective treatment for depression. In the present study, we investigated the mechanism underlying antidepressant effect of acupuncture. The rats were subjected to chronic unpredictable mild stress (CUMS) for 28days to induce depressive-like behaviors. Acupuncture treatment was applied once every other day during the 28-day stress period. The behavioral tests (body weight, sucrose consumption and locomotor activity) were performed. The expressions of nitric oxide (NO), prostaglandin E2 (PGE2), inducible nitric oxide synthase (iNOS), cyclooxygenase-2 (COX-2), and nuclear factor kappa B (NF-κB) were determined in the rat hippocampus and prefrontal cortex. CUMS induced depressive-like behavior in rats, which was alleviated by acupuncture treatment. The increased levels of NO, PGE2, iNOS and COX-2 induced by CUMS, were all significantly decreased in the hippocampus and prefrontal cortex by acupuncture. Moreover, acupuncture markedly inhibited the activation of NF-κB in rats. These findings showed that the antidepressant-like effect of acupuncture might be mediated by inhibition of inflammatory mediators via modulation of NF-κB in the brain regions.

[Effect of Acupuncture Intervention on Expression of NF-κB Signal Pathway in the Hippocampus of Chronic Stress-induced Depression Rats].

OBJECTIVE: To observe the influence of acupuncture intervention on the expression of pivotal pro-inflammatory molecules nuclear factor-κB (NF-κB), cyclooxygenase-2 (COX-2), and prostaglandin E2 (PGE2) of NF-κB inflammatory signal pathway in the hippocampus of depression rats, so as to explore its mechanism underlying improvement of depression. METHODS: Thirty-six male Sprague-Dawley rats were randomly divided into four groups: control, model, acupuncture, and medication (fluoxetine, Flu) (n = 9 rats in each group). The depression model was established by using chronic unpredictable stress stimuli combined with solitary feeding for 28 days. Acupuncture treatment was applied to "Baihui" (GV 20) and "Neiguan" (PC 6) once every other day for 28 days. Fluoxetine was given to rats of the medication group (10 mg/kg) by gavage (p. o.) everyday for 28 days before the stress stimulation. The expression of NF-κB protein in the hippocampus tissue was detected by Western blot, and the contents of COX-2 and PGE2 were detected by ELISA. RESULTS: Compared to the control group, the levels of NF-κB protein expression, COX-2 and PGE2 contents in the hippocampus were significantly increased in the model group (P < 0.01). Compared to the model group, the levels of NF-κB protein expression, COX-2 and PGE2 contents in the hippocampus were significantly down-regulated in both the acupuncture and medication groups (P < 0.05; P < 0.01). There was no significant differences between the acupuncture and medication groups in the NF-κB protein expression, and COX-2 and PGE2 contents (P > 0.05). CONCLUSION: Acupuncture intervention can effectively reduce hippocampal NF-κB expression, and COX-2 and PGE2 levels in depression rats, which may contribute to its anti-depressant effect by inhibiting pro-inflammatory pathway to protect the neurons of hippocampus.

[Progress of researches on mechanisms of acupuncture underlying improvement of depression in the past five years].

Depression is a state of low mood and aversion to activity that has a negative effect on the patient's thoughts, behavior, feelings, and physical well-being. In the past five years, a significant progress has been made in understanding the mechanism of acupuncture therapy for improving depression. In the present paper, the authors summarize mechanisms of acupuncture for depression from 1) upregulating levels of monoamine neurotransmitters, gamma-aminobutyric acid, 5-HT, receptor binding, and hypothalamic neuropeptide Y, beta-endorphine, and mu-receptor expression, and down-regulating hippocampal glutamate content, etc.; 2) upregulating expression of hippocampal brain-derived neurotrophic factor protein and mRNA and its receptor TrkB, and activating adenyl cyclase-cAMP-PKA-CREB signaling pathway; 3) increasing hippocampal growth-associated protein 43 level and suppressing hippocampal c-Jun N-terminal kinase activation and cellular apoptosis; 4) upregulating expression of glial fibrillary acidic protein (activating glia cells); 5) regulating activities of hypothalamus-pituitary-adrenal axis and hypothalamus-pituitary-sex gland axis; 6) down-regulating serum IL-1beta, IL-6, and tumor necrosis factor-alpha levels. Moreover, the authors also put forward some suggestions about the further research on the mechanisms of acupuncture intervention for depression in the future.