Future experiments from the Moon dedicated to the study of the Cosmic Microwave Background

Transcription

1 Future experiments from the Moon dedicated to the study of the Cosmic Microwave Background C. Burigana, A. De Rosa, L. Valenziano, R. Salvaterra, P. Procopio, G. Morgante, F. Villa, and N. Mandolesi

2 Cosmic Microwave Background Radiation (CMB) Anisotropies Angular power spectrum Polarization P 2 = Q 2 + U 2 Example: Scattering Thomson of radiation with quadrupole anisotropy generates linear polarization Spectrum Photon distribution function

3 Motivation & context The absence of atmospheric emission and radio-millimetre interferences + the feasibility of having in situ instrumentation of remarkable size up-gradable with time the Moon is a potentially ideal place for accurate measurements of CMB: polarization anisotropies, total intensity anisotropies at small angular scales, spectral distortions Although extremely challenging, these kinds of measures are of fundamental relevance for our understanding of the cosmic evolution, from the epoch of inflation to the plasma era, and, finally, to the epoch of cosmological re-ionization related to the cosmic structure formation We carried out a feasibility study of experiments dedicated to the CMB B-mode polarization and to absolute temperature measurements at centimetre and decimetre wavelengths Italian Vision for Moon Exploration, Observation of the Universe from the Moon (Studio Osservazione dell Universo dalla Luna), Final Report, Contratto I/032/06/04 - ASI Perspectives for future experiments and studies on cosmic background radiation from the Moon (WP1420, WP1430, WP1430cm) by C. Burigana, L. Valenziano, A. De Rosa, R. Salvaterra, P. Procopio, G. Morgante, F. Villa, N. Mandolesi

4 Polarization anisotropies of CMB

5 WMAP Courtesy WMAP Science Team

6 Multifrequency is needed! Courtesy WMAP Science Team

7 WMAP 3y Power Spectrum

8 Planck perspectives: TT, TE, EE

9 Measure of E and B modes of the CMB primordial polarisation anisotropy Synchrotron range without Galactic cut The same but excluding Galactic plane or in a clean region Sensitivity required to accurately determine E and B modes. 70GHz case, not observable from the Earth, where foreground contamination is minimum. La Porta et al., 2006

10 B-mode polarization APS from lensing need for about 10 arcmin resolution

11 Constraining Neutrino Mass and Cosmic Reionization with CMB Polarization as a function of neutrino mass Measurable in E mode Small effect in total intensity reionization bump Burigana et al., 2004

12

13

14 Sensitivity: a very high sensitivity is required since the predicted level of the signal is a free parameter of the theory. Therefore, the working hypothesis depends on the theoretical model considered, in this way requirements can be obtained in detail. The sensitivity requirement of the detector is S < 0.1 mk * sec-1/2. With this sensitivity, or better, the B modes can be measured till multipoles l ~ 500 for a signal dt > 0.1 mk and till l ~ for dt > 0.01 mk at clean cosmological frequencies. FWHM: 1 arcmin a 100 GHz Lifetime: 4 full sky surveys. This requirement reflects the trade-off between detector s sensitivity and redundancy of observations to allow an accurate separation of systematic effects. Number of detectors: at least N*1000, where N is the frequency band. The millimetre detectors, both bolometers and radiometers, have sensitivity near the quantum limit. Therefore, in order to obtain the sensitivity required by the predicted observational time it is necessary to have a number of detectors of the order of thousands. This number is necessary not only in cosmological bands, but also in the near bands in order to remove the foregrounds with a comparable accuracy.

15 Technology: HEMT from ~ 20 to 100; Bolometers from ~ 70 to 500 GHz. The detectors based on HEMT are used, for CMB measurements, in experiment on Earth and on the Planck mission. They proved great stability, reliability, cleanness in measurements and they can be used at temperatures of almost 20K; this temperatures can be obtained with active coolers. Recent developments raised the operational frequency over 300 GHz with predicted sensitivity of almost 2.5 times the quantum noise. They are candidates as ideal detectors for frequencies above 100 GHz. See the following figures where measurements and LAN HEMT InP models with gate length 35 nm are reported. The bolometers actually are the most sensitive millimetre, but the cryogenic apparatus needed to reach a temperature of almost 100 mk is more complex. They are the only available broad band detectors at high frequencies. It is important that in a mission like this, where the systematic effects are the limiting effect for the observations, the technologies of observations have a band of overlap.

