Fermi Gamma-ray Space Telescope

The Fermi Gamma - ray Space Telescope ( FGST, formerly Gamma -ray Large Area Space Telescope, GLAST ) is a space telescope for gamma-ray astronomy. FGST is a joint project of NASA and the U.S. Department of Energy, with additional investments from the USA, France, Germany, Japan, Italy and Sweden.

The proposal for GLAST written by Peter F. Michelson and William B. Atwood (1992 ) - the latter was awarded the Panofsky Prize and both received for the Bruno Rossi Prize with the team from the Fermi telescope.

Objective of the mission

FGST to find sources of high- energy gamma rays such as active galactic nuclei, pulsars, stellar black holes, blazars, supernova remnants, gamma-ray bursts, flares of the sun and of stars and investigate their properties, and the diffuse gamma radiation. This should otherwise be determined only difficult to measure properties such as the magnetic fields in cosmic particle accelerators, or infrared radiation fields between gamma-ray sources and earth. By over previous gamma telescopes greatly improved properties, there is also hope for the discovery of new phenomena, such as the detection of a diffuse background radiation in the gamma radiation range, the evidence of exotic particles ( neutralino ) could be from the predictions of particle physics and a variance of the speed of light with high-energy photons in support of the loop quantum gravity.

Launch and orbit

FGST launched on 11 June 2008 at 16:05:00.521 UTC clock with a Delta II 7920H - 10C. After 75 minutes of flight time GLAST was suspended at 17:20 UTC clock in the planned circular orbit at 585 km altitude with 28.5 ° inclination to the equator. After completing a 60 - day trial period, then began the scientific use. On 26 August 2008 the satellite has been renamed to the name of the Fermi Gamma - ray Space Telescope, in honor of the nuclear physicist Enrico Fermi.

Technical structure

FGST has two instruments:

The Large Area Telescope (LAT ) for imaging a field of view of 2 steradians in the energy range 20 MeV to 300 GeV. Masked energy, sensitivity, field of view ( 20 % of the sky ), angular resolution and time resolution (10 microseconds ) to be compared to its predecessor EGRET instrument on the Compton Gamma Ray Observatory significantly improved. The instrument consists of 16 identical Teilchenspurdetektoren of 40 × 40 × 87.5 cm size. This in turn consist of thin tungsten films on which form of gamma rays when striking electron-positron pairs. The foils are mounted between 18 stacked silicon detectors, with which the orbits of the electron-positron pairs can be tracked. At the end of the stack defines a semiconductor calorimeter from eight layers with twelve cesium iodide scintillator rods and photodiodes as a detector then the energy of the particles. To distinguish the cosmic gamma radiation from a thousand times higher radiation background, the LAT is also surrounded by a segmented anti-coincidence detector constructed from plastic scintillators and photomultipliers. This sorted out with the help of computer technology impacts of particle ( hadrons ) in the LAT. The LAT has a weight of three Tonnen.Es thus makes the most of the weight of GLAST from.
The GLAST Burst Monitor (GBM ) to search for gamma-ray bursts in the entire part of the sky, seen from low Earth orbit by GLAST from not obscured by the Earth. The GBM is mainly composed of twelve sodium iodide scintillation detectors with photomultipliers connected and corresponding evaluation electronics. The detectors have attached by the flat shape of the crystals (cylinder 1.27 cm in height and 12.7 cm in diameter) a certain direction and sensitivity are such that they are each in a different direction. By analyzing the signals from multiple detectors can be so grossly the direction ( Onbord to 15 °, with post-processing of the signals down to 3 °) are determined by the gamma-ray source. The area covered by these detectors, the energy is 10 keV to 1 MeV.
In order to also capture the energy range between the detection range of the LAT and the sodium iodide scintillation detectors of the GBM (ie the range between 1 and 20 MeV), the GBM is still with two BGO scintillation detectors of 12.7 × 12.7 cm Bismutgermanatkristallen ( Bi4Ge3O12 → BGO) equipped hold for registration of the resulting light per two photomultiplier. The two non- direction-sensitive BGO scintillation detectors are mounted on the two sides of GLAST and watch one half of the sky.

Specifications

Mass: 4.5 tons
Orbit: circular orbit 565 kilometers above
Height: 2.9 meters
Span of solar panels: 15 meters
Power supply: two solar panels with a total of 650 watts of power
Telemetry: Communication in the S-band and Ku-band

Discoveries

Fermi discovered that the resulting in thunderstorms gamma radiation to form electron -positron pairs leads that escape into space and fly along the lines of the geomagnetic field.