Chandra X-ray Center Martin Elvis Smithsonian Astrophysical Observatory Welcome to the 4 th Chandra – CIAO Workshop 20 – 22 May 2002

Chandra X-ray Center

Martin ElvisSmithsonian Astrophysical Observatory

Welcome

to the 4th

Chandra – CIAO

Workshop20 – 22 May 2002


Chandra X-ray Observatory Overview

Martin Elvis

Smithsonian Astrophysical Observatory

CIAO Workshop

20 May 2001


NASA Great Observatories

CHANDRA


Focusing X-rays


2 Imaging Focal Plane Science Instruments– ACIS (Advanced CCD Imaging Spectrometer)

– HRC (High Resolution Camera)

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

¼ arcsecond resolution. Sub-0.5arcsec in practice

10-m Focal Length Wolter -1 Mirror: 4 nested Mirror Pairs Energy Range: 0.1-10 keV

Design Lifetime > 5 Years (in NASA plan for 10 year life)

2 Objective Transmission Gratings for Dispersive Spectroscopy– LETG (Low-Energy Transmission Grating)

– HETG (High-Energy Transmission Grating)


Mission and Observatory Description


High Resolution Mirror Assembly

polished to 3A -> low scattering

high dynamic range

4 pairs of concentric thin-walled zerodur, grazing incidence Wolter Type-I mirrors ->large area. ->800cm2 E<2keV

figured to 0.5” FWHM -> sensitivity,

-> megapixel images

Focal length 10 m. -> response to 10keV

1.6”

95%


Aspect Camera and Fiducial Transfer System

4.25inch dia. 15”pixels

Aspect Camera

<0.25” r ms (typical)


Chandra Science Instruments

Advanced CCD Imaging Spectrometer (ACIS)– CCD array with 16’x16’ field of view (ACIS-I)– grating readout array (ACIS-S)

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)– transmission grating pairs for medium and high energy

Low Energy Transmission Grating Spectrometer (LETG)– transmission grating for low energy

ACIS-I

ACIS-S

HRC-I

HRC-S

BI BI

Z+

Y+


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


ACIS IssuesCTI

Front Iluminated (FI) chips suffered proton damage just after launch. -> charge transfer inefficiency (CTI) -> much degraded energy resolution

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 Sherpa

CTI correction (Townsley, PSU) restores linearity, most dE/E

Low Energy Calibration Non-linear gain Changing QE See L. David talk


Chandra Grating Spectrometers

m=2

m=1

m=0

m=-1

m=-2

IncomingRadiation

m = d sin

d


Grating Spectrometers

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

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 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

CXO

CXCOCC

sssssssssssssssssssssss

6. Chandra X-ray Center Architecture

uplinkdownlink


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


enjoy the workshop!

Documents

Chandra X-ray Center Martin Elvis Smithsonian Astrophysical Observatory Welcome to the 4 th Chandra – CIAO Workshop 20 – 22 May 2002