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• Three characteristically different plasma structures viz. EMSTID, plasma depletion and non-electrified MSTID were observed simultaneously. • The individual structures underwent evolution, distortion, and dissipation separately. • The lack of mutual interaction between these three structures, despite existing simultaneously, is highly unusual. An unusual event of three characteristically different plasma structures on a geomagnetically quiet night (Ap = 4) of 08 July 2018 has been investigated in this paper using an all-sky imager installed at Hanle, Ladakh (32.7°N, 78.9°E; Mlat. ∼ 24.1°N), India. These structures include a freshly generated electrified medium scale traveling ionospheric disturbances (EMSTID), ambiguous plasma depletions, and a northward propagating non-electrified MSTID. One of the most fascinating aspects of this event was the lack of mutual interaction between the three structures, even though they existed simultaneously and propagated in different directions. They individually underwent evolution, distortion, and dissipation separately. One of the structures was an EMSTID, which got generated within the imager's field-of-view (FOV) and evolved with time. As time progressed, different strip-like structures travelled southwestward, merged with each other to form the EMSTID. The second structure was plasma depletions which appeared in the southeastern part of the FOV. They eventually merged into a single band, which propagated nearly westward. The merged band evolved with time, extended further northward, and dissipated later. Along with these, a very rare non-electrified MSTID structure with east–west aligned fronts was observed which propagated northward. Its fronts underwent distortion, became curved and dissipated. In this study, we have explored the role of electrodynamics behind the observed unique features of the three plasma structures. [ABSTRACT FROM AUTHOR]

The Surface Water and Ocean Topography (SWOT) mission, which is scheduled to launch in 2022, would offer India with unprecedented hydrologic applications. This study presents the preliminary results of the CNES Large-Scale SWOT Hydrology Simulator to illustrate how SWOT data can be used to monitor reservoir water levels. Except for some factors such as effects due to topography, and error due to idealized water detection, the CNES simulator accounts for practically all of the probable noise expected in future SWOT data. In this paper, we look at how SWOT can be used to monitor reservoirs in difficult situations. SWOT will monitor the reservoir in two swaths in this case, with an unmonitored zone in the middle. This paper provides a strategy for extrapolating data across two swaths to determine reservoir volume. The results demonstrate that the proxy water surface elevation (WSE) created by the CNES simulator has a great potential in scientific research relating to reservoir characteristics and surface water dynamics. It is observed that the reservoir volume estimated using proxy SWOT data has a maximum bias of −7.65 % and a minimum bias of −2.19 %. [ABSTRACT FROM AUTHOR]

Total electron data (TEC) from GPS nowadays can be used as a tool for understanding the space weather phenomena. The development of prediction model for TEC is quiet crucial and challenging due to the dynamic behavior of the ionosphere, since it depends on different factors such as seasonal, diurnal and spatial variations, solar geomagnetic conditions etc. In this paper, an attempt is made for predicting the GPS derived TEC values for different GNSS stations over India using a hybrid method based on Ensemble empirical mode decomposition (EEMD) and Long Short-Term Memory (LSTM) deep learning method. The daily TEC time series data from the IISc Bangalore (Latitude 13.021, Longitude 77.570), Lucknow (Latitude 26.912, Longitude 80.956) and Hyderabad (Latitude 17.417, Longitude 78.551) stations over India during the period 2008 to 2015 of solar cycle 23 and 24 is used for analysis. The assessment of model performance for testing predicted output compared with LSTM and EMD-LSTM models, and their comparison results show that the hybrid EEMD-LSTM model presents better than the other models. [ABSTRACT FROM AUTHOR]

