Chandra X-ray Center Chandra X-ray Observatory Overview Roger Brissenden Smithsonian Astrophysical Observatory CIAO Workshop 23 April 2001

Chandra X-ray Center Overview 1.Mission Summary, Launch and Architecture 2.Mission and Observatory Description 3.Spacecraft Subsystems 4.High Resolution Mirror Assembly 5.Science Instruments 6.Chandra X-ray Center Architecture

Chandra X-ray Center NASA Great Observatories CHANDRA

Chandra X-ray Center uLaunch July 23, 1999 –STS-93/ Inertial Upper Stage / Integral Propulsion System –10,000 km x 140,000 km, 28.4 o Inclined Orbit uDesign Lifetime > 5 Years u10-m Focal Length Wolter -1 Mirror: 4 nested Mirror Pairs uEnergy Range: KeV u2 Imaging Focal Plane Science Instruments –ACIS (Advanced CCD Imaging Spectrometer) –HRC (High Resolution Camera) u2 Objective Transmission Gratings for Dispersive Spectroscopy –LETG (Low-Energy Transmission Grating) –HETG (High-Energy Transmission Grating) 1. Chandra Mission Summary

Chandra X-ray Center Chandra Launch uLaunched on Space Shuttle Columbia 7/23/99 on the third attempt uShuttle placed Chandra and IUS in 150 mile orbit uChandra was the longest and heaviest payload launched on the Shuttle uPayload bay doors open 1.5 hours after launch uChandra/IUS deployed 7.5 hours after launch

Chandra X-ray Center Chandra Deployment and Orbit uInertial Upper Stage (IUS) boosted Chandra from shuttle orbit to transfer orbit. Two stage rocket with two 2 minute burns. uChandra separated from the IUS 9.5 hr into mission with orbit of 300km x 74,000km uChandra’s Integral Propulsion System fired 5 times over 15 days to reach final orbit: 10,000 km x 140,000 km. Orbit of 64 hrs and going 1/3 of way to moon

Chandra X-ray Center Chandra Operations uMission science plan converted to command loads and uplinked to Chandra uX-ray events collected and stored on Solid-State Recorders (SSR) uGround contact established every ~8 hours through Deep Space Network –SSR data downlinked –new command load uplinked (up to 72 hours of stored commands) uData transferred to OCC through JPL for science processing CXO CXC OCC sssssssssssssssssssssss

Chandra X-ray Center S/C Support & Eng Analysis Attitude Det. & Sensor Cal Mission Planning & Scheduling Command Management Data Capture Telemetry Processing Command Processing Communication Ops Simulator Operations Database Off-Line SystemOn-Line System Flight S/W Maint Fac IPIs, Guest Observers CXC Observation Request Mission Schedules Telemetry Proposed Observation Science Data S/W Changes Telemetry Commands DSN Scheduling State Vector Telemetry Commands Deep Space Network Telemetry Commands (Via Shuttle) Telemetry Commands OCC Chandra

Chandra X-ray Center 2. Mission and Observatory Description

Chandra X-ray Center Focusing X-rays

Chandra X-ray Center

3. Spacecraft Systems uCommand, Control and Data Management –2 low gain antennas, 2 S-band transponders –Two solid state recorders, each 1.8 GB –Redundant 16-bit On Board Computers (OBC), interface units, command and telemetry units, remote command and telemetry units –32 kbps telemetry with usual 24 kbps science and 8 kbps engineering uElectrical Power –Generates, stores and distributes electrical power to the spacecraft –2 solar wings provide 2112 watts –3 Ni Hydride batteries capacity 120 Amp hours for eclipses uThermal Control –Passive elements include multi-layer insulation and radiators –Active elements include thermostats and sensors –OBC controls HRMA at 70 +/- 2.5 deg with active elements

