10 results about "Star tracker" patented technology

To reduce the memory access frequency and the calculation time in star position calculation in comparison to a conventional technique.SOLUTION: A star tracker outputs an image by imaging a star with imaging means, searches for a peak pixel having a higher luminance value than a luminance value of an adjacent pixel in the plurality of pixels constituting the image, decides an extraction range for cutting out a partial image including a peak pixel from the image, and calculates a star position based on the luminance value of the plurality of pixels constituting the partial image. Here, the extraction range is decided such that noise included in the partial image is reduced on the basis of at least one of the luminance value of the peak pixel, the position of the peak pixel in the image and a parameter correlated to the temperature of the imaging means.SELECTED DRAWING: Figure 1

Techniques are disclosed for improving daylight performance of a star tracker. A region of interest (ROI) within a field of view of sky is obtained. The region of interest is divided into sub-ROIs. Sub-ROIs including a candidate celestial object are identified. An angular velocity of each candidate celestial object is determined. The known celestial object is a candidate celestial object identified as having a angular velocity, during a time period, that is within a range of angular velocities about a known angular velocity associated with the known celestial object.

Disclosed is a method for joint estimation of stellar atmospheric refraction and star tracker attitude, including: capturing, by a star tracker, an image of stars, and recognizing the image to obtain a matching relationship between an observed star and a reference star; transforming the reference star to a terrestrial reference frame based on time and position of observation to obtain a true zenith distance of the reference star; calculating an estimated stellar atmospheric refraction based on a simplified atmospheric refraction model, the true zenith distance, and an initial atmospheric refractive coefficient, and subjecting the reference star to stellar atmospheric refraction compensation; calculating the star tracker attitude, and re-projecting the observed star to the terrestrial reference frame to calculate the observed stellar atmospheric refraction and the stellar atmospheric refraction error; if the observed stellar atmospheric refraction is misaligned with the estimated stellar atmospheric refraction, adjusting the atmospheric refractive coefficient based on the stellar atmospheric refraction error, and then recompensating the reference star and calculating the attitude, till the observed stellar atmospheric refraction is aligned with the estimated stellar atmospheric refraction, whereby joint estimation results of the stellar atmospheric refraction and the star tracker attitude are obtained. The disclosure realizes real-time, autonomous estimation and cancelation of stellar atmospheric refraction without being limited by external sensors or empirical formulae.

The present application provides a kind of calibration method of astronomical navigation equipment, including optical calibration method and digital calibration method, optical calibration method first calibrates calibration tool with ship reference collation, then collation of the azimuth of star tracker base, level and calibration tool, finally, according to the calibration deviation, correction is carried out, so that the output information of astronomical navigation is unified with the real state of ship. Digital calibration method synchronously records ship main inertial navigation and astronomical navigation equipment navigation data, calculates the navigation deviation angle of two equipment through software, and is bound to astronomical navigation equipment, to realize the unity of astronomical navigation equipment and ship reference. The calibration method of the present application fills the gap of ship technology class based on laser gyro astronomical navigation equipment floating state calibration and digital calibration method in the market, solves the problem of detecting and correcting the zero position of high-precision equipment under the condition and engineering environment, and to some extent, provides the means of increasing the information output equipment of ship navigation system.

The application discloses an aerial calibration method of an aviation celestial navigation device, combines a flight route in a flight task of an airplane, integrates aerial calibration work of a celestial navigation system into the flight route, and synchronously carries out tracking and positioning work of a star tracker and a navigation processor in the celestial navigation device after the airplane enters a calibration task area; according to a task route plan, the airplane enters each side of a route path once, and the celestial navigation system completes aerial calibration once under the condition that a heading determination meets a requirement; after completing calibration of the last side, a calibration result is output, and the aerial calibration is completed. The application shifts the environment of calibration work of the celestial navigation device from the ground to the top of the clouds in the air, and synchronously carries out the calibration work with a task, avoids important influence of change of the clouds in the air on a calibration success rate, improves the calibration success rate, saves a large amount of input of manpower and material resources, and can be popularized to the fields of spaceflight and navigation, and has a good guiding role for application, popularization and development of the celestial navigation device.

