Abstract: Unmanned aerial vehicle control systems are disclosed herein. In one embodiment, a method of controlling an unmanned aerial vehicle includes transmitting an indication of a take-off or landing location to the unmanned aerial vehicle. The unmanned aerial vehicle is launched. A control mode of the unmanned aerial vehicle is switched from an autonomous mode to a manual mode. The control mode of the unmanned aerial vehicle is switched from the manual mode to another autonomous mode, and the unmanned aerial vehicle is landed at the landing location.

Abstract: A system and method for assessing the risk of conjunction of a rocket body with orbiting and non-orbiting platforms. Two-body orbital dynamics are used to initially determine the kinematic access for a ballistic vehicle. The access may be represented in two ways: as a volume relative to its launcher and also as a geographical footprint relative to a target position that encompasses all possible launcher locations.

Abstract: A system and method for assessing the risk of conjunction of a rocket body with orbiting and non-orbiting platforms. Two-body orbital dynamics are used to initially determine the kinematic access for a ballistic vehicle. The access may be represented in two ways: as a volume relative to its launcher and also as a geographical footprint relative to a target position that encompasses all possible launcher locations.

Abstract: A method and a system for assisting air traffic controllers that automatically detects conflicts between aircraft trajectories and selects the conflicts that can be solved by minor modification(s) of aircraft speed, climbing rates or descending rates and lateral shifts of route. Minor modifications are selected so as to not interfere with current controllers' decision making process thereby circumventing the basic rule of uniqueness of control in a given piece of airspace. The minor modifications are automatically transmitted to aircraft for execution without requiring controllers' prior agreement. Thus, the method solves most conflicts, such that the air traffic delivered to the controllers is free of most of the pre-existing conflicts.

Abstract: An object in motion has a force applied thereto at a point of application. By moving the point of application such that the distance between the object's center-of-mass and the point of application is changed, the object's orientation can be changed/adjusted.

Abstract: An apparatus for trapping high-speed particles, such as space debris, is provided. The apparatus includes a first front tapping surface and at least one rear trapping surface. The front and rear trapping surfaces are arranged substantially parallel to each other and are spaced apart from each other in the normal direction.

Abstract: An unmanned aerial vehicle variable autonomy control system is disclosed herein. In one embodiment, the system includes a control mode interface that provides a plurality of selectable control modes for an unmanned aerial vehicle, wherein one of the plurality of selectable control modes comprises a target tracking mode. Also included is a target editor interface provided in response to a selection of the target tracking mode, wherein the target editor interface facilitates receipt of an input indicative of a ground based moving target. The system also includes a communications component that transmits a command to the unmanned aerial vehicle, wherein the command is based at least in part on the input indicative of a target.

Abstract: Methods and systems for displaying assistance messages to aircraft operators are disclosed. A method in accordance with one embodiment includes receiving an input from an aircraft operator at an aircraft flight deck, comparing a characteristic of the input to at least one target value for the characteristic, and, if the characteristic of the input differs from the at least one target value for the characteristic by at least a threshold amount, displaying an assistance message to the aircraft operator. The assistance message can include a complying input and/or an instruction for creating a complying input. The input and the assistance message can be displayed simultaneously.

Abstract: A display system and method for an aircraft displays, in real-time, the protected airspace associated with a CTL maneuver. The system processes aircraft approach category data and determines the protected airspace based at least in part on the processed aircraft approach category. An image representative of the determined protected airspace is displayed on the aircraft flight deck display system.

Abstract: One embodiment of the invention includes a spacecraft system. The system includes a spacecraft payload system coupled to a spacecraft frame. The system also includes a plurality of spacecraft panels disposed about the spacecraft frame. Each of the plurality of spacecraft panels can be communicatively coupled together via a network and configured substantially identically with respect to each other, and can include a processor and associated spacecraft control components. The processors of each of the spacecraft panels controlling the respective spacecraft control components independently to cooperatively and autonomously implement spacecraft control functions to implement a common mission objective.

Abstract: A method of controlling inertial attitude of an artificial satellite in order to perform a navigation function and to maximize terrestrial coverage of the Earth by the satellite. The method includes deploying the artificial satellite in an orbit about the poles of the Earth; applying gyroscopic precession to the artificial satellite spin axis to precess and maintain the satellite near the ecliptic pole; deploying the artificial satellite so that the spin axis is initially perpendicular to or substantially perpendicular to sun lines; and applying gyroscopic precession to the artificial satellite spin axis to precess the spin axis away from an initial deployed attitude at a selectively-variable precession rate and to maintain the spin axis perpendicular to or substantially perpendicular to a the sun lines.

