NOPR Collection:

Some anomalous behaviour of GPS/GLONASS constellations during meteor shower of 18 Nov. 1998

Mon, 01 Feb 1999 00:00:00 GMT

Title: Some anomalous behaviour of GPS/GLONASS constellations during meteor shower of 18 Nov. 1998 Authors: Banerjee, P; Mukherjee, Somik; Mathur, B S Abstract: Anticipating that during the recent visit of the comet 55p(Temple-Tuttle), the overall system performance of GPS/GLONASS would be affected, the GPS/GLONASS signals were monitored during that time at National Physical Laboratory, New Delhi. Initial observation indicated a significant degradation of position accuracy in GPS/GLONASS mix mode. The accuracy had been found to reach its nominal value in about 25 h after the event. Anomalies were also found in residual errors of pseudoranges. Page(s): 53-54

Simulation of secondary radiation pattern of MSMR antenna

Mon, 01 Feb 1999 00:00:00 GMT

Title: Simulation of secondary radiation pattern of MSMR antenna Authors: Sharma, S B; Sriharsha, C Abstract: Simulation of secondary radiation pattern of the multi frequency scanning microwave radiometer (MSMR) has been presented in this paper. Simulated patterns are used, as many practical difficulties have been encountered during measurements. Aperture integration in conjunction with geometric theory of diffraction has been used for simulation of secondary pattern of offset parabolic reflector. The simulated and measured results are presented and fairly good agreement has been observed between them. Page(s): 43-52

Field aligned current and parallel electric field between magnetosphere and ionosphere of Mars

Mon, 01 Feb 1999 00:00:00 GMT

Title: Field aligned current and parallel electric field between magnetosphere and ionosphere of Mars Authors: Haider, S A; Seth, S P; Raina, K S Abstract: A steady state kinetic model is used to estimate the electron current density at different potential differences between the magnetosphere and ionosphere of Mars. For this calculation it is assumed that Mars has a weak dipole magnetosphere whose plasma sheet is connected to the ionosphere along the magnetic field lines. The total electron flux of 5.79×10⁸ cm^-2 s^-1 is calculated in the Martian magnetosphere corresponding to the downward current density of 1.0×10^-6 A/m² at zero potential difference. The maximum flux of thermal electrons escaping towards the plasma sheet of Mars at zero current density is calculated to be 3.0×10⁸ cm^-2 s^-1. At zero current density the precipitating flux of plasma sheet electrons is approximately equal to maximum escape flux of thermal electrons. The calculated results are found to be in reasonable agreement with the experimental data obtained from Hyperbolic Ret arding Potential Analyzer (HARP) experiment onboard Phobos-2 . Page(s): 36-42

Performance analysis of an HF radio link between India and Antarctica

Mon, 01 Feb 1999 00:00:00 GMT

Title: Performance analysis of an HF radio link between India and Antarctica Authors: Pasricha, P K; Vijayakumar, P N; Aggarwal, S; Lakshmi, D R; Reddy, B M Abstract: This paper presents an analysis of the performance of the HF radio link, via the ionosphere, between a place near Delhi and the indian Antarctic station Maitri. The observations pertain to the rising part of solar activity in 1988-89. An analysis of optimum traffic frequency (FOT) and circuit reliability has been made separately at the two stations. The operational frequencies are found to be compatible with some of the available predictions of FOT. The theoretically computed periods of HF propagation are seen to match with the observed operation periods and demonstrate the utility of HF for communications with Antarctica. Page(s): 26-35