A constellation of Earth-orbiting spacecraft includes a first spacecraft disposed in a first orbit and a second spacecraft disposed in a second orbit. Each of the first orbit and the second orbit is substantially circular with a radius of approximately 42,164 km. The first orbit and the second orbit have a respective inclination with respect to the equator within a range of 5 to 20. The first orbit has a first right ascension of ascending node (RAAN1) and the second orbit has a second RAAN (RAAN2) of approximately RAAN1+90.

A constellation of Earth-orbiting spacecraft, the constellation having an orbital maneuver lifetime life (OML), includes a first spacecraft disposed in a first orbit and a second spacecraft disposed in a second orbit, each of orbit being substantially circular with a radius of approximately 42,164 km and having a respective inclination with respect to the equator specified within a range of 10 to 20. The first orbit has, at beginning of life (BOL), a first right ascension of ascending node (BOL-RAAN1) and the second orbit has, at BOL, a second RAAN (BOL-RAAN2) the BOL-RAAN1 and the BOL-RAAN2 being separated by a first angular separation -RAAN1. A first stationkeeping delta-V (V1) applied over the OML to the first spacecraft, in combination with a second delta-V (V2) applied over the OML to the second spacecraft, maintains the -RAAN1 approximately constant and an actual inclination within specification, and V1 approximately equals V2.

Systems, methods, and apparatus for a structural propellant for ion rockets (SPIR) are disclosed. In one or more embodiments, a method for in-space propulsion of a spacecraft involves removing, by a removal device, a portion of a structure of the spacecraft. The method further involves feeding, by the removal device, the portion into a Hall thruster system. Further, the method involves utilizing, by the Hall thruster system, the portion as propellant to produce thrust. In one or more embodiments, the structure is an upper stage of the spacecraft. In at least one embodiment, the upper stage comprises at least one structural support and/or at least one upper stage housing. In some embodiments, the structure is manufactured from magnesium, bismuth, zinc, and/or indium.

Disclosed is a method (70) for monitoring a phase for transferring a satellite (20) from one earth orbit, called initial orbit, to another earth orbit, called mission orbit, in particular a transfer using electric propulsion unit. The monitoring method includes a step for estimating the direction of the satellite during the transfer phase by way of an earth array antenna (30) including a plurality of elementary antennas (31), each elementary antenna having a primary radiation lobe with a width greater than or equal to 20, the elementary antennas (31) being oriented such that their respective fields of vision overlap, the direction of the satellite being estimated based on at least one useful phase difference measurement between signals corresponding to a target signal, transmitted by the satellite and received on a pair of elementary antennas (31).

A method for rendezvous with an orbiting object comprising: launching a tug and a servicer into a client orbit; separating the servicer from the tug; and docking the servicer with a client. A system for rendezvous with an orbiting object comprising: a first spacecraft comprising a tug capable of towing a second spacecraft, wherein the second spacecraft is a servicer configured to dock with a tumbling client orbiting object.

A vehicle is described herein that is capable of operating in space. The vehicle comprises a memory that stores computer-executable instructions. The vehicle further comprises a processor in communication with the memory, wherein the computer-executable instructions, when executed by the processor, cause the processor to: derive an equation of motion for the vehicle; determine an initial guess of a first value of a costate of the vehicle; determine the first value of the costate for a minimum propellant transfer in averaged orbit dynamics using the equation of motion, the initial guess, and a single shooting technique; determine a second value of the costate for the minimum propellant transfer in full-state orbit dynamics using the first value of the costate and the single shooting technique; and adjust a path of the vehicle to cause the vehicle to travel along an optimal transfer in full-state orbit dynamics.

A terrestrial-based system for is described herein that can determine a minimum time transfer for an extraterrestrial vehicle. The terrestrial-based system comprises a memory that stores computer-executable instructions. The terrestrial-based system further comprises a processor in communication with the memory, wherein the computer-executable instructions, when executed by the processor, cause the processor to: derive an averaged equation of motion for the extraterrestrial vehicle; determine an initial guess of a first value of a costate of the extraterrestrial vehicle; determine the first value of the costate for the minimum time transfer in averaged orbit dynamics; determine a second value of the costate for the minimum time transfer in full-state orbit dynamics; generate instructions for causing the extraterrestrial vehicle to travel along an optimal transfer in full-state orbit dynamics; and cause the extraterrestrial vehicle to adjust trajectory based on the generated instructions.

A vehicle is described herein that is capable of operating in space. The vehicle comprises a memory that stores computer-executable instructions. The vehicle further comprises a processor in communication with the memory, wherein the computer-executable instructions, when executed by the processor, cause the processor to: derive an equation of motion for the vehicle; determine an initial guess of a first value of a costate of the vehicle; determine the first value of the costate for a minimum time transfer in averaged orbit dynamics using the equation of motion, the initial guess, and a single shooting technique; determine a second value of the costate for the minimum time transfer in full-state orbit dynamics using the first value of the costate and the single shooting technique; and adjust a path of the vehicle to cause the vehicle to travel along an optimal transfer in full-state orbit dynamics.

A terrestrial-based system for is described herein that can determine a minimum propellant transfer for an extraterrestrial vehicle. The terrestrial-based system comprises a memory that stores computer-executable instructions. The terrestrial-based system further comprises a processor in communication with the memory, wherein the computer-executable instructions, when executed by the processor, cause the processor to: derive an averaged equation of motion for the extraterrestrial vehicle; determine an initial guess of a first value of a costate of the extraterrestrial vehicle; determine the first value of the costate for the minimum propellant transfer in averaged orbit dynamics; determine a second value of the costate for the minimum propellant transfer in full-state orbit dynamics; generate instructions for causing the extraterrestrial vehicle to travel along an optimal transfer in full-state orbit dynamics; and cause the extraterrestrial vehicle to adjust trajectory based on the generated instructions.

Energy efficient satellite maneuvering is described herein. One disclosed example method includes maneuvering a satellite that is in an orbit around a space body so that a principle sensitive axis of the satellite is oriented to an orbit frame plane to reduce gravity gradient torques acting upon the satellite. The orbit frame plane is based on an orbit frame vector.