Lightning is a sudden release of electrostatic energy that plays a significant role in the ionospheric-magnetospheric coupling process. A short-term increase in the particle count rates (CR) in the Van Allen Radiation Belt (VAB) is known as the particle bursts. Due to lightning events, the increase in the number of high-energy particles in the inner region of the VAB (L < 2) is a fascinating research to implement. This paper tries to determine the number of lightning-induced particles, which can successfully establish a connection between the two regions of the atmosphere (the ionosphere and the magnetosphere). Lightning-generated electromagnetic radiation propagates through the Earth Ionosphere Waveguide (EIWG), where some energy leaks through and scatters particles in the radiation belt. By lowering the pitch angle, some particles precipitate into the ionosphere and cause secondary ionization. This excess particle count caused by lightning strokes is detected using data from the NOAA-15 satellite and data from the World Wide Lightning Location Network (WWLLN) is used to verify the relationship between lightning stroke and particle count. In this paper, we process our work by using lightning locations over a specific region of India and the geographic/geomagnetic conjugate locations. The monthly variation shows a high correlation between the lightning stroke number and the particle counts within the conjugate geomagnetic location, while the correlation with the particle counts within the conjugate geographic location is significantly lower. In the second half of the paper, we use an automated energy filtration method, for the computation of the particle counts induced by maximum energetic lightning (having lightning energy value > 104 J and the particle counts induced by minimum energetic lightning (having lightning energy value < 104 J). The results of this analysis demonstrate that the variation of PCs in the conjugate geomagnetic location is more closely related to the maximum energetic lightning variation than the lowest energetic lighting variation. This paper will demonstrate the coupling process between the ionosphere and the magnetosphere based on counting the particles produced by lightning. [ABSTRACT FROM AUTHOR]

India has been voluntarily following the guidelines on space debris mitigation recommended by UN-COPUOS (United Nations Committee on the Peaceful Uses of Outer Space) and IADC (Inter-Agency Space Debris coordination Committee) to the maximum possible extent towards safe and sustainable operations in outer space. As a part of the ongoing efforts for better compliance with these guidelines, post-mission disposal of Low-Earth-Orbit (LEO) objects has been carried out in the recent past. Cartosat-2, which was operational at 630 km altitude, is the first satellite to be de-orbited at its end-of-life through a series of perigee reduction orbit maneuvers to minimize its presence in the LEO region. Consequently, the post-mission orbital lifetime was reduced from more than 30 years to less than 5 years in compliance with the 25-year rule recommended in IADC space debris mitigation guidelines. The de-orbiting exercise utilizing left-over propellant also achieved the objective of minimising any accidental break-up risk. This paper outlines the relevant analyses and planning aspects of post-mission de-orbiting for Cartosat-2. The lessons learnt and recommendations on post-mission disposal for future LEO missions are also presented. [ABSTRACT FROM AUTHOR]

• A detail study of rain fade at Ka band over tropical region has been done. • Performance comparison of experimental link at 20/30 GHz with ITU-R model done. • "s" parameter relating fade slope to filter characteristics is calculated. Dynamic characteristics of Ka band rain fade (or rain attenuation) over tropical region are relatively less studied, though they are essential for implementation of suitable fade mitigation techniques. In this paper, dynamic characteristics of rain fade at 20 GHz and 30 GHz from GSAT-14 satellite are reported with experimental measurements at Ahmedabad, India. ITU-R model for fade slope probability distribution has been analyzed in this paper and Ka band rain fade has been investigated based on this fade-slope analysis. The ITU-R model is found to closely match 20 GHz measurements, though differences increase at 30 GHz. Fade slopes are found to be within ±0.5 dB/s at both 20 and 30 GHz. Both positive and negative slopes of the fade slope distributions are quasi-similar. ITU-R model's s parameter, relating fade slope to filter characteristics, is found to be very close to the measured value for this region. Distributions of fade slopes are also found to be dependent on the standard deviation values similar to ITU-R recommendation at 20 GHz, but significant deviation is observed at 30 GHz. This observed frequency dependency might be due to increase in cloud attenuation at high frequencies or may be due to limited data set. Results indicate needs of further experimental data at high frequencies from other tropical regions to gain further insight into the fade slope characteristics. This will ultimately help in designing a better prediction model in future. [ABSTRACT FROM AUTHOR]

We have installed a multi-wavelength allsky airglow imager over the Indian Himalayan region at Hanle, Leh Ladakh, (32.7°N, 78.9°E; dip lat. ∼24.1°N). This is the first of its kind that is installed in the Himalayan region at an altitude of around 4200 m above the mean sea level. The high sensitive thermoelectrically cooled CCD based imager is equipped with two interference filters (557.7 nm and 630.0 nm with a bandwidth of 2 nm). The airglow imaging observations have been carried out during moonless nights since June 2018. This paper presents the detailed steps of the image processing techniques to transform the raw images into the geospatially-calibrated images and discusses the process for the estimation of gravity wave parameters (horizontal wavelength, apparent phase velocity and periodicities) from the processed images. In addition, we report a few interesting events like Ripple-type structures, gravity waves and mesospheric bores in the mesopshere and lower thermosphere (MLT) region and the plasma disturbances in the ionospheric F region observed for the first time over Hanle, Leh Ladakh. [ABSTRACT FROM AUTHOR]

