Multipoint measurements of large electric fields and shears in the Auroral zone

This work presents results from the Auroral Turbulence II (AT II) sounding rocket launched from the Poker Flat Research Range, near Fairbanks, Alaska, on February 11, 1997. The rocket consisted of three identically instrumented payloads that reached an apogee of 550 km and flew through several arc structures in a pre-midnight auroral breakup. Three payload measurements were desired to separate the temporal from spatial aspects of auroral forms, and to investigate three dimensional flows and fields that cannot be resolved using traditional single point measurements. The focus of this study has been in the structure and changes in the dc electric field. Although the AT II payloads traversed many auroral arc structures, most of the forms had negligible electric fields associated with them. The one exception was when the payloads crossed a large, stable arc at nearly 500 km altitude. In the middle region of the arc, and near the poleward boundary, the payloads measured significant electric fields, as much as 450 mV/m in the poleward region of the arc. The payloads also measured different electric field structures, while approximately three kilometers apart, indicating a gradient in the field between measurements. Spectral analysis of the ac electric field data show broadband electrostatic waves in the regions of enhanced dc electric field. The multiple measurements indicate a region of spatially localized electric field, electric field shear and wave activity that both drifts in space and changes amplitude temporally. In-situ changes in the electric field are examined in parallel with all-sky imagery obtained near the footpoint of the payload trajectories. We have determined that there are errors in the dc electric field measurements that are most likely explained by a shadowing of the potential spheres by the payload. Despite the uncertainty in absolute, magnitudes of the dc field, there are clear differences in the field signatures between payload measurements that can be shown to be spatial shears. The shear in the localized electric field, the observed broadband electrostatic waves, and the low field aligned currents measured by the magnetometers indicate an instability mechanism responsible for the wave growth. The most likely candidate, given the environment, is the inhomogeneous energy density driven instability (IEDDI), which we believe to be responsible for the observed electrostatic waves observed near the oxygen cyclotron frequency

The Rogue Alpha and Beta Mission: Operations, Infrared Remote Sensing, LEO Data Processing, and Lessons Learned From Three Years on Orbit With Two Laser Communication-Equipped 3U CubeSats

The Aerospace Corporation\u27s Rogue-alpha, beta program was a rapid prototyping demonstration aimed at building and deploying an infrared remote sensing capability into low Earth orbit within 18 months. The two satellites and their data were then used for three years as an experimental testbed for future proliferated low Earth orbit (pLEO) constellations. Their launch took place on November 2, 2019, followed by boost and deployment of two identical spacecraft (Rogue-alpha and beta) by the Cygnus ISS cargo vessel into circular 460-km, 52° inclined orbits on January31, 2020. The primary sensors were 1.4-micron band, InGaAs short wavelength infrared (SWIR) cameras with640x512 pixels and a 28° field-of-view. The IR sensors were accompanied by 10-megapixel visible context cameras with a 37° field-of-view. Star sensors were also tested as nighttime imaging sensors. Three years of spacecraft and sensor operations were achieved, allowing a variety of experiments to be conducted. The first year focused on alignment and checkout of the laser communication systems, sensor calibration, and priority IR remote sensing objectives, including the study of Earth backgrounds, observation of natural gas flares, and detection of rocket launches. The second year of operations added study of environmental remote sensing targets, including severe storms, wildfires, and volcanic eruptions, while continuing to gather Earth backgrounds and rocket launch observations. The final year emphasized advanced data processing and exploitation techniques applied to collected data, using machine learning and artificial intelligence for tasks such as target tracking, frame co-registration, and stereo data exploitation. Mission operations continued in the final year, with an emphasis on collecting additional rocket launch data, and higher frame rate backgrounds data. This report summarizes the Rogue alpha, beta mission’s outcomes and presents processed IR data, including the detection and tracking of rocket launches with dynamic Earth backgrounds, embedded moving targets in background scenes, and the use of pointing-based registration to create fire line videos of severe wildfires and 3D scenes of pyrocumulonimbus clouds. Lessons learned from the experimental ConOps, data exploitation, and database curation are also summarized for application to future pLEO constellation missions

Remote Sensing Experiments Using the Rogue-alpha,beta CubeSats as a Constellation: High Frame Rate Environmental Observations from Agile, Taskable, Infrared and Visible Sensors in Low Earth Orbit

