Design of Orbit Controls for a Multiple CubeSat Mission Using Drift Rate Modulation

For the low-cost improvement of laser communication, which is critical for various applications such as surveillance systems, a study was conducted on relative distance control based on orbital drift rate modulations for multiple CubeSats during formation flying. The VISION mission covered in this paper comprises two CubeSats to demonstrate laser communication technology in space. During the mission, the deputy CubeSat changes the relative distance to execute mission objectives within various scenarios. Impulsive controls decrease, maintain, and increase the relative distance between the CubeSats by changing the orbital drift rates. The simulation results indicated that the desired orbital operation can be conducted within a given ΔV budget. In addition, the errors in the orbit determination, thrust maneuvers, and time synchronization were analyzed to satisfy the mission requirements. The mass-to-area ratio should be matched to adjust the relative distance between satellites with different properties by drift rate modulation. The proposed orbit control method appropriately operated the VISION mission by adjusting the drift rate modulation. The results of this study serve as a basis for the development of complex orbit control simulations and detailed designs that reflect the characteristics of the thrust module and operational aspects.

Intra-Group Orca Call Rate Modulation Estimation Using Compact Four Hydrophones Array

Acoustic emissions are vital for orca (Orcinus orca) socializing, hunting, and maintaing spatial awareness. Studying the acoustic emissions of orcas on an individual basis often results in interference with their natural behaviors through mounting tags or following by boat. In order to analyze their inter- and intra-group communication, we propose a study allowing us to associate vocalizations with their emitter (matriline and when possible individual). Such a non-interfering device for allocating calls to individual orcas could substantially boost our understanding of their complex acoustic world. Our experimental protocol was based on a compact array of four hydrophones fixed near the shore, operable up to 1 km away from the path of orcas. It was used during summer 2019 at the research station OrcaLab, northern Vancouver Island, Canada. A total of 722 calls were extracted, jointly with visual identification and azimuth of surfacing orcas, allowing validation of the acoustic diarization and azimuth estimations of the orca calls. We then calculated the Call Rate (CR) for each matriline or when possible individual in order to describe their acoustic activity. Preliminary results show that CR could be modulated according to the distance of the signaler from a group, the presence of another group, or anthropic pressure.

Development of a metric for predicting people's responses to gusting wind noise in automobiles

Automobile manufacturers are trying to improve the interior noise environment in their cars. A more thorough understanding of how people perceive the noise is an important step towards this goal. The focus of the current research is on modeling the acceptability of time-varying wind noises containing gusts. A listening test was designed containing sounds that were simulated on the computer, based on pre-defined airflow profiles. The time-varying noises in the test follow one of two simple gusting scenarios. The primary scenario contained two segments of steady wind flanking a series of consecutive equal-strength gusts. The number, duration, and strength of the gusts were varied between sounds. This was done to examine general trends of acceptability with modulation rate, modulation depth, and duration. The second scenario contained two gusts of equal or unequal strength, occurring either without a break or separated by a time gap. This was done to examine the relationship between people's reactions to the individual gusts in a pattern and their reactions to the whole pattern. A small number of steady-wind noises were included for reference. Terms in an acceptability model containing a previously proposed gusting metric were estimated. Possible refinements to the metric and model are discussed.

Experience-Driven Rate Modulation is Reinstated During Hippocampal Replay

Replay, the sequential reactivation of a neuronal ensemble, is thought to play a central role in the hippocampus during the consolidation of a recent experience into a long-term memory. Following a contextual change (e.g. entering a novel environment), hippocampal place cells typically modulate their in-field firing rate and shift the position of their place field, providing a rate and place representation for the behavioral episode, respectively. However, replay has been largely defined by only the latter- based on the fidelity of sequential activity across neighboring place fields. Here we show that dorsal CA1 place cells in rats can modulate their firing rate between the replay of two different contexts, mirroring the same pattern of rate modulation observed during behavior. This context-driven rate modulation within replay events was experience-dependent, observable during both behavioral episodes and throughout the subsequent rest period, but not prior to experience. Furthermore, we demonstrate that both the temporal order and firing rate of place cells can independently be used to decode contextual information within a replay event, revealing the existence of two separable but complementary neural representations available for memory consolidation processes.

Selective modulation of population dynamics during neuroprosthetic skill learning

Learning to control a brain-machine interface (BMI) is associated with the emergence of coordinated neural dynamics in populations of neurons whose activity serves as direct input to the BMI decoder (direct subpopulation). While previous work shows differential modification of firing rate modulation in this population relative to a population whose activity was not directly input to the BMI decoder (indirect subpopulation), little is known about how learning-rated changes in cortical population dynamics within these groups compare. To investigate this, we monitored both direct and indirect subpopulations as two macaque monkeys learned to control a BMI. We found that while the combined population increased coordinated neural dynamics, this coordination was primarily driven by changes in the direct subpopulation while the indirect subpopulation remained relatively stable. These findings indicate that motor cortex refines cortical dynamics throughout the entire network during learning, with a more pronounced effect in ensembles causally linked to behavior.