NASA's "Great Observatories" program used four separate satellites to cover a different part of the spectrum. 1st. Great Observatories. 2nd. 3rd. 4th. Uhuru, launched in 1970 was the first earth-orbiting mission dedicated entirely to celestial X-ray astronomy and operated for 3 years.
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NASA's "Great Observatories" program used four separate satellites to cover a different part of the spectrum.
Uhuru, launched in 1970 was the first earth-orbiting mission dedicated entirely to celestial X-ray astronomy and operated for 3 years.
It consisted of two proportional counters and made the first comprehensive and uniform all sky survey.
Uhuru spun making one revolution every 12 minutes whilst mapping out a scan of space either 0.5º or 5º wide between 2 - 20 keV.
The second NASA Satellite (SAS-2) launched in 1972 was dedicated to gamma-ray astronomy in the energy range above 35 MeV using a wire spark-chamber aligned with satellite spin axis. It provided the first detailed look at the gamma-ray sky.
Imaging Compton Telescope (COMPTEL), sensitive from 1 eV to 30 MeV. Gamma rays from active galaxies, radioactive supernova remnants, and diffuse gamma rays from giant molecular clouds were studied with this instrument. Upper detector = liquid scintillator. Lower detector = NaI crystal
Energetic Gamma Ray Experiment Telescope (EGRET) was sensitive to gammas from 20 MeV to 30 GeV. EGRET made detailed observations of gamma-ray bursts, cosmic rays, pulsars, and AGNs.
EGRET used high-voltage gas-filled spark chambers which allowed the determination of the direction of the original gamma ray. Rays produce an electron-positron pair of particles which create ionisation trails and cause sparks. Particle energy recorded by a NaI crystal beneath the spark chambers.
Up and down: Launched in 1999, may function until 2020.
Chandra has imaged remains of exploded stars, and taken spectra showing the dispersal of elements. It has observed the region around the supermassive black hole in the centre of our Milky Way, and found black holes across the universe.
Task: Make all-sky survey in soft X-rays (0.1-10 keV ).
Interesting fact: Found evidence for dark matter.
Main detector: Wolter telescope coupled to CCD camera/spectrograph.
Bullet cluster formed after collision of two large clusters of galaxies. Hot gas (false pink) contains most baryonic matter. Blue areas contain most of the mass determined by gravitational lensing. Evidence that nearly all of the matter in cluster is dark.
X-ray auroras observed near the poles of Jupiter caused by interaction of sulphur and oxygen ions in the outer magnetic field with solar wind. Auroras are a thousand times more powerful than auroras seen on Earth.
Up and down: Launched in 2003, cooling helium exhausted in 2009 .
Task: Make all-sky survey in infrared.
Interesting fact: Named by general public after man who first suggested the value of extraterrestrial observatories.
Main detector: Infrared CCD camera and infrared spectrometer
Composite of four images: 3.6 (blue), 4.5 (green), 5.8 (orange), and 8.0 (red) microns.
Helix nebula: Infrared light from the outer gaseous layers is represented in blues and greens. The white dwarf is visible as a tiny white dot in the centre of the picture. The red colour in the middle of the eye denotes the final layers of gas blown out when the star died.
Up and down: Launched in 2008, still up there.
Task: Make all-sky survey of AGNs, Pulsars, GRBs, other high energy events.
Interesting fact: Budget cuts meant there is only one main detector.
Main detector: Large Area Telescope (next slide shows how it works).