Abstract: Systems and methods for refueling a chemical propulsion system are provided. The systems can include multiple pressurant reservoirs to supply pressure to one or more fuel tanks. During a refueling operation, pressurant is released, fuel is added to the fuel tank, and then the fuel tank is repressurized using pressurant from a secondary pressurant tank. In other configurations, during a refueling operation pressurant is cooled to depressurize the fuel tank, fuel is added to the fuel tank, and then the pressurant is heated to repressurize the fuel tank. The systems and methods can be used to refuel operationally deployed space craft.

Abstract: Chemical propellant storage and supply systems and methods for use on spacecraft are provided. The systems and methods include a fluid pump for moving chemical propellant within the system at selected pressures. This can include operating the fluid pump to supply propellant to a thruster system at a selected pressure. A fuel tank can be refilled by connecting a propellant resupply source to the system, and operating the fluid pump to move propellant from the propellant resupply source to the fuel tank. In a system with multiple fuel tanks, the fluid pump can be operated to move propellant from a donor fuel tank to a recipient fuel tank. The chemical propellant can be stored in one or more fuel tanks at a relatively low pressure. In addition, the chemical propellant is not pressurized by a gaseous pressurant while it is stored in the fuel tank.

Abstract: Phased array antenna systems and methods for operating phased array antenna systems to efficiently generate multiple beams from a single phased array aperture are disclosed. Elements included in a phased array antenna are randomly assigned to generate one of first or second beams. A phase index for the first set of elements is iterated n times, and a total difference in phase amounts for neighboring elements belonging to different ones of the first and second sets is calculated for each of the n iterations. The phase index resulting in the smallest calculated difference is applied to generate the first beam. The first and second beams are generated from the single phased array aperture simultaneously.

Abstract: An antenna system with integrated electromagnetic interference (EMI) shielded heat sink is disclosed. The system includes an antenna circuit board with a plurality of antenna or radiating elements formed on a common plane comprising a first surface. Circuit elements are placed on a second surface of the antenna circuit board. In addition, the second surface of the antenna circuits board is connected to a pocketed EMI shielding cover with individual shield pockets serving as an EMI shield and a heat sink containing a cooling fluid. At least some adjacent pockets can be in fluid communication with one another.

Abstract: A novel architecture for a network of deep reinforcement modules that enables cross-functional and multi-system coordination of autonomous systems for self-optimization with a reduced computational footprint is disclosed. Each deep reinforcement module in the network is comprised of either a single artificial neural network or a deep reinforcement module sub-network. DReMs are designed independently, decoupling each requisite function. Each module of a deep reinforcement module network is trained independently through deep reinforcement learning. By separating the functions into deep reinforcement modules, reward functions can be designed for each individual function, further simplifying the development of a full suite of algorithms while also minimizing training time.

Abstract: Systems and methods for providing a broadband antenna are described. The systems and methods involved providing a current sheet array. The current sheet array comprises a plurality of unit cells coupled together. Each unit cell comprises a slot and a stripline feed. The stripline feed couples to a dipole array through the slot. An electric field in the slot of a first unit cell is perpendicular to one or more of the stripline feed of the first unit cell and one or more dipoles of the first unit cell.

Abstract: A spacecraft sunshade is provided. The sunshade includes a surface that is maintained in a sun facing orientation. Adjustments to a position of the sunshade are made in a plane that is transverse to a line of sight to the sun, in order to block sunlight from being directly incident on an instrument associated with the spacecraft. The sunshade can include photovoltaic elements on the sun-facing surface of the sunshade. In addition, the sunshade can be formed from an opaque material, and further from a material that absorbs heat from the sun and reradiate that heat to the instrument. The sunshade can perform stray light blocking, electrical power generation, and radiational heating functions.

Abstract: Systems and methods for limiting rotation of a supported object about an axis of rotation are provided. A system as disclosed includes a stop system that engages at a selected amount of rotation about an axis of rotation to provide a balanced force countering further rotation. The stop system includes one or more pairs of stop mechanisms, with one stop mechanism in a pair disposed to act from a first side of the axis of rotation, and a second stop mechanism in the pair disposed to act from a second side of the axis of rotation. Each stop mechanism can include stops that engage a flexure at a selected amount of rotation.

Abstract: A hetero-junction phototransistor with a first layer comprising an InP N buffer and substrate, a second layer comprising an InGaAs N collector on the InP N buffer and substrate, a plurality of InGaAs P bases on the InGaAs N collector layer, and a plurality of InAIAs N emitters is described. Each emitter of the plurality of InAIAs N emitters is on a different base of the plurality of InGaAs P bases. The hetero-junction phototransistor comprises a plurality of InGaAs N+ caps, wherein each cap of the plurality of InGaAs N+ caps is on a different emitter of the plurality of InAIAs N emitters. The hetero-junction phototransistor comprises one or more electrical contacts. Each of the one or more electrical contacts is on a different cap of the plurality of InGaAs N+ caps.

Abstract: Systems and methods for operating a focal plane array are provided. The operations can be stored as command sequences stored in a command queue established in memory provided as part of reconfigurable focal plane electronics. Each command sequence can include definitions of a plurality of image frames that are executed in series. The configurations of the defined frames can be the same as or different from one another. Moreover, the frame definitions can specify a number of focal plane array parameters, such as gain, full frame or window, and integration time. The sequence of focal plane array parameters can be provided to the focal plane array as a command stream at the direction of a state machine implemented by the reconfigurable focal plane electronics. New commands containing different frame commands can be loaded into the command queue without requiring reconfiguration of the electronics.