Abstract: An unmanned aerial vehicle variable autonomy control system is disclosed. In one embodiment, the system includes a control mode interface that provides a plurality of selectable control modes for an unmanned aerial vehicle, wherein one of the plurality of selectable control modes comprises an autonomous landing mode. Also included is a route editing interface that, following a selection of the autonomous landing mode, facilitates a receipt of an input indicative of a landing location. The system also includes a communications component that transmits a command to the unmanned aerial vehicle, wherein the command is based at least in part on the input indicative of the landing location.

Abstract: Unmanned aerial vehicle take-off and landing systems are disclosed herein. In one embodiment, a method of landing an unmanned aerial vehicle includes programming a landing location for the unmanned aerial vehicle utilizing a user input device. The unmanned aerial vehicle is launched. Communications between the unmanned aerial vehicle and the user input device are interrupted, and the unmanned aerial vehicle is landed at the landing location based on the programmed landing location and not based on any real-time communication between the unmanned aerial vehicle and the user input device.

Abstract: Collision probability analysis for spherical objects exhibiting linear relative motion is accomplished by combining covariances and physical object dimensions at the point of closest approach. The resulting covariance ellipsoid and hardbody are projected onto the plane perpendicular to relative velocity by assuming linear relative motion and constant positional uncertainty throughout the brief encounter. Collision potential is determined from the object footprint on the projected, two-dimensional, covariance ellipse. To accommodate nonlinear motion in accordance with the disclosed embodiments, the dimension associated with relative velocity is reintroduced by segmenting the collision tube volume into a plurality of mitered tube sections modeled as bundles of parallelepipeds in Mahalanobis space. Disclosed embodiments compute the probability of each parallelepiped as the combined object passes through the space, and sums.

Abstract: A method and apparatus for determining long term orbit (LTO) models using variable time-horizons to improve the orbit and clock model accuracy. The method and apparatus use either historic ephemeris or historic measurements for at least one satellite to produce an orbit parameter prediction model (an LTO model). The parameter predicted by the model is compared to an orbit parameter of a current broadcast ephemeris. The result of the comparison (an indicia of accuracy for the model) is used to establish a time-horizon for the orbit parameter prediction model for that particular satellite. Such a time-horizon may be established in this manner for each satellite within a satellite constellation.

Abstract: In a satellite control system, a liquid is ejected by thermal ejection from holes in a substrate structure to create a reactive force on the satellite allowing the position, such as the attitude, of the satellite to be adjusted.

Abstract: In a satellite control system, a liquid is ejected by thermal ejection from holes in a substrate structure to create a reactive force on the satellite allowing the position, such as the attitude, of the satellite to be adjusted.

Abstract: Propellant management systems and methods are provided for controlling the delivery of liquid propellants in a space launch vehicle utilizing multiple rockets. The propellant management systems and methods may be configured to enable substantial simultaneous depletion of liquid propellants in each of a plurality of active rockets during operation of various booster stages of the launch vehicle.

Abstract: A spacecraft includes a plurality of thrusters, a thruster firing logic, an actuator assembly, an attitude control system, and a torque calibration system. The plurality of thrusters is configured to apply torque to the spacecraft. The thruster firing logic is configured to control firing of the plurality of thrusters. The actuator assembly is configured to apply torque to the spacecraft. The attitude control system is configured to sense an attitude of the spacecraft and to provide an attitude control torque. The torque calibration system is configured to provide a thruster feedforward torque. A machine-readable medium includes instructions for a method for providing torque calibration to a spacecraft.

Abstract: A method of estimating the alignment of a star sensor (20) for a vehicle (12) includes generating star tracker data. A vehicle attitude and a star sensor attitude are determined in response to the star tracker data. A current alignment sample is generated in response to the vehicle attitude and the star sensor attitude. A current refined estimate alignment signal is generated in response to the current alignment sample and a previously refined estimate alignment signal via a vehicle on-board filter (38).

Abstract: Methods and systems are provided for reorienting an agile vehicle, such as a satellite or spacecraft, using a control moment gyroscope (CMG) array. The CMG array comprises a plurality of CMGs onboard the agile vehicle. A method comprises obtaining an input torque command for reorienting the vehicle using the CMG array and, when the angular momentum of the CMG array violates or is approaching a momentum boundary criterion, decreasing the input torque command in the kinetic momentum direction, resulting in a modified torque command, and operating the CMG array using the modified torque command.

