A new space mission Ultra-Fast Flash Observatory (UFFO) for observation of prompt photons from GRBs

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1 A new space mission Ultra-Fast Flash Observatory (UFFO) for observation of prompt photons from GRBs IL H. PARK (Ewha W. Univ., Seoul) for the UFFO Collaboration Deciphering the Ancient Universe with Gamma-Ray Bursts, April 19 23, 2010, Kyoto, Japan Heuijin Lim Oct Bright gamma-ray burst, GRB B 1 Credit: NASA/Swift/Mary Pat Hrybyk-Keith and John Jones

2 Major Contributors Korea : I.H. Park, J.W. Nam, H. Lim, S.M. Jeong, J.E. Kim (Ewha W. U.), C.-H. Lee (Pusan Nat l U.) USA : B. Grossan, E. V. Linder, G. F. Smoot (UC Berkeley) Russia : B.A. Khrenov, G.K. Garipov, M. Panasyuk (Moscow State U.) Taiwan : Pisin Chen (Nat l Taiwan U.) Contents Motivation and present limitation in observation of early photons Our new approach : Ultra-Fast Flash Observatory The UFFO Pathfinder Summary

3 Past and Present Space Missions for GRB BATSE (1991) (Burst and Transient Source Experiment) HETE-2 (2000) (High Energy Transient Explorer-2) SWIFT (2004) GRB dedicated mission Fermi Gamma-ray Space Telescope (2008) Discovery of optical afterglows, ending 30 year mystery of the GRB distance scale Afterglows and host galaxies led to the origin of some types of GRB Discovery of the most distant GRB at z=8.2 Great achievements since the launch of SWIFT in 2004 What is the next? Just replacement or follower? If not, what is that for? 3

4 Future Space Missions for GRB Aims and performance Larger statistics with wider FOV and higher sensitivity Higher z with larger aperture and higher sensitivity Wider band in wavelength, if possible, together with neutrinos Faster response measurements for early/prompt photons UFFO (Ultra-Fast Flash Observatory) UFFO (2015) Pathfinder (2011) 4

5 Richness and complexity of optical light curves Huge variation in light curves, fastrising and slow-rising bursts Complex with decays, plateaus, changes in slope, and others features that are not yet understood Narrow peaked luminosity distribution has promise as a kind of standard candle, so need a larger sample and better resolution at early times Are there more features in the early light curve that are missed by such sparse sampling? Does any feature of the rise correlate with the luminosity or a particular aspect of the physics? How many bursts are mis-classified because the rapid rise was missed? (Taken from Panaitescu & Vestrand 2008) 5

6 Short-hard GRBs and Dark GRBs Short-hard GRBs only about 8 UV-optical measurements, again suffering from poor time resolution in their light curves What is the shape of the rise? Is the shape homogeneous? The physical origin remains an outstanding mystery Is there any prompt UV-optical emission from such events? What would we see if we observe in the sub-minute or subsecond regime? Are there ultra-short events on the accretion disk dynamical timescale of compact objects (that are beamed so we can see them)? "Dark" GRBs Recently, extinction has been found to be the dominant source of dark GRB (Perley, D. A. et al., 2009) An alternative scenario, however, suggests that some "Dark" GRB are simply due to a faster decay for optical than X-ray emission 6

7 Internal or External Shock Early Gamma-X light curves with multiple peaks were measured Indicate the presence of internal shock, producing prompt emission. What about UV/optical emission at early time? believed to be from external shocks(piran 2004), but, also from internal shocks! Need to measure them at the beginning time after trigger and with shorter time scale Measurement of the bulk Lorentz factor Molinari et al shows that the bulk Lorentz factor depends on the time of the early UVoptical emission peak See Bruce Grossan s poster presentation (no #) for detail discussion of science with UFFO 7

