A coordinated set of instruments
Gamma carried three telescopes, all capable of pointing at the same source. Together, they were designed to examine radiation across a broad range of energies, from X-rays to gamma rays.
Gamma-1 was the main instrument. It used two scintillation counters and a gas Cerenkov counter to observe gamma rays between 50 MeV and 6 GeV. Its effective collecting area was about 0.2 square metres. A Telezvezda star tracker could follow stars as faint as apparent magnitude 5 and was designed to improve pointing accuracy to two arcminutes.
Instrument problems in flight
The intended precision did not last. Power to a spark chamber failed, leaving Gamma-1 with an angular resolution of about 10 degrees for most of the mission, rather than its initial performance. Angular resolution describes how precisely a telescope can distinguish the direction of incoming radiation.
Disk-M covered a lower energy range, from 20 keV to 5 MeV, using sodium iodide crystals. It had an angular resolution of 25 arcminutes, but stopped working shortly after launch. Pulsar X-2 operated between 2 and 25 keV, with a 30-arcminute resolution and a field of view measuring 10 by 10 degrees.
What Gamma watched
Despite these limitations, Gamma observed the Vela Pulsar, the Galactic Center, Cygnus X-1, Hercules X-1 and the Crab Nebula. It also measured the Sun during peak solar activity.
The mission’s instruments promised complementary views of energetic phenomena. Their uneven performance shows how much a space observatory’s scientific reach can depend on the survival of a single component.