This review article briefly brings out the historical development of atmospheric sodium (Na) measurements over India and the importance of coordinated measurements with multiple techniques to address physical processes in the Earth's upper atmosphere. These measurements were initiated in the early 1970s by observing Na airglow emission intensities with broad band airglow photometer from Mt. Abu, a low-latitude hill station in India. Considerable amount of night-to-night variations in nocturnal emission intensities of the Na airglow were observed. Later, investigations regarding the dependence with the magnetic activities from the equatorial and low latitudes were carried out and double-humped structures in the nocturnal variation of intensities were reported. With the advent of Na lidar at Gadanki around 2005, the measurements of atmospheric neutral Na atom concentration became possible and more frequent occurrences of sporadic Na layers over the magnetic low latitude station compared to other latitudes were detected indicating the role played by electrodynamics. Later, a possible relationship between E-region field aligned plasma irregularities and the concentration of neutral Na atoms was investigated using coordinated measurements of VHF radar and Na lidar. Further, simultaneous measurements with Na lidar and a narrow band airglow photometer with narrow field of view brought out the importance of coordinated observation wherein the characterization of gravity waves could be carried out and also revealed the importance of collisional quenching due to ambient molecules in the Na airglow emission processes. In addition, combining the ground based measurements of Na lidar and meteor wind radar along with satellite measurements made possible to hypothesize the over-turning Kelvin–Helmholtz billow in the Na layer manifests "C-type" or inverted lambda shape structures in the height-time-concentration map of neutral Na atoms. This review paper presents a synoptic view mostly based on the previously reported observations of Na airglow emission, Na lidar and coordinated Na airglow and Na lidar observations from the Indian sector and highlights the importance of simultaneous measurements of mesospheric Na and its emissions along with satellite-borne measurements to address interesting geophysical processes in the Earth's upper atmosphere. [ABSTRACT FROM AUTHOR]

Abstract Indian Space Research Organization (ISRO) has developed an indigenous system named Indian Regional Navigation Satellite System (IRNSS) or NavIC (Navigation with Indian Constellation), that consists of 7 satellites and transmits navigation signal in L and S bands. ISRO, for validation of the system, has installed many IGS (IRNSS/GPS/SBAS) receivers scattered over the Indian region. Using preliminary data from two geographically widely separated stations over India, this paper presents the results on studies on parameters of IRNSS signal quality and discusses how these parameters may be used to study the ionospheric behavior over the Indian region. The results show the importance and advantages of using IRNSS data for such studies. [ABSTRACT FROM AUTHOR]

Abstract Indian region is expected to receive signal from multiple satellite-based navigation systems for multi-GNSS hybrid operation. Even in presence of GPS, GLONASS and GALILEO signals together, it is regularly found that, during some parts of the day no GNSS satellite is available above 60° elevation angle from large parts of India. This may cause problem in seamless navigation solutions in the locations, where visibility of the satellites is also obstructed in the lower elevation angles, which is a common feature in Indian urban conditions; the situation also degrades satellite geometry. IRNSS/NavIC is Indian indigenous regional navigation system operational since 2016. This paper presents theoretical, simulated and initial results of real-time studies on IRNSS/NavIC visibility from India using a IRNSS-GPS-SBAS (IGS) receiver. The studies show that, in such situations of inferior GNSS satellite visibility, IRNSS/NavIC operating together with GPS, can augment this time-dependent degraded visibility conditions. The Indian satellite navigation system ensures presence of at least one satellite above 60° elevation for use with GPS over the Indian region, supports multi-GNSS operation towards seamless solution, and improves satellite geometry. [ABSTRACT FROM AUTHOR]

