Abstract: A satellite for implementing a protocol associated with a distributed satellite position verification system is provided. The satellite, on implementing the protocol, verifies records of positions of one or more other satellites in the distributed satellite position verification system. According to the protocol, the satellite performs, at different time instances, a first operation, a second operation, or a third operation to act as a first satellite, a second satellite, or a third satellite, respectively in the distributed satellite position verification system. When the first satellites performs the first operation, the first satellite verifies at least some positions in the records of positions of the second satellite such that the first satellite: determines a verified position of the second satellite; calculates a deviation between the verified position and a prior estimated position of the second satellite; and records the verified position into the records, based on the calculated deviation.

Abstract: A computer-implemented method for maintaining a spacecraft near an orbit comprises steps of detecting that a distance from the spacecraft to the orbit is greater than a spacecraft threshold and in response, linearizing dynamics of the spacecraft from a current time over a time horizon with respect to a high-fidelity reference trajectory to produce a state transition matrix (STM) for an uncontrolled motion of the spacecraft within the time horizon. The STM includes non-expanding eigenvectors with magnitudes less than or equal to one and expanding eigenvectors with magnitudes greater than one. The method further comprises determining a control action that changes an upcoming state of the spacecraft to a linear combination of the non-expanding eigenvectors of the STM and generating a control command to an actuator of the spacecraft.

Abstract: Drift-based rendezvous control system for controlling an operation of a spacecraft to rendezvous the spacecraft to a goal region over a finite time (FT) horizon. The system including accepting data including values of spacecraft states at a specified time period within the FT horizon. A processor at the specified time period selects a set of drift regions corresponding to a desired goal region at a location on an orbit where the target is located at the specified time period. Update a controller having a model of dynamics of the spacecraft with the accepted data. Formulate the set of drift regions as a penalty in a cost function of the updated controller. Generate control commands resulting in a real-time drift-based control policy where upon entering the drift region, the thrusters are turned off in order to minimize an amount of operation of the thrusters while rendezvousing with the desired goal region.

Abstract: Systems and methods controlling an operation of a vehicle in real time to rendezvous the vehicle with a target over a finite time horizon having multiple specified time periods. Select a set of unsafe regions from stored unsafe regions, the set of unsafe regions represents regions of space around the target in which any operation of the PSNO thrusters does not avoid collision with the target, guaranteeing collision trajectories with the target. Formulating the set of unsafe regions as safety constraints, and updating a controller having a model of dynamics of the vehicle with the accepted data. Generating control commands by subjecting the updated controller to the safety constraints to produce a rendezvous trajectory that avoids the set of unsafe regions, guaranteeing an operation of at least the PSNO thrusters, in the event of partial vehicle thruster failure results in a trajectory that does not collide with the target.

Abstract: A system for optimizing a low-thrust trajectory of a spacecraft trajectory for orbital transfer includes an interface to receive data, a memory to store scheduled geostationary transfer orbit (GTO) data and scheduled geostationary Earth orbit (GEO) data and computer-executable programs, and a processor.

Abstract: A method and system for activating thrusters of a vehicle for trajectory-tracking control of the vehicle. A transfer orbit generator to generate a transfer orbit for the vehicle from an initial orbit to a target orbit, and a feedback stabilization controller. Compute the target orbit for the vehicle about the celestial body. Compute a free trajectory with patch points along the free trajectory using a free trajectory module, each patch point includes a position and a velocity. Determine a feedback gain at each patch point using a feedback gain module, wherein a state penalty function at each patch point is set to match a state uncertainty function at the same patch point. Apply the feedback gain at each patch point to map the position and the velocity at each patch point to delta v commands, to maintain the target orbit using a feedback stabilization controller.

Abstract: The present disclosure provides a system and a method for controlling a motion of a spacecraft in a multi-object celestial system while avoiding an unauthorized entry into a keep-away region during a normal and an abnormal operation of the spacecraft. The method includes executing, during the normal operation of the spacecraft, a nominal control law subject to constraints on maintaining a state of the spacecraft within a union of a plurality of control invariant sets of values of the state of the spacecraft. The state of the spacecraft includes a location of the spacecraft and at least one or a combination of a velocity and an acceleration of the spacecraft. The method further includes executing, upon detecting the abnormal operation of the spacecraft, an abort control law associated with the control invariant set including a current state of the spacecraft.

