PILOT balloon experiment

Transcription

1 PILOT balloon experiment J.-Ph. Bernard CESR Toulouse Context: Planck & B-pol Polarized foregrounds The PILOT experiment

2 PILOT:Science Objectives Polarized Instrument for Long-Wavelength Observations of the Tenuous ISM Observe the linear polarization of dust emission in order to : - Reveal the structure of the magnetic field which controles the structuration of the Interstellar medium and the collapse leading to the formation of new stars - The nature of dust grains through their geometric and magnetic properties Understand the polarized foreground for future CMB polarized missions An accurate subtraction of this foreground emission will require a deep understanding of its origin. It also requires detection of dust polarization in faint diffuse cirrus clouds. These objectives require high sensitivity and fast mapping and therefore the use of bolometer filled arrays.

3 PILOT:Consortium France: CESR Toulouse (J.P. Bernard, C. Marty) IAS Orsay (B. Leriche) CEA Saclay (L. Rodriguez) CNES Toulouse (Div ballon) Europe: ESTEC Netherlands: (J. Tauber, G. Pilbrat) Cardiff U. UK (M. Griffin, P. Hargrave) Manchester U. UK (B. Maffei) Roma Italy (S. Masi, P. debernardis)

4 PILOT:Description Photometer Azimuth scanning Stellar sensor Primary miror Elevation change CNES gondola

5 Characteristics Instantaneous FOV: 46'*23'

6 FIR/submm Planck Planck should allow to detect λ-variations of the dust polarization (at 3-σ every 1 below Av=0.5 mag). Detecting more precisely smaller variations toward more diffuse clouds may require using a polarized instrument at higher frequency like PILOT Planck: polarized Planck: unpolarized

7 PILOT vs Planck λ-coverage Planck: polarized Planck: unpolarized PILOT

8 PILOT:Description Gondola : «standard» CNES (LPMA/IASI), about 500kg Rotation in azimut allowing scans on the sky Telescope : = 1m, off-axis Gregorian. Angular resolution = 550 µm Stellarsensor:large format CCD. Scanning sky at 1.5 /s. hopefuly day/night. Photometer : - 2 photometric 240 µm and 550 µm - Detectors cooled down to 300 mk

9 PILOT: Optics Telescope: -off-axis parabolic primary mirror (M1) -off-axis ellipsoid secondary mirror (M2) -Mitsugushi-Dragone config. Reimaging Optics: -Two lenses (L1 & L2). -Lyot stop (L). -Half-wave plate (WP). -Telecentric objective config. -WP and L next to a pupil (image of M1) of the optics. - Polar analysis grid (G)

10 PILOT:Detectors 0.3 K J.-Ph. Bernard, CNES CCT, Toulouse, Nov. 15th 2006

11 PILOT:Detectors J.-Ph. Bernard, CNES CCT, Toulouse, Nov. 15th 2006

12 PILOT:Detectors terconnection rcuit Bolometer arrays developped by CEA/LETI for Herschel/PACS multiplexed readout NEP = W/Hz -1/2 16*16 pixels Thermometer Silicon Grid + Absorber Reflector Indium Bumps PILOT will have a total of 2048 individual bolometers!! (to be compared with less than 100 for previous instruments)

13 Polarization Measurement rinciple of the polarization measurement with PILOT input linear polarization Bi-refringent material 1/2 wave plate Reflection detector Grid analyzer

14 Polarization Measurement rinciple of the polarization measurement with PILOT input linear polarization Bi-refringent material 1/2 wave plate Reflection detector Grid analyzer

15 Polarization Measurement rinciple of the polarization measurement with PILOT Most existing experiments rotate the HWP at constant velocity and detect modulated signal on detectors. For PILOT, we change HWP positions by discrete steps because: 1/ we do not want to modulate even a tiny fraction of the background (background is 10 4 times the scientific signal, ie 10 6 times the polarization) 2/ sky mapping while spinning would be too fast for the available detectors.

16 Polarization Measurement

17 PILOT: scanning strategy Elevation 550 µm 240 µm Azimuth

18 Polarization Measurement For one position ω of the waveplate, one measures : (Transmission array) (Reflection array) At least 2 positions are needed to measure I, Q, U Q,U derived from differences I measured from average

19 Polarization Measurement Wave-plate angle "Paralactic" angle Instrumental rotation

20 PILOT:Calibration Source No unpolarized calibration source on sky Internal calibration source= Spare of the Herschel SPIRE calibration source - Very accurate repeatability - Fast on/off switch - Low consumption - Used to calibrate Response flat-field J.-Ph. Bernard, CNES CCT, Toulouse, Nov. 15th 2006

21 PILOT: Sensitivity Results : Galactic plane 30 mn 240 µm, 250 /hr Input Intensity Recovered Intensity Polarization (%) Max=6% (Red) Min=4% (blue)

22 Simulations Max=3% (Rouge Min=8% (bleu) Results : Cirrus (Av=2 mag) 1hr 240 µm, 16 /hr Input Intensity Recovered Intensity Polarization (%)

23 Mission Planning Objective on astronomical targets - Galactic plane survey - Deep field on cirrus clouds - Large and Small Magellanic Clouds Source visibility requires combination of 3 flights from different launch sites (different latitudes) Preliminary study with: - Kiruna - Sweeden (lat = 60, flight #1, winter 2008) -Trapani - Italy (lat=38, flight#2, summer 2009) -Alice-Spring or Sao-Jose-Dos Campos- Brazil (lat = -23, flight#3, spring 2010) Simulations performed with realistic parameters: - mapping speed: 300 2/h - vscan=24'/s - scan amplitude=20 Observational constraints: - 20 < elevation < 60 - night-time observations only

24 Mission Planning Kiruna Trapani AliceSpring Sao-Jose ~ 90% of the Galactic plane is surveyed within a hrs total integration time 12 to 16 hrs left for others tagets (Cirrus, Magellanic clouds, calibration ) We insist on the fact that it would be much more convenient and safe for the scientific return of each flight to be able to observe during day-time, even though it is not formally required. -> a day-operating stellar sensor would be a goal to reach for the two last flights.

25 The END PILOT will attempt at measuring the linear polarization from dust emission in our Galaxy to very high accuracy levels at high frequencies The goal is to understand the physics of dust polarization, to ultimately help with component separation for future cosmology missions PILOT is a test-bed for the use of compact multiplexed bolometer arrays for polarization measurements PILOT is funded by CNES. Detailed definition is ending and realization of the instrument is starting. First flight expected in end-2008 (Kiruna) PILOT

26 The END PILOT will attempt at measuring the linear polarization from dust emission in our Galaxy to very high accuracy levels at high frequencies The goal is to understand the physics of dust polarization, to ultimately help with component separation for future cosmology missions PILOT is a test-bed for the use of compact multiplexed bolometer arrays for polarization measurements PILOT is funded by CNES. Detailed definition is ending and realization of the instrument is starting. First flight expected in end-2008 (Kiruna) PILOT ILOT is the pilot fish Future CMB-pol mission?

27 CMB Anisotropy/Polarization map from B2K (2003)

28 BOOMERanG-FG We plan to re-fly B03 with an upgraded forcal plane, to go after foreground cirrus dust polarization. This information is essential for all the planned B-modes experiments (e.g. BICEP, Dome-C etc.) and is very difficult to measure from ground. The BOOMERanG optics can host an array of >100 PSB at >350 GHz.

29 OOMERanG GHz PSB 240 GH 340 GH OOMERanG- FG 340 GHz PSB 140 GH PSB Frequency range complementary to PILOT

30 From