Vikram Sarabhai Space Centre

About: Vikram Sarabhai Space Centre is a facility organization based out in Thiruvananthapuram, India. It is known for research contribution in the topics: Aerosol & Ultimate tensile strength. The organization has 2092 authors who have published 3058 publications receiving 47975 citations. The organization is also known as: VSSC.

Aerosol characteristics at a remote island: Minicoy in southern Arabian Sea

Abstract: Extensive measurements of aerosol optical and microphysical properties made at a remote island, Minicoy in southern Arabian Sea for the period (February 2006–March 2007) are used to characterize their temporal variability and Black Carbon (BC) mass mixing ratio. Large decrease in aerosol BC (from ∼800 ng m−3 to ∼100 ng m−3) was observed associated with change in airmass characteristics and monsoon rains. The total aerosol mass varied between ∼80 and 20 μg m−3. Though the total mass fell drastically, a slight increase in super micron mass was observed during the June–August period associated with high winds. The mass fraction of Black Carbon aerosols during the prevalence of continental airmass is found to be ∼1.2% of the composite aerosols, which is much lower than the values reported earlier for this region.

Epoxy‐cyanate ester shape memory thermoset: some aspects of phase transition, viscoelasticity and shape memory characteristics

Abstract: A shape memory thermoset comprising of a co-reacted system of epoxy resin (diglycidylether of bisphenol A), cyanate ester (bisphenol A dicyanate ester) and phenol telechelic poly(tetramethylene oxide) (PTOH) was investigated for its morphology, viscoelasticity and shape memory characteristics at the transition temperature regime. The system exhibited a switching temperature (Tswitch) centered at about 105°C. Atomic force microscopy analyses at different temperatures provided evidences for the existence of a discrete phase at Tswitch regime. Polarized light microscope images gave evidence for the birefringence and tubular crystal formation due to PTOH segments in the shape memory thermoset. It is concluded that the Tswitch has its origin from melting transition of PTOH and Tg of the thermoset matrix, the latter being lowered through plasticization by PTMO segments. Reversibility of Tswitch, and stress relaxation behavior of the blend were investigated by dynamic mechanical analysis (DMA). The reversibility of transition temperature was ascertained by cyclic DMA. Temperature dependency of shape memory properties implied fast recovery of original shape above the Tswitch. The cured system manifests shape memory properties even below Tswitch though it is a slow process. The extent of shape recovery increased with temperature and became faster in league with the trend in temperature dependency of stress relaxation of the polymer. Copyright © 2013 John Wiley & Sons, Ltd.

Observation of suprathermal argon in the exosphere of Mars

Abstract: The altitude profiles of argon-40 (Ar) in the Martian exosphere are reported using Mars Exospheric Neutral Composition Analyser aboard Indian Mars Orbiter Mission (MOM) from four orbits during December 2014 (Ls = 250°–257°), when MOM's periapsis altitude was the lowest. The upper limit of Ar number density corresponding to this period is ∼5 × 105 cm−3 (∼250 km), and the typical scale height is ∼16 km, corresponding to an exospheric temperature of ∼275 K. However, on two orbits, the scale height over this altitude region is found to increase significantly making the effective temperature >400 K. Neutral Gas and Ion Mass Spectrometer observations on the Mars Atmosphere and Volatile Evolution mission also indicate that the change in slope in Ar density occurs near the upper exosphere (around 230–260 km). These observations indicate significant suprathermal CO2 and Ar populations in the Martian exosphere. Significant wave-like perturbations are observed but only on certain days when suprathermal population is seen. Pickup ion-induced heating is discussed as the other viable source.

Seasonal dependence of the "forecast parameter" based on the EIA characteristics for the prediction of Equatorial Spread F (ESF)

Abstract: In an earlier study, Thampi et al. (2006) have shown that the strength and asymmetry of Equatorial Ioniza- tion Anomaly (EIA), obtained well ahead of the onset time of Equatorial Spread F (ESF) have a definite role on the subse- quent ESF activity, and a new "forecast parameter" has been identified for the prediction of ESF. This paper presents the observations of EIA strength and asymmetry from the Indian longitudes during the period from August 2005-March 2007. These observations are made using the line of sight Total Electron Content (TEC) measured by a ground-based bea- con receiver located at Trivandrum (8.5 N, 77 E, 0.5 N dip lat) in India. It is seen that the seasonal variability of EIA strength and asymmetry are manifested in the latitudinal gra- dients obtained using the relative TEC measurements. As a consequence, the "forecast parameter" also displays a def- inite seasonal pattern. The seasonal variability of the EIA strength and asymmetry, and the "forecast parameter" are discussed in the present paper and a critical value for has been identified for each month/season. The likely "skill fac- tor" of the new parameter is assessed using the data for a total of 122 days, and it is seen that when the estimated value of the "forecast parameter" exceeds the critical value, the ESF is seen to occur on more than 95% of cases.