Status of the ECLAIRs mission for
Gamma-Ray Burst multi-wavelength observation
http://www.oamp.fr/ECLAIRS/
Abstract: Gamma-ray bursts (GRB) − at least those with a duration longer
than a few seconds − are the most energetic events in the Universe and
occur at cosmological distances. The ECLAIRs micro-satellite, to be
launched in 2009, will provide multi-wavelength observations of GRB, to
study their astrophysics and to use them as cosmological probes.
Furthermore in 2009 ECLAIRs is expected to be the only space borne
instrument capable of providing a GRB trigger in near-realtime with sufficient
localization accuracy for GRB follow-up observations with the powerful
ground based robotic telescopes available by then.
A "Phase A study" of the ECLAIRs project has recently been launched by
the French Space Agency CNES, aiming at a detailed mission design and
selection for flight in 2006. The ECLAIRs mission combines a payload for
GRB detection onboard a CNES micro-satellite of the successful "Myriade"
family with a set of wide field-of-view ground-based telescopes for the
detection of the GRB prompt emission.
The ECLAIRs space-borne instrument, the X/gamma-ray camera (CXG)
has a wide field-of-view of about 2 sr and will detect about 100 GRB per year
in the 4-50 keV energy band. It will localize the GRB on the sky with an
accuracy of about 10 arcmin and transmit this information in a few seconds
to ground for follow-up observations. The CXG is inspired from the
INTEGRAL imager IBIS and uses a CdTe detection plane covering about
2
1000 cm , placed 46 cm below a coded mask. The ECLAIRs CXG detects in
real-time a GRB event and forwards this low-data volume information to
ground via a network of VHF ground-receivers, from which the GRB
scientific community is informed. All photons acquired by the CXG during
GRB events are sent to ground when in reach of a high data-rate X-band
ground-receiver.
As a second instrument of the ECLAIRs mission, the optical camera
network (UDV), is sensitive to magnitude-15 stars and covers 1/4th of the
CXG field-of-view. It will observe the prompt emission and the possible
precursor of about 10 GRB per year in the visible-band. The UDV acquires
continuously images of the sky, dumped into a buffer memory. A seek-back
in memory is launched in case a GRB trigger issued by the space-borne
CXG is received in order to search for the GRB prompt emission and optical
precursor.
1967 - First GRB detection
1991 - 2000 : Uniform sky distribution
short gamma-ray count rate increase
of 2704 GRB detected
by BATSE/CGRO
[GLAST]
0.5-400keV
15k-1MeV
10-120keV
20k-0.3TeV
2005
2008
2008
0,2
0,1
0,05
REM
optical
optical+nIR
80%
2007
102
103
104
104
0
0,0
1
0,1
1
10
ECLAIRs scientific specifications
Detect and localize more than 200 GRB during the entire mission,
by sky monitoring in the X and γ-ray domains
Observe for 30 GRB during the entire mission the simultaneous
emission in the visible band (before and after the event)
Detect and localize X-ray rich GRB and X-ray flashes (E > 4 keV)
Event localization on the sky with an accuracy of 10 arcmin
Reveal the progenitor star
(necessary in order to use GRB as deep-cosmological probes)
VLT / X-Shooter
2008
Near real-time alert for follow-up observations (within 10’s of seconds)
Store all X/γ-ray photons, for GRB studies and non-GRB astrophysics
Study the star formation rate at high redshift, detection of first stars?
(γ-rays can be seen across the whole Universe)
Problem : after 2008, no space-borne trigger ?
Store visible images at a ~10 s rate minutes before and after the event
Mission lifetime of at least 2 years
Not studied : prompt X-ray and visible emission !
