litebird a small satellite for the studies of b-mode polarization and inflation from cosmic...
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LiteBIRD A Small Satellite for the Studies of B-mode
Polarization and Inflation from Cosmic Background Radiation
Detection Masashi Hazumi Institute of Particle and Nuclear Studies
High Energy Research Accelerator Organization (KEK) Tsukuba, Japan
On behalf of the LiteBIRD working group [1] I am going to talk
about LiteBIRD, which is a small satellite for the studies of
B-mode polarization and inflation from cosmic background radiation
detection. 2012/08/15 Inflation Probe Science Analysis Group
(IPSAG) Workshop, Washington DCMasashi Hazumi (KEK) LiteBIRD
project overview
Scientific goal Stringent tests of cosmic inflation at the
extremely early universe Observations Full-sky CMB (i.e. mm wave)
polarization survey at a degree scale Strategy Roadmap includes
ground-based projects as important steps Focus on signals of
inflationary gravitationalwaves imprinted in CMB polarization
Synergy with ground-based super-telescopes Project status/plans
Working group authorized by SCSS, supported by JAXA Mission
definition review in 2013, target launch year ~2020 CMB : Cosmic
Microwave Background [6] The scientific goal of LiteBIRD is to make
stringent tests of cosmic inflation, the leading hypothesis at the
extremely early universe. To this end, we need to carry out a
full-sky CMB polarization survey at a degree scale. As for our
strategy, our roadmap includes ground-based projects as important
steps, which I explain in the next slide. We focus on signals of
inflationary gravitational waves imprinted in CMB polarization. At
the same time, we plan to have a strong ground-based
super-telescope program accompanied, so that the synergy between
space and ground-based measurements gives a wide range of
scientific outputs as a whole in a very cost-effective manner. The
LiteBIRD working group was authorized by Japanese steering
committee for space science and is supported by JAXA. Studies
toward the mission definition review are in progress, with a target
launch year around 2020. 2012/08/15 Inflation Probe Science
Analysis Group (IPSAG) Workshop, Washington DCMasashi Hazumi (KEK)
LiteBIRD roadmap POLARBEAR-2 LiteBIRD POLARBEAR GroundBIRD
[3] The LiteBIRD roadmap includes ground-based projects, POLARBEAR,
POLARBEAR-2 and GroundBIRD, as important steps. These are useful
for verification of key technologies, yet they themselves are
designed to produce good scientific results. Ground-based projects
as important steps Verification of key technologies Good scientific
results International projects 2012/08/15 Inflation Probe Science
Analysis Group (IPSAG) Workshop, Washington DCMasashi Hazumi (KEK)
LiteBIRD working group
58 members (as of Aug.15, 2012) International and interdisciplinary
KEK Y. Chinone K. Hattori M. Hazumi (PI) M. Hasegawa K.
Ishidoshiro* N. Kimura T. Matsumura H. Morii M. Nagai** R. Nagata
N. Sato T. Suzuki O. Tajima T. Tomaru M. Yoshida ISAS/JAXA H. Fuke
H. Matsuhara K. Mitsuda S. Sakai Y. Takei N. Yamazaki T. Yoshida UC
Berkeley A. Ghribi W. Holzapfel A. Lee (US-PI) H. Nishino P.
Richards A. Suzuki UT Austin E. Komatsu ATC/NAOJ K. Karatsu T.
Noguchi Y. Sekimoto Y. Uzawa RIKEN K. Koga C. Otani IPMU N.
Katayama Tohoku U. M. Hattori Yokohama NU. S. Murayama S. Nakamura
K. Natsume Y. Takagi Kinki U. I. Ohta + Korea U. under
consideration McGill U. M. Dobbs ARD/JAXA I. Kawano A. Noda Y. Sato
K. Shinozaki H. Sugita K. Yotsumoto CMB experimenters (Berkeley,
KEK, McGill, Eiichiro) LBNL J. Borrill X-ray astrophysicists (JAXA)
Okayama U. H. Ishino A. Kibayashi S. Mima Y. Mibe Tsukuba U. S.
