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Earlier sources: Space
Space research and engineering study the universe and build the systems used to reach and observe it. Follow astronomy, spacecraft, launch systems, satellites, exploration, and Earth observation.
SYMTRI organizes observations from public sources into a living map. Connections reflect shared subject matter; they do not establish causation or endorse a source.
Open in the map ↗532 classified signals in the fourteen-day window. Recent momentum: steady. These counts include signals awaiting readable evidence.
Earlier sources
Up to ten sources with readable evidence, ordered by their feed timestamp. These archive sources can be older than the live fourteen-day window. This list is a sample, not a measure of total activity. Dates distinguish paper publication, repository creation, model/dataset activity, Hacker News posts, and KEV catalog additions. “First archived” records when SYMTRI first stored the signal.
- arXiv · Published · First archived
On the altitude profile of lower ionospheric D-region response time delay during solar flares ↗
The D-region ionosphere is sluggish in nature while responding to the incoming solar radiation. We study the altitude (h) profile of mid-latitude D-region response time delay (Delta t) during three chosen solar flares, namely, C5.2, M5.2, and X2.2 classes. We solve "electron continuity equation" numerically at each and every h to obtain Delta t-h profile. We investigate the 1) latitudinal variation (over both Northern and Southern hemispheres) and 2) seasonal variation (throughout the year) of Delta t-h profiles of each of these solar flares separately. We go over noteworthy variations of Delt…
- arXiv · Published · First archived
QCD Crossover Transfer Functions for Scalar-Induced Gravitational Waves in the PTA Band ↗
Pulsar timing array (PTA) collaborations have reported evidence for a stochastic gravitational wave (GW) background in the nHz band. Should scalar-induced GWs, sourced at second order by enhanced primordial curvature perturbations, contribute to this signal, a coincidence of scales makes them directly sensitive to the softening of the equation of state around the QCD crossover. We solve the tensor and scalar equations of motion across the Standard Model (SM) thermal history and tabulate the transfer functions for direct use in present and future PTA analyses. We show that this SM effect modifi…
- arXiv · Published · First archived
Matter density perturbations in Quadratic Gravity ↗
We investigate linear matter-density perturbations in full quadratic gravity. Working in the longitudinal gauge and adopting the sub-horizon and quasi-static approximations, we obtain an algebraic expression for the effective gravitational coupling in the theory and the equation for evolution of matter density perturbations. We identify the positive-real poles of this coupling and map their dependence on the quadratic couplings. In the formal infrared continuation, the reduced coupling recovers its general-relativistic value, whereas at large physical wavenumber it is suppressed when both quad…
- Hacker News · Posted on Hacker News · First archived
SpaceX given unique access to classified DoD space tracking data, sources say ↗
Hacker News discussion.
- arXiv · Published · First archived
Uber-calibration-based Two-level Radial-velocity Zero-point Correction for APOGEE ↗
APOGEE delivers high-resolution, near-infrared spectroscopy and highly precise radial velocities (RVs), with extensive repeat observations spanning more than a decade. Long-term RV repeatability is nevertheless limited by instrumental zero-point systematics: exposure-to-exposure drift and fiber-dependent offsets that are only partially tracked by lamp-based wavelength calibration, and that can evolve as fibers are serviced or replaced. We infer and remove these zero points directly from the published per-visit RVs using an uber-calibration framework based on shared repeat observations. We solv…
- arXiv · Published · First archived
A Possible Complication of Using the 4.14 μm band to Assess D/H Ratios on Icy Bodies ↗
Determining isotopic ratios on the surfaces of extraterrestrial objects can provide insight into their formation conditions and evolution. Recently, remote-sensing detections of the 4.14 μm HDO absorption band have enabled astronomers to estimate the D/H ratio on several icy objects in the outer solar system. Here, we quantify how ice phase and radiation processing affect the 4.14 μm absorption band. While the band is visible in H2O-ice samples with a crystalline component, we cannot detect it in amorphous H2O-ice. Furthermore, we find that radiation processing, using 10 keV electrons as a pro…
- arXiv · Published · First archived
A Collisional Origin for Ice-rich Iapetus and Titan's Anomalous Eccentricity ↗
We test whether collisions involving Titan can eject enough water-rich material onto sufficiently distant Saturn-bound orbits to form Iapetus, while also accounting for Titan's orbital eccentricity. Three-dimensional impact calculations and post-impact trajectories examine initially Saturn-unbound and bound impactors. In the oblique unbound case with a differentiated impactor roughly a tenth the mass of Titan at a speed of 10 km s\(^{-1}\), outgoing predominantly icy material from a selected population totaling about 3.5 times Iapetus's mass remains Saturn-bound for days after impact. We track…
- Hacker News · Posted on Hacker News · First archived
Calculating atmospheric drag on satellites for a Cubesat [pdf] ↗
Hacker News discussion.
- OpenAlex · Published · First archived
Robust Adaptive Beamforming via MEPS-Based Covariance Matrix Reconstruction and Steering Vector Estimation in Space-Polarization Joint Domain for Mainlobe Interference Suppression ↗
In scenarios where mainlobe interference and steering vector (SV) mismatch coexist, conventional robust adaptive beamforming techniques are prone to main-beam distortion, desired signal self-cancellation, and degradation of output performance. To address this problem, this paper proposes a mainlobe interference suppression method based on robust adaptive beamforming in the space-polarization joint domain. Firstly, the extended form of the Maximum Entropy Power Spectrum (MEPS) for polarization-sensitive arrays is theoretically derived. Owing to the high-resolution capability of MEPS under limit…
- OpenAlex · Published · First archived
A Harmonic-Energy Regional-Control Jamming Method Based on a Radiating Space–Time-Modulated Digital Metasurface ↗
Complex electromagnetic warfare poses increasingly stringent requirements on the spatial selectivity of jamming systems. Existing jamming methods mainly focus on false-target generation, while research on regional coverage of harmonic energy remains limited. In this paper, a harmonic-energy regional-control jamming method based on a radiating space–time-modulated digital metasurface is proposed. By optimizing the turn-on instants and duty cycles of 1-bit programmable elements, the amplitude, phase, and far-field superposition of the target harmonic are controlled, thereby constructing a predef…
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How to assess evidence about Space
Check each original source for its methods, release status, limitations, and supporting data. A repository announcement, a preprint, and a published study provide different kinds of evidence. SYMTRI’s subject classification helps discovery; it does not independently validate the source’s claims.
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