System and method for determining a position of a target in an unbiased 3D measurement space: generating 2D measurement data in focal planes of each sensor; calculating a line of sight (LOS) from the target for each sensor; intersecting the LOSs and finding the closest intersection point in a 3D space; calculating a boresight LOS in 3D for each sensor; intersecting the boresight lines of sights for each sensor, and finding the closest intersection point in the 3D space to define an origin for forming the unbiased 3D measurement space; and forming local unbiased 3D estimates of the position of the target in the unbiased 3D measurement space as a difference between a closest point of the target LOS and a closest point of the boresight LOS.

A small, ultra-light-weight star tracker for space applications uses an out-of-field rejection filter to reduce the physical size and mass of the star tracker by effectively eliminating the need for a sun shade. The out-of-field rejection filter combines a converter for converting randomly polarized light to p-polarized light with an angular selectivity filter that can reject out-of-field p-polarized light. The underside of the angular selectivity filter can be used to reflect a calibrated light source into the optical path.

An image pickup apparatus capable of generating a high-quality trail simulation image with little noise, without degrading usability. An image pickup unit shoots a first image, a black image, and a second image in this order. A noise reduction unit executes a process for reducing noise in at least one image of the first image and the second image using the black image. A trail generation unit generates a predicted trail of an object on the basis of a movement of the object between the first image and the second image. A synthesis unit synthesizes the first image or the second image in which the noise has been reduced and the generated trail and generates a trail simulation image of the object. A display unit displays the synthesized trail simulation image.

A zero-optical-path-length-difference optical phased array built with essentially planar photonic devices determines a direction to an incoherent optical source, such as a star. The phased array can replace a 3-dimensional star tracker with a nearly 2-dimensional system that is smaller and lighter. The zero-optical-path-length-difference phased array can be optically connected to an interferometer. Driven by a light source, the zero-optical-path-length-difference phased array can be used as an optical projector.

Described are systems and methods for direct sun imaging by a star tracker. Disclosed in a certain example is a direct sun imaging star tracker that includes an imaging sensor and a baffle. The baffle includes a star port, a sun port, and a beam splitter. The star port is configured to image first viewing environment while the sun port is configured to image a second viewing environment that includes the sun. The beam splitter is configured to combine electromagnetic radiation from the star port and the sun port into a combined image. In various examples, the systems and techniques described herein allow a star tracker to simultaneously view both the sun and the stars.

A zero-optical-path-length-difference optical phased array built with essentially planar photonic devices determines a direction to an incoherent optical source, such as a star. The phased array can replace a 3-dimensional star tracker with a nearly 2-dimensional system that is smaller and lighter. The zero-optical-path-length-difference phased array can be optically connected to an interferometer. Driven by a light source, the zero-optical-path-length-difference phased array can be used as an optical projector.

A celestial navigation system includes an optical device for receiving light from a celestial object, a spectrometer for measuring a spectrum of the light in sufficient detail to identify absorption and/or emission features, and a processor for processing the spectrum to match the spectrum, or a processed version thereof, against a set of reference spectra information in a database, a device for measuring the pointing direction of the optical device and a clock. The matching may be on a maximum likelihood basis. The system is thus able, on identification of a single star, and, using commonly available navigational almanacs, to calculate a geographical position. Celestial navigation takes place even when only one celestial object (that is also within the database) is visible, although improved accuracy may be obtained with multiple observations. Advantageously, the database includes stars of the K and/or M type, that have more characteristic spectral content.

A navigation system determines a position by referring to artificial or natural satellites or other space objects during daylight or when the objects are in a planet's shadow. A telescope and image sensor observe and image shadows of the objects as the objects transit the sun or a sunlit surface of a planet or moon, thereby solving problems related to the two key times during which traditional SkyMark navigation is difficult or impossible.

A method of determining position of an object using an imaging device includes imaging a celestial object using an imaging device. A difference between an expected position of the celestial object and an actual position of the celestial object is determined. Pointing of the imaging device is in-flight calibrated to improve position determining by nulling the difference between the expected position of the celestial object and the actual position of the celestial object. Systems for determining position of an object relative to a vehicle are also described.

An apparatus for improving a pointing capability of an optical pointing system includes a star tracker attitude control system for maintaining an alignment between the optical pointing system and a target, a beam steering mirror controlled by the star tracker attitude control system to direct an optical signal to impinge on the target, a fixed optical assembly configured to direct a portion of the optical signal from the bean steering mirror into a field of view of a star tracker telescope of the star tracker attitude control system, and a detector array for detecting the portion of the optical signal superimposed over a location in a current star scene in the star tracker telescope field of view, where the star tracker attitude control system is configured to operate the beam steering mirror to maintain the optical signal on the target by maintaining the superimposed signal on the location in the star scene.