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A moment of terror: During the first week of successful operation, there was an initial moment of terror when the engineers checking out Astrosat, India’s first space telescope, thought the spacecraft was unable to point at its target accurately.
During the first orbit, there was a difficulty in detecting this Crab Nebula as the satellite happened to pass through the South Atlantic Anomaly (SAA) region when Crab was in the field of view. SAA avoidance zone was deliberately kept wide to protect the instruments, and detectors were switched OFF in this interval during the initial days of Astrosat operation. When all the data were systematically analysed and data were selected based on the availability of Crab in the detector field of view, one could see the Crab emerging from Earth’s shadow (Fig 3).
Using the Crab Nebula as Astrosat’s first target, the check-out has been proceeding well, with full research operations expected to begin in the next few weeks.