U R Rao
Articles written in Proceedings – Section A
Volume 47 Issue 1 January 1958 pp 30-40
Expressions have been obtained for the Geometrical Sensitivity as a function of the zenith angle of a cosmic ray telescope comprising of counter trays of rectangular dimensions. The Radiation Sensitivity and Cumulative Sensitivity have also been calculated, assuming a zenith angle attenuation of the form Iθ=Iθ.cos2θ for cosmic ray intensity.
Volume 66 Issue 6 December 1967 pp 353-359
The observations of omnidirectional X-ray flux at the top of the atmosphere have been extended upto 200 KeV using a balloon-borne NaI (Tl) scintillator detector at Hyderabad, India. The omnidirectional flux at 60 KeV is found to be 0·0066±0·0014 photons/cm.2 sec. ster. KeV. The X-ray flux in the energy range 50–290 KeV can be adequately represented by the spectrum Ke−2.2±0.4. New upper limits to the hard X-ray flux from the quiet sun have also been obtained from the same measurement.
Volume 70 Issue 6 December 1969 pp 257-274
The results on the flux of low energy X-rays in the range 2–18 Kev from Sco-X1, Tau-X1 and Cen-X2 celestial sources observed during two rocket flights, flown from the Thumba Equatorial Rocket Launching Station (TERLS), Trivandrum, India, are presented. The absolute flux and the energy spectrum obtained for these sources are compared with other similar observations. The results indicate a long-term exponential decrease in the energy flux of X-rays from Sco-X1 over the period 1965–1968. The X-ray source Cen-X2, which showed a remarkable outburst of X-rays in April 1967, had ceased to be active after May 1967. We present here the first evidence of the rediscovery of the low energy, X-ray flux from Cen-X2 since May 1967. These short-lived X-ray out-bursts may be attributed to a shock wave from the nova outburst expanding into the circumstellar medium.
Volume 72 Issue 5 November 1970 pp 236-245
The present paper describes the construction and working of a high frequency capacitance rocket payload for the measurement of electron concentration in the ionosphere, designed and fabricated mostly with indigenous components. This payload was flight-tested in the first and second Indian Centaure test rocket launched on 26-2-1969 and 7-12-1969 from Thumba Equatorial Rocket Launching Station. The paper also presents the calibration procedures and some of the preliminary results obtained from the first flight to show the capabilities of the instrument.
Volume 73 Issue 3 March 1971 pp 134-147
The results of the first low energy gamma-ray (0.2 to 1 MeV) measurements at equatorial latitudes conducted by two-balloon flights over Hyderabad, India (7.6° N GM), are presented. The energy resolution of the detectors was sufficient to detect the γ-ray peak at 0.5 MeV due to the electron-positron annihilation. The flux of the 0.5 MeV photons was found to be 0.090 ± 0.012 photons/cm2 sec at an atmospheric depth of 10 gm cm2 and 0.048 ± 0.011 photons/cm2 sec at the top of the atmosphere. Comparison of our results with those obtained at higher latitudes, show the existence of a considerable latitude variation of the 0.5 MeV flux, about a factor of 4 between 55° and 7° latitudes at an altitude of 10 gm/cm2.