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Granat X-ray and Gamma-ray Observatory

The Granat X-ray and gamma-ray observatory was launched 1 December 1989 by a Proton booster into a highly elliptical, 4-day orbit of 1,760 km by 202,480 km with an initial inclination of 51.9 degrees. During Granat's nearly 5-year active life, its orbit was perturbed by solar-lunar perturbations, drastically increasing the inclination and reducing the eccentricity (Reference 275). By the end of operations in September, 1994, the orbital parameters were 59,025 km by 144,550 km and an inclination of 86.7 degrees.

Granat was the last of the Venera-class spacecraft produced by the Lavochkin Scientific Production Association and was similar to the observatory which was functional during 1983-1989. The 4.4 metric ton Granat carried a multi-national scientific payload of almost 2.3 metric tons and stood 6.5 m tall with a total span across its solar arrays of 8.5 m (Figure 5.35). Power provided by the 3-axis-stabilized spacecraft to the payload was approximately 400 W.

The major instrument on Granat was the French-built, one-metric-ton Sigma gamma ray telescope designed to detect energy in the 30 keV to 2 MeV band with a 7 degree by 7 degree field-of-view. Adjacent to Sigma on one side were four Soviet ART-P imaging X-ray telescopes created by the Institute of Space Research and in particular its Frunze Special Design Bureau. The ART-P telescope covered the energy range of 3-100 keV with a narrow 1.8 degree by 1.8 degree field-of-view. On the other side of Sigma were four ART-S spectral X-ray telescopes designed by the same team which built the ART-P and covering the same energy regime with a 2 degree by 2 degree field-of-view. The Frunze Special Design Bureau also provided the Podsolnukh installation consisting of an X-ray telescope (2-25 keV, 2.5 degrees by 2.5 degrees FOV) mounted on a rapidly moving platform which is aimed after being cued by the Konus-Ball-sky, gamma-ray burst detector provided by the Leningrad Physical-Technical Institute. Rounding out the deep space payload suite were the French Phoebus spectrometer (200 keV-40 MeV) and the Danish Watch X-ray burst detector (5-150 keV), both of which were all-sky instruments (References 276-279).

Granat was caught in two ways by the fall of the USSR. First, the main spacecraft control center was located at Ukraine's Yevpatoriya facility in the Crimea region where data collection and spacecraft operations were accomplished via a 70-m diameter dish antenna. The newly declared independence of Ukraine, coupled with the historical close ties of the Crimea to the Russian Federation, introduced new political obstacles. The most significant problem, however, was in financing the ongoing mission. The French space agency, with its substantial investment in Granat, directly subsidized continuing operations. The benefit was clear in the scientific discoveries of the spacecraft (References 280-286).