16 Cryogenics: According to the mission design (single payload, separate payload), to the number and to the type of detectors and their requisites of dissipation, different cryogenic chains can be hypothesized. As example we report an evolution of the chain used on Planck satellite, where the two different chains cohabit in the same focal plane. From T-env to ~50K passive cooling through radiators (V-Grooves like), located always in a area of shade. This radiators can be joined with mechanical coolers active at low vibrations or of sorption-cooler type. From ~50K to ~20-30K (Operating temperature for detectors based on HEMT technology and pre-cooling phase for cryogenic phases at lower temperatures), sorption/jt cooler with H2 or Ne; otherwise mechanical coolers can be used (as example a pulse tube with a small level of vibrations). Even if theoretically possible, the use of cryogenic liquids or solids H2 o Ne is not favoured due to the operating complexity.

17 From ~20-30K to ~5K (pre-cooling for 0.1K cooler): sorption/jt He cooler, technology under development, for systems of great heat-lift, by different research institutes. Also in this case cryogenic liquids can be used, with the remarks previously listed. Depending on the level of vibrations admitted by the microphony of detectors, mechanical cryogenerators (pulse tube) can be used. From ~5K to 0.1K: the technology for obtaining temperatures of almost 100 mk with a high heat lift is of dilution kind. The system used on Planck, for example, consents to cool more than 50 detectors at 100 mk, but its operative time is limited by the available quantity of He3, which is dispersed in space at the and of the cycle. For a new generation mission is necessary to develop new closed-cycle systems, which theoretically allow a infinite operative time.

18 Architecture based on OMT for an accurate separation of polarized signals. The Ortho Mode Transducer are the components that allow the most clean separation of the polarized components in the millimetre range. A mission dedicated to the measurements of CMB polarization with a so high sensitivity requires a separation of the components of almost 60dB.

19 Instead of a single big experiment, we can assume to have a set of 4 smaller payloads which exploit at full the synergies. In this case a excessively big antenna for high frequencies and the complications deriving from a very crowded focal region could be avoided. One (or two, given the low frequency) at low frequencies: HEMTbased for foregrounds measurements (from 20 to 60 GHz) One at intermediate frequencies: HEMT and/or Bolometers (e.g. from 70 to 200 GHz) for the cosmology One at high frequency: Bolometers (e.g. from 300 to 500 GHz) for foregrounds measurements.

20 Spectral Distortions of CMB

21 CMBR SPECTRUM T 0 = ± K (Mather et al. 1999) Redshift Dimensioneless frequency Has the CMBR a black body spectrum?

22 CMB Spectrum measures Recent measures of CMB spectrum (collected by Burigana and Salvaterra, 1999) λ>1cm: typical error > 0.1 K FIRAS measures: typical error ± K

23 Impact of various sources of errors: note the atmosphere relevance

24 Spectral distortions In the primordial universe some processes can lead the matter-radiation fluid out of the thermal equilibrium (energy dissipation because of density fluctuations,physical processes out of the equilibrium, radiative decay of particles, energy release related to the first stages of structures formation, free-free distortions) The photon distribution function isn t a Planckian one The Kompaneets equation in cosmological contest provides the best tool to compute the evolution of the photon distribution function, but a numerical code is needed! KYPRIX An extremely precise fortran based code, able to simulate the effects of the primordial physical processes that can affect the thermodynamic equilibrium of the CMBR

25 Primordial distortions BIG BANG Cosmological applications z term z BE z z ric z today Bose-Einstein like spectrum Superposition of black bodies with µ function of X where Free-free distortions Late distortions Related (mainly) to the reionization history of the universe Cosmological application of a numerical code for the solution of the Kompaneets equation, P.Procopio and C.Burigana, INAF-IASF Bologna, Internal Report, 421

26 Theoretical CMB Spectral Distortions Middle age Free-free Early Bose-Einstein like Late Comptonization like Distorted spectra in the presence of a late energy injection with Δε/ε i = 5 x 10-6 plus an early/intermediate energy injection with Δε/ε i = 5 x 10-6 occurring at y h =5, 1, 0.01 (from the bottom to the top; in the figure the cases at y h =5 and 1 are indistiguishable at short wavelengths; solid lines) and plus a free-free distortion with y B =10-6 (dashes).

