Chandra (satellite)

|- ! align=" left" | Organization | NASA , SAO , CXC |- ! align=" left" | Field | X-rays |- ! align=" left" | Orbits | strongly elliptique
10 000-140 161 km (period: 64h 18mn) |- ! align=" left" | Launching | July 23rd 1999 |- ! align=" left" | Extraction | in operation |- ! align=" left" | Mass | 4,800 kg |- ! align=" left" | Other names | Advanced X-ray Astrophysics Facility (AXAF) |- ! align=" left" | Program | Large observatories |- ! align=" left" | Web page | http://chandra.harvard.edu/ |- ! colspan=" 2" style=" background: #6295DA; text-align: center; " | Physical characteristics |- ! align=" left" | Technology | 4 pairs of parabolic/hyperbolic reflectors |- ! align=" left" | Diameter | 1.2 m |- ! align=" left" | Surface | 400 cm |- ! align=" left" | Focal distance | 10m |- ! colspan=" 2" style=" background: #6295DA; text-align: center; " | Instruments |- style=" vertical-align: signal; " | ACIS || Spectrometer X |- style=" vertical-align: signal; " | HRC ||camera X |- style=" vertical-align: signal; " | HETGS || Spectrometer X with high-resolution (diffraction pattern) |- style=" vertical-align: signal; " | LETGS || Spectrometer X with high-resolution (diffraction pattern) |}

The satellite Chandra is a Télescope with x-rays. It was launched in 1999 by the Space shuttle Columbia at the time of the mission STS-93.

Its name comes from that of the Physicien Subrahmanyan Chandrasekhar which is known to have evaluated the limiting mass of the white dwarf to become neutron stars. In an adequate way, the term Sanskrit of Chandra means luminous (and the the Moon indicates).

Before its launching, Chandra also bore the name of Advanced X-ray Astrophysics Facility ( AXAF ).

Discovered

Chandra deeply transformed our knowledge of the universe and brought a considerable number of new or unexpected information. Among those one can count:

the first image, of the remainders of the Supernova Cassiopée has, gave a first impression in connection with the compact object which is in its center (a neutron star or a Black hole).
In the Nebulous of the Crab, other remainders of a supernova, Chandra showed an unknown ring around the central Pulsar and of the jets which were only guessed on the former images.
first x-emission observed comes from the supermassif Black hole of the center of our galaxy (the Milky Way): Sagittarius A* .
Chandra observed Gaz much colder than envisaged orbiting in spiral towards the center of the Galaxie of Andromède.
For the first time, Chandra detailed faces of pressure in Abell 2142, where groups of galaxies are melting itself.
the first images of the shock waves of a Supernova were taken in SN 1987A.
Chandra presented for the first time of the images of the absorption of small a Galaxie cannibalized by larger (in an image of Perseus has).
In the galaxy M82, a new type of Black hole was observed with semi way in the face between the stellar black holes and the black holes supermassifs.
For the first time, Chandra made it possible to associate a x-emission with a Sursaut gamma, GRB 991216.
Of the high-school pupils, by exploiting data of Chandra, discovered a neutron star in the remainders of the supernova IC 443.
the common observations of Chandra and BeppoSAX suggest that the starts gamma are in the areas of intense star formation.
the data of Chandra suggest that the objects RXJ1856 and 3C 58, that one believed previously to be Pulsar S, would be rather objects much denser, strange stars. These results are not the subject yet however of a clear consensus.
the brown Naine TWA 5B was observed orbits about it around a star similar to the sun (in a binary sytème).
Chandra located the sound waves coming from the violent activity around a supermassif Black hole in the cluster Perseus.
Chandra observed the shadow in x-rays of Titan passing in front of the Nébuleuse of the Crab.

Technical description

Contrary to the optical telescopes which are satisfied with parabolic surfaces like mirrors, the telescopes with x-rays use complex surfaces (parabolic and hyperbolic) with which surface is covered with Iridium. Photons X have an energy such as the traditional mirrors are crossed and that it is rather necessary to use an angle of incidence shaving to reflect them (see also the article Focalization (optical) #Télescopes with x-rays ). Chandra uses 4 pairs of mirrors which, in partnership with the bearing structure, bear the name of High Resolution Mirror Assembly (HRMA). The mirrors of Chandra (much better than those covered with gold of first telescopes X in orbit) authorize a angular Résolution record of 0,5 Seconde of arc (2,4 µrad).

The elliptic Orbite strongly of Chandra authorizes periods of observation to him going up to 55 hours (for one 65 hours orbital period).

Instruments

The Science Instrument Modulates (SIM) carries the two instruments of the focal plan, ACIS ( Advanced CCC Imaging Spectrometer ) and HRC ( High Resolution Camera ), to place them in position of observation according to the required program.

ACIS comprise 10 CCC and provide images as well as spectral information of the objects observed. He works in the range from 0.2 to 10 KeV. HRC comprises two plates with microchannels ( microphone-Chanel punts ) and covers the range from 0.1 to 10 KeV. It has also a resolution of 16 Microseconde S. These two instruments can be used only or in partnership with one of both diffraction patterns .

The diffraction patterns, which can be placed in the optical axis behind the mirrors, offer the capacity of a Spectroscopie to high-resolution. The HETGS ( High Energy Transmission Grating Spectrometer ) works in the range from 0.4 to 10 KeV and has a spectral resolution of 60-1000. The LETGS ( Low Energy Transmission Grating Spectrometer ) works in the range from 0.09 to 3 KeV and a resolution of 40-2000.

History

In 1976, Chandra (still named AXAF at this time) was proposed with NASA by Riccardo Giacconi and Harvey Tananbaum. The following year, work started with the Marshall Space Flight Center (MSFC) and with the Smithsonian Astrophysical Observatory (SAO). Meanwhile, in 1978, NASA launched and put into orbit the first Télescope at X-rays Einstein (HEAO-2). In 1992, to reduce of them the costs, the satellite was radically re-studied. Four of the twelve mirrors envisaged were eliminated (with two of the six scientific instruments). The orbit of Chandra was transformed into a strongly elliptic orbit whose most distant point is at a third of the distance Ground - the Moon. These transformations completely eliminated the possibility of missions from maintenance or maintenance by the Space shuttle but placed the major part of the orbit beyond the Ceinture of Van Allen (zone of intense radiations).

AXAF acquired its new name of Chandra in 1998 and was launched in 1999 by the Space shuttle Columbia at the time of the mission STS-93. At this time, it was the heaviest load ever carried by a space shuttle, for a good portion because of the Booster which was to insert it in its high orbit (the Inertial Upper Stage ).

One month after its launching, Chandra started to return data of observation. It does it continuously since. The operations are led by the SAO to the Chandra X-ray Center to Cambridge, Massachusetts, with the assistance of the Massachusetts Institute off Technology and of the Northrop Grumman Space Technology. The CCC of ACIS were damaged by the first passages in the Ceinture of Van Allen. To prevent that does not reproduce, a systematic procedure of withdrawal of this instrument out of the focal plan at the time of these passages was installation.

See too

Internal bonds

Large observatories (NASA)

External bonds

Chandra X-ray Observatory Center
STS-93 Close Kit

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