1. “Expected Performances of the JEM-EUSO mission”
A. Santangelo1,2 & M. Bertaina3
IAAT, University of Tübingen, Germany
RIKEN, Japan
University of Torino, Italy
On behalf of the JEM-EUSO Collaboration
Beijing, August, 2011
International Cosmic Ray Conference 2011

2. International Cosmic Ray Conference 2011
Take home messages:
Physics and Astrophysics at E>5×1019 eV
But also…
Explore new physics in the energy range E≈ eV
Highest statistics and therefore largest exposures at extreme energies
But also … lower energies are important for overlapping with ground-based detectors and make
a statistically significant comparison!
Beijing, August, 2011
International Cosmic Ray Conference 2011

3. Key observation and instrument requirements
Observation area (Nadir)
≥1.3×105 (Horbit/400[km])2 km2
Arrival direction determination accuracy
≤ 2.5° (at E=1020 [eV] and 60° zenith angle)
Energy determination accuracy
≤ 30% (E=1020 [eV] and 60° zenith angle)
Xmax determination accuracy
≤ 120 [g/cm2] (E=1020 [eV] and 60°zenith angle)
Energy threshold
≤ 5.5×1019 [eV]
Duty cycle
≥ 17%
Lifetime
> 3 years (goal: > 5 years)
How is defined here the Observation duty cycle
How is defined the Instrument duty cycle?

4. International Cosmic Ray Conference 2011
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

5. Which is the annual exposure?
Of course it depends on the zenith angle and energy…
It is determined by three factors:
Determined by the trigger efficiency
Determined by the background (and operation)
Determined by the cloud coverage
Beijing, August, 2011
International Cosmic Ray Conference 2011

6. International Cosmic Ray Conference 2011
Duty cycle estimation
P.Bobik et al., ID886
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

7. International Cosmic Ray Conference 2011
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

8. 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

9. RELATIVE OCCURENCE OF CLOUDS BETWEEN 50 N & 50 S (TOVS DATA)
Cloud Coverage
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
2.4
3.7
6.8
OD<0.1
29.2
<0.1
1.2
Optical Depth
Do not look at the graphics: it can be improved. Do you have the original table from Lupe?
Which is the key conclusion here? See next slide…
Occurence of clouds (in %) between 50° N and 50° S on TOVS database. The matrix Optical depth vs. Cloud-top altitude is shown.
Confirmed by ISCCP,CACOLO & MERIS database 9
RELATIVE OCCURENCE OF CLOUDS BETWEEN 50 N & 50 S (TOVS DATA)
OPTICAL
DEPTH
CLOUD-TOP ALTITUDE
<3 km
3-7 km
7-10 km
>10 km
>2
17.2
5.2
6.4
6.1
1-2
5.9
2.9
3.5
3.1
0.1-1
2.4
3.7
6.8
<0.1
29.2
1.2
Relative occurrence (%) of clouds between 50 N and 50 S latitudes on TOVS database in the matrix of cloud-top altitude vs optical depth. Daytime and ocean data are used for the better accuracy of the measurement
YELLOW  reconstruction possible only for limited range of ZA
GREEN  reconstruction possible for every Zenith Angle (ZA)
RED  reconstruction severely affected by cloud presence

10. L.Saez et al., ID1034 OK OK BAD OK Signal attenuated 10 10
Qua sono elencate le situazioni elencate precendeentemente.
Signal attenuated 10
L.Saez et al., ID1034 10

11. Cloud-impact to trigger efficiency
L.Saez et al., ID1034, K.Shinozaki et al. ID979
Cloud-impact to trigger efficiency
E>5·1019eV
Cloud top
<3 km
3-7 km
7-10 km
>10 km
OD>2
90%
65%
35%
20%
OD:1-2
70%
45%
25%
OD:0.1-1
80%
75%
OD<0.1
Optical Depth
Average efficiency* = 82% above 50 EeV
*A spectral distribution dN/dE∝E-3 is assumed 11

12. International Cosmic Ray Conference 2011
L.Saez et al., ID1034,
K.Shinozaki et al. ID979
Ratio vs clear sky
efficiency
♦ All trig events with cloud impact
▼ Xmax > H_cloud-top OR tau_cloud < 1
Basic conclusion:
Energy [eV]
In more than 70% of the cases the UV track including Xmax is observable
Do we have a significant plot to support the above statement?
*Different geometrical conditions for optically thick or optically thin clouds
Beijing, August, 2011
International Cosmic Ray Conference 2011 12

13. Trigger Probability (Zenith angle vs. Energy)
q=75
q=60
q=45
q=30
Updated
q=15
K.Shinozaki et al., ID979
Full FoV, bckg = 500 ph/m2/ns/sr

14. Trigger Probability for Central FoV (R<125 km)
q=75
q=60
q=45
q=30
Updated
q=15
K.Shinozaki et al., ID979

15. Normalised Aperture: Efficiency
PRELIMINARY
Better Statistics is needed!
3x1019eV
K.Shinozaki et al., ID979

16. Optics Throughput Spot size QE PMT FS layout Trigger ×2.3
OVERALL NET IMPROVEMENT
Optics
Throughput
Spot size
QE PMT
FS layout
Trigger
Trigger Efficiency (%)
JEM-EUSO
ESA-EUSO
×2.3
Energy (eV)
Energy threshold of JEM-EUSO lowered by a factor more than 2 compared to the old ESA-EUSO

17. Instantaneous Aperture
4.5·105 km2sr
1.5·105 km2sr
4·104 km2sr
The new plots (see later) show too many curves: the message is diluted!
K.Shinozaki et al., ID979

18. Annual Exposure (…Nadir)
TA×h×k
~14%
60,000 km2sr yr
20,000 km2sr yr
5,000 km2sr yr
K.Shinozaki et al., ID979

19. International Cosmic Ray Conference 2011
Why JEM-EUSO? Large exposure + Full sky coverage
1 MLinsley
High energy 50% full efficiency: please explain
Beijing, August, 2011
International Cosmic Ray Conference 2011
K.Shinozaki et al., ID979

20. International Cosmic Ray Conference 2011
Angular Resolution
♦ 7e19 eV
▲3e20 eV ×
a(deg)
× Requirement
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

21. International Cosmic Ray Conference 2011
Energy Resolution
♦ log(E/eV)=19.6
■ log(E/eV)=19.9
■ log(E/eV)=20.1
× Requirement
E=1020eV, q=60° ×
ΔE/E (%)
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

22. Comparison with current observatories
Observatory
Aperture km2 sr
Status
Start
Lifetime
Duty cycle
Annual Exposure
km2 sr yr
Relative to Auger
Auger
7,000
Operations
2006
4 (16) 1
7000 TA
1,200
2008
2 (14)
0.2
TUS
30,000
Developed
2012 5
0.14
4,200
0.6
JEM-EUSO (E≈1020 eV)
430,000
Design
2017
60,000 9
JEM-EUSO (highest energies)
Tilted mode 35°
1,500,000
200,000 28
All numbers must be updated and changed!
Number of events must be given!

23. 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 improved and so have been the performances…

24. THANK YOU!

25. Hmax & ZA dependence Protons, 1019<E(eV)<1021 QGSjet-II
F.Garino et al., ID398