Abstract: A satellite for implementing a protocol associated with a distributed satellite position verification system is provided. The satellite, on implementing the protocol, verifies records of positions of one or more other satellites in the distributed satellite position verification system. According to the protocol, the satellite performs, at different time instances, a first operation, a second operation, or a third operation to act as a first satellite, a second satellite, or a third satellite, respectively in the distributed satellite position verification system. When the first satellites performs the first operation, the first satellite verifies at least some positions in the records of positions of the second satellite such that the first satellite: determines a verified position of the second satellite; calculates a deviation between the verified position and a prior estimated position of the second satellite; and records the verified position into the records, based on the calculated deviation.

Abstract: A controller controls a spacecraft to rendezvous a non-center-of-mass point of the controlled spacecraft with a non-center-of-mass point of an uncontrolled celestial body. The controlled spacecraft and the uncontrolled celestial body form a multi-object celestial system, and the controller produces control commands to thrusters of the controlled spacecraft using a non-linear model predictive control (NMPC) optimizing a cost function over a receding horizon that minimizes an error between coordinates of the non-center-of-mass point of the spacecraft and the non-center-of-mass point of the celestial body subject to joint dynamics of the multi-object celestial system coupled with joint kinematics of the multi-object celestial system.

Abstract: Drift-based rendezvous control system for controlling an operation of a spacecraft to rendezvous the spacecraft to a goal region over a finite time (FT) horizon. The system including accepting data including values of spacecraft states at a specified time period within the FT horizon. A processor at the specified time period selects a set of drift regions corresponding to a desired goal region at a location on an orbit where the target is located at the specified time period. Update a controller having a model of dynamics of the spacecraft with the accepted data. Formulate the set of drift regions as a penalty in a cost function of the updated controller. Generate control commands resulting in a real-time drift-based control policy where upon entering the drift region, the thrusters are turned off in order to minimize an amount of operation of the thrusters while rendezvousing with the desired goal region.

Abstract: Systems and methods controlling an operation of a vehicle in real time to rendezvous the vehicle with a target over a finite time horizon having multiple specified time periods. Select a set of unsafe regions from stored unsafe regions, the set of unsafe regions represents regions of space around the target in which any operation of the PSNO thrusters does not avoid collision with the target, guaranteeing collision trajectories with the target. Formulating the set of unsafe regions as safety constraints, and updating a controller having a model of dynamics of the vehicle with the accepted data. Generating control commands by subjecting the updated controller to the safety constraints to produce a rendezvous trajectory that avoids the set of unsafe regions, guaranteeing an operation of at least the PSNO thrusters, in the event of partial vehicle thruster failure results in a trajectory that does not collide with the target.

Abstract: A system for controlling an operation of a vehicle to rendezvous with a target over a finite time horizon, wherein the vehicle and the target form a multi-object celestial system. A processor to formulate passive unsafe regions as passive safety constraints. The passive unsafe regions represents regions of space around the target guaranteeing collision trajectories with the target, in an event of total thruster failure. Update a controller having a model of dynamics of the vehicle with received data, and subject the updated controller to the passive safety constraints to generate control commands that produce a collision free rendezvous trajectory which avoids unsafe regions for the specified time period, guaranteeing a collision free trajectory with respect to the target in the event of the total vehicle thruster failure, so the vehicle does not collide with the target. Output the control commands to activate or not activate thrusters of the vehicle.

Abstract: Resin formulation including: a mixture of low volatility oligomers is about 40% to 75% weight of the resin formulation; a plasticizer is about 25% to 55% by weight of the resin formulation; a photoinitiator is about 0.1% to 3.0% by weight of the resin formulation; a thermal inhibitor is about 0.001% to 4% by weight of the resin formulation; and a defoaming agent is about 0.0001% to 0.1% by weight of the resin formulation. Wherein the mixture of low volatility oligomers is combined with the photoinitiator, the thermal inhibitor and the defoaming agent, and mixed, then degassed at a temperature of about 60 deg C. and at a pressure of less than 10 kPa for at least 10 minutes.

Abstract: A control system of a vehicle for controlling motion of the vehicle traveling on a road shared with a set of moving objects include a memory to store a set of regions of states of lateral dynamic of the vehicle corresponding to a set of equilibrium points. Each region defines a control invariant set of the states of the lateral dynamic determined for different speeds of the vehicle, such that the vehicle having a state within a region determined for a speed is capable to maintain its states within the region while moving with the speed. Each region includes a corresponding equilibrium point and intersects with at least one adjacent region. Each equilibrium point is associated with one or multiple regions determined for different speeds.