Takada [2] There are more than 50 members in the working group,
including CMB experimenters, X-ray astrophysicists, infrared
astronomers, JAXA engineers and superconducting device developers.
It is international and interdisciplinary. Infrared astronomers
(JAXA) SOKENDAI Y. Inoue A. Shimizu H. Watanabe Superconducting
Device (Berkeley, RIKEN, NAOJ, Okayama, KEK etc.) JAXA engineers
and Mission Design Support Group 2012/08/15 Inflation Probe Science
Analysis Group (IPSAG) Workshop, Washington DCMasashi Hazumi (KEK)
LiteBIRD mission Check representative inflationary models
requirement on the uncertainty on r stat. syst. foreground lensing)
dr < 0.001 No lose theorem of LiteBIRD Many inflationary models
predict r>0.01 >10sigma discovery Representative inflationary
models (single-large-field slow-roll models) have a lower bound on
r, r>0.002, from Lyth relation. no gravitational wave detection
at LiteBIRD exclude representative inflationary models (i.e. 95%
C.L.) Early indication from ground-based projects power spectra at
LiteBIRD ! [1+3] Now I come to the mission of LiteBIRD. The mission
is to check representative inflationary models. period. To be more
specific, we require that the total uncertainty on r be less than
0.001, where the uncertainty includes those from statistical and
systematic errors, as well as from foregrounds and lensing. This
requirement leads to a kind of no lose theorem of LiteBIRD. I tell
you why. Many inflationary models predict r greater than If that is
the case, we expect a discovery with more than 10 sigmas with
LiteBIRD. Furthermore, it is known that representative inflationary
models have a lower bound on r, r greater than 0.002, from Lyth
relation. Therefore, if there is no gravitational wave detection at
LiteBIRD, we exclude all the representative inflationary models
with 95% C.L.which gives a severe constraint on cosmology. Last of
all, in case some indication of the signal is obtained from
ground-based projects, that means r is fairly large, large enough
that LiteBIRD can measure the B-mode power spectrum, which gives
much more information in identifying the correct model of
inflation. So, LiteBIRD will give a huge impact on cosmology in any
case. Huge impact on cosmology in any case 2012/08/15 Inflation
Probe Science Analysis Group (IPSAG) Workshop, Washington DCMasashi
Hazumi (KEK) LiteBIRD system overview Spin axis Bore sight 2ndary
HWP mirror (4K)
Super- conducting Focal plane (100mK) Primary mirror (4K)
Cryocoolers (ST/JT + ADR) [1+2] Here is an overview of the LiteBIRD
system. From the sky side to the detector side, key components are
rotating HWP, the primary mirror, the secondary mirror, and the
super-conducting focal plane. With the cryocooler system, mirrors
are cooled down to 4K, and the bath temperature for the focal plane
is 100mK. Solar panels Standard bus system for JAXAs small
satellites 2012/08/15 Inflation Probe Science Analysis Group
(IPSAG) Workshop, Washington DCMasashi Hazumi (KEK) Three key
technologies to make LiteBIRD light
Prototype crossed Mizuguchi-Dragone mirror Small mirrors (~60cm)
Warm launch with mechanical coolers Technology alliance with
SPICAfor pre-cooling (ST/JT) Alliance with DIOS (X-ray mission)for
ADR Multi-chroic focal plane ~2000 TES (Tbath=100mK, dn/n ~ 0.3),
or equivalent MKIDs Technology demonstration with ground-based
projects (POLARBEAR, POLARBEAR-2, GroundBIRD) 2ST/JT BBM 100GHz
220GHz 150GHz Bolometers Sinuous antenna Fabricated Triplexer
Filter {1+3} There are three key technologies to make LiteBIRD
