In the relative measurement for the space non-cooperative target, the analysis to the optical property of the target is one of premises of the sensor design. The article is targeted on GEO satellites. From the perspective of photometry and based on the blackbody radiation law, we analyze the visible light energy of the sun outside the atmosphere, and consider the impact of satellite thermal control multilayer, model the luminosity feature related to the solar incident angle and the sensor observing angle. Finally we get the equivalent visual magnitude of the target satellite at the pupil of the camera. Our research could effectively direct the design and development of the visible relative measurement sensor.
In space rendezvous and docking missions, pose estimation of non-cooperative targets is challenging as priori information about motion and structure are unknown. The extraction and recognition are far more difficult conducted on a whole target. To solve this problem, a pose estimation method based on docking surface is proposed. The docking surfaces have more sophisticated structure with similar appearance among different countries than other surfaces. So docking surface is easy to automatically recognize or manually mark in images. In this paper, a control point representing mark information is chosen to assist with docking surface detection. The vertices of docking surface can be used to estimate pose. Firstly, binocular images are obtained by 3-D simulation technology. Then, a novel framework is proposed to detect edges of the docking surface in each image. Specifically, we detect lines in an image and group them according to the slopes. The control point is utilized to pick out the edges from the lines detected. Finally, the pose of the target is calculated by the four vertices of the docking surface. Simulation result shows that the position errors and attitude errors meet the requirement of pose estimation. The method provides a new solution for pose estimation of the non-cooperative target, and has potential significance for space rendezvous and docking technology.
Pose estimation is playing the vital role in the final approach phase of two spacecraft, one is the target spacecraft and the other one is the observation spacecraft. Traditional techniques are usually based on feature tracking, which will not work when sufficient features are unavailable. To deal with this problem, we present a stereo camera-based pose estimation method without feature tracking. First, stereo vision is used to reconstruct 2.5D of the target spacecraft and a 3D reconstruction is presented by merged all the point cloud of each viewpoint. Then a target-coordinate system is built using the reconstruction results. Finally, point cloud registration algorithm is used to solve the current pose between the observation spacecraft and the target spacecraft. Experimental results show that both the position errors and the attitude errors satisfy the requirements of pose estimation. The method provides a solution for pose estimation without knowing the information of the targets and this algorithm is with wider application range compared with the other algorithms based on feature tracking.
Ultraviolet (UV) sensors on a geostationary orbit (GEO) have important potential value in atmospheric remote sensing, but
the satellites orbit mode of it is quit different from sun-synchronous orbit satellites, which result in the significant diurnal
and seasonal variations in radiation environment of earth observation and radiation signal of sensors, therefore, the effect to
sensor radiometric performance, such as signal to noise ratio for atmospheric ultraviolet remote sensing caused by
variations of solar angle is significant in the performance design of sensors. The synthetic ultraviolet sensor is set at the
geostationary orbit, 36000 km away from the sea level of the Equator with 8.75 degree field of view, and the subsatellite
track point of which is located at 90 degrees east longitude and Equator. The Satellite scanning angles (SA) from 0 to 8.648
degree that cover the earth surface are selected corresponding to the 10 degrees equal interval view zenith angle, and the
SA from 8.648 to 8.785 degree cover the earth lamb 100 km far away from earth tangent point. Based on the MODTRAN4
model, on normal atmospheric conditions, the distributions of the UV upwelling radiance from surface or limb viewing
path of the earth could be simulated with the change of sun's right ascension. Moreover, the average signal to noise ratio to
the atmospheric sounding is obtained in different UV spectra using the Sensor signal to noise ratio model. The results show
that the thresholds range, tendency and shape of signal to noise ratio have a variety of features affected by variation of Sun
hour angles and declinations. These result and conclusions could contribute to performance design of UV sensors on the