平成 29 年度共同利用研究・研究成果報告書
FY2017 Joint Usage research・Research result report
研究課題名:Research subject
和文(in Japanese)：紫外線撮像望遠鏡による TA サイトでの空気シャワー蛍光光の観測
英文(in English)：Observation of airshower fluorescence light at the TA FD site byusing an Imaging UV telescope
研究代表者: Principal Investigator

Marco Casolino 理化学研究所 EUSO チーム チームリーダー
参加研究者:Participating researcher

戎崎俊一 理化学研究所 戎崎計算宇宙物理研究室 主任研究員
滝澤慶之 理化学研究所 戎崎計算宇宙物理研究室 専任研究員
梶野文義 甲南大学 理工学部 教授
福島正己 東京大学 宇宙線研究所 教授
佐川宏行 東京大学 宇宙線研究所 教授
竹田成宏 東京大学 宇宙線研究所 助教
荻尾彰一 大阪市立大学 理学部 教授
研究成果概要:Research results summary
The JEM-EUSO collaboration aims to study Ultra-High Energy cosmic rays from spacewith the development of a large area telescope to be installed on board the InternationalSpace Station. It is carried forth by a collaboration of about 200 researchers from 13
countries. Several precursor instruments on ground, stratospheric balloons or space havebeen built or are under completion. The core of these activities is the EUSO-TA installation
at the Telescope Array site in Utah. EUSO-TA is housed in a building in front of the TA
fluorescence detector in Black rock mesa.
EUSO-TA detector consists of two, 1 square meter Fresnel lenses with 11 degrees of field ofview and a focal surface of 36, 64-channel Multi-Anode photomultipliers, for a total of 2304
pixel. Data are sampled every 2.5 microseconds (thee speed is determined by the shower
development in the atmosphere as seen from space at an altitude of 400 km) and stored
locally.
At EUSO-TA, we also tested the gondola of the EUSO-SPB (Super Pressure Balloon)
detector. EUSO-SPB is a NASA sponsored long-term duration balloon flight which wassuccessfully launched from New Zealand in April 2017. Following the success of EUSO-SPB,
a second super pressure balloon flight is currently under development (EUSO-SPB2) andthe flight is planned by 2021 to sturdy both Ultra High energy cosmic rays and Cherenkov
light emitted by tau neutrino induced showers.
Mini-EUSO, a standalone detector with 2304 pixel and a two Fresnel lens optics will beplaced on board the ISS by beginning of 2018. K-EUSO, the first space-borne UHECR
detector has begun phase A/B in Russia, with the construction of the prototypes of the optics
and electronics under way.
The possibility of observing cosmic ray events triggered by TA or generated by TA Central
Laser Facility (CLF) has been an invaluable help in characterizing and improving theperformance of the electronics and optics of all the systems and calibrate the various
telescopes.

Figure 1: Sum of 1280 frames acquiredwith EUSO-TA with the position of thebrightest stars superim posed, using
the Hipparcos catalogue. Each star islabelled with the catalogue number orthe star name in case of Vega, followedby the star’s magnitude in the Johnson
B filter for objects of MB ≤ 5.5. The
colour scale denotes the brightness ofeach pixel in arbitrary units after flat
fielding.

Figure 3: An average of 259 tracks of
the CLF laser, for a telescope
elevation angle of 10 deg. The panel
shows a zoomed part of a single frame
containing the laser. The colour scale
denotes the uncalibrated detector
counts.

Figure 2: A meteor track detected by
EUSO-TA. The picture shows the overlapof four averages of 1280 frames. The
color scale denotes the uncalibrated
detector counts. The apparent brightnessof the meteor in collected data variedfrom M B = 2.4 to M B = 4.06.

Figure 4: All UHECR detected by TAFD
in the EUSO-TA field of view during its
operationwith non-detected events and laser shots
superimposed. The vertical axis shows
the distance to the shower axis. The fit to
the detected points, explained in themain text, suggests a conservative
estim ate of the EUSO-TA detectionenergy threshold.

In FY2017 the activities have focused on:
1. Analysis of the data gathered with the EUSO-TA telescope and the payload of theEUSO-SPB (Super Pressure Balloon) at the Telescope Array. This has included thecalibration of the focal surface, the measurement with constant or slow moving
signals such as stars, clouds and planes, the observation of meteors and UHECRevents.
2. The upgrade work of the EUSO-TA focal surface module with a second-generation
readout based on the one of Mini-EUSO. This readout will allow for a full focal
surface trigger (both autonomous and triggered externally by Telescope Array) andreadout of various classes of events, from the fast Ultra-high Energy Cosmic rays toslower atmospheric phenomena such as lighting to meteors and search for spacedebris. With this upgrade of the PDM readout, it will be possible to broaden thescience objectives and greatly improve the duration of the operations, also thanks to aremote-controlled acquisition system. Work is foreseen to be completed by FY2018
整理番号:Reference number

E25