light. Small mirrors, warm launch with mechanical coolers, and the
multi-chroic focal plane. The LiteBIRD cooling system is rather
similar to SPICAs pre-cooling, and ADR is very similar to one of
future X-ray missions DIOS., so we have a good technology alliance
here. Multi-chroic focal plane is doable with about 2000 sensors,
which is large but within a reach. UC Berkeley TESoption 2012/08/15
Inflation Probe Science Analysis Group (IPSAG) Workshop, Washington
DCMasashi Hazumi (KEK) Major system requirements
Item Requirements Remarks Orbit LEO (~500km) or L2 Launch vehicle:
Epsilon or H2 Observing time > 2 years Weight < 450kg from
Epsilon payload requirement Power < 500W from JAXAs standard bus
system Total sensitivity < 3mKarcmin 2mKarcmin as the design
goal Angular resolution < 30arcmin for 150GHz descoping requires
justification Observing frequencies GHz (or wider) 4 bands
Modulation/Demodulation HWP rotation > 1Hz HWP = Half Wave Plate
1/f knee (f) scan rate (R) R/f > 0.06 rpm/mHz (e.g.R>1.2rpm
for f=20mHz) spec. for the case HWP stops Telemetry > 10GB/day
w/ Planck-type data suppression Total systematic errors < 18nK2
on CBB (l=2) [1+1] Major system requirements are listed here. We
are studying right now both LEO and L2 orbits, with JAXAs Epsilon
or H2 rocket. The observing time is more than 2 years, Requirements
on the weight and power are based on constraints from the Epsilon
rockets payload and JAXAs standard bus system, which may be relaxed
if you go for the H2 option. The total sensitivity should be better
than 3microkelvin arcminute, the angular resolution should be
better than 30arcmin for 150GHz, and observing frequencies should
cover GHz with 4 or more bands. We plan to use continuously
rotating HWP, but the minimal success should be achieved even if
the HWP stops. For that purpose we have requirements on the 1/f
knee frequency and scan rate. Our data are a little less than
10GB/day assuming Planck-type data suppression. So the requirement
is to download more than 10GB/day. The total systematic error
should be well below the lensing B-mode floor. Because of the
limited time I cannot go into details of systematic error studies
today. These requirements are still subject to modifications in the
feasibility studies 2012/08/15 Inflation Probe Science Analysis
Group (IPSAG) Workshop, Washington DCMasashi Hazumi (KEK) LiteBIRD
scan strategy: LEO case
150 Mkm Sun Earth Satellite 0.38 Mkm Earth Moon = 76 degs = 34 degs
x y z Spin axis Anti-sun Boresight altitude 500 km - Spin axis
rotation about anti-sun axis (i.e. satellite period around the
earth) fs = 90 min - Boresight axis rotation about spin axis fb ~
0.6 rpm 6000K 300K 175K : relative angle betw/n moon and boresight
(60 degs) scan uniformity cross link [3] Requirements for scan
strategy include uniform density in the sky, wide daily coverage,
and good crosslinkings. In both L2 and LEO, we are considering scan
strategy with off-spin-axis boresight and spin axis rotation, as if
the telescope were a spinning top undergoing a slow precession.
Here I show the LEO case as an example, which has more constraints
than the L2 case. It turns out that uniformity and cross link are
nearly as good as those at L2. LEO 2012/08/15 Uniformity and cross
link nearly as good as those at L2 Inflation Probe Science Analysis
Group (IPSAG) Workshop, Washington DCMasashi Hazumi (KEK) LiteBIRD
optics 4K Reflective Optics HWP example Boresight 2ndary
Crossed Mizuguchi-Dragone 30cm 2ndary mirror HWP (f30cm) T.
