Gamma

The Gamma USSR/France gamma/x-ray astronomical telescope spacecraft was derived from the Soyuz manned spacecraft and had an unusually long gestation. The basic design was first conceived in 1965 as part of a 'Cloud Space Station' - a primary space station from which a number of man-tended, free-flying spacecraft would operated. This evolved by the early 1970's into the MKBS/MOK space station complex. Various spacecraft with specialized laboratories or instrument sets would fly autonomously away from the huge N1-launched main station. Gamma was originally to be a free-flyer of this complex. The Soyuz propulsion system was used, but the descent and orbital modules were replaced by a large pressurized cylinder containing the scientific instruments.

Work on the instrument payload for Gamma began in 1972, and French participation began in 1974. However that same year the N1 launch vehicle, and the MKBS space station, were cancelled.

The Soviet space program was completely reformulated in a resolution of February 1976, which included authorization to develop the free flyer in conjunction with the DOS-7/DOS-8 space station (which would eventually evolve into Mir). The draft project for Gamma was completed in 1978, and production was authorized together with Mir on 16 February 1979. At this point Gamma included a passive docking port so that the spacecraft could be serviced by Soyuz manned spacecraft. It was planned that at six and twelve months into its one year mission Gamma would be visited by a two-crew Soyuz, who would replace film cassettes and repair or replace instruments. This approach was dropped in 1982 when it became apparent that the spacecraft was overweight and that all planned Soyuz would be needed for support of the Mir station itself. All film systems were removed and replaced with purely electronic data return methods.

By that time Gamma was scheduled originally for launch in 1984, but further severe technical delays resulted in a 1990 launch, 35 years after it was first conceived. In the end the satellite's research in the field of high-energy astrophysics, conducted jointly with France and Poland, did not produce many noteworthy results.

Gamma offered the possibility of locating COS-B sources with a precision of a few arcminutes. The mission lasted ca. 2 years.

Instrumentation

The science instrumentation included the Gamma-1 telescope (with a Telezvezda star tracker), the Disk-M telescope, and the Pulsar X-2 telescope. All 3 instruments were mounted coaxially on the observatory, allowing for simultaneous observation of any given region of the celestial sphere.

The Gamma-1 telescope was the principle instrument aboard the Gamma observatory. It was designed to perform detailed studies in the energy range 50 MeV - 6 GeV. The system consisted of 2 scintillation counters and a gas Cerenkov counter. It had an effective area of ~2000 sq-cm. Its angular resolution at 100 MeV was 1.5 degrees. The imaging field of view was +/- 2.5 degrees. The energy resolution was 12% at 100 MeV. Rather late in the game, it was decided to include a tungsten coded aperture mask which could be moved in and out of the field of view. The mask itself was made of 2 1-D masks each having a unit cell size of 1 mm. The basic resolution achieved by the mask was ~20 arcminutes for the weakest sources (4-sigma). Shortly after launch, the power to the spark chamber failed. This resulted in the angular resolution for most of the mission being only ~ 10 degrees. The telescope was a joint Soviet-French endeavor.

The Telezvezda star tracker worked together with the Gamma-1 telescope. It had a 6 deg x 6 deg field of view, and a 5th stellar magnitude sensitivity. It had an angular resolution of 2 arcmin, making it possible to determine the Gamma-1 pointing direction to the same accuracy.

The Disk-M telescope was designed to measure fluxes in the range 20 keV - 5 MeV. The detector consisted of NaI scintillation crystals. The angular resolution of the telescope was ~ 25 arcmin. The Disk-M telescope stopped working not long after launch.

The Pulsar X-2 telescope covered 2-25 keV with ~ 30 arcmin resolution and a 10 deg x 10 deg field of view. The telescope was a joint Soviet-French endeavor.

Science

Studies were made of the Vela pulsar, the galactic center region, the Cygnus binaries, the Heming gamma source in Taurus, and Her X-1. The observatory also gathered information about the high-energy emissions of the Sun during peak solar activity.

Typical orbit: 384 km circular orbit, 51.5 deg inclination. Length: 7.70 m (25.20 ft). Maximum Diameter: 2.70 m (8.80 ft). Span: 12.00 m (39.00 ft). Mass: 7,350 kg (16,200 lb). Associated Launch Vehicle: Soyuz 11A511U2.

• 1976 February 17 - Energia; Buran; Mir; Luch; Potok approved; N1 formally cancelled. - Launch Vehicle: N1, N1F, Energia.

  Central Committee of the Communist Party and Council of Soviet Ministers Decree 'On work on Energia-Buran, DOS-7K nos. 7 and 8, Gamma. Geyzer (Potok), and Altair (Luch) and cancellation of the N1' was issued. The design of an improved model of the Salyut DOS-17K space station was authorised as part of the third generation of Soviet space systems in a decree. At that time it was planned that the two stations (DOS-7 and DOS-8) would be equipped with two docking ports at either end of the station and an additional two ports at the sides of the forward small diameter compartment. Luch and Potok were elements of the second generation global command and control system (GKKRS) deployed in the first half of the 1980's. Luch satellites, analogous to the US TDRS, provided communications service to the Mir space station, Buran space shuttle, Soyuz-TM spacecraft, military satellites, and the TsUPK ground control center. They also served to provide mobile fleet communications for the Soviet Navy.Additional Details: Energia; Buran; Mir; Luch; Potok approved; N1 formally cancelled. (22882).

• 1990 July 11 - Gamma - Launch Site: Baikonur. Launch Vehicle: Soyuz 11A511U2. Mass: 7,350 kg (16,200 lb). Perigee: 382 km (237 mi). Apogee: 387 km (240 mi). Inclination: 51.60 deg. Period: 92.30 min. Duration: 1,388.41 days.

  Spacecraft mission was research in the field of high-energy (gamma/x-ray) astrophysics conducted jointly with France and Poland. The satellite was based on the Soyuz manned spacecraft and had an extremely long gestation - conceived in 1965, authorised in 1976, scheduled originally for launch in 1984, but further severe technical delays resulted in a 1990 launch.

• JPL Mission and Spacecraft Library, Jet Propulsion Laboratory, 1997. Accessed at: http://msl.jpl.nasa.gov/home.html.

• Siddiqi, Asif A, The Soviet Space Race With Apollo, University Press of Florida, 2003. ISBN: 0813026288. The definitive history of the Soviet manned space program in the 1960's to the early 1970's. Originally published as the the latter part of 'Challenge to Apollo' by NASA in 2000 as NASA SP-2000-4408. More at amazon.com...

• Voevodin, Sergey A, VSA072 - Space Apparatus, "Sergey A. Voevodin's Reports", . Accessed at: http://home.attbi.com/~rusaerog/spacecraft.html.

• McDowell, Jonathan, Jonathan's Space Home Page, Harvard University, 1997-present. Jonathan McDowell's complete on-line listing of all objects orbited and over 20,000 rocket launches Accessed at: http://www.planet4589.org/jsr.html.

• USAF Satellite Database, USAF Institute of Technology, 1995. Accessed at: ftp://archive.afit.af.mil/pub/space/.

• Hendrickx, Bart, Journal of the British Interplanetary Society, "The Origins and Evolution of Mir and Its Modules", Vol. 51, P. 203-222, 1998..