Chandra X-ray Center Spacecraft Subsystems uPropulsion –Integral propulsion system used for transfer orbit, deactivated –Momentum unloading propulsion system for unloading momentum from reaction wheels uPointing Control and Attitude Determination –Sensors and control hardware to point, slew, solar array positioning and momentum unloading –Pointing requirements a modest ~30” due to photon counting nature of the science instruments –Pointing direction determined from aspect camera tracking 5-8 stars and gyroscopes –Photon positions are reconstructed using aspect camera data during ground processing –Performance of aspect system gives ~3” absolute pointing, 0.3” image reconstruction and 0.6” celestial location –System includes 6 reaction wheels for attitude control, coarse and fine sun sensors for pointing without aspect camera –Spacecraft dithered during observations with ~16 arcsec Lissajous

Chandra X-ray Center Aspect Camera and Fiducial Transfer System

Chandra X-ray Center 4. High Resolution Mirror Assembly u4 pairs of concentric thin-walled, grazing incidence Wolter Type-I mirrors uFabricated from Zerodur, polished to 3A and coated with Ir uDiameters range from 0.65 to 1.23m and total weight 1484 Kg uCharacteristics –Focal length10m –Plate Scale48.8 microns/arcsec –PSF (FWHM)0.5 arcsec –Ghost-free FOV30’ diameter –Effective 0.25 keV keV keV100 cm^2

Chandra X-ray Center HRMA and Associated Structures

Chandra X-ray Center HRMA Effective AreaHRMA Encircled Energy

Chandra X-ray Center 5. Chandra Science Instruments uAdvanced CCD Imaging Spectrometer (ACIS) –CCD array with 16’x16’ field of view (ACIS-I) –high energy grating readout array (ACIS-S) uHigh Resolution Camera (HRC) –microchannel plate imager with 31’x31’ field of view (HRC-I) –low energy grating readout array (HRC-S) uHigh Energy Transmission Grating Spectrometer (HETG) –transmission grating pairs for medium and high energy uLow Energy Transmission Grating Spectrometer (LETG) –transmission grating for low energy ACIS-I ACIS-S HRC-I HRC-S bb Z+ Y+

Chandra X-ray Center Science Instrument Module uACIS and HRC mounted on SIM along the Z axis uSIM provides 20 inches of motion in Z to select ACIS-I, ACIS-S, HRC-I or HRC-S uProvides 0.8 inches of motion in X to adjust focus ACIS Sun Shade ACIS ACIS Radiator Shade HRC Optical Bench Top Hat and Lean-to TSC PSMC BTU RCTU FLCA

Chandra X-ray Center Advanced CCD Imaging Spectrometer (ACIS) uTen 1024x1024 pixel CCDs – 2x2 array for imaging: ACIS-I labeled I0-I3 –1x6 array for imaging or spectroscopy: ACIS-S labeled S0-S5 –6 chips can be operated simultaneously –Array Size 16.9x16.9 arcmin (ACIS-I), 8.3x50.6 arcmin (ACIS-S) –Pixel Size 0.49 arcsec u8 Front-illuminated and 2 back-illuminated chips –BI chips are S1 and S3 –BI response extends lower that FI –Average energy resolution of BI chips better than FI

Chandra X-ray Center Advanced CCD Imaging Spectrometer (ACIS)

Chandra X-ray Center High Resolution Camera (HRC) uMicrochannel plate device with imaging and spectroscopy detectors uTime resolution 16 microseconds uEnergy Range 0.08 – 10 keV uPixel readout size 6.4 microns = 0.13 arcsec/pix uDetection sequence for X-ray –Passes through UV-ion shield –Through photocathode yields photo emission –Photoelectrons accelerated by electric field –Pass through second microchannel plate for additional gain –Electron cloud (2e7 electrons/photon) detected with wire cross grid detector

Chandra X-ray Center High Resolution Camera

Chandra X-ray Center Grating Spectrometers uHETG –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) for use with outer 2 mirrors –High Energy Gratings (HEG) for use with inner 2 mirrors –Mounted at different angles to form an “X” dispersed pattern uLETG –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) 0.15 keV

Chandra X-ray Center Chandra Grating Spectrometers m=2 m=1 m=0 m=-1 m=-2 Incoming Radiation m = d sin   d

6. Chandra X-ray Center Architecture

Chandra X-ray Center