1
• Satellite (X/γ-Ray Camera & trigger)
• Visible band cameras (on ground)
• Network
• Observers
2
• X/γ-Ray Camera (CXG;
detection of the GRB)
• VHF net (real-time alert)
• Robotic Telescopes (refine
position for X-shooter/VLT)
• UDV (Visible Detection Unit;
search prompt emission)
• X-band and S-band net
(delayed photon dump and
satellite control)
3
4
5
ECLAIRs payload on a “Myriade” Microsatellite
• CXG (X/γ -Ray Camera,
imaging in 4-50 keV,
spectra up to 500 keV)
• UTS
(Scientific Trigger Unit:
on-board real-time GRB
detection & localization)
• EGCU
(Payload Management
and Mass Storage)
3
5
Coded Mask
(localization 10’)
Lateral shield
(Ta, Sn, Cu, Al)
CdTe detector
• 6400 pixels
• 1024 cm2
GRB
4
Simulation of ECLAIRs sources imaging
Field-of-view
(large, 2 sr)
Sky simulation
(sky direction of photons
hitting the detector)
• e.g. GRB of 10 s
- intensity 50 ph/cm2
- location [30,30]
extragalactic γ-ray bkg
• Sky 88°× 88°
- field of view 2 sr
- sky pixel size ~ 0.5°
- optical axis [0,0]
Solar panel
2
Myriade / CNES
mirco-satellite
platform
(cubic, 60 cm)
1
60 cm
ECLAIRs system
Allow follow-up observations with large telescopes for determination
of the redshift of the host galaxy (in 75% of the cases)
Detect and localize GRB independently of their duration (~ ms to min)
Physics of relativistic outflows
(also relevant for AGN and Microquasars)
optical+nIR
Star-tracker
(attitude control)
VHF antenna
(GRB alerts)
X-band antenna
(Data dump)
ECLAIRs on board γ-ray camera (CXG)
46 cm
36 cm
241
300
Counts
Am source
3.5 keV threshold
noise 30-50 e- RMS
“Polycell”
200
1.6 keV FWHM
• localization precision 12 arcmin for S/N > 5.5 σ
• sensitivity 200 mCrab in 4-10 keV for 10 s exposure
• with a threshold of 4 keV ECLAIRs is more sensitive than:
SWIFT for GRB with E pk <40 keV
BATSE for GRB with Epk<70 keV
exposure=1 s; S/N=5.5 σ
GRB with α =-1; β =-2
ECLAIRs
Imaging 4 - 50 keV
SW
IF
T
0
10
20
30
40
50
Sky deconvolution
• mask-detector correlation
• detection of source (e.g. 80 σ)
• localization ~10 arcmin
• 5 σ-sensitivity for a 10 s exposure:
1.5 ph/cm2/s (center of field of view)
Count rate increase trigger
(DAPNIA, CEA Saclay)
(γ-ray detector)
- count rate (R) in different
energy bands (4-10-20-50 keV),
time intervals (ms-s) & sectors
- background rate monitoring
- detect count rate increase/bkg
CXG (16 ADCs)
Energy (keV)
EGCU
Telecommand, Control
(config, acquisition, diagnostic)
Status, Housekeeping
γ photon Stream
(Time, Pixel, Energy)
S-band
delayed, 600 kb/s
Ctrl Conf Stat Test
AbsTime
1 Hz
γ dump
γ receive
TimeBase
Sat Attitude
bulk-mem
receiver in reach
count rate & bkg rate
(per E-band, Time-bin, CXG sector)
EGCU
Trigger : rate increase
local-mem
R-B > λ sqrt(B)
Alert Type 1,
AbsTime, Duration, Sigma
X-band
delayed, 16 Mb/s
Build Time-Window
GRB alert (via VHF)
predefined, or around Type 1
- real-time transmission (10 s)
to VHF network along equator
(time, position, error-box)
Epeak = peak energy of GRB (keV)
(payload manager)
Config
Status / HK
VHF-HK
VHF
stream
Freeze
memory
VHF
real-time, 600 b/s
Detector Shadowgram
Sky image (deconvolve,FFT)
Source position (catalogue)
Data dump (via X-band)
60
Detection plane
(counts in each detector pixel)
• CdTe pixel size 4 mm
• 0.5 mm gap between pixels
• 80×80 = 6400 pixels
• sensitive area 1024 cm2
ECLAIRs on-board trigger and data acquisition
GRB Trigger scheme
- shadowgram in time window
- γ-ray sky image (deconvolution)
- sources search in sky image
- association to catalog sources
- trigger if unknown source found
- refine position after PSF fit (10’)
100
• 400 “Polycells” of 16 pixels
• CdTe pixel size 4× 4×2 mm
Mask (example)
• 46 cm above detector
• white = opaque 4-50 keV
• red = transparent
• mask pixel size 4.5 mm
• random, self-holding
Source detection trigger
E
TS
BA
Ta 0.2 mm
Sn 0.5 mm
Cu 0.3 mm
Al 0.5 mm
Expected ECLAIRs CXG performance
• coded aperture telescope (with mask)
• 2 sr field of view
• detection plane 6400 pixels (1024 cm2)
• read-out electronics (IDeF-X)
(CEA Saclay - CNES R&D program)
techno AMS 0.35 µm
• Power ~ 1 mW / pixel
• 4 - 50 keV imaging, < 500 keV spectra
• Spectral result with this electronics:
Fp [1-1000 keV] (ph.cm-2.s-1)
54 cm
X, V
T90 (s)
Exploration of the central engine, with precursor
(first photon signal, deep probe inside the object)
(ground-based) afterglow within minutes
= 100 x a SN in the visible,
or = 1 x Ecin of a SN explosion
100
Physical process, emission zone of prompt X-ray and visible emission
• Spectroscopic Telescopes
1051 ergs in γ-rays (jets)
Optical afterglow emission
20
0,02
0,01
γ
Very energetic event
40
a better understanding of the nature of the GRB itself
by observation of emission
prior to the GRB, the prompt emission, and the early afterglow
over a large spectral range (from visible to gamma-rays)
(ground-based) localization (arcsec)
TAROT
60
ECLAIRs aims at...
