1. 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 DC Masashi Hazumi (KEK)

2. 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 gravitational waves 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 DC Masashi Hazumi (KEK)

3. 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 DC Masashi Hazumi (KEK)

4. 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 DC Masashi Hazumi (KEK)

5. 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.
<CLICK>
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 DC Masashi Hazumi (KEK)

6. 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
JAXA’s small satellites
2012/08/15
Inflation Probe Science Analysis Group (IPSAG) Workshop, Washington DC Masashi Hazumi (KEK)

7. Three key technologies to make LiteBIRD light
Prototype crossed Mizuguchi-Dragone
mirror
Small mirrors (~60cm)
Warm launch with mechanical coolers
Technology alliance with SPICA for 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 SPICA’s 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 TES option
2012/08/15
Inflation Probe Science Analysis Group (IPSAG) Workshop, Washington DC Masashi Hazumi (KEK)

8. 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 JAXA’s 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 JAXA’s 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 rocket’s payload and JAXA’s 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 DC Masashi Hazumi (KEK)

9. 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 DC Masashi Hazumi (KEK)

10. 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 ~0.5°angular 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 DC Masashi Hazumi (KEK)

11. Focal plane requirement
Noise level: goal = 2mK・arcmin
(requirement: < 3mK・arcmin)
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 DC Masashi Hazumi (KEK)

12. 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 DC Masashi Hazumi (KEK)

13. 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 Δν/ν~1.
Above three constraints naturally
put us to the band locations. CO
J J J3-2
Large pixel (Δν/ν=1) Small pixel (Δν/ν=1)
Δν/ν=0.23 per band Δν/ν=0.3 per band
GHz GHz GHz GHz 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 TES option
2012/08/15
Inflation Probe Science Analysis Group (IPSAG) Workshop, Washington DC Masashi Hazumi (KEK)

14. LiteBIRD focal plane design
tri-chroic（140/190/280GHz）
UC Berkeley
TES option
2022 TES
bolometers
Tbath = 100mK
tri-chroic（60/78/100GHz）
1.8mKarcmin
(w/ 2 effective years)
Strehl ratio>0.8
POLARBEAR
focal plane as
a prototype
[4]
An example implementation with UC Berkeley’s multi-chroic TES technology is shown here.
We need 2022 TES bolometers.
All pixels are within an area of high Strehl ratio,
<CLICK>
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 DC Masashi Hazumi (KEK)

15. LiteBIRD focal plane design
tri-chroic（140/190/280GHz）
Band centers can be
distributed to increase the
effective number of bands
UC Berkeley
TES option
2022 TES
bolometers
Tbath = 100mK
tri-chroic（60/78/100GHz）
Strehl ratio>0.8
POLARBEAR
focal plane as
a prototype
More space to place <60GHz detectors
[3]
I also point out that this design is flexible enough to be more colorful.
Band centers can be distributed to increase the effective number of bands.
We can also accommodate another band below 60 GHz using two corners shown here.
2012/08/15
Inflation Probe Science Analysis Group (IPSAG) Workshop, Washington DC Masashi Hazumi (KEK)

16. TES signal multiplexing
Frequency-domain
multiplexing (MUX)
used in
POLARBEAR,
SPT, EBEX etc.
(8-16 MUX)
toward
LiteBIRD
[3]
TES signal multiplexing is also important. Members of LiteBIRD have been using the frequency-domain multiplexing scheme in several CMB projects including POLARBEAR, SPT, EBEX, where MUX factor is up to 16.
Toward LiteBIRD, we plan to replace the analog feedback loop with Digital Active Nulling to achieve 64 MUX factor.
This work is being done with a collaboration of Berkeley, KEK, McGill and NIST, lead by the McGill group supported by Canadian space agency.
Frequency-domain multiplexing
Replace analog feedback loop with Digital Active Nulling (DAN) to achieve 64 MUX
led by McGill University (supported by CSA)
Berkeley-KEK-McGill-NIST
2012/08/15
Inflation Probe Science Analysis Group (IPSAG) Workshop, Washington DC Masashi Hazumi (KEK)

17. MKID option for higher MUX factor
300 mK stage
102 pixel MKID
NAOJ
KEK
OKAYAMA
RIKEN
LiteBIRD is currently
the guiding force for
the MKID development
in Japan
Si lens-array
[2]
There is also an MKID option for even higher MUX factors.
R&Ds are going on with a collaboration of NAOJ, RIKEN, KEK and Okayama university.
Double slot antenna + Al MKID
Electrical noise measurement
M. Naruse et al. 2012
2012/08/15
Inflation Probe Science Analysis Group (IPSAG) Workshop, Washington DC Masashi Hazumi (KEK)

18. Expected sensitivity on r
with 2 effective years
Foreground limited
Foreground rejection
parameter
Lensing limited
Cosmic variance limited
Foreground limited
[4]
The expected sensitivity on r is shown here.
You see from the 3sigma curve that even if r is you can obtain 3sigma evidence for primordial gravitational wave.
Note that this study already takes statistics, foreground and lensing into account.
We are starting more advanced simulation studies. One thing is with JAXA engineers to evaluate systematic uncertainties based on detailed specifications of components we want to use. This sort of studies is essential to consider realistic systematic uncertainties.
Katayama-Komatsu
Cosmic variance limited
2012/08/15
Inflation Probe Science Analysis Group (IPSAG) Workshop, Washington DC Masashi Hazumi (KEK)

