About Chandra



Chandra at a Glance

Useful Numbers and Information about Chandra Instruments


Click on the table title for the relevant chapter in the Proposers' Observatory Guide.


High Resolution Mirror Assembly (HRMA)
OpticsWolter Type-I
Mirror coatingsIridium
Mirror outer diameters (1, 3, 4, 6)1.23, 0.99, 0.87, 0.65 m
Mirror lengths84 cm
Unobscured clear aperture1145 cm2
Focal length10.066 m
Plate scale48.8 µm/arcsec
PSF FWHM (with detector)0.5 arcsec
Ghost-free field of view30 arcmin diameter
Effective area:
@ 0.25 keV800 cm2
@ 5.0 keV400 cm2
@ 8.0 keV100 cm2

Advanced CCD Imaging Spectrometer (ACIS)
Focal plane arrays:
I-array (ACIS-I)4 CCDs placed to lie tangent to the focal surface, used for imaging
S-array (ACIS-S)6 CCDs in a linear array tangent to the grating Rowland circle, used for either imaging or as a grating readout
CCD format1024 by 1024 pixels
Pixel size24.0 µm (0.492 ± 0.0001 arcsec)
ACIS-I array size16.9 by 16.9 arcmin
ACIS-S array size8.3 by 50.6 arcmin
On-axis effective area of frontside illuminated (FI) chips (integrated over the PSF to >99% encircled energy):
@ 0.5 keV110 cm2
@ 1.5 keV600 cm2
@ 8.0 keV40 cm2
Quantum efficiency for FI chips:> 80% between 3.0 and 5.0 keV
> 30% between 0.8 and 8.0 keV
Quantum efficiency for backside illuminated (BI) chips:> 80% between 0.8 and 6.5 keV
> 30% between 0.3 and 8.0 keV
Maximum readout rate per channel~ 100 kpix/sec
Minimum row readout time2.8 ms
Nominal frame time3.2 sec (full frame)
Allowable frame times0.2 to 10.0 sec
Frame transfer time41 µs (per row)
Point-source sensitivity4 X 10-15 ergs/cm2/s in 104 s (0.4 to 6.0 keV)

High Resolution Camera (HRC)
Focal plane arrays:
HRC-I:CsI-coated microchannel plate pairs, 90 X 90 mm
HRC-S:CsI-coated microchannel plate pairs, 3-100 X 20 mm
Field of view:HRC-I: ~ 30 X 30 arcmin
HRC-S: 6 X 90 arcmin
Spatial resolution, FWHM:~ 20 µm, ~ 0.4 arcsec
Energy range:0.08 - 10.0 keV
Spectral resolution (E/dE):~ 1 @ 1 keV
Quantum efficiency:30% @ 1.0 keV
10% @ 8.0 keV
On-axis effective area:133 cm2, HRC-I @ 0.277 keV
227 cm2, HRC-I @ 1 keV
Time resolution16 µs
Limiting sensitivity
  (point source, 3 sigma detection in 3 X 105 s)		9 X 10-16erg/cm2/s
On-orbit quiescent background (before ground processing):HRC-I: 9 X 10-6cts/s/arcsec2
HRC-S: 1.8 X 10-4cts/s/(res. elm.)

High Energy Transmission Grating (HETG)
HETGS range:0.4 - 10.0 keV (31 - 1.2 Å)
High Energy Grating (HEG) range:0.8 - 10.0 keV (15 - 1.2 Å)
Medium Energy Grating (MEG) range:0.4 - 5.0 keV (31 - 2.5 Å)
Effective area (MEG+HEG first orders, with ACIS-S):
@ 0.5 keV7 cm2
@ 1.0 keV59 cm2
@ 1.5 keV200 cm2
@ 6.5 keV28 cm2
Resolving power (E/dE):
HEG:65 - 1070 (1000 @ 1 keV, 12.4 Å)
MEG:80 - 970 (660 @ 0.826 keV, 15 Å)
Resolution:
d lambda, HEG:0.012 Å FWHM
d lambda, MEG:0.023 Å FWHM
Absolute wavelength accuracy:
HEG:± 0.006 Å
MEG:± 0.011 Å
Wavelength scale:
HEG:0.0055595 Å / ACIS pixel
MEG:0.0111185 Å / ACIS pixel

Low Energy Transmission Grating (LETG)
Wavelength range:1.7 - 170 Å (HRC-S)
1.4 - 63 Å (ACIS-S)
Energy range:0.07 - 7.29 keV (HRC-S)
0.20 - 8.86 keV (ACIS-S)
Resolution: (d lambda, FWHM)0.05 Å
Resolving power: (E/dE)>= 1000 (50 - 160 Å)
~ 20 X lambda (3 - 50 Å)
Dispersion1.148 Å/mm
Plate scale48.80 µm/arcsec
Effective area (with HRC-S):1 - 2 cm2 (125 - 170 Å)
3 - 7 cm2 (60 - 120 Å)
7 - 12 cm2 (44 - 60 Å)
4 - 8 cm2 (19 - 40 Å)
10 - 25 cm2 (6 - 18 Å)
3 - 5 cm2 (2 - 5 Å)
Background (quiescent)0.12 counts/pixel/100-ksec (HRC-S, on-orbit)
~ 0.04 counts/pixel/100-ksec (HRC-S, after filtering)
« 0.01 counts/pixel/100-ksec (ACIS-S, on-orbit)

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Last modified: 12/14/17