8 Current Limits of Rapid Response Measurements B BATA T X R T UV OT UVOT XRT Spacec raft Swift UVOT response times The BAT produces a crude sky position via a coded mask technique, then the entire observatory spacecraft slews to point the UVOT at the GRB position After nearly 5 years of operation, only a handful of responses have occurred in less than 60 s, and none at al below 40 s Due to finite mission lifetime, SWIFT cannot be expected to significantly increase this number of sub-minute responses The SWIFT limit of 60 s response is therefore the practical minimum for sensitive UV-optical GRB studies for the near to mid-term future. UFFO will explore the blank parameter space, the fast- and ultra-fast regimes below 40 s, in a systematic survey, for the first time 8

9 A NEW APPROACH: MOVE THE OPTICAL PATH, NOT THE SPACECRAFT Secondary MEMS Mirror Array Mirror and/or Rotating Mirror Plate Primary Mirror Photo- Detector Modified Ritchey-Chrétien telescope Fast sub-minute with rotating mirror Ultra-fast sub-second with MEMS Mirror Array(MMA) (MEMS : Micro-Electro-Mechanical Systems)

10 Metal pad Inner spring 2-axis Analog Micromirror Array of Ewha Mirror plate Mirror post Lower comb Hidden actuators: fill-factor of 84% in an 8 x 8 array Reflector: 340 µm 340 µm Resonance frequency: 3 khz Tilting angle : ±6 comb actuator (mirror plate removed) Upper comb Gimbal Outer spring Bottom electrode Revealed actuator See Jiwoo Nam s poster (067) for details of MEMS Micromirror Array

11 First Small MEMS Tracking Mirror Telescope (MTEL) Wide FOV, fastest zoom-in and tracking (Sep. 2008) 3x3 mm 2 aperture MMA Aperture Telescope box Optics Express 16(2008) Introduced in Laser Focus World, Feb

12 MTEL in Space (Launched in Sep. 17, 2009) Russian Microsatellite Tatyana-2 Payload: MTEL (MEMS Telescope for Extreme Lightning), 3x3 mm2 aperture Extremely Large Transient Sparks

13 Demonstration : Tracking of Light Source

14 deg New Design of Ewha MEMS Micromirror (2009-) Tilting angle ± 10 ( optically ± 20 ) Size of element 1mm x 1mm Resonant frequency ~ 500 Hz with mirror plate Applied voltage vs. Tilting angle volt 14

15 Latest Micromirror Array of Ewha Microscope image of fabricated micro mirror on back side view 15

16 The UFFO Instrument Oct Heuijin Lim Bright gamma-ray burst, GRB B Credit: NASA/Swift/Mary Pat Hrybyk-Keith and John 16 Jones

17 UFFO Payload 950 mm UBAT (UFFO Burst Alert & (X-ray) Trigger telescope) 500 mm UTAT (UV/Optical Trigger Assistant Telescope) 1090 mm Mass: 120kg Power: 200Watts ON/OFF Gamma ray Monitor Energy Meas. Processing Data Position SMT (Slewing Mirror Telescope) Precise position information Heuijin Lim 17

18 Parameters Telescope Concept Design parameters of UFFO UBAT (X-ray for primary trigger) UTAT (UV trigger) SMT (UV-optical for afterglow) Coded mask Double Fresnel Lens Ritchey-Chrétien + MMA with motorized plate Aperture Coded mask: 51x95 cm 2, Detector: 20x40 cm 2 30 x 30 cm 2 30 cm diameter FOV 2.0 sr 60 x 60 (pixel FOV = 0.1 x0.1 ) # of channels > 5,000 ~300 x 300 ~256 x x 0.3 (pixel FOV= 4 x 4 ) Exposure time 1 s 100 ms 1s (for 17.5 mag) Location Accuracy 17 arcmin. ~3 arcmin. ~ 0.5 arcsec. Energy range 4 ~ 250 kev 200 ~ 650 nm 200 ~ 650 nm Focal plane detector Processing time CdTe ISiPM Intensified CCD 1.1 s Readout~20 ms Total Time ~ 0.12s Motor slewing ~ 1s Readout ~ 50 ms Total time ~ 1s See J. Nam s (067) and H. Lim s (046) poster presentations 18

