“Expected Performances of
the JEM-EUSO mission”
A. Santangelo1,2 & M. Bertaina3
1)
IAAT, University of Tübingen, Germany
2) RIKEN, Japan
3) University of Torino, Italy
On behalf of the JEM-EUSO Collaboration
Beijing, August, 2011
International Cosmic Ray Conference 2011
Andrea Santangelo,
Kepler Center-Tü
Take home messages:
Physics and Astrophysics at E>5×1019 eV
But also…
Explore new physics in the energy range E≈1020-1021eV
Highest statistics and therefore largest exposures at
extreme energies
20-21
E » 10
eV
But also … lower energies are important for
overlapping with ground-based detectors and make
a statistically significant comparison!
19
E < 5´10 eV
Beijing, August, 2011
International Cosmic Ray Conference 2011
Andrea Santangelo,
Kepler Center-Tü
Key observation and
instrument requirements
Observation area (Nadir)
Arrival direction determination
accuracy
Energy determination
accuracy
Xmax determination accuracy
Energy threshold
Duty cycle
Lifetime
≥1.3×105 (Horbit/400[km])2 km2
≤ 2.5° (at E=1020 [eV] and
60° zenith angle)
≤ 30% (E=1020 [eV] and 60°
zenith angle)
≤ 120 [g/cm2] (E=1020 [eV] and
60°zenith angle)
≤ 5.5×1019 [eV]
≥ 17%
> 3 years (goal: > 5 years)
Andrea Santangelo,
Kepler Center-Tü
Part II: Performances
Directly referring to posters:
F. Fenu et al. ‘ESAF Simulation’, ID592
T. Mernik et al. ‘ ESAF Reconstruction’, ID633
K. Shinozaki et al. ‘Aperture estimation’, ID979
L. Saez et al. ‘Trigger studies in cloudy conditions’, ID1034
P. Bobik et al. ‘ Duty Cycle’, ID886
F. Garino et al. ‘Cloud distribution’, ID398
K. Higashide et al. ‘STM Simulation’, ID1240
Indirectly referring to:
Several posters related to the hardware development
Beijing, August, 2011
International Cosmic Ray Conference 2011
Andrea Santangelo,
Kepler Center-Tü
Which is the annual exposure?
• Of course it depends on the zenith angle and
energy…
• It is determined by three factors:
TA ´ h ´ k
by the
TA ® Trigger Aperture Determined
trigger efficiency
h ® duty cycle Determined by the background
(and operation)
k ® cloud impact
Beijing, August, 2011
Determined by the cloud
coverage
International Cosmic Ray Conference 2011
Andrea Santangelo,
Kepler Center-Tü
P.Bobik et al., ID886
Duty cycle estimation
defined as the fraction of time in which the
nightglow background doesn’t hamper EAS
observation
• Based on the Universitetsky Tatiana satellite
G. K. Garipov et al. 2005a, 2005b
• Scaling of the UV intensity from Tatiana’s to
the ISS orbit
The JEM-EUSO duty cycle has been estimated
for a set of Solar Zenith angles assuming an
UV background < 1500 photons/(m2 ns sr)
Beijing, August, 2011
International Cosmic Ray Conference 2011
Andrea Santangelo,
Kepler Center-Tü
P.Bobik et al., ID886
Duty cycle (2)
Note that:
Selecting bckg < 1500
photons/(m2 ns sr) with
its relative occurrence
gives a trigger efficiency
curve equivalent to an
average bckg of 500
photons/(m2 ns sr)
We can also operate at
higher background rates
(higher energies)
Beijing, August, 2011
International Cosmic Ray Conference 2011
Andrea Santangelo,
Kepler Center-Tü
Duty cycle: EUSO old estimate
C. Berat et al. 2003
F. Montanet et al. 2004
Independent estimate
All these results are in
very good agreement
with and actually better
than the conservative
value assumed by the
JEM-EUSO
consortium: 20%
Beijing, August, 2011
International Cosmic Ray Conference 2011
Andrea Santangelo,
Kepler Center-Tü
Cloud Coverage
Optical Depth
F.Garino et al., ID398
Cloud top
<3 km
3-7 km
7-10 km
>10 km
OD>2
17.2
5.2
6.4
6.1
OD:1-2
5.9
2.9
3.5
3.1
OD:0.1-1
6.4
2.4
3.7
6.8
OD<0.1
29.2
<0.1
<0.1
1.2
Occurence of clouds (in %) between 50° N and 50° S on TOVS
database. The matrix Optical depth vs. Cloud-top altitude is shown.