afterglow>60s
X-ray/optical
• Robotic Telescopes
Host galaxy detected
Redshift measured (z=3.42)
Cosmological distances
80
Epic
GRB events
Flux (cm-2 s-1 keV-1)x[E/100] 2
1
0,5
Energy (keV)
(space-borne) within 10’s of seconds : localization (arcmin)
SWIFT
“Collapsar”
T + 12 h
Beppo-SAX detection of X-ray afterglow (GRB971214)
Future GRB studies, a 3 steps strategy
INTEGRAL
T + 6.5 h
by Vela satellites
nuclear test-ban
surveillance
• GRB-Trigger
HETE-2
1997 : GRB of cosmological origin
Alert Type 1 & 2,
Position, Sigma
Refine position (fit)
- delayed transmission (<10 h)
- high priority to GRB photons
UTS
(GRB trigger system)
Collaborating Institutes
ECLAIRs visible-band detection unit (UDV)
ECLAIRs ground-system
ECLAIRs mission status
Scientific requirements
sensitivity (5 σ) > mag 15 (V-band, for 15 s exposure)
one GRB per month detected in visible band
→ UDV monitors permanently at least a 30°× 30° box
inside the field-of-view of the ECLAIRs satellite
→ 3 sites (e.g. Canries, Hawaii, Hanle)
Design “à la ROTSE”
1 orbit ~ 90 min
Canaries
Hanle
HETE-2
i=2°
Each UDV site
• simultaneous observation with sat. passage
• one image every 15 s
• 35°× 35° field-of-view (FOV)
• 20 commercial cameras
(e.g. Canon, F=200 mm, F/D=1.8, 8° FOV)
• CCDs 2048×2048 full frame + shutter
• arcmin localization accuracy
• automatic acquisition system
(local data storage, automatic dome control)
• quick analysis in case of GRB detected by sat.
other science when sat. occulted by Earth
(Swift FOV, search for transients & moving obj)
Per site: angle over horizon (°) vs time
ECLAIRS
i=20°
Hawaii
Status
• DAPNIA (CEA-Saclay)
• CNES “Myriad” platform
• up to now: 6 in flight
• lifetime > 2 yr
CNES selection in 2004
Phase A started May 2005
(mission design phase)
Phase B expected in 2006
(design of subsystems)
Phase C expected in 2007
(construction)
scientific management (PI)
payload project lead & integration
payload GRB trigger system (UTS)
ASICs for CXG-“Polycells”
ground segment contribution
• photo: DEMETER,
the 1st of “Myriad”,
launched June 2004.
• date: 2009 expected
• launcher: PSLV (India)
• passenger of the
Indian/French satellite
“Megha-Tropiques”
Mission Control Center (CNES,Toulouse) Observers
(up to 29, 14 from HETE-2)
X-band stations
• Telecommand via S-band stations
• Telemetry form X-band stations
(Malindi, Kourou?)
Scientific Mission Center (CEA,Saclay?)
UDV stations
• Telemetry from VHF stations, alert processing
• Scientific (X-band) data analysis
• Weekly observation plan
(Hawaii, Canaries, Hanle?)
• GRB public
alerts & data
• other data
reserved for
CoI institutes
microsatellite project lead
payload management unit (EGCU)
Microsatellite
Launch
VHF stations
• CNES (Toulouse)
Orbit
• Low Earth orbit
(680-800 km,
below radiation belts),
Payload
Mass 50 kg, Power 60 W • Low Inclination (20°,
avoid S-Atlantic-Anomaly)
• CESR (Toulouse)
X/γ-ray camera (CXG)
• OAMP (Marseille)
visible band detectors (UDV)
• APC (Paris)
mask and shielding
• LATT (Toulouse-Tarbes)
ground segment contribution
• IAP (Paris)
theoretical group
• TIFR (Mumbai)
scientific interface with ISRO,
X-band? (Bangalore), UDV? (Hanle)
• IASF (Milano)
X-band (Malindi)
• MIT (Cambridge)
[email protected]
June 2005
DSM DAPNIA $5
VHF network
Saclay