Abstract: A method of determining an orbit of an orbital object includes computing predicted tracking measurement values based on the orbit computed from the initial conditions factoring in any modeled environmental forces and realistic maneuvers; computing the differences between the actual and predicted tracking measurements; determining an improved estimate of the initial conditions that reduces the measurement errors using a minimization or root finding algorithm; after the algorithm has converged, reviewing the hypothetical maneuvers in the force model, taking each value and determining which values came up as near-zero in the minimized solutions and which values came up as those of measurable thrust; determining overall burn duration using the first and last burn times; determining the thrust profile of the orbital object over the observation period using the integrated thrust values; and determining the actual maneuver based on the observation data.

Abstract: Provided is a satellite control system based on integrated satellite operation data and a method thereof. The satellite control system includes: a satellite operation data schema editing means for creating a document type definition file and defining a schema; a mission planning means for creating a mission timeline and recording the mission timeline; a command planning means for converting a task into telecommands and recording the telecommand; a command preparing means for creating a telecommand procedure and recording the telecommand procedure; a command transmitting means for creating a telecommand code, transmitting the telecommand code to a satellite and recording the telecommand code; a command verifying means for receiving telemetry data and recording a telecommand verification result; and a performance result reporting means for creating a mission performance result and recording the mission performance result.

Abstract: Techniques for providing singularity escape and avoidance are disclosed. In one embodiment, a method for providing control moment gyroscope (CMG) attitude control singularity escape includes calculating a Jacobian A of a set of control equations, calculating a measure of closeness to a singularity, and comparing the calculated closeness to a threshold value, when the calculated closeness is less than or equal to the threshold value, recalculating the Jacobian A. Recalculating may include determining a new direction of virtual misalignment of ? and ?, recalculating the Jacobian inputting the new direction of the virtual misalignment, recalculating the measure of closeness to a singularity, and comparing the measure of closeness to the threshold value. Further, the method may include calculating a gimbal rate command if the of closeness is greater than the threshold value and generating a torque from the gimbal rate command to control the attitude of a satellite.

Abstract: A method for controlling the attitude of a satellite in orbit around a celestial object, the satellite including an observation instrument, a solar panel, a radiator and a star sensor which are arranged on the satellite such that, in a reference frame associated with the satellite and defined by three orthogonal axes X, Y, and Z, the observation instrument has its observation axis parallel to the Z-axis, the solar panel is parallel to the Y-axis, the radiator is arranged on one of the sides ?X, +Y, or ?Y of the satellite, and the star sensor points to the negative X values side. The roll and pitch attitudes of the satellite are controlled during an activity period to direct the observation instrument towards areas of the celestial object to be observed, and the yaw attitude of the satellite is controlled to keep the sun on the positive X values side and ensure that a solar panel minimum insolation constraint is satisfied during observation phases of the activity period.

Abstract: A control device (D), for a spacecraft (S1) of a group of spacecraft moving in formation, comprises i) an assembly consisting of three antennas (A1-A3) installed on a face of the spacecraft (S1) and capable of emitting and/or receiving first and second RF signals exhibiting first and second frequencies spaced apart by a chosen frequency gap, ii) first measurement means (M1) charged with determining first and second differences in path length between antennas (A1-A3), corresponding to the first frequency and to the frequency gap, on the basis of the first and second signals received by the antennas and originating from another spacecraft, iii) second measurement means (M2) charged with delivering measurements of rotation undergone by the spacecraft (S1), and iv) processing means (MT) a) charged with coarsely estimating the direction of transmission of the signals received on the basis of first and second initial path length differences, b) with ordering the positioning of the spacecraft (S1) so that a chosen a

Abstract: A system for controlling an aerospace vehicle using on-line inertia estimation may include an attitude sensor to measure an attitude of the aerospace vehicle. The system may also include a processor on board the aerospace vehicle. An inertia estimator operable on the processor may generate an on-line inertia estimate of the aerospace vehicle. A rate and attitude estimator operable on the processor may determine an angular position and angular velocity of the aerospace vehicle using the attitude measurement of the aerospace vehicle and the on-line inertia estimate for controlling movement and orientation of the aerospace vehicle without any rates of rotation of the aerospace vehicle being required.

