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.

Dynamic mechanical properties of thermoplastic elastomers from polypropylene–natural rubber blend

Abstract: The dynamic mechanical properties of thermoplastic elastomers from polypropylene natural rubber blends have been evaluated with special reference to the effect of blend ratio and extent of dynamic crosslinking of the elastomer phase The effects of HAF black and silica fillers have also been studied It has been found that increasing the proportion of elastomer phase reduced the storage modulus and increased the loss tangent values of the blends The effect of dynamic crosslinking was found to be more prominent in blends containing higher proportion of elastomer phase The improvement in storage modulus and decrease in loss tangent values were quite remarkable with increase in extent of crosslinking in these blends The 70:30 NR:PP blend was found to exist as a two-phase system, both the components forming continuous phases of the blend

Low energy neutral atom imaging on the Moon with the SARA instrument aboard Chandrayaan-1 mission

Abstract: This paper reports on the Sub-keV Atom Reflecting Analyzer (SARA) experiment that will be flown on the first Indian lunar mission Chandrayaan-1. The SARA is a low energy neutral atom (LENA) imaging mass spectrometer, which will perform remote sensing of the lunar surface via detection of neutral atoms in the energy range from 10 eV to 3 keV from a 100km polar orbit. In this report we present the basic design of the SARA experiment and discuss various scientific issues that will be addressed. The SARA instrument consists of three major subsystems: a LENA sensor (CENA), a solar wind monitor (SWIM), and a digital processing unit (DPU). SARA will be used to image the solar wind-surface interaction to study primarily the surface composition and surface magnetic anomalies and associated mini-magnetospheres. Studies of lunar exosphere sources and space weathering on the Moon will also be attempted. SARA is the first LENA imaging mass spectrometer of its kind to be flown on a space mission. A replica of SARA is planned to fly to Mercury onboard the BepiColombo mission.

Dynamics of solar wind protons reflected by the Moon

Abstract: [1] Solar system bodies that lack a significant atmosphere and significant internal magnetic fields, such as the Moon and asteroids, have been considered passive absorbers of the solar wind. However, ion observations near the Moon by the SELENE spacecraft show that a fraction of the impacting solar wind protons are reflected by the surface of the Moon. Using new observations of the velocity spectrum of these reflected protons by the SARA experiment on board the Chandrayaan-1 spacecraft at the Moon, we show by modeling that the reflection of solar wind protons will affect the global plasma environment. These global perturbations of the ion fluxes and the magnetic fields will depend on microscopic properties of the object's reflecting surface. This solar wind reflection process could explain past ion observations at the Moon, and the process should occur universally at all atmosphereless nonmagnetized objects.

Threshold height (h′F)c for the meridional wind to play a deterministic role in the bottom side equatorial spread F and its dependence on solar activity

Abstract: [1] Detailed investigations have been carried out on the occurrence of bottom side Equatorial Spread F (ESF) and the thermospheric meridional wind characteristics just before the former's initiation using ground based ionospheric data corresponding to the equinoctial periods of 1993–1998, from Trivandrum (8.5°N, 76.5°E, dip = 0.5°N) and Sriharikota (13.7°N, 80.2°E, dip ∼ 10°N) in the Indian longitudes. Critical analysis of the base height of the F-region h′F at the time of triggering of ESF and the polarity of the meridional winds revealed that, if the h′F is above a certain level ESF occurred under both equatorward and poleward wind conditions. Below that level, ESF occurred only when equatorward winds were present implying that the equatorward winds must somehow be able to offset the reduced growth rate of the plasma instability responsible for ESF. A plausible explanation linking Equatorial Ionization Anomaly (EIA) and the consequent Equatorial Temperature and Wind Anomaly (ETWA) and the consequent neutral dynamics effectively enabling the instability even at lower height has been offered. The threshold height (h′F)c gleaned out on the basis of the polarity of the meridional winds has been shown to bear a linear relation to the solar activity and sheds light on the enigmatic short and long term variability of ESF.