U R Rao Satellite Centre

We present a comprehensive spectro-polarimetric and timing analysis of 12 black hole X-ray binaries, namely Cyg X-1, 4U 1630-47, Cyg X-3, LMC X-1, 4U 1957 + 115, LMC X-3, Swift J1727.8-1613, GX 339-4, Swift J151857.0-572147, IGR J17091-3624, MAXI J1744-294, and GRS 1915 + 105, using quasi-simultaneous observations from IXPE (Imaging Xray Polarimetry Explorer), NICER (Neutron star Interior Composition Explorer), NuSTAR (Nuclear Spectroscopic Telescope Array), and AstroSat. Timing analyses reveal type-B and type-C quasi-periodic oscillations across different spectral states, often associated with episodic radio ejections. Broad-band (0.7-60 keV) spectral modelling, employing disc, Comptonization, and reflection components, reveals degeneracies in constraining disc-corona geometries. Polarimetric measurements in 2-8 keV band detect significant polarization degrees (PDs) ranging from 3 per cent-20.6 per cent (1.2 per cent-21.4 per cent) in harder (softer) states, with moderate to strong energy dependence, except for LMC X-1, Swift J151857.0-572147, and MAXI J1744-294, where no significant polarization is detected. We report polarization detections of Cyg X-3 (PD similar to 21.4 per cent, soft intermediate state), LMC X-3 (PD similar to 2.4 per cent, high-soft state), and IGR J17091-3624 (PD similar to 9 per cent , low-hard state) using recent IXPE observations. A positive correlation is found between PD and Comptonized photon fraction (cov(frac)), while an anticorrelation is observed with disc-to-Comptonized flux ratio (F-ratio) across spectral states. Combined timing, spectral, and polarimetric results, together with constraints from radio jet observations, suggest a radially extended corona within a truncated disc for Cyg X-1, Swift J1727.8-1613, IGR J17091-3624, and GX 339-4, whereas the disc-corona geometry remains poorly constrained for 4U 1957 + 115, LMC X-3, and 4U 1630-47. We discuss the implications of these findings for understanding accretion geometries and highlight prospects for future X-ray polarimetric studies.

With the rise of environmental concerns, the use of polymer materials obtained from renewable and bio-based resources has become a vital sustainable practice. Bio-based aerogels obtained from naturally occurring polymer resources offer numerous advantages. However, they face challenges such as fragility and sensitivity to surface conditions. To address these issues, our work focuses on the development of chitosan-Al3+-microcrys-talline cellulose based aerogel, for flame retardancy, thermal insulation and sound absorption applications. The aerogel prepared was having very low density (0.08 +/- 0.004 g/cm3) and excellent flame retardancy with a LOI, PHRR and THR value of 48%, 14.46 kW/m2 and 2.3 MJ/m2 respectively. The surface modification of the prepared aerogel was done by crosslinking using silane mixture which significantly improved the hydrophobicity and other properties. The modified aerogel obtained was having low density (0.102 +/- 0.003 g/cm3), high contact angle (131 degrees +/- 0.25), high thermal stability (180 degrees C) and a high sound absorption coefficient value of 0.98 at 6300 Hz. The LOI, PHRR and THR value of the modified aerogel was 42%, 39.10 kW/m2 and 10 MJ/m2 respectively. Additionally, the aerogels show good chemical resistance, long term stability and low environmental impact during life cycle assessment. These exceptional properties of the obtained aerogels show their promising potential in the field of sustainable insulation, fire retardancy and sound proofing applications for aerospace, automobile and construction sector.

Satellites operate in a remote and inaccessible environment, making in-orbit maintenance and repair extremely challenging. Continuous telemetry is therefore monitored to assess spacecraft health and support timely decision-making. With the availability of large volumes of historical telemetry data, data-driven approaches have become essential for automated health monitoring and early anomaly warning. This paper presents a forecasting-based early anomaly detection framework for satellite telemetry. The proposed approach first predicts future telemetry values and then detects anomalies based on violations of statistically derived upper and lower control limits. Classical time-series models, namely Auto Regressive Integrated Moving Average (ARIMA) and Seasonal Auto Regressive Integrated Moving Average (SARIMA), are evaluated alongside deep learning models, including Long Short-Term Memory (LSTM) and Gated Recurrent Unit (GRU) networks. A case study using offline telemetry from the Dynamically Tuned Gyro (DTG) subsystem of a decommissioned satellite is presented. The models are trained on historical data to forecast upcoming telemetry values, and the predicted values are used to provide early warning of anomalies. The results demonstrate that the proposed forecasting-based detection approach can successfully provide advance indication of anomaly occurrence, with predicted anomaly timing closely matching the actual event.The case study focuses on a known anomaly observed . The proposed model successfully generated an anomaly alert, demonstrating a one-day early warning capability. The presented framework can be extended to real-time monitoring of critical telemetry parameters for in-service satellites, enabling proactive health management and improved operational reliability.

The Chandrayaan-3 mission, ISRO’s first successful lunar landing mission consisted of a Propulsion Module (PM) and a Lander Module (LM), with Rover accommodated inside Lander. Chandrayaan-3 Lander was a challenging mission considering the critical mission operations and stringent requirements on propulsion, structure and other bus systems of the spacecraft. The biggest challenge in this mission was to design and develop the entire satellite and conduct the sufficient ground tests within a minimal period to target the optimum launch opportunity. The configuration and panel layout design of the bus systems and the payloads posed a challenge in terms of mass optimization, thermal requirements, field of view clearances for sensors, payloads, Center of Gravity (CG) and Inertia control and the short time available for realization. The paper presents the details of the aspects considered by the Integration team for the configuration design, panel layout and development of this prestigious satellite and the strategies worked out to meet these challenges.

We present a broadband X-ray study of the transient hyperluminous X-ray source (HLX), 2SXPS J111416.1+481833, in the galaxy NGC 3583, using archival XMM-Newton, NuSTAR, Chandra data, and long-term Swift/XRT monitoring. The source episodically enters the hyperluminous regime with X-ray luminosities L_X > 10^41 erg s^-1 and drops by a factor of >45 from its peak into a deep low state. We detect a clear spectral cutoff at ∼5-6 keV in the broadband spectra, which are well modeled by a soft thermal component combined with optically thick thermal Comptonization or an inner advection-dominated disk. In the XMM-Newton spectra, we detect a statistically significant (≳ 3.9 σ) absorption line centered at E_ line≈ 1.97 ± 0.04 keV with a width of σ_ line≈ 74 ± 40 eV. We primarily interpret the line as a candidate proton Cyclotron Resonance Scattering Feature (CRSF), implying a local magnetic field strength of B ∼ 4 × 10^14 G. Alternative interpretations, such as an origin in an ionized outflow, were explored and found to be less likely. We do not detect coherent X-ray pulsations, placing 90