19 Fast and Ultra-fast Slewing Reflector System of MEMS Mirror Array + Rotating Mirror Plate GRB GRB Rotating Mirror Plate MEMS Mirror Array Detector Detector Initial Stage MMA Tilting RMP Tilting With zero MMA tilt 0 sec 1 ms - 1 s 1 sec - Trigger given Captures very early photons with a limited resolution Precision measurement of early photons (position, spectrum). See Soomin Jeong s poster presentation (036)

20 Payload Parameters and Collaboration Platform for launch in 2015 Korean Russian NASA SALMON Present participation Ewha-RCMST, Ewha- IEU, PNU, KASSI Berkeley BCCP, SSL Moscow State U. Nat l Taiwan U. Denmark Space Lab. (under discussion) Physical size: 60 x 70 x 90 cm 3 Mass: 120 kg Power: 200 W Data: 110 kbps 20

21 The UFFO Pathfinder Oct Heuijin Lim Bright gamma-ray burst, GRB B Credit: NASA/Swift/Mary Pat Hrybyk-Keith and John 21 Jones

22 300 mm (h) UFFO Pathfinder Payload UBAT (UFFO Burst Alert & (X-ray) Trigger telescope) Trigger fired SMT (Slewing Mirror Telescope) X-ray information UV/Optical-ray information zenith h d w Processing Data 22

23 Specifications of UBAT and SMT UBAT : UFFO Burst Alert Telescope FOV PSF Coded mask aperture camera ~2 sr (89 x89 ) 17 arcmin Energy range 4 ~ 250 kev Detector CdTe Effective size 307 cm 2 Pixel size 1.2 x 1.2 x 1 mm 3 Number of pixels 146 x 146 Spectral energy resolution Sensitivity 2 kev FWHM at 60 kev 310 mcrab in 10 s exposure at 5.5σ 4~50 kev SMT: Slewing Mirror Telescope Aperture F-number 6 FOV Detector Detection Element Pixel Scale Location Accuracy Wavelength Range Sensitivity Bright Limit Ritchey-Chrétien + MMA with rotator 20 cm diameter 17 x 17 armin Intensified CCD 256 x 256 pixels 4 arcsec 0.5 arcsec 200 nm ~ 650 nm B=23.5 in white light in 1000 sec. mv = 6 mag Effective FOV : 60 x 60 See Soomin Jeong s poster presentation (036) 23

24 Spacecraft for the UFFO Pathfinder Lomonosov satellite is processed under the Russian federal space program. Payload : TUS + UFFO Pathfinder Spacecraft & Builder Launch Date Nov Orbit Height Total Mass Mission Lifetime Payload Payload Mass Payload Power Lomonosov & ROSCOSMOS-VNIIEM 550 km 300 kg 3 years TUS for UHECR, UFFO Pathfinder, etc. 100 kg (UFFO:20 kg) 100 ~ 150 W Space viewing UFFO pathfinder Earth viewing TUS telescope for UHECR 24

25 Expectation of UFFO Pathfinder Short + Long GRBs 67 UVOT Bursts/year triggered by UBAT. Short-hard GRBs Studied from the Swift gamma-x fluence for the period of Jan. 24, 2005 ~ Sep. 21, 2009 UBAT sensitivity is ~ 10x poor than SWIFT BAT, but fraction of bursts lost is small (~10 %). 25

26 Summary The need for fast detection of UV/optical photons is clear and compelling We propose UFFO, equipped with slewing mirror telescope based on fast response MMA, to measure early photons from GRBs, down to sub-minute and sub-second timescales for the fist time, which allows a deeper understanding of the GRB mechanism, particularly as a cosmological probe The UFFO Pathfinder, scaled down version of UFFO but with several tens of early photon triggers, will be launched on the Lomonosov satellite in the end of 2011 (see arxiv as well as 4 contributed posters) 26

27 arxiv MEMS 우주망원경연구단 27