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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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great observatories

NASA's "Great Observatories" program used four separate satellites to cover a different part of the spectrum.

1st

Great Observatories

2nd

3rd

4th

problems associated with earth based observation

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.

Problems associated with Earth based observation

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.

problems associated with earth based observation1

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.

Problems associated with Earth based observation

great observatories1

ROSAT (1990-1999)

Up and down: Launched in 1990, it was turned off in 1999.

Great Observatories

Task: make all-sky survey in soft X-rays (0.1 keV-2 keV),

Interesting fact: Sensitivity to X-rays was over 1000 times greater than Uhuru.

Main detector: Wolter I telescope coupled to microchannel plate.

great observatories2

ROSAT (1990-1999)

Cool results:

Great Observatories

UP: Shows smooth extragalactic background and number of bright extended Galactic objects .

LEFT: 1572 Tycho SNR

great observatories3

Hubble Space Telescope (1990)

Up and down: Launched in 1990, still working until 2014.

Great Observatories

Task: Ultra deep field images in visible spectrum.

Interesting fact: Pivotal in deducing accurately expansion of Universe.

Main detector: Optical camera/ spectrometer, wide field optical camera.

great observatories4

Hubble Space Telescope (1990)

The Sombrero Galaxy - It has 800 billion stars

Cool results:

Eskimo PN

Great Observatories

Cone Nebula

Cat's Eye PN

The Ant Nebula lies within our galaxy between 3,000 and 6,000 light years from Earth

great observatories5

The Compton Gamma Ray Observatory (1991)

Up and down: Launched in 1991, de-orbited in 2000.

Great Observatories

Task: All sky survey high energy photon spectrum.

Interesting fact: Four instruments that covered from 30 keV to 30 GeV.

Main detectors: 4 big ones in 17 tonne satellite (heaviest ever)!

great observatories6

The Compton Gamma Ray Observatory (1991)

Burst And Transient Source Experiment (BATSE)

8 sodium iodide detectors on corners of satellite (20 keV to over 1 MeV) to detect gamma-ray bursts.

Great Observatories

great observatories7

The Compton Gamma Ray Observatory (1991)

Oriented Scintillation Spectrometer Experiment (OSSE) consisted of four sodium iodide detectors, sensitive to gammas from 50 keV to 10 MeV.

Great Observatories

great observatories8

The Compton Gamma Ray Observatory (1991)

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

Great Observatories

great observatories9

The Compton Gamma Ray Observatory (1991)

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.

Great Observatories

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.

great observatories10

Chandra X-ray Observatory (1999)

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.

Great Observatories

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.

great observatories11

Chandra X-ray Observatory (1999)

Cool results:

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.

Great Observatories

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.

great observatories12

Spitzer Space Telescope (2003)

Up and down: Launched in 2003, cooling helium exhausted in 2009 .

Great Observatories

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

great observatories13

Spitzer Space Telescope (2003)

Cool results:

Composite of four images: 3.6 (blue), 4.5 (green), 5.8 (orange), and 8.0 (red) microns.

Great Observatories

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.

great observatories14

Fermi Gamma ray Space Telescope (2008)

Up and down: Launched in 2008, still up there.

Great Observatories

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).