Abstract This paper investigated the performance of the latest International Reference Ionosphere model (IRI-2016) over that of IRI-2012 in predicting total electron content (TEC) at three different stations in the Indian region. The data used were Global Positioning System (GPS) data collected during the ascending phase of solar cycle 24 over three low-latitude stations in India namely; Bangalore (13.02°N Geographic latitude, 77.57°E Geographic longitude), Hyderabad (17.25°N Geographic latitude, 78.30°E Geographic longitude) and Surat (21.16°N Geographic latitude, 72.78°E Geographic longitude). Monthly, the seasonal and annual variability of GPS-TEC have been compared with those derived from International Reference Ionosphere IRI-2016 and IRI-2012 with two different options of topside electron density: NeQuick and IRI01-corr. It is observed that both versions of IRI (i.e., IRI-2012 and IRI-2016) predict the GPS-TEC with some deviations, the latest version of IRI (IRI-2016) predicted the TEC similar to those predicted by IRI-2012 for all the seasons at all stations except for morning hours (0500 LT to 1000 LT). This shows that the effect of the updated version is seen only during morning hours and also that there is no change in TEC values by IRI-2016 from those predicted by IRI-2012 for the rest of the time of the day in the Indian low latitude region. The semiannual variations in the daytime maximum values of TEC are clearly observed from both GPS and model-derived TEC values with two peaks around March-April and September-October months of each year. Further, the Correlation of TEC derived by IRI-2016 and IRI-2012 with EUV and F10.7 shows similar results. This shows that the solar input to the IRI-2016 is similar to IRI 2012. There is no significant difference observed in TEC, bottom-side thickness (B0) and shape (B1) parameter predictions by both the versions of the IRI model. However, a clear improvement is visible in hmF2 and NmF2 predictions by IRI-2016 to that by IRI-2012. The SHU-2015 option of the IRI-2016 gives a better prediction of NmF2 for all the months at low latitude station Ahmedabad compare to AMTB 2013. [ABSTRACT FROM AUTHOR]

Abstract: The paper deals with the study of temporal and spatial variation of equatorial ionization anomaly (EIA) phenomenon along with its dependence on solar activity and season during the 19th solar cycle by using seven Indian ionosonde stations. Present study is an attempt to carry out the comprehensive study of EIA by using the limited number of ground based instruments. This has been achieved by performing the Gaussian fitting over the latitudinal distribution of F2-region critical frequency (foF2) data. Results reveal that the phenomenon of EIA has a strong dependence on solar activity and seasons. The EIA crest exhibits the feature of latitudinal shifting and expansion with increasing solar activity. It is found out that the effect of solar cycle and seasons on EIA is local time dependent. The observations were also compared with the IRI-2001 model predictions and results reveal that the model values are in general agreement with the observed values with some discrepancies, particularly during the high solar activity period and morning sector. The results have been discussed in the light of relative contribution from transequatorial interhemispheric neutral wind and strength of equatorial fountain process during different local time, season and solar activity levels. Furthermore, an attempt is made to parameterize the location and foF2 of the EIA crest by using the regression analysis. These results can be used to predict the latitudinal position and foF2 of the EIA crest for any given 12-month running average sunspot number (R12). [Copyright &y& Elsevier]

Abstract: The paper describes behavior of surface ozone, its precursor gases, BC along with TOCC, TWVC, AOT1020nm as well as UV and IR radiation intensities observed during the partial solar eclipse of 15th January, 2010 over Udaipur, where 52% solar disc is obscured due to the moon’s shadow. During the beginning to main eclipse phase, the deviation values of several air pollutants concentrations from eclipse to control day values vary in a small range from −9 to −2ppb in case of surface ozone and −180 to −80 ppb for CO. The corresponding change in the values of BC observed from −3.3 to −.5μg/m3. No significant change is found in NO2, NO or in ratio of NO2/NO values during the partial eclipse time. TOCC values decrease from 3 to 5DU along with a reduction in UV radiation intensity from 20 to 35% from starting to the main eclipse phase. The AOT1020nm values are found to increase from .2 to 1.0 along with a reduction in IR radiation intensity order of 50%. However, TWVC values decrease from .22 to .1cm during the eclipse hours. The low level of dilution in surface ozone in eclipse period may be attributed with change in local atmospheric boundary layer dynamic conditions or limited air pollutants dispersion, in term of decreases in planetary boundary layer height, wind speed and hence ventilation coefficient in the same eclipse hours. Thus, present studies support the argument for the leading roles of photochemical reactions with its precursor gases under presence of solar radiation in surface ozone variability. Other possible controlling factors are advection of air pollutants from the polluted region as evident from backward wind trajectories and altering the local meteorological conditions. [Copyright &y& Elsevier]