Abstract: A method and system for activating thrusters of a vehicle for trajectory-tracking control of the vehicle. A transfer orbit generator to generate a transfer orbit for the vehicle from an initial orbit to a target orbit, and a feedback stabilization controller. Compute the target orbit for the vehicle about the celestial body. Compute a free trajectory with patch points along the free trajectory using a free trajectory module, each patch point includes a position and a velocity. Determine a feedback gain at each patch point using a feedback gain module, wherein a state penalty function at each patch point is set to match a state uncertainty function at the same patch point. Apply the feedback gain at each patch point to map the position and the velocity at each patch point to delta v commands, to maintain the target orbit using a feedback stabilization controller.

Abstract: A control system uses a set of regions of states of lateral dynamic of the vehicle corresponding to a set of equilibrium points to control a vehicle. Each region defines a control invariant set of the states of the lateral dynamic determined such that the vehicle having a state within a region is capable to maintain its states within the region. Each region includes a corresponding equilibrium point and intersects with at least one adjacent region. The control system identifies collision-free regions at different time steps of control to produce a collision free sequence of regions forming a union of regions in space and time connecting a region including an initial displacement with a region including a target displacement. The control system produces a trajectory within the union connecting the initial displacement with the target displacement and control the vehicle according to the trajectory.

Abstract: Resin formulation including: a mixture of low volatility oligomers is about 40% to 75% weight of the resin formulation; a plasticizer is about 25% to 55% by weight of the resin formulation; a photoinitiator is about 0.1% to 3.0% by weight of the resin formulation; a thermal inhibitor is about 0.001% to 4% by weight of the resin formulation; and a defoaming agent is about 0.0001% to 0.1% by weight of the resin formulation. Wherein the mixture of low volatility oligomers is combined with the photoinitiator, the thermal inhibitor and the defoaming agent, and mixed, then degassed at a temperature of about 60 deg C. and at a pressure of less than 10 kPa for at least 10 minutes.

Abstract: A positioning system for a global navigational satellite system (GNSS) includes a receiver to receive carrier signals and code signals transmitted from a set of GNSS satellites that include a carrier phase ambiguity as an unknown integer number of wavelengths of the carrier signal traveled between the satellite and the receiver, and a processor to track a position of the receiver. The processor is configured to determine a set of possible combinations of integer values of the carrier phase ambiguities consistent with the measurements of the carrier signal and the code signal according to one or combination of the motion model and the measurement model within bounds defined by one or combination of the process noise and the measurement noise and execute a set of position estimators determining positions of the receiver using different combinations of integer values of the carrier phase ambiguities selected from the set of possible combinations.

Abstract: A spacecraft including a set of thrusters for changing a pose of the spacecraft. At least two thrusters mounted on a gimbaled boom assembly and are coupled together sharing the same gimbal angle. A model predictive controller (MPC) to produce a solution for controlling thrusters of the spacecraft by optimizing a cost function over a receding horizon using a model of dynamics of the spacecraft effecting a pose of the spacecraft and a model of dynamics of momentum exchange devices of the spacecraft effecting an orientation of the spacecraft. A modulator to modulate magnitudes of the thrust of the coupled thrusters determined by the MPC as pulse signals specifying ON and OFF states of each of the coupled thruster, wherein the ON states of the coupled thrusters sharing the same gimbal angle do not intersect in time. A thruster controller to operate the thrusters according to their corresponding pulse signals.

Abstract: A spacecraft including a spacecraft bus and a set of thrusters for changing a pose of the spacecraft. Wherein at least two thrusters are mounted on a gimbaled boom assembly connecting the two thrusters with the spacecraft bus, such that the two thrusters are coupled thrusters sharing the same gimbal angle. A model predictive controller to produce a solution for controlling thrusters of the spacecraft by optimizing a cost function over multiple receding horizons. The cost function is composed of a cost accumulated over the multiple receding horizons, including a cost accumulated over a first horizon using a dynamics governing a north-south position of the spacecraft, and a cost accumulated over a second horizon using a model of dynamics of the spacecraft governing an east-west position. A thruster controller to operate the thrusters according to their corresponding signals.