Fermi Gamma-ray Space Telescope

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Fermi Gamma-ray Space Telescope
Fermi Gamma-ray Space Telescope
Type: Space telescope
Country: United StatesUnited States United States
Operator: NASA / DoE
COSPAR-ID : 2008-029A
Mission dates
Dimensions: 4303 kg
Begin: June 11, 2008, 16:05 UTC
Starting place: Cape Canaveral LC-17B
Launcher: Delta II 7920H-10C D333
Status: in orbit
Orbit data
Rotation time : 95.7 min
Orbit inclination : 25.6 °
Apogee height :  562 km
Perigee height :  542 km
Illustration of the FGST (GLAST) satellite

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

The suggestion for GLAST comes from Peter F. Michelson and William B. Atwood (1992) - the latter received the Panofsky Prize for this and both received the Bruno Rossi Prize with the team from the Fermi telescope.

Mission goal

FGST aims to find sources of high-energy gamma rays such as active galactic nuclei , pulsars , stellar black holes , blazars , supernova remnants , gamma -ray bursts , flares from the sun and stars and investigate their properties and those of diffuse gamma radiation. The aim is to determine properties that are difficult to measure in any other way, for example the magnetic fields in cosmic particle accelerators or the infrared radiation fields between gamma sources and the earth. Due to the greatly improved properties compared to earlier gamma telescopes, there is also hope for the discovery of new phenomena, such as B. the detection of a diffuse background radiation in the gamma radiation range, which could indicate exotic particles ( neutralino ) from the predictions of particle physics or a variance in the speed of light with high-energy photons to underpin the loop quantum gravity .

Takeoff and orbit

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

technical structure

Launch of GLAST on a Delta 7920H rocket
Structure of FGST

FGST has two tools:

  • The Large Area Telescope (LAT) is an imaging high-energy gamma ray telescope that is equipped with a large field of view and measures in the energy range from under 20 megaelectronvolts to more than 300 gigaelectronvolts. The energy range covered, sensitivity, field of view (20% of the sky), angular resolution and time resolution (10 µs) should be significantly improved compared to the previous EGRET instrument at the Compton Gamma Ray Observatory . The instrument consists of 16 similar particle track detectors, each 40 × 40 × 87.5 cm in size. These in turn consist of thin tungsten foils on which electron-positron pairs are formed from the gamma rays when they strike. The foils are attached between 18 stacked silicon detectors , which can be used to track the paths of the electron-positron pairs. At the end of a stack determines semiconductor - calorimeter from eight layers with twelve cesium iodide - scintillator rods and photodiodes as detector then also the energy of the particles. In order to distinguish the cosmic gamma radiation from the radiation background which is a thousand times higher, the LAT is additionally surrounded by a segmented anti- coincidence detector made of plastic scintillators and photo multipliers. This sorts out impacts of particle radiation ( hadrons ) in the LAT with the help of computer technology . The LAT weighs three tons. It thus makes up most of the weight of GLAST.
  • The GLAST Burst Monitor (GBM) to search for gamma-ray bursts over the entire part of the sky that is not covered by the earth when viewed from GLAST's low-earth orbit. The GBM mainly consists of twelve sodium iodide scintillation detectors with connected photomultipliers and the corresponding evaluation electronics. The detectors have a certain directional sensitivity due to the flat shape of the crystals (cylinder 1.27 cm high and 12.7 cm diameter) and are mounted so that they each point in a different direction. By evaluating the signals from several detectors, the direction (onboard to 15 °, with post-processing of the signals up to 3 °) of the gamma ray source can be roughly determined. The energy range recorded by these detectors is 10 keV to 1 MeV.
  • In order to be able to record the energy range between the detection range of the LAT and the sodium iodide scintillation detectors of the GBM (i.e. the range between 1 and about 20 MeV), the GBM is equipped with two BGO scintillation detectors measuring 12.7 × 12.7 cm Bismuth germanate crystals (Bi 4 Ge 3 O 12 → BGO) which each have two photomultipliers for registering the resulting light. The two non-directional BGO scintillation detectors are attached to both sides of GLAST and each observe half of the sky.

Technical specifications

  • Mass: 4.5 tons
  • Orbit: circular orbit at an altitude of 565 kilometers
  • Height: 2.9 meters
  • Span of the solar cell wings: 15 meters
  • Energy supply: two solar panels with a total of 650 watts of power
  • Telemetry: transmission in S-band and Ku-band

Discoveries

Fermi discovered that the gamma radiation generated in thunderstorms leads to the formation of electron - positron pairs, which escape into space and fly along the lines of the Earth's magnetic field.

In August 2017, the telescope discovered a brief gamma-ray flash from the collision of two neutron stars , a gravitational wave signal of which LIGO had discovered shortly before . This was the first simultaneous observation of an electromagnetic and gravitational wave signal from a common source and the first evidence of colliding neutron stars as the cause of short gamma-ray bursts.

See also: Terrestrial gamma-ray flash

Web links

Commons : Fermi Gamma-ray Space Telescope  - collection of images, videos and audio files

literature

  • The GLAST mission. A look into the cosmic cauldron . In: Stars and Space . May 2008, pp. 40-48.

Individual evidence

  1. ↑ Lee Smolin: Loop Quantum Gravity - Quanta of Spacetime . In: Spectrum of Science . May 2005, pp. 32-41.
  2. ↑ http://www.spaceflightnow.com/delta/d333/status.html
  3. ↑ NASA Renames Observatory For Fermi, Reveals Entire Gamma-Ray Sky
  4. ↑ William B. Atwood, Peter F. Michelson, and Seven Ritz: A Window to the Hot Universe . In: Spectrum of Science . April 2008, pp. 34-41. ISSN  0170-2971
  5. ↑ Holger Dambeck: Surprising find, satellite discovers antimatter over storm clouds in Spiegel Online, Date: January 11, 2011, Accessed: January 15, 2011
  6. ↑ NASA's Fermi Catches Thunderstorms Hurling Antimatter into Space, Date: January 11, 2011, Accessed: January 15, 2011
  7. ↑ A. Goldstein et al. a .: An Ordinary Short Gamma-Ray Burst with Extraordinary Implications: Fermi-GBM Detection of GRB 170817A, Astrophysical Journal Letters, Volume 848, 2017, No. 2, Abstract , published October 16, 2017
  8. ^ BP Abbott et al. a .: GW170817: Observation of Gravitational Waves from a Binary Neutron Star Inspiral, Phys. Rev. Lett., Volume 119, 2017, p. 161101, abstract