Training opportunities in remote sensing in India

The paper deals with the Indian experience in training the resources scientists in the fast developing field of remote sensing and the facilities available for obtaining such training in India. The necessity of imparting training to the scientists at different levels is brought out. An outline of the training curriculum of a leading institution is described in some detail.     

Model calculations of the dayside ionosphere of Venus

Model calculations of the dayside ionosphere of Venus are presented. The coupled continuity and momentum equations were solved for O₂⁺, O⁺, CO₂⁺, C⁺, N⁺, He⁺, and H⁺ density distributions, which are compared with measurements from the Pioneer Venus ion mass spectrometer. The agreement between the model results and the measurements is good for some species, such as O⁺, and rather poor for others, such as N⁺, indicating that our understanding of the dayside ion composition of Venus is incomplete. The coupled heat conduction equations for ions and electrons were solved and the calculated temperatures compared with Pioneer Venus measurements. It is shown that fluctuations in the magnetic field have a significant effect on the energy balance of the ionosphere.     

On kinematics of gas clouds in the broad-line region of active galactic nuclei and quasars

The kinematics of gas clouds in broad-line region of active galactic nuclei and quasars is considered. The motion of the clouds is governed by three forces — gravitational influence from the central supermassive body, radiational pressure from the continuum radiation, and resistance of the intercloud medium. Clouds moves radial but only outward motion gives a velocity field, which is in accordance with the observational data. The profiles of the permited lines are obtained in some simplify assumptions for the emissive capacity of the gas in clouds, and are in good agreement with the observational data. In the framework of the model under consideration there is a possibility to estimate some physical parameters of the nuclei such as mass of the central body and density of the intercloud medium.     

Sunspot motions and magnetic shears as precusors of flares

Using full-disc white light photoheliograms, we have studied umbrae motion and variations in sunspot areas in a large activity complex over 4 solar rotations. On the basis of the observational data we illustrate with typical examples to what extent rapid spot motions are associated with flare occurrences.     

An instrument for DC electric field and AC electric and magnetic field measurements aboard ‘Intercosmos-Bulgaria-1300’ satellite

The instrument IESP-IPMP represents the complex unit measuring the vector of the DC electric field, the vectors of the electric and magnetic field in the frequency range of 0.2 – 6.5 Hz (wave form), autocorrelation functions of waves with frequencies of 0.1 – 5 kHz, and wave amplitudes in 8 bandpass channels. Some results are shown and compared in the various frequency ranges.     

The pinhole/occulter facility

The Pinhole/Occulter Facility concept uses a remote occulting mask to provide high resolution observations of the solar corona and of astronomical X-ray sources. With coded-aperture and Fourier-transform techniques, the Pinhole/Occulter makes images at a resolution of 0.2 arc sec for 2 - 120 keV X-rays, using a 50-m boom erected from the payload bay of the Space Shuttle or mounted on a free-flying platform. The remote occulter also creates a large shadow area for solar coronal observations; the Pinhole/Occulter concept includes separate optical and ultraviolet telescopes with 50-cm apertures. These large telescopes will provide a new order of resolution and sensitivity for diagnostic observations of faint structures in the solar corona. The Pinhole/Occulter is a powerful and versatile tool for general-purpose X-ray astronomy, with excellent performance in a broad spectral band complementary to that accessible with AXAF. The large collecting area of 1.5 m² results in a 5σ detection threshold of about 0.02 μJy for the 2 - 10 keV band, or about 10^?5 ph(cm²sec keV)^?1 at 20 keV.     

Notes on SCPC-FM System Design and Performance

In many domestic satellite communication systems single-channel per-carrier FM (SCPC-FM) has become the accepted transmission method for thin route communication. The SCPC-FM modem operates over a wide range of carrier frequencies and is designed to use satellite power and bandwidth efficiently. It incorporates elements which make the signal transfer complex, so the system behavior is not immediately obvious. This article investigates the signal processes and analyzes the performance of a companded and preemphasized SCPC-FM system and it furnishes insight into the choice of crucial system parameters.     

Soviet launch failures reviewed

The USSR has always been reluctant to reveal details of failures in its space programme, and only a few failures have been annouced publically. Some official US sources list failures in the Soviet programme, although these official listings end in mid-1964. The aviation press often reports rumoured failures, and it is the job of an analyst to try and separate the wheat from the chaff.