Abstract: A system and method are disclosed for simultaneous attitude maneuver and momentum dumping. The attitude maneuver is performed using nominal wheel control to minimize propellant usage, while applying a momentum management command to the thruster control loop in order for the wheels to accomplish the desired spacecraft maneuver while simultaneously being reset to a de-saturated target state. The system and method involve a wheel system comprised of reaction wheels and/or a control moment gyroscope (CMG), at least one thruster, and control logic that is in communication with the wheel system and thruster(s). If a spacecraft maneuver is in progress, the control logic biases an error input signal to a thruster control loop to track the wheel maneuver to prevent unnecessary propellant consumption. The control logic is further operable to output thruster torque commands and wheel torque commands that accomplish the maneuver while achieving the desired final momentum target.

Abstract: The present system and methods enable simultaneous momentum dumping and orbit control of a spacecraft, such as a geostationary satellite. Control equations according to the present system and methods generate accurate station-keeping commands quickly and efficiently, reducing the number of maneuvers needed to maintain station and allowing station-keeping maneuvers to be performed with a single burn. Additional benefits include increased efficiency in propellant usage, and extension of the satellite's lifespan. The present system and methods also enable tighter orbit control, reduction in transients and number of station-keeping thrusters aboard the satellite. The present methods also eliminate the need for the thrusters to point through the center of mass of the satellite, which in turn reduces the need for dedicated station-keeping thrusters. The present methods also facilitate completely autonomous orbit control and control using Attitude Control Systems (ACS).

Abstract: A display system is provided that renders a horizontal situation indicator that includes required navigation performance (RNP) and estimated position uncertainty (EPU) values rendered non-numerically and in a fairly intuitive manner. A processor receives at least data representative of a desired course of the aircraft, data representative of the RNP for the aircraft, and data representative of the EPU for the aircraft. The processor renders, on a display device, a horizontal situation indicator that includes an aircraft symbol representative of a top-down view of the aircraft, an RNP boundary graphic representative of at least one RNP boundary for the aircraft, and an EPU graphic representative of the EPU for the aircraft. The aircraft symbol is rendered at a position that is representative of actual aircraft position relative to the desired course, and the RNP boundary graphic is rendered at a position relative to the rendered aircraft symbol.

Abstract: An active vibration damping (AVD) control system for spacecraft provides a simple-to-implement and robust formulation that provides a novel damping control method for reducing spacecraft structural vibrations and improving antenna and instrument pointing. The AVD control system comprises an excitation signal generator configured to generate excitation input signals, and a damping model identification unit configured to receive system identification data and configured to produce control model parameters, the system identification data comprising the excitation input signals and information associated with motion of the spacecraft. The AVD control system further comprises an AVD control unit configured to receive the control model parameters, the AVD control unit configured to produce AVD control signals to control one or more actuators of the spacecraft.

Abstract: Apparatus, Systems, and Methods are provided for controlling motion of a spacecraft. One apparatus includes a non-contacting actuator and a passive mechanical system coupled in parallel with one another. A system includes a payload, a bus, and a hybrid actuator including a non-contacting actuator and a passive mechanical system coupled in parallel, and coupled between the bus and the payload. The system also includes an inertial actuator configured to maneuver the bus to maintain a relative position and/or attitude of the bus with respect to the payload. One method includes receiving a signal instructing a first controller to change the position and/or attitude of a payload and utilizing a hybrid system to change the position and/or attitude of the payload. The method also includes receiving the signal at a second controller and utilizing a system to change a position and/or attitude of the bus independent of the payload.

Abstract: Disclosed herein are systems and methods of angular rate and position measurement that combine a small footprint with hardening and isolation technologies that allow it to function in acceleration, angular rate, noise and vibration environments that cause other gyroscopes to either fail or to produce erroneous outputs. An example embodiment contains a triad of accelerometers, a triad of gyroscopes, analog and digital ancillary electronics and a processor housed within a housing which is also filled with vibration reducing encapsulating compound. The disclosed systems and methods of angular rate and position measurement are capable of measuring and correcting internal errors and perturbations caused by the longitudinal and angular accelerations and temperature excursions of aerospace vehicles, isolating the gyroscope elements from the effects of acoustic noise and vibration, and accurately measuring the relatively small pitch and yaw oscillations of the vehicle in its flight path trajectory.