Matsumura, doctoral thesis super-conducting bearing wide-band AR
(EBEX) Focal plane Primary mirror Mirror diameter ~60cm for
~0.5angular resolution is sufficient for both reionization and
recombination bumps [1+2] This is a slide about LiteBIRD optics. We
employ a compact crossed Mizuguchi-Dragone design with the mirror
size of about 60cm for a half degree angular resolution, which is
sufficient for both reionization and recombination bumps. With this
design the diameter of HWP is 30cm. Prototype mirrors 2012/08/15
Inflation Probe Science Analysis Group (IPSAG) Workshop, Washington
DCMasashi Hazumi (KEK) Focal plane requirement
Noise level: goal = 2mKarcmin (requirement: < 3mKarcmin) To be
well below lensing floor [2] The focal plane requirement,
3microkelvin-arcminutes, comes from the fact that the lensing
B-mode behaves as the external noise unless you find a way to
reduce the effect. Then if the noise level should be well below the
lensing floor, that is enough. 2012/08/15 Inflation Probe Science
Analysis Group (IPSAG) Workshop, Washington DCMasashi Hazumi (KEK)
Foreground removal and observing bands
Foreground removal 4 bands in GHz N. Katayama and E. Komatsu, ApJ
737, 78 (2011) (arXiv: ) pixel-based polarized foreground removal
model-independent very small bias r~0.0006 with 60,100,240GHz (3
bands) [3] Foreground removal and observing bands were studied
based on the template cleaning method and results were described in
the paper listed here. They achieved a very small bias less than
From the results, we require that our observations should have 4 or
more bands in b/w 50 to 270. 2012/08/15 Inflation Probe Science
Analysis Group (IPSAG) Workshop, Washington DCMasashi Hazumi (KEK)
LiteBIRD band selection for multi-chroic pixels
We chose the band locations with the following reasons.
Katayama-Komatsu (2010) suggested the range of frequency from GHz
based on the template subtraction. We want to exclude the CO lines.
From the practical consideration such as AR coating on a lenslet
array, it is reasonable to limit the bandwidth to /~1. Above three
constraints naturally put us to the band locations. CO J J J3-2
Large pixel (/=1) Small pixel (/=1) /=0.23 per band /=0.3 per band
GHzGHz GHzGHz GHz GHz 50-320GHz 100GHz 220GHz 150GHz Bolometers
Sinuous antenna Fabricated Triplexer Filter [2] We chose the band
locations with 3 reasons. First of all, we take suggestions in the
Katayama-Komatsu paper, which I already mentioned. Secondly, we
also want to exclude the CO lines. Thirdly, from the practical
consideration such as AR coating on a lenslet array, it is
reasonable to limit the bandwidth to about 100% for each pixel.
Then we naturally comes to the band selection shown here. Three
bands with centers at 60,78 and 100 GHz for the low-frequency
pixel, and another set of three bands at 143, 190 and 280 GHz, so
that in total the focal plane covers from 50 to 320 GHz with 6
bands. UC Berkeley TESoption 2012/08/15 Inflation Probe Science
Analysis Group (IPSAG) Workshop, Washington DCMasashi Hazumi (KEK)
LiteBIRD focal plane design
tri-chroic140/190/280GHz UC Berkeley TESoption 2022 TES bolometers
Tbath = 100mK tri-chroic60/78/100GHz 1.8mKarcmin (w/ 2 effective
years) Strehl ratio>0.8 POLARBEAR focal plane as a prototype [4]
An example implementation with UC Berkeleys multi-chroic TES
technology is shown here. We need 2022 TES bolometers. All pixels
are within an area of high Strehl ratio, and we achieve the total
sensitivity of 1.8microkelvin-arcmin, which meets our requirement.
2ST/JT BBM 2012/08/15 Inflation Probe Science Analysis Group
(IPSAG) Workshop, Washington DCMasashi Hazumi (KEK) LiteBIRD focal
plane design
tri-chroic140/190/280GHz Band centers can be distributed to
increase the effective number of bands UC Berkeley TESoption 2022
TES bolometers Tbath = 100mK tri-chroic60/78/100GHz Strehl
ratio>0.8 POLARBEAR focal plane as a prototype More space to
place
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