Mission Overview

This spacecraft, named after the famous Indian astronomer, was India's first satellite and was completely designed and fabricated in India. It was launched by a Soviet rocket from a Soviet cosmodrome. The spacecraft was quasispherical in shape containing 26 sides and contained three experiments for the measurement of cosmic X rays, solar neutrons, and Gamma rays, and an ionospheric electron trap along with a UV sensor. The spacecraft weighed 360 kg, used solar panels on 24 sides to provide 46 watts of power, used a passive thermal control system, contained batteries, and a spin-up gas jet system to provide a spin rate of not more than 90 rpm. There was a set of altitude sensors comprised of a triaxial magnetometer, a digital elevation solar sensor, and four azimuth solar sensors. The data system included a tape recorder at 256 b/s with playback at 10 times that rate. The PCM-FM-PM telemetry system operated at 137.44 MHz. The necessary ground telemetry and telecommand stations were established at Shar Centre in Sriharikota, Andhra Pradesh.

Launch Date: 1975-04-19 at 07:40:00 UTC
Launch Vehicle: Intercosmos II, Russia
Launch Site: Kapustin Yar, India
Decay Date: 1992-02-11

Trajectory Details
Type: Orbiter
Central Body: Earth
Epoch start: 1975-04-19 00:00:00 UTC

Orbital Parameters
Periapsis 568.0 km
Apoapsis 611.0 km
Period 96.5 minutes
Inclination 50.70000076293945°
Eccentricity 0.003083999967202544


X-Ray Astronomy

This experiment used an argon plus carbon-dioxide-filled proportional counter with an 8-deg FWHM field of view parallel to the spacecraft spin axis to detect X rays in the 2.5-15 keV range and two nai scintillation telescopes, one blocked for instrumental background, mounted perpendicular to the spin axis to detect emission in the 10-100 keV range.

Solar Neutron and Gamma Rays

This investigation was concerned with the study of energetic neutrons from 20 to 500 MeV and gamma rays from 0.2 to 24 MeV. Although it was intended to measure those particles and photons associated with violent outbursts from the sun, the data were only accumulated in real time from 11 orbits. This permitted a study of atmospheric neutrons and gamma rays. During this time, some events showing sudden increases in gamma ray counting rates were recorded. The detector system consisted of a 12.5-cm-diameter, 1.27-cm-thick csi (TL) crystal coupled to a 12.5-cm-diameter pm tube that was completely enclosed in a 1-cm thick, plastic, scintillator anticoincidence shield. This shield was viewed by four 3.8-cm-diameter pm tubes.

A pulse shape discriminator was used for energy deposition in the csi crystal › 5 MeV to distinguish neutrons from gamma rays, and pulse height analysis was accomplished by a 64-channel analyzer. For pulses below 5 MeV, attributed to low-energy gamma rays, three energy-loss windows of 0.2 to 0.4, 0.4 to 1 and 1 to 4 MeV were measured. The charged particle flux was monitored by measuring the coincidence rates between the central and shield crystals as well as the singles rate of the shield. The data rates were scanned every second and transmitted through the spacecraft telemetry.

Ionospheric Electron Trap and UV Chambers

This experiment objective was to used an electron trap to measure electron energies up to 100 eV, and to use UV chambers to monitor the scattered Lyman-alpha radiation and oxygen emissions in the night sky.


The data produced a spectrum of the diffuse background over the energy range 14-200 keV.