Systems and methods for detecting and tracking resident space objects (RSOs) are provided. In an embodiment, the system uses an optical sensor on some or all spacecraft in a constellation to track RSOs for space domain awareness. The system performs RSO detection and tracking onboard individual satellites using data collected by the respective sensors and performs further RSO detection and tracking using outputs from multiple spacecraft. In an embodiment, the optical sensor may be a wide field of view optical sensor, such as a star tracker sensor. The star tracker sensor may be a repurposed star tracker sensor configured to operate in a different manner from its typical or traditional star tracking function.

The application discloses a high-dynamic smearing star image exposure center time image plane positioning method, and belongs to the field of telescope optical detection image processing. The method comprises the following steps: firstly, filtering a high-dynamic star map through an anisotropic Gaussian kernel to obtain an enhanced image and a direction image, and then accurately extracting the exposure center position of a star image based on the enhanced image and the direction image; performing linear fitting on each extracted star image by using a least square method to obtain a motion trajectory of the star image; and calculating an integral midpoint along the motion trajectory of the star image as the exposure center position of the star image by using the gray level accumulation sum of the normal direction of each point on the trajectory. The application realizes accurate pixel position determination of a smearing star image under a high-dynamic background, can effectively deal with the problem that the star image center position is difficult to accurately obtain under complex smearing conditions caused by high-dynamic star image smearing and platform turntable jitter, significantly increases the star image exposure center time image plane positioning precision compared with a traditional centroid algorithm, and finally improves the performance of a star tracker.

A method for determining the position of a satellite rotating about an axis of rotation using at least a star tracker which is aligned along an optical axis with a recorded light object field, the axis of rotation and the optical axis being at a fixed angle relative to one another and a light sensor having a sensor surface which is perpendicular to the optical axis and contains a sensor coordinate system having an arrangement of light-sensitive pixels in rows being provided. To achieve improved position control of the satellite, image data recorded in the individual rows of the light sensor are recorded row by row and sequentially, the image data for each row are convoluted with a predefined number of pixels over a predefined time interval using a boxcar operator, a light maximum is identified using the boxcar operator, the light maximum is assigned to a location of a light object on the basis of a position of the row and within the row in the sensor coordinate system, and an object list containing light object coordinates, the light maximum and a measurement time is identified from a plurality of light objects using an over the entire sensor coordinate system.

The subject matter disclosed herein is generally directed towards systems and methods for estimating vehicle attitude information using position data of stars and astronomical objects in the sky. Considerable advantages may be realized by equipping vehicles with low-cost star trackers adequate for filtering images based on statistical-based techniques, which could provide a robust and reliable attitude determination. The methods described herein provide algorithms to reduce the amount of processing capacity and memory for finding stars and astronomical objects. In some instances, the provided systems and methods allow the prediction of the next location of the stars and / or other astronomical objects to enhance the search by looking for them at the predicted location. The algorithms may be applied in real-time and are suitable for movable platforms with limited resources such as satellites and spacecraft.

The invention discloses a speed feed-forward and extended state estimation fused star tracker servo control method. The method comprises the following steps: step 1, preliminarily establishing a kinetic model of a star tracker servo system; 2, designing a linear expansion state observer, and constructing a third-order linear expansion state observer; step 3, designing a composite controller PID fusing speed feed-forward and extended state estimation; and step 4, system integration and control simulation: integrating the dynamic model of the star tracker servo system, the three-order linear expansion state observer and the composite controller into a servo control system, and establishing a simulation model. According to the method, the anti-interference capability is high, internal and external disturbances such as model uncertainty, friction and vibration are regarded as total disturbances through the extended state observer, real-time estimation and active compensation are carried out, and the robustness and the stability precision of the system in a complex flight environment are remarkably improved.