Andrea Santangelo,
Confirmed by ISCCP,CACOLO & MERIS database Kepler Center-Tü
OK
OK
BAD
OK
Signal attenuated
10
L.Saez et al., ID1034
Andrea Santangelo,
Kepler Center-Tü
L.Saez et al., ID1034, K.Shinozaki et al. ID979
Cloud-impact to trigger efficiency
Optical Depth
E>5·1019eV
Cloud top
<3 km
3-7 km
7-10 km
>10 km
OD>2
90%
65%
35%
20%
OD:1-2
90%
70%
45%
25%
OD:0.1-1
90%
80%
75%
70%
OD<0.1
90%
90%
90%
90%
Average efficiency* = 82% above 50 EeV
*A spectral distribution dN/dE∝E-3 is assumed
Andrea Santangelo,
Kepler Center-Tü
K.Shinozaki et al. ID979
1.0
efficiency
L.Saez et al., ID1034,
0.9
Ratio vs clear sky
0.8
0.7
0.6
0.5
0.4
0.3
0.2
0.1
♦ All trig events with
cloud impact
▼ Xmax > H_cloudtop OR tau_cloud < 1
0.0
1.00E+019
1.00E+020
1.00E+021
Energy [eV]
Basic conclusion:
In more than 70% of the cases the UV
track including Xmax is observable
*Different geometrical conditions for optically thick or optically thin clouds
Beijing, August, 2011
International Cosmic Ray Conference 2011
Andrea Santangelo,
Kepler Center-Tü
Trigger Probability (Zenith angle vs. Energy)
q=75
q=60
q=45
q=30
q=15
K.Shinozaki et al., ID979
Full FoV, bckg = 500 ph/m2/ns/sr
Andrea Santangelo,
Kepler Center-Tü
Trigger Probability for Central FoV
(R<125 km)
q=75
q=60
q=45
q=30
q=15
K.Shinozaki et al., ID979
Andrea Santangelo,
Kepler Center-Tü
Normalised Aperture: Efficiency
PRELIMINARY
3x1019eV
K.Shinozaki et al., ID979
Andrea Santangelo,
Kepler Center-Tü
Trigger Efficiency (%)
OVERALL NET IMPROVEMENT
JEM-EUSO
×2.3
•Optics
Throughput
•Spot size
ESA-EUSO •QE PMT
•FS layout
•Trigger
Energy (eV)
Energy threshold of JEM-EUSO lowered by a factor more than 2
Andrea Santangelo,
compared to the old ESA-EUSO
Kepler Center-Tü
Instantaneous Aperture
4.5·105 km2sr
1.5·105 km2sr
4·104 km2sr
K.Shinozaki et al., ID979
Andrea Santangelo,
Kepler Center-Tü
Annual Exposure (…Nadir) TA×h×k
~14%
60,000 km2sr yr
20,000 km2sr yr
5,000 km2sr yr
K.Shinozaki et al., ID979
Andrea Santangelo,
Kepler Center-Tü
Why JEM-EUSO? Large exposure + Full sky coverage
1 MLinsley
Beijing, August, 2011
K.Shinozaki et al., ID979
International Cosmic Ray Conference 2011
Andrea Santangelo,
Kepler Center-Tü
Angular Resolution
♦ 7e19 eV
▲3e20 eV
a(deg)
×
× Requirement
a<2.5°@
E=1020eV, q=60°
Zenith Angle q(deg)
End to end simulations show that the requirement is met.
Beijing, August, 2011
International Cosmic Ray Conference 2011
T.Mernik et al., ID633
Andrea Santangelo,
Kepler Center-Tü
Energy Resolution
♦ log(E/eV)=19.6
■ log(E/eV)=19.9
■ log(E/eV)=20.1
0.4
ΔE/E (%)
0.35
×
0.3
×19.9
Requirement
19.6
DE/E<30% @
E=1020eV, q=60°
0.25
0.2
0.15
0.1
0.05
0
0
20
40
60
80
ZENITH Angle q(deg)
End to end simulations show that the requirement is met.
DXmax < 70gr/cm2 (Requirement DXmax < 120gr/cm2) OK
Beijing, August, 2011
International Cosmic Ray Conference 2011
T.Mernik et al., ID633
Andrea Santangelo,
Kepler Center-Tü
Comparison with current observatories
Observatory
Aperture
km2 sr
Status
Start
Lifetime
Duty
cycle
Annual
Relative
Exposure to Auger
km2 sr yr
Auger
7,000
Operations
2006
4 (16)
1
7000
1
TA
1,200
Operations
2008
2 (14)
1
1,200
0.2
30,000
Developed
2012
5
0.14
4,200
0.6
430,000
Design
2017
5
0.14
60,000
9
1,500,000
Design
2017
5
0.14
200,000
28
TUS
JEM-EUSO
(E≈1020 eV)
JEM-EUSO
(highest energies)
Tilted mode 35°
Andrea Santangelo,
Kepler Center-Tü
Conclusions
• The JEM-EUSO duty cycle and cloud impact have been thoroughly
estimated to be η≈20% and κ > 70%.
•
JEM-EUSO is designed to have a annual exposure about 9xAuger at
1020 eV in nadir mode and 28xAuger at the highest unexplored
energies in tilt mode.
• To reach/approach 1ML integrated exposure it is necessary to
operate the mission also in tilted mode.
• Simulations in nadir mode shows that the energy, angular and Xmax
resolution meet the requirements.
• JEM-EUSO will have enough exposure and reconstruction capability
at 3x1019 eV to overlap with current generation observatory.
• JEM-EUSO is not EUSO! Optics and PMTs QE have been greatly
Andrea Santangelo,
improved and so have been the performances…
Kepler Center-Tü
THANK YOU!
Andrea Santangelo,
Kepler Center-Tü
Hmax & ZA dependence
Protons, 1019<E(eV)<1021 QGSjet-II
F.Garino et al., ID398
Andrea Santangelo,
Kepler Center-Tü