The Aerospace Corporation’s Rogue-alpha,beta program built and launched two 3-Unit CubeSats in 18-months, each equipped with modified commercial infrared camera payloads, visible context cameras, laser communications and precision pointing capabilities. Launched on November 2, 2019, the two spacecraft (Rogue-alpha and beta) were boosted and released from the International Space Station Cygnus NG-12 robotic resupply spacecraft on January 31, 2020 into a circular 460-km, 52° inclined orbit. The primary Rogue IR sensor is a 1.4-micron band, 640x512 pixel, 28° field of view, InGaAs short wavelength infrared (SWIR) camera. It is accompanied by a panchromatic, 10-megapixel, 37° field of view visible context camera. In addition, the narrow- and wide-field-of-view star sensors may also be utilized as nighttime sensors. During the first two years of spaceflight, the Rogue satellites conducted a series of experiments using both spacecraft to conduct cooperative remote sensing observations and to test the capabilities of the 1.4-micron water overtone band. These included: 1) fore-aft pointing using two spacecraft for stereo observations of cloud structure and altitude, 2) horizon-pointed imaging in all directions relative to the spacecraft orbit (fore, aft, port, and starboard) to maximize the imaged field of view, 3) pre-programmed point-and-stare imaging, 4) nadir-pointed operations for vicarious calibration with other satellites. All of these modes of operation are usually conducted in multi-frame collections at 1-20 frames-per-second for dozens to thousands of frames. During the mission we investigated different modes of collecting data, taking advantage of the evolving orbital spacing of the pair of CubeSats. Initial close satellite spacing allowed along-track fore-aft stereo observations of weather formations, as well as pre-programmed tip-and-queue observations, and sequential point-and-stare experiments aimed at collecting minutes of data on targets of interest. Cloud altitude was measured on weather events by simultaneous stereo observations, and by mono observations using the changing view angles during a constant point along track or slewing during a pass. Observations were collected on hurricanes, typhoons, thunderstorms, monsoon storms, and forecasted tornadic weather. Unique observations of severe wildfires were collected, exploring the capability for our 1.4micron band to detect fires during daytime, and to characterize pyrocumulonimbus clouds. Nighttime observations were also made of human lighting, infrared sources, and moonlight-illuminated clouds, including observations utilizing the Rogue satellites’ star sensors for remote sensing tests. These experiments collectively explored the possibilities for dynamically tasked, high-frame-rate, low-earth-orbit sensors to carry out weather and environmental monitoring missions in ways that differ from traditional scanned or push-broom satellite sensor systems. We will present a summary of our tasking ConOps, observations of weather events and fires, and highlight results and techniques for cloud height characterization by our two CubeSat constellation during its first two years on orbit. Our results with two satellites demonstrate possibilities for future missions using cooperative tasking in larger constellations of dynamically tasked sensors in low Earth orbit

Flight Operations of Two Rapidly Assembled CubeSats with Commercial Infrared Cameras: The Rogue-Alpha,Beta Program

The Aerospace Corporation’s Rogue-alpha, betaprogram, co-funded by the Space and Missile Systems Center’s Development Corps, is a rapid prototyping effort that built and launched two 3-Unit CubeSats equipped with modified commercial IR camera payloads, laser communications and precision pointing capabilities in 18-months. Launched on 2 November 2019, the two spacecraft were released from the ISS Cygnus NG-12 robotic resupply spacecraft on 31 January 2020 into a circular 460-km, 52° inclined orbit. The two Rogue spacecraft are serving as testbeds for studying wide-field-of-view fast-framing imaging, on-orbit stellar calibration techniques for small IR payloads, and associated spacecraft flight operations. Precision pointing is enabled by three star sensors. High data rate sensor observations are enabled by the ultra-compact 200 Mbps lasercom system, which downlinks gigabytes of stored data during a single laser contact, using The Aerospace Corporation’s prototype ground stations located in El Segundo, California. The Rogue-alpha, beta IR sensor is a 1.4 micron band, 640x512 pixel, 28° field of view, InGaAs SWIR camera. It is accompanied by a panchromatic, 10-megapixel, 37° field of view visible context camera. Modes of sensor operation have included: 1) horizon-pointed imaging in all directions relative to the spacecraft orbit (fore, aft, port, and starboard) which is designed to maximize the imaged field of view, 2) point-and-stare imaging, 3) nadir-pointed, and 4) stereo fore-aft pointing using both spacecraft. All of these modes of operation are usually conducted in multi-frame collections at 1-20hz for dozens to thousands of frames. Highlights from the Rogue-alpha, beta sensor Earth remote sensing observation experiments will be presented. These have included impressive video imagery of hurricanes, typhoons, thunderstorms, and high clouds in the intra-tropical convergence zone. Infrared and visible point sources studied include gas flares, wildfires, active volcanos, nighttime lights, and other phenomena, including the first infrared CubeSat observations of space launch upper stages in flight. Stereo cloud imaging observations were also conducted with an aim of better understanding Earth backgrounds from low Earth orbit. Highlights from the CubeSat flight operations experiments include: 1) spacecraft-to-spacecraft boresight alignment of Rogue’s lasercom systems, and 2) metric and radiometric calibration of Rogue’s flight cameras using bright infrared stars. The results from the Rogue-alpha, beta460-km orbit show the exciting possibilities for wide-field-of-view missions from low earth orbit