Abstract: An active vibration damping (AVD) control system for spacecraft provides a simple-to-implement and robust formulation that provides a novel damping control method for reducing spacecraft structural vibrations and improving antenna and instrument pointing. The AVD control system comprises an excitation signal generator configured to generate excitation input signals, and a damping model identification unit configured to receive system identification data and configured to produce control model parameters, the system identification data comprising the excitation input signals and information associated with motion of the spacecraft. The AVD control system further comprises an AVD control unit configured to receive the control model parameters, the AVD control unit configured to produce AVD control signals to control one or more actuators of the spacecraft.

Abstract: Techniques for providing singularity escape and avoidance are disclosed. In one embodiment, a method for providing control moment gyroscope (CMG) attitude control singularity escape includes calculating a Jacobian A of a set of control equations, calculating a measure of closeness to a singularity, and comparing the calculated closeness to a threshold value, when the calculated closeness is less than or equal to the threshold value, recalculating the Jacobian A. Recalculating may include determining a new direction of virtual misalignment of ? and ?, recalculating the Jacobian inputting the new direction of the virtual misalignment, recalculating the measure of closeness to a singularity, and comparing the measure of closeness to the threshold value. Further, the method may include calculating a gimbal rate command if the of closeness is greater than the threshold value and generating a torque from the gimbal rate command to control the attitude of a satellite.

Abstract: A mechanical flight control system for a rotary-wing aircraft is disclosed. The flight control system comprises an upstream portion, a downstream portion, and an assembly for connecting the upstream portion to the downstream portion. The assembly may comprise dual concentric valve actuators and/or a variety of system load limiting features.

Abstract: A mover such as a vehicle acquires the information, which has been updated by broadcasting/communication during an engine stall or in an unreceivable state, after the engine start or the recovery of reception. The engine stall period and the unreceivable state continuation period of the mover are monitored and are notified after the engine start from a communication device to an information center and a mounted device. In response to this notification, the information center extracts the information, which has been updated during the engine stall period and the unreceivable state continuation period, and transmits the information to the communication device of the mover. As a result, the mover can always hold the latest information of a broadcast receiving device, the communication device and an information service device.

Abstract: A method and apparatus for determining the attitude of a satellite using crosslink information is disclosed. The method and apparatus integrates data from the crosslinks with data available from other sources including, for example, star sensors, inertial sensors, and earth limb sensors to derive an accurate estimate of the satellite attitude, even in harsh nuclear environments.

Abstract: Computer-based systems and methods for determining attitude of a moveable object. Attitude is determined by a transformation matrix {right arrow over (U)} from a body coordinate frame of the moveable object to an inertial reference frame. The transformation matrix is determined by: (i) determining a slew rate vector, {right arrow over (?)}, for time tN for the moveable object that represents a change in direction of an angular rate vector, {right arrow over (?)}, for the moveable object over the time interval from tN?1 to tN in the body coordinate frame; (ii) determining an update to the transformation matrix for time tN that is based on a product of two matrices, the first matrix being related to a sum of {right arrow over (?)} and {right arrow over (?)}, and the second matrix being related to ?{right arrow over (?)}; and (iii) multiplying a transformation matrix for time tN?1 and the update to the transformation matrix for time tN to obtain the transformation matrix for time tN.

Abstract: An automatic charging system for charging a vehicle for using an infrastructure delimited by a boundary during a charging period Tc based on Global Navigation Satellite Systems (GNSS) location with guaranteed performance. The system includes an onboard receiver with integrity guarantee which, in addition to providing position information, provides additional information relating to the error that can be expected in the position consisting of a health flag (denoting a Healthy/Unhealthy status), and a Radial Protection Level (RPL) relating to the amount limiting the horizontal position error according to one direction and with a probability equal to a known value IRx.

Abstract: A spacecraft system is provided, including a measurement device configured to measure information associated with position of a spacecraft, a filter configured to process the measured information and to provide estimated pre-maneuver information associated with position of the spacecraft and estimated post-maneuver information associated with position of the spacecraft, a propagator configured to predict post-maneuver information associated with position of the spacecraft based upon the estimated pre-maneuver information associated with position of the spacecraft and a model of a maneuver of the spacecraft, an error calculator configured to calculate an acceleration error based upon the estimated post-maneuver information associated with position of the spacecraft and the predicted post-maneuver information associated with position of the spacecraft, and a maneuver archive configured to store the acceleration error for updating the model of the maneuver.