Abstract: Occurrence of Spread F is more or less a daily phenomenon in the equatorial and low latitudinal stations during high to moderate sunspot number years. In this paper efforts have been made to identify possible precursors of Equatorial Spread F (ESF) using the Total Electron Content (TEC) data of seven GAGAN (GPS Aided Geo Augmented Navigation) stations in India during the two equinoxes of moderate sunspot number year 2004. Large Scale Periodic Structures found prior to TEC bite out can be taken as possible precursors to ESF. A threshold value of the peak to peak amplitude of this wave structure is chosen 2.6 TEC unit above which there is a possibility of ESF or TEC bite out with S4>0.26. [Copyright &y& Elsevier]

Abstract: Increasing demand of bandwidth in communication satellites has forced satellite links to be designed in Ku bands and above. But at these frequencies, rain and other tropospheric elements result in large attenuation. To mitigate the tropospheric attenuation of microwave satellite signals above 10GHz using any standard Fade Mitigation Technique (FMT), it is essential to have a priori knowledge about the level of attenuation. Hence, short-term rain attenuation prediction models play a key role in maintaining the link in which necessary compensation can be applied depending on the early information of attenuation. This paper presents a method of attenuation prediction using Adaptive Artificial Neural Network. Here In situ Learning Algorithm (ILA) has been used to enable the system to track the non-stationary nature of the attenuation. To validate this, Ku Band data, collected at three different sites in India have been used for the purpose of prediction. The performance of the algorithm is determined through the estimation of prediction accuracy by comparing the predicted values with the measured data. Results obtained using the mentioned technique shows considerably good accuracy even up to 20s of prediction interval with acceptable ratio between the under and over predictions. The prediction performance is evaluated for different prediction intervals. Furthermore the present model is also compared with the persistence model and the relative performance is quantified. [Copyright &y& Elsevier]

Abstract: GPS satellites data obtained at Bhopal (23.16° N, 77.36° E, geomagnetic latitude 14.23° N) India were analyzed to study the TEC changes during several geomagnetic storms (−300nT

Abstract: It is shown in this paper for the first time that the intensity of the daytime thermospheric O(1D) 630.0nm airglow as measured by the ground-based dayglow photometer over Trivandrum (8.5°N; 77°E; dip lat. 0.5°N), a geomagnetic dip equatorial station, exhibit a direct correlation with the electron density at 180km. This altitude is about ∼40km lower than the believed centroid of the O(1D) 630.0nm dayglow emission i.e. 220km. This observation is contrary to the understanding of the behavior of O(1D) 630.0nm dayglow over equatorial/low latitudes. Over these latitudes, the variations of the measured intensity of O(1D) 630.0nm dayglow are known to be associated with the changes in the electron density at altitudes around 220km, the centroid of this emission. In this context, the present results indicating the lowering of the peak altitude of O(1D) 630.0nm emission from ∼220 to ∼180km over the dip equator is new. Recent results on solar XUV flux indicate that this could be an important parameter that controls the O(1D) 630.0nm dayglow excitation rates through modulations in the neutral and ionic composition in lower thermosphere-ionosphere region. However, the lowering of the centroid of O(1D) 630.0nm emission, as shown in this study, has been ascribed primarily to the fountain effect associated with the equatorial ionization anomaly. [Copyright &y& Elsevier]

Abstract: Highly sophisticated balloon-borne scientific payloads have stringent requirement on the telemetry and command system. The development and fabrication of the on-board TT&C package for telemetry, tracking, command, safety and ranging for these experiments is done in-house at the National Balloon Facility (NBF) at Hyderabad. In the last few years, we have made major improvements both in the ground station and the on-board sub-systems, thereby improving the data quality, data handling speed and the general flight control along with aviation safety. The new system has telemetry data rate up to 1Mbps. A reduction in weight, power and cost of the reengineered on-board integrated package has also lead to the ease of operation during field tests prior to launch and at remote recovery sites. In this paper, we describe the details of the new control package, its flight performance and our plans for portable S-band telemetry and telecommand system to cater to the balloon flights from Antarctic station and long duration balloon flights. [ABSTRACT FROM AUTHOR]

