Transcript Astrosat (India)

Indian Astronomy Satellite Mission
(ASTROSAT)
Kallol Mukerjee
Department of Astronomy and Astrophysics
Tata Institute of Fundamental Research (TIFR), Mumbai, INDIA
National Institutions
1.
ISRO, Bangalore
2.
TIFR, Mumbai
3.
IIA, Bangalore
4.
RRI, Bangalore
5.
PRL, Ahmedabad
International Institutions
1.
University of Leicester, UK
2. Canadian Space Research Centre, Canada
ASTROSAT
• The first fully dedicated multi-wavelength Indian astronomy mission
• To be launched from India in 2008 using PSLV at 600 km near
equator at low inclination angle <10 degrees
• Cover wide X-ray energy band 0.3-100 keV along with UV and
Optical wave bands
• Timing, Spectroscopy, Imaging and long term monitoring
• Every instrument is configured in its own inherent features to
achieve scientific requirements in specified wave band
• ASTROSAT is conceived with the prime objective is to do front
ranking research utilising multi-wave length capabilities
ASTROSAT Instrument Configuration
Large Area X-ray Proportional Counter (LAXPC)
UV Imaging Telescope (UVIT)
Soft X-ray Telescope (SXT)
Scanning X-ray Sky monitor (SSM)
Cadmium Zinc Telluride Imager (CZT)
Soft X-ray Telescope (SXT)
CCD-22 based Focal Plane Camera
SXT Characteristics
Telescope Focal Length
2.0 metres
Telescope Mirrors
Conical shells
Telescope PSF
3 - 4 arcmin
Field of view
41.3 x 41.3 arcmin
Detector
MAT CCD-22 (cooled to -80 deg C)
Detector Format
600 x 600 pixels
Pixel Scale
4.13 arcsec/pixel
Detector Readout Modes
Photon counting, Imaging & Timing
Energy Range
0.3 – 8.0 keV
Effective Area
200 cm2 @ 1.5 keV
20 cm2 @ 6.5 keV
Sensitivity
10µ Crab (5 ; 10 4 s)
Position Accuracy
30 arcsecs
Large Area X-ray Proportional Counter (LAXPC)
LAXPC Characteristics
Collimator field of view
1 0 x 10 for all the LAXPCs
Collimator height
45 cm for FOV collimator
Material for the Collimator
50µ Sn + 25µ Cu + 100µ Al
Absorber Gas
90 % Xenon + 10 % Methane
Gas Pressure
~ Two atmosphere (1670 torr)
Detector Window
50 (or 25) µ thick Mylar coated one
side with 500 Å thick Aluminium
Energy range
3-80 keV
Average detection efficiency
100% (E < 20 keV)
~ 50 % in 20-100 keV
Time resolution
10 ms (10µ sec for event mode)
Sensitivity
14000 counts per sec per Crab Unit
CZT Imager Assembly
Radiator Holding Bracket
Heat Pipe
Radiator Plate
X connector
CAM with Holder
Collimator
Alpha Box
CZT Top Housing
CZT Bottom Housing
Mounting/Interface Lug
CZT Characteristics
Area
1024 cm 2
Pixels
16384
Pixel size
2.5 mm X 2.5 mm (5 mm thick)
Read-out
ASIC based (128 chips of 128 channels)
Imaging method
Coded Aperture Mask (CAM)
Field of View
17o X 17o (CAM) > 100 keV
6o X 6o (10 – 100 keV)
Angular resolution
8’ (21’ geometric)
Energy resolution
5% @ 60 keV
Energy range
10 – 100 keV
Up to 1 MeV (Photometric)
Sensitivity
0.5 mCrab (5 ; 10 4 s)
Principal Science Objectives of Astrosat
X-ray instruments
1. Timing studies of X-ray Binaries

Measure periodicities and their evolution including Pulsations, QPOs, Binary
periods etc. (Studies of QPOs above 20 keV is relatively unexplored field).

Timing and spectral evolution of X-ray bursts, flares and other sporadic variability.

Studies of X-ray Transients and their temporal and Spectral characteristics.

Long and Short term variability in AGNs.
2. Studies of continuum X-ray emission over a broad band of 3-80 keV.
X-ray Binaries, Supernova remnants (SNRs), CVs, Stellar Coronae, AGNs etc.
Principal Science Objectives of Astrosat X-ray instruments (continued…)
3. Detection of non-thermal components in the X-ray spectra of SNRs
and Clusters of Galaxies
By accurate spectral measurements in 3 – 80 keV band in combination with
Simultaneous measurements from SXT in 0.3 – 8 keV region to understand
the acceleration processes and origin of cosmic rays in the case of SNRs.
4. Measuring magnetic fields of neutron stars
By detection and studies of cyclotron lines, most of which lie in 10 – 60 keV region
in the spectra of X-ray pulsars.
5. Correlated time variations of intensity
In 3-80 keV band with those in the visible, UV and soft X-ray (0.3-8 keV) bands
to investigate the origin and mechanism of emission of radiation in different wave
bands.
Scientific Objectives of SSM

To detect and locate new transients
Long period Be binaries, X-ray novae, etc.

Alert observers
Point Astrosat, carry out optical identification and obtain system parameters like
mass function, binary period, mass of the compact object etc..

Study X-ray binary sources over a large dynamic range
L – 1033 to 10 38 erg/s; dM/dt.

Source states
Low hard state, High soft state, Intermediate, very high etc.

Super orbital period in HMXBs
Precession period of disc/neutron star

Long term cycles and Irregular variations in LMXBs
Mass transfer instabilities?

Pulsar studies
Spin up/down phases of pulsars.
Ultraviolet Imaging Telescope (UVIT)
Two Telescopes each of 38 cm Aperture (Twin Richey Chretian 2
mirror system)
Three channels simultaneously
Far UV (130 nm – 180 nm),
Near UV (180 nm – 300 nm) and
visible (350 nm – 600 nm)
Photon counting + CCD based UV and optical detectors
Filters: FUV: 135 nm, CIV (155 nm), 165 nm;
NUV: CIII (190.9 nm), 225 nm, CII (235 nm), O II (247 nm), 255 nm, 285 nm
Sensitivity = 21 mag (in 1000 seconds)
Field of view = 30 arcmins (>50 times that of HST)
Angular resolution = 1.8 arcsec (2-3 times better than GALEX)
Time resolution = 1 s
Scientific Objectives with UVIT
Deep Surveys: UV sky survey, Detection of galaxies at z ~ 2, Faint quasars and AGNs.
Lyman-a Surveys: Nearby galaxies & clusters of galaxies.
Galaxies in UV: Evolution of stellar populations, OB stars, Dust properties, morphology.
Hot Stars in the local group of galaxies : global studies of young population
In the Milky Way:
•
Studies of populations of sub-classes of White Dwarfs, WDs in the globular clusters
•
High Mass Stars and luminous blue variables – distance calibrators
•
Interstellar Matter Probes
•
Stellar Solar Connection (cool stars; Rotation, magnetic activity, UV flares)
•
Cataclysmic Variables and X-ray Binaries
ASTROSAT: Key Scientific Objectives
1.
SIMULTANEOUS COVERAGE (UV, Soft X-rays and Hard X-rays):
Environment of BLACK-HOLES and other ACCRETION POWERED
sources.
2.
WIDE BAND X-ray SPECTROSCOPY:
Continuum + line emission;
Separation of thermal and non-thermal components.
3.
TIMING: Pulsars, QPOs etc.
4.
TRANSIENT SOURCES
5.
UV SURVEY, Young stellar Populations