Welcome
to the 4th
Chandra – CIAO
Workshop
20 – 22 May 2002
Martin Elvis
Smithsonian Astrophysical Observatory
Chandra X-ray
Chandra X-ray Observatory
Overview
Martin Elvis
Smithsonian Astrophysical Observatory
CIAO Workshop
20 May 2001
Chandra X-ray
NASA Great Observatories
CHANDRA
Chandra X-ray
Focusing X-rays
Chandra X-ray
Chandra Mission Summary
 Launch: July 23, 1999
– STS-93/ Inertial Upper Stage / Integral Propulsion System
– 10,000 km x 140,000 km, 28.4o Inclined Orbit
 Design Lifetime > 5 Years (in NASA plan for 10 year life)
 10-m Focal Length Wolter -1 Mirror: 4 nested Mirror Pairs
 Energy Range: 0.1-10 keV
¼ arcsecond resolution. Sub-0.5arcsec in practice
 2 Imaging Focal Plane Science Instruments
– ACIS (Advanced CCD Imaging Spectrometer)
– HRC (High Resolution Camera)
 2 Objective Transmission Gratings for Dispersive Spectroscopy
– LETG (Low-Energy Transmission Grating)
– HETG (High-Energy Transmission Grating)
Chandra X-ray
Mission and Observatory Description
Chandra X-ray
High Resolution Mirror Assembly
 4 pairs of concentric thin-walled zerodur,
grazing incidence Wolter Type-I mirrors >large area. ->800cm2 E<2keV
Antennae galaxies
 figured to 0.5” FWHM -> sensitivity,
-> megapixel images
 Focal length 10 m. -> response to 10keV
Many independent pixels
High sensitivity
Iridium edge
 polished to 3A -> low scattering
high dynamic range
PSR nebula
PKS1127-145
95%
High energy sources
1.6”
Chandra X-ray
100:1 AGN/jet contrast
Aspect Camera and Fiducial Transfer System
Aspect Camera
4.25inch dia.
15”pixels
<0.25” r ms (typical)
Chandra X-ray
Chandra Science Instruments
Z+
ACIS-I
 Advanced CCD Imaging Spectrometer (ACIS)
– CCD array with 16’x16’ field of view (ACIS-I)
– grating readout array (ACIS-S)
BI
 High Resolution Camera (HRC)
– microchannel plate imager with 31’x31’ field of view (HRC-I)
– low energy grating readout array (HRC-S)
– High time resolution
 High Energy Transmission Grating Spectrometer
(HETG)
BI
Y+
ACIS-S
HRC-I
– transmission grating pairs for medium and high energy
 Low Energy Transmission Grating Spectrometer
(LETG)
– transmission grating for low energy
Chandra X-ray
HRC-S
Advanced CCD Imaging Spectrometer (ACIS)
 Ten 1024x1024 pixel CCDs (any 6
simultaneously)
– Intrinsic energy resolution ~100eV ->
imaging spectroscopy
– ACIS-I: 2x2 array for imaging
(16x16 arcmin)
– ACIS-S: 1x6 array for imaging
(8x8arcmin) or spectroscopy
– 2 `back illuminated’ (BI) chips: good
low E QE, higher throughput
Chandra X-ray
ACIS Issues
CTI
 Front Iluminated (FI) chips suffered
proton damage just after launch. ->
charge transfer inefficiency (CTI) ->
much degraded energy resolution
 CTI correction (Townsley, PSU)
restores linearity, most dE/E
Pileup
 3.2 s full frame readout time -> for
sources >0.1ct/s suffer “pileup” I.e.
2 photons in same pixel/frame -> loss
of energy information, and -> loss of
PSF peak
 Pileup correction (J.Davis, MIT) available in
CIAO, Sherpa
Chandra X-ray
Low Energy Calibration
 Non-linear gain
 Changing QE
 See H. Donnely talk
Chandra Grating Spectrometers
m=2
Incoming
Radiation
d
m=1

m=0
m=-1
m = d sin
Chandra X-ray
m=-2
Grating Spectrometers:HETG
 HETG: High Energy Transmission Gratings
– Designed for use with ACIS-S providing E/delta(E) to 1000
between 0.4 and 10.0 keV
– Two sets of gratings
– Medium Energy Gratings (MEG) use outer 2 mirrors
– High Energy Gratings (HEG) use inner 2 mirrors
– Mounted at different angles to form an “X” dispersed pattern
Capella HETG spectrum
Chandra X-ray
Grating Spectrometers: LETG
 LETG High Energy Transmission Gratings
–
–
–
–
Provides highest resolving power at low energies
Designed for use with HRC-S with 0.07 – 7.29 keV
E/delta(E) > 1000 for 0.07 < E < 0.15 keV
E/delta(E) < 1000 for E > 0.15 keV
Chandra X-ray
Chandra Operations
 Mission science plan
converted to command loads
and uplinked to Chandra
 X-ray events collected and
stored on Solid-State
Recorders (SSR)
 Ground contact established
every ~8 hours through Deep
Space Network
– SSR data downlinked
– new command load uplinked
(up to 72 hours of stored
commands)
 Data transferred to OCC
through JPL for science
processing
Chandra X-ray
sssssssssssssssssssssss
CXO
CXC
OCC
6. Chandra X-ray Center Architecture
uplink
downlink
Chandra Observing Cycle
 High (66%) observing efficiency
 TOOs, solar flares ->big hit on
mission planning team
 Annual Proposal Cycle:
 Next Deadline: 15 March 2003
(anticipated)
 + Archive, Theory grants
 Funding expected to 2009
Chandra X-ray
enjoy the workshop!
Chandra X-ray