Abstract: In this paper, the shortwave and longwave anisotropy for clear sky Indian desert scene has been estimated using long-term surface data, radiative transfer calculations and Helmholtz reciprocity for missing values. This study is important in the perspective of the low inclination satellites like Megha–Tropiques (MT) mission, carrying Scanner for Radiation Budget (ScaRaB) payload, which will provide broadband radiative fluxes at the top of the atmosphere (TOA). Due to low inclination angle, the angular models for clear sky land scenes for the MT-ScaRaB orbits will be dominated by desert points. The Angular Distribution Models (ADMs) determined in this study were compared with existing desert models. It is observed that for longwave radiation, the largest disagreement is observed for higher values of viewing zenith angle, especially for the summer season, where the difference in flux can reach up to 13W/m2. For the shortwave radiation, higher values of both solar zenith angle and viewing zenith angle cause largest incongruity in the computed albedo from the different models, suggesting the need of caution in interpretation of the flux computations from these bins. In fact at the higher solar zenith angle bin, the disparity in albedo can go up to 6.4%. [Copyright &y& Elsevier]

Abstract: The present study deals with the impact of extensive anthropogenic activities associated with festivities and agricultural crop residues burning in the Indo-Gangetic Plains (IGP) on satellite-derived reflectance during November 2007. Intense smoke plumes were observed in the IRS-P4 OCM satellite data over IGP associated with agricultural crop residue burning during the study period. Terra-MODIS AOD and CALIPSO LIDAR backscatter datasets were analysed over the region to understand the spatial and temporal variation of the aerosol properties. Ground-based measurements on aerosol optical properties and black carbon (BC) mass concentration were carried out during 7–14 November 2007 over urban region of Hyderabad, India. Top of the Atmosphere (TOA) reflectance estimated from IRS-P4 Ocean Color Monitor (OCM) data showed large variations due to anthropogenic activities associated with crop residue burning and fireworks. Atmospheric corrections to OCM satellite data using 6S radiative transfer code with inputs from ground and satellite measurements could account for the variations due to differential aerosol loading. Results are discussed in this paper. [Copyright &y& Elsevier]

Abstract: The present paper deals with the application of Support Vector Machine (SVM) and image analysis techniques on NOAA/AVHRR satellite image to detect hotspots on the Jharia coal field region of India. One of the major advantages of using these satellite data is that the data are free with very good temporal resolution; while, one drawback is that these have low spatial resolution (i.e., approximately 1.1km at nadir). Therefore, it is important to do research by applying some efficient optimization techniques along with the image analysis techniques to rectify these drawbacks and use satellite images for efficient hotspot detection and monitoring. For this purpose, SVM and multi-threshold techniques are explored for hotspot detection. The multi-threshold algorithm is developed to remove the cloud coverage from the land coverage. This algorithm also highlights the hotspots or fire spots in the suspected regions. SVM has the advantage over multi-thresholding technique that it can learn patterns from the examples and therefore is used to optimize the performance by removing the false points which are highlighted in the threshold technique. Both approaches can be used separately or in combination depending on the size of the image. The RBF (Radial Basis Function) kernel is used in training of three sets of inputs: brightness temperature of channel 3, Normalized Difference Vegetation Index (NDVI) and Global Environment Monitoring Index (GEMI), respectively. This makes a classified image in the output that highlights the hotspot and non-hotspot pixels. The performance of the SVM is also compared with the performance obtained from the neural networks and SVM appears to detect hotspots more accurately (greater than 91% classification accuracy) with lesser false alarm rate. The results obtained are found to be in good agreement with the ground based observations of the hotspots. This type of work will be quite helpful in the near future to develop a hotspots monitoring system using these operational satellites data. [Copyright &y& Elsevier]

Abstract: In this paper we report pulsing hiss emissions observed at the low latitude station, Jammu (geomag. lat. 22°26′N, L =1.17) in which intensity decreases with the increase in frequency. The entire dynamic spectra contain somewhat irregular structure. To explain these we propose that the hiss emissions are generated through Doppler-shifted cyclotron interactions near the equator and propagate to the earth in the whistler-mode. Further, ULF waves present in the generation region modulate the intensity of the emission resulting in the pulsing nature. The growth rates are computed and discussed in the light of recent works. [Copyright &y& Elsevier]