27 T e /T R = 10 4 z R = 20 dε/ε = 10-5 Cosmological application One of the representative cases Distortions due to reionization of the universe at low redshifts Ω m = 1 Ω Λ = 0 Ω m = 0.29 Ω Λ = 0.73

28 In the Planckian Hypothesis: limits achievable with a new low frequency experiment DIMES Example: 6 freq. channels between 2 & 90 GHz Limits achievable with a low frequency experiment with the same FIRAS sensitivity Current limits Hypothesis to be checked Burigana and Salvaterra, 2003 Cosmic time

29 CMB spectrum: Key parameters Configuration A and B Frequency operating range: GHz ( cm) Spectral resolution: 10% Angular resolution: 7 /8 Sensitivity: < 1 mk sec -1/2 Field of View: > 10 4 deg 2 Final sensitivity (E.O.L) better than 0.1 mk per resolution element Low sidelobes optics Ground shield avoid ground signal pickup thermal stability Channel Frequency (GHz) Wavelength (cm)

30

31 Calibrator requirements Return Loss < -60dB in the whole frequency range Intercalibration between frequency bands better than 30 μk Thermal stability better than 1 mk with well sampled temperature monitoring (temperature accuracy better than 10 μk) The ARCADE calibrator

32 Radiometers Differential radiometers (using low noise amplifiers) Absolute calibration One of the ARCADE radiometers (Kogut, 2002)

33 Sketch of the large payload Mass: ~1000 Kg, height ~ 6 m, deployed in a shaded crater

34 Scientific performance as function of (low) frequency coverage C = 2, 5, 8 freq. channels, 0.48, 1.9, 7.54 cm D = 3, 6, 9 freq. channels, 0.75, 3.0, 11.9 cm E = 3, 5, 7 freq. Channels, 0.75, 1.9, 4.75 cm R = recent λ 1cm F = COBE/FIRAS Note that even with λ 5cm the improvement is very good!

35 New Concept Design Requirements Mass < 300 Kg Simplify cooling system Location at the pole Continuous operation (day and night) Simplify pointing system Autonomous, unmanned operation Simplify deployment

36 Reduce Dimension and Mass Reduce the number of channels Use a smaller payload Use a smaller cooler Select highest frequency bands Reduce horn and calibrator dimension Enlarge FOV (14 FWHM) Reduce horn dimensions Passive cooling for the optics Use a smaller cooler Introduce steerable optical system Reduce horn dimension Avoid an alt-az mounting

37 New Location Select a location at the Pole Reduce the size of passive cooling radiators Reduce the observed portion of the sky (acceptable from the scientific point of view) Avoid rover and deployment system (reduce mass) Shaded crated location not strictly required Simplified deployment on the final site Operation on the landing module possible Power generation from solar panels on the payload Operation from the near side of the Moon Higher frequency less affected by man-made interference

38 New Payload Concept (conf. E) 3 channels 6 GHz 15 GHz 63 GHz FOV: 14 deg Passive cooling for the optics Steerable optical element at horn aperture 63GHz Channel Internal 15GHz Channel Thermal 6GHz Channel Steerable Mirror Feed Horn Absolute Reference@4K Thermal Cold Head

39 New Payload Concept - I 15GHz Channel 63GHz Channel Cold Head 6GHz Channel Pointing system obtained using steerable mirrors and Moon rotation Electonics box Compressor

40 New Payload Concept - II

41 Location External passive cooling Shield Internal passive cooling shield Solar panel Instrument Cooler s Radiators Middle Shield Location at the Pole Passive cooling possible. Smaller radiators Easy deployment, unmanned operation Shields deployed in-situ Operation from the lander possible Solar panels on the payload

42 Estimated mass: < 200 Kg In situ overall dimension: diameter: 8 m, height: 3 m Passive shield deployed Estimated power requirements: 3 kw Continuous operation possible

43 CONCLUSIONS I CMB general Moon advantages: absence of atmospheric emission and radio-millimetre interferences in situ instrumentation of remarkable size up-gradable with time Moon is a potentially ideal place for accurate measurements of CMB of very high scientific interest: B-mode Polarization Anisotropy (large equipments): inflation physics lensing cosmic reionization (through B & extremely accurate E mode) Spectral Distortions in particular at λ > 1 cm ( large equipments): cosmic reionization (FF & Compt. Dist.) dissipation various cosmic scales (FF, Compt,, BE) particle decays & annihilations (BE, full shape)

44 CONCLUSIONS II CMB spectrum The Moon is a unique opportunity for accurate cm & dm CMB spectrum measures free from atmosphere contamination dm observations requires 10 3 Kg experiments cm observations need 10 2 Kg experiments and 0.1 mk sensivity, a great improvement with respect to the current observation status in particular for free-free distortions & BE-like (early) distortions A compact design for early cm experiments has been proposed Definitive cm & dm missions will map the cosmic thermal history with high precision up redshifts of ~ 10 7 Options: The payload can be integrated with the lander that could supply power No critical dependence on choice of exact position, provided that it is well known Possible implementation on free-flyer, using any available Moon mission

45 Thanks for the attention!