Glial Purinergic Signaling in Neurodegeneration

International audiencePurinergic signaling regulates neuronal and glial cell functions in the healthy CNS. In neurodegenerative diseases, purinergic signaling becomes dysregulated and can affect disease-associated phenotypes of glial cells. In this review, we discuss how cell-specific expression patterns of purinergic signaling components change in neurodegeneration and how dysregulated glial purinergic signaling and crosstalk may contribute to disease pathophysiology, thus bearing promising potential for the development of new therapeutical options for neurodegenerative diseases

Exacerbation of C1q dysregulation, synaptic loss and memory deficits in tau pathology linked to neuronal adenosine A2A receptor

International audienceAccumulating data support the role of tau pathology in cognitive decline in ageing and Alzheimer's disease, but underlying mechanisms remain ill-defined. Interestingly, ageing and Alzheimer's disease have been associated with an abnormal upregulation of adenosine A2A receptor (A2AR), a fine tuner of synaptic plasticity. However, the link between A2AR signalling and tau pathology has remained largely unexplored. In the present study, we report for the first time a significant upregulation of A2AR in patients suffering from frontotemporal lobar degeneration with the MAPT P301L mutation. To model these alterations, we induced neuronal A2AR upregulation in a tauopathy mouse model (THY-Tau22) using a new conditional strain allowing forebrain overexpression of the receptor. We found that neuronal A2AR upregulation increases tau hyperphosphorylation, potentiating the onset of tau-induced memory deficits. This detrimental effect was linked to a singular microglial signature as revealed by RNA sequencing analysis. In particular, we found that A2AR overexpression in THY-Tau22 mice led to the hippocampal upregulation of C1q complement protein-also observed in patients with frontotemporal lobar degeneration-and correlated with the loss of glutamatergic synapses, likely underlying the observed memory deficits. These data reveal a key impact of overactive neuronal A2AR in the onset of synaptic loss in tauopathies, paving the way for new therapeutic approaches

The role of infiltrating immune cells in dysfunctional adipose tissue

Adipose tissue (AT) dysfunction, characterized by loss of its homeostatic functions, is a hallmark of non-communicable diseases. It is characterized by chronic low-grade inflammation and is observed in obesity, metabolic disorders such as insulin resistance and diabetes. While classically it has been identified by increased cytokine or chemokine expression, such as increased MCP-1, RANTES, IL-6, interferon (IFN) gamma or TNFα, mechanistically, immune cell infiltration is a prominent feature of the dysfunctional AT. These immune cells include M1 and M2 macrophages, effector and memory T cells, IL-10 producing FoxP3+ T regulatory cells, natural killer and NKT cells and granulocytes. Immune composition varies, depending on the stage and the type of pathology. Infiltrating immune cells not only produce cytokines but also metalloproteinases, reactive oxygen species, and chemokines that participate in tissue remodelling, cell signalling, and regulation of immunity. The presence of inflammatory cells in AT affects adjacent tissues and organs. In blood vessels, perivascular AT inflammation leads to vascular remodelling, superoxide production, endothelial dysfunction with loss of nitric oxide (NO) bioavailability, contributing to vascular disease, atherosclerosis, and plaque instability. Dysfunctional AT also releases adipokines such as leptin, resistin, and visfatin that promote metabolic dysfunction, alter systemic homeostasis, sympathetic outflow, glucose handling, and insulin sensitivity. Anti-inflammatory and protective adiponectin is reduced. AT may also serve as an important reservoir and possible site of activation in autoimmune-mediated and inflammatory diseases. Thus, reciprocal regulation between immune cell infiltration and AT dysfunction is a promising future therapeutic target