Abstract: The paper reports the nightglow observations of hydroxyl (8–3), (7–2) and (6–2) Meinel band carried out at a low latitude station Kolhapur (16.8°N, 74.2°E, dip latitude 10.6°N), India during November 2002 to May 2005 with the objective of investigating mesopause dynamics based on derived OH rotational temperature. Overall, 132 nights of quality data were collected using filter-tilting photometer and an all-sky scanning photometer. The mean mesopause temperature observed at Kolhapur is 195±11, 196±9 and 195±7K from OH (8–3), (7–2) and (6–2) band emissions, respectively, using transition probabilities given by Langhoff et al. [Langhoff, S.R., Werner, H.J., Rosmus, P. Theoretical transition probabilities for the OH Meinel system. Journal of Molecular Spectroscopy 118, 507–529, 1986]. Small wave-like variations (periodicities ∼ few hours) existing over long period variations in derived temperatures are also present. A steady decrease of emission intensities from evening to dawn hours has been observed in approximately 59% of nights. No significant change of nightly mean temperatures has been noted. Furthermore, about 62% of observed nightly mean temperatures lie within one error bar of MSISE-90 model predictions. [Copyright &y& Elsevier]

Abstract: In this paper, the variability of F2-layer critical frequency foF2 is examined, using modern digital ionosonde observations at a low-middle latitude station, New Delhi (28.6°N, 77.2°E, Dip 42.4°N). Data used for the present study are the hourly values of foF2 for the periods of high (2001–2002) and low (2004–2006) solar activity. To investigate the foF2 variability, the values of median, lower quartile and upper quartile are estimated at each hour for different seasons, during both the solar activity periods. The variability index (henceforth referred to as VI) of foF2 is then obtained by using inter-quartile difference and its percentage ratio to the median. Results show that VI is in general, lower during daytime hours than by night during high solar activity for all the seasons, while during low solar activity, VI behavior is irregular during all the seasons. A solar activity dependence of VI is found with maximum values during periods of low solar activity in all the seasons except for winter during pre-dawn and post-sunset hours. Comparisons of observations with IRI-2001 model [Bilitza, D. International Reference Ionosphere 2000. Radio Sci. 36 (2), 261–275, 2001] show in general good agreement during both the solar activity periods, with model values lying within inter-quartile range. [Copyright &y& Elsevier]

Abstract: Established in 1971, the National Balloon Facility operated by TIFR in Hyderabad, India, is a unique facility in the country, which provides a complete solution in scientific ballooning. It is also one of its kind in the world since it combines both, the in-house balloon production and a complete flight support for scientific ballooning. With a large team working through out the year to design, fabricate and launch scientific balloons, the Hyderabad Facility is a unique centre of expertise where the balloon design, research and development, the production and launch facilities are located under one roof. Our balloons are manufactured from 100% indigenous components. The mission specific balloon design, high reliability control and support instrumentation, in-house competence in tracking, telemetry, telecommand, data processing, system design and mechanics is its hallmark. In the past few years, we have executed a major programme of upgradation of different components of balloon production, telemetry and telecommand hardware and various support facilities. This paper focuses on our increased capability of balloon production of large sizes up to 780,000m3 using Antrix film, development of high strength balloon load tapes with the breaking strength of 182kg, and the recent introduction of S-band telemetry and a commandable timer cut-off unit in the flight hardware. A summary of the various flights conducted in recent years will be presented along with the plans for new facilities. [Copyright &y& Elsevier]

Abstract: Dust storms are common during the summer season over the Indo-Gangetic basin and are considered to be a major health hazard to millions of people living in the basin. In countries like India, there is no early warning made for dust outbreaks and as a result the day-to-day life is affected by these dust events. In this paper, efforts have been made to utilize multi sensor data to study the characteristics of dust storms. Moderate Resolution Imaging Spectroradiometer and Multiangle Imaging SpectroRadiometer images clearly show dust storm events over the Indo-Gangetic basin. The Total Ozone Mapping Spectroradiometer (TOMS) Aerosol Index and the Advanced Microwave Sounding Unit (AMSU) data over the western end of the Indo-Gangetic basin have been analyzed. These data show characteristic behavior of brightness temperature and Aerosol Index due to dust, which change significantly as dust migrates towards east over Kanpur. The TOMS Aerosol Index and the AMSU brightness temperature (T b) show a characteristic anti-correlation, which confirms the presence of a dust storm over Indo-Gangetic basin. [Copyright &y& Elsevier]