Abstract: Technology for predicting and correcting a trajectory is described. The technology can create a model to predict a position of the reusable launch vehicle at a time in the future; observe a wind condition during ascent of the reusable launch vehicle; store the observed wind condition in a wind map; predict during ascent a position and a terminal lateral velocity of the reusable launch vehicle at a terminal altitude; and correct a flight trajectory of the reusable launch vehicle based on the wind map.

Abstract: The present invention relates to a method and a system for monitoring the following of a reference trajectory by an aircraft.

Abstract: The subject of the present invention is a method for improving route and 4D prediction calculations by FMS in the framework of ATC tactical flight instructions, which method enables the FMS of an aircraft to carry out its usual predictions as precisely as possible when it has left or anticipates leaving its initial flight plan following an instruction from the air traffic controller, and has no instructions telling it where and when to return to the initial flight plan, and the invention is characterized in that it consists in transmitting to the aircraft, from an air traffic control centre, information enabling the FMS system to be aware of traffic crossing points (X1) and control sector changes, and to use this information to predict the coordinates of a point (X2) at which it is supposed to rejoin its initial flight plan at the earliest opportunity after the crossing point that required an alteration of trajectory and at the latest opportunity on the last point of the current sector.

Abstract: Method for the computer-assisted determination of an optimum-fuel control of nozzles according to a control instruction b=Ax. A defined matrix transformation of starting constraints for the mass flow of the nozzles and of the minimization criterion thereby takes place in a computer-assisted manner, a data processing representation of a geometric description of the matrix-transformed starting constraints, a computer-assisted determination of limiting point sets of the geometric description of the starting constraints through a computer-assisted geometric search procedure in the vector space and the application of the matrix-transformed minimization criterion to the points of the limiting point sets.

Abstract: A system and method for navigation utilizes sources of modulated celestial radiation. A spacecraft, satellite, or other vehicle (12) includes one or more modulated radiation sensors (22a-22x) for detecting a modulated signal (14) generated by one or more pulsars or other celestial objects (16). Pulse time of arrival at a respective pulse sensor (22a-22x) is measured by comparing the pulse signal (14) with a known pulse profile. A processor (30) calculates a timing difference between the measured pulse time of arrival at sensor (22a-22x) with a calculated pulse time of arrival at a selected reference point (100). Positions and pulse profile characteristics of the pulsars (16) are stored. Combining the calculated time difference with the known positions of pulsars (16), navigational parameters such as position, velocity, and attitude for spacecraft (12) with respect to the selected localized reference point (100) can be calculated.

Abstract: A control system for adjusting the attitude of a spacecraft comprises a set of control moment gyroscopes (CMGs) configured to allow null space maneuvering. The control system further comprises a momentum actuator control processor coupled to the set of CMGs and configured to determine a mandatory null space maneuver to avoid singularities and determine an optional null space maneuver to increase available torque. The mandatory null space maneuver can be calculated based upon certain gimbal angles, and can be implemented by augmenting the inverse-Jacobian control matrix.

Abstract: A method of and apparatus for determining and controlling the inertial attitude of a spinning artificial satellite without using a suite of inertial gyroscopes. The method and apparatus operate by tracking three astronomical objects near the Earth's ecliptic pole and the satellite's and/or star tracker's spin axis and processing the track information.

Abstract: A method and device for assisting the lateral control of an aircraft running on a runway employ a detector for measuring a lateral deviation of the aircraft relative to a lateral alignment beam transmitted by a radio transmitter installed on the ground, the lateral deviation representing an angular deviation between a straight line passing through the radio transmitter and the detector and the centerline of the runway. A calculator calculates a first distance, defined along the runway, between the position of the pilot in the cockpit and the radio transmitter. A central unit determines, from the lateral deviation and the first distance, a line intended to correspond with the centerline of the runway. A head up display device displays the line on a display screen, superimposed on the environment existing in front of the aircraft and the centerline of the runway.

Abstract: The apparatus of the present invention uses radar altimeter measurements and stored terrain altitude profiles to provide pre-filtered observations to a Kalman filter for estimating barometric offset at the airport runway, and barometric scale factor for offsets above the runway. These offsets are used with the smoothed baro-inertial output from an inertial reference system to provide 3 dimensional constant rate of descent approach procedures to replace non-precision approach procedures based on constant barometric altitude step approaches. The horizontal positions used as reference for the stored terrain altitude profiles are obtained from a prior art navigation apparatus. The integrity of all measurements is assured by using long term averages of the Kalman filter residuals to detect failures. In addition, the estimated baro offset at the runway is compared for consistency with the baro offset obtained by the pilot from the airport by radio.