19. L2 vs. LEO
3sigma discovery region
(statistical error only)
LEO L2
[4]
This plot shows the 3sigma discovery regions for L2 and LEO cases.
Both cases satisfy the mission of LiteBIRD as far as the statistical error is concerned.
The difference mainly comes from the fact that we need to cut some data when the Moon is too close to the boresight.
In this plot you also see that LiteBIRD nicely covers this colorful river, which are predictions from inflationary models.
Both cases satisfy the requirement on statistical error
2012/08/15
Inflation Probe Science Analysis Group (IPSAG) Workshop, Washington DC Masashi Hazumi (KEK)

20. Advantages of LiteBIRD
Not a pathfinder; small but no compromise in r sensitivity
More launch options than a big satellite
Less expensive
With LiteBIRD plus ground-based super-telescopes (e.g. O(100K) bolometers w/ arcminute angular resolution) as one package, science reach nearly as good as a large CMB polarization mission with ~1/5 total cost
Better in terms of cooling (mirrors and baffles)
The whole spacecraft can be tested in a large cryogenic test chamber
Better calibration data  less systematic uncertainties
Better pre-flight investigations  less chance of failure
[8]
There are several advantages of LiteBIRD.
It is not a path finder, small but no compromise in r sensitivity.
Since it is small, we have more launch options than a big satellite.
It is less expensive.
With LiteBIRD plus ground-based super-telescope as one package, science reach is nearly as good as a large CMB polarization mission with much less cost.
The small mirrors are better in terms of cooling.
Last of all, the whole spacecraft can be tested in a large cryogenic test chamber, so that we can obtain better calibration data, which will result in less systematic uncertainties,
also we can perform better pre-flight investigations, which is important to reduce the chance of failure.
2012/08/15
Inflation Probe Science Analysis Group (IPSAG) Workshop, Washington DC Masashi Hazumi (KEK)

21. Funding
“Cosmic Background Radiation” selected as one of “innovative areas for research” by MEXT (PI: M. Hazumi)
JFY2009 – JFY2013: 14.3M$
QUIET, POLARBEAR, LiteBIRD, CIBER etc.
Joint budget request (KEK, NINS) in consideration
~100M$ needed (+ launch cost)
International collaboration should be pursued actively.
Detector development matching fund from NASA will help a lot
Launch not limited to Epsilon or H2 depending funding progress
As for funding, Cosmic Background Radiation was selected as one of innovative areas for research in 2009 by MEXT, our funding agency.
Programs currently running under this grant include QUIET, POLARBEAR, LiteBIRD and CIBER.
For LiteBIRD, a joint budget request by KEK and NINS is in preparation.
I want to emphasize that intetnational collaboration is essential for LiteBIRD.
Depending on the funding progress, launch options should not be limited to JAXA’s launch vehicles.
2012/08/15
Inflation Probe Science Analysis Group (IPSAG) Workshop, Washington DC Masashi Hazumi (KEK)

22. Support from research communities
Japanese High Energy Physics (HEP) community has identified CMB polarization measurements and dark energy survey as two important areas of their “cosmic frontier”.
Japanese radio astronomy community also expressed their support to LiteBIRD.
Cosmology community (theory) is also supporting LiteBIRD and contributing to the science case.
SCSS added “fundamental physics” as a target for space programs in next 20 years
We have a good support from Japanese High Energy Physics community,
radio astronomy community, the cosmology community.
In particular, Japanese High Energy Physics community has identified CMB polarization and dark energy
as two important areas of cosmic frontier research.
Steering Committee for Space Science added fundamental physics as a target for space programs in next 20 years.
LiteBIRD nicely fits this target.
2012/08/15
Inflation Probe Science Analysis Group (IPSAG) Workshop, Washington DC Masashi Hazumi (KEK)

23. Conclusion CMB polarization will be the frontier in post-Planck era
Best probe to discover primordial gravitational waves
Unique tests of inflation and quantum gravity
The goal of LiteBIRD is to search for primordial gravitational waves with the sensitivity of dr<0.001, for testing all the representative inflationary models.
The strategy of LiteBIRD is to focus on r measurements. The powerful duo (LiteBIRD and ground-based super-telescopes) will be the most cost-effective way.
No show-stopper in design studies so far. Technology verification in ground-based projects in next ~3 years will be crucial. The LiteBIRD roadmap includes such ground-based projects.
[7]
In conclusion, CMB polarization is the frontier in the post-Planck era, because it is the best probe to discover primordial gravitational waves, which allow us to perform unique tests of inflation and quantum gravity.
The goal of LiteBIRD is to search for primordial gravitational waves with the sensitivity of r about 0.001, for testing all the representative inflationary models.
The strategy of LiteBIRD is to focus on r measurements. The powerful duo of LiteBIRD and ground-based super-telescopes will be the most cost-effective way.
There is no show-stopper in design studies so far.
Technology verification in ground-based projects in next 3 years or so will be crucial.
The LiteBIRD roadmap includes such ground-based projects.
That is all. Thank you.
2012/08/15
Inflation Probe Science Analysis Group (IPSAG) Workshop, Washington DC Masashi Hazumi (KEK)

24. Contacts
LiteBIRD WG
PI: Masashi Hazumi (KEK)
US-PI: Adrian T. Lee (UC Berkeley)
JAXA contact: Kazuhisa Mitsuda (ISAS/JAXA)
ISAS/JAXA office for international strategy and coordination
Director: Tadayuki Takahashi (ISAS/JAXA)
Steering Committee for Space Science (SCSS)
Chair: Saku Tsuneta (ATC/NAOJ)
I finish my talk by showing contact people. For US CMB physicists Adrian is the contact,
and for NASA people Tadayuki Takahashi is the contact, he is the PI of Astro-H
but at the same time the director for international strategy and coordination.
2012/08/15
Inflation Probe Science Analysis Group (IPSAG) Workshop, Washington DC Masashi Hazumi (KEK)