Abstract: Methods and systems for generating an estimate of a bit error rate of a signal are provided. Methods and systems include obtaining an eye mask for a receiver, receiving a signal with the receiver, generating an eye mask probability density function of the eye mask, generating an eye diagram probability density function based on the signal, calculating a product of the eye mask probability density function and the eye diagram probability density function, summing the product of the eye mask probability density function and the eye diagram probability density function, and estimating the bit error rate of the signal based on the summing of the product of the eye mask probability density function and the eye diagram probability density function.

Abstract: Integrated chemical propellant and cold gas propulsion systems and methods are provided. A storage or fuel tank containing the chemical propellant is pressurized by a pressurant. The chemical propellant is selective passed to a propellant thruster through a first port of the storage tank and a propellant valve. The pressurant is selectively passed to a cold gas thruster through a second port of the storage tank and a cold gas valve. In addition, a pressurant tank can be provided. Pressurant contained within the pressurant tank can be selectively placed in communication with the pressurant contained within the storage tank via a pressurant valve, or can be selectively passed to the cold gas thruster through the cold gas thruster valve. Systems can also include bi-propellant thrusters, with a first and second chemical compounds and volumes of pressurant stored in first and second storage tanks respectively.

Abstract: Transmitter tracking systems and methods are provided that utilize a phased array antenna. With the antenna forming a beam that is pointed in a first direction for a first frequency, a plurality of radio frequency (RF) signals, each associated with different carrier frequency and produced by a first transmitter, are received. The amplitudes of the received signals are used to determine whether the beam is pointed at the first transmitter. The amplitude information can also be used to determine a direction in which to point the beam if it is determined that the beam is not pointed at the first transmitter. The systems and methods can be applied to 5G, satellite communication, or other systems incorporating a phased array antenna.

Abstract: Systems and methods for forming radio frequency beams in communication systems are provided. Signals from one or more devices are received at a base station and are processed using a vector based deep learning (VBDL) model or network. The VBDL model can receive and process vector and/or spatial information related to or part of the received signals. An optimal beamforming vector for a received signal is determined by the VBDL model, without reference to a codebook. The VBDL model can incorporate parameters that are pruned during training to provide efficient operation of the model.

Abstract: An antenna system circuit board stack with feed vias and with non-feed vias is disclosed. An antenna system circuit board stack as disclosed herein can include a plurality of patches or radiating elements formed on a common plane comprising a first surface of a circuit board. Each radiating element is electrically connected to one or more feed vias. In addition non-feed vias extend through, but are electrically isolated from, the radiating elements. An antenna system as disclosed herein enables the costs associated with multiple beam antenna systems, including but not limited to 5G communication systems, to be reduced as compared to alternative techniques.

Abstract: Microwave radiometers (MRs) and methods for detecting microwave emissions using an electro-optical receiver that incorporates a photonic integrated circuit are provided. The electro-optical receiver includes an electro-optic modulator that modulates received radio frequency signals onto an optical carrier signal supplied by a pump laser. The resulting upconverted signal, containing the full spectrum of the radio frequency signals, is divided into channels by an optical filter. Each of the channels is connected to a corresponding photodetector, which produces an electrical output having an amplitude that is proportional to the amplitude of the received optical signal. The components included in the photonic integrated circuit can be formed on a single substrate. In addition, the optical filter can filter the received full spectrum optical signal into a large number of channels (e.g. greater than 50).

Abstract: Methods and systems for generating an estimate of a bit error rate of a signal are provided. Methods and systems include obtaining an eye mask for a receiver, receiving a signal with the receiver, generating an eye mask probability density function of the eye mask, generating an eye diagram probability density function based on the signal, calculating a product of the eye mask probability density function and the eye diagram probability density function, summing the product of the eye mask probability density function and the eye diagram probability density function, and estimating the bit error rate of the signal based on the summing of the product of the eye mask probability density function and the eye diagram probability density function.

Abstract: Heat transfer systems and methods are provided. The heat transfer system includes an evaporator section integrated with or thermally joined to a heat dissipating system. The evaporator section is connected to a condenser section by a conduit. Together, portions of the evaporator section, the condenser section, and the conduit form a closed volume containing a heat transfer fluid. A superhydrophobic surface is present on at least a portion of the condenser section forming a part of the closed volume. The superhydrophobic surface can include a plurality of carbon nanotubes. The carbon nanotubes can be provided as a forest of carbon nanotubes extending from a rough surface.

Abstract: Methods and systems for identifying occupied areas of a radio frequency (RF) spectrum, identifying areas within that RF spectrum that are unusable for further transmissions, and identifying areas within that RF spectrum that are occupied but that may nonetheless be available for additional RF transmissions are provided. Implementation of the method then systems can include the use of multiple deep neural networks (DNNs), such as convolutional neural networks (CNN's), that are provided with inputs in the form of RF spectrograms. Embodiments of the present disclosure can be applied to cognitive radios or other configurable communication devices, including but not limited to multiple inputs multiple output (MIMO) devices and 5G communication system devices.

Abstract: Systems and methods for isolating radio frequency (RF) signals in high frequency circuit assemblies, including but not limited to 5G communication systems, are provided. The circuit assemblies include an RF suppression structure, which can be in the form of a low ohm resistor, that extends across a transmission line, and that has contacts that are electrically joined to a ground plane. Alternatively or in addition, the circuit assemblies include a low ohm resistor that extends over a transition between a signal via and an end of a transmission line, and that has contacts that are electrically joined to a ground plane. A circuit assembly as disclosed herein can further include multiple low ohm resistors spaced apart from one another by a distance that is a fraction of a wavelength of a highest frequency signal carried by the transmission line.