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著者人数: 22名, Accepted: 2011-11-09, 資料番号: SA1003234000

著者人数: 20名, Accepted: 2011-05-04, 資料番号: SA1003239000

著者人数：19名, Accepted: 2009-10-07, 資料番号: SA1000727000

The Scientific Balloon Center of ISAS/JAXA has managed balloon-borne experiments in Japan. Since 1971 domestic balloon campaigns have been carried out at Sanriku Balloon Center. In 2007 ten scientific experiments were conducted by seven balloon flights at Sanriku. We have also developed next generation super-pressure balloons and ultra-thin balloons. In order to meet recent user requirements, i.e., stable flights of heavier payloads at the highest possible altitude, Japanese scientific balloons will be operated at Taiki, Hokkaido from 2008. This new balloon facility was constructed to launch the first balloon in May 2008. Standardization of balloons and the balloon system is also in progress, in order to maximize the reliability for our operation of larger balloons with heavier payloads. In this paper, we introduce the new balloon facility in Taiki and discuss the strategy of the Japanese scientific balloon activities. The status of the development of new balloon technologies and international collaborati...

著者人数: 23名, 資料番号: SA1000072000

著者人数: 18名, 資料番号: SA1000073000

We accomplished a balloon observation of the high-energy cosmic-ray electrons in 10-1000GeV to reveal the origin and the acceleration mechanism. The observation was carried out for 13 days at an average altitude of 35km by the Polar Patrol Balloon (PPB) around Antarctica in January 2004. The detector is an imaging calorimeter composed of scintillating-fiber belts and plastic scintillation counters sandwiched between lead plates. The geometrical factor is about 600cm^2sr, and the total thickness of lead absorber is 9 radiation lengths. The performance of the detector has been confirmed by a test flight at the Sanriku Balloon Center and by an accelerator beam test using the CERN-SPS (Super Proton Synchrotron at CERN). The new telemetry system using the Iridium satellite, the power system supplied by solar panels and the automatic flight level control operated successfully during the flight. We collected 5.7×10^3 events over 100GeV, and selected the electron candidates by a preliminary data analysis of the shower images. We report here an outline of both detector and observation, and the first result of the electron energy spectrum over 100GeV obtained by an electronic counter.

We have observed cosmic-ray electrons from 10 to 1000 GeV by a long duration balloon flight using Polar Patrol Balloon (PPB) in Antarctica. The observation was carried out for 13 days at an altitude of 35 km in January 2004. The detector is an imaging calorimeter composed of scintillating-fiber belts and plastic scintillators inserted between lead plates. The geometrical factor of detector is about 600 cm 2 sr and the total thickness of lead absorber is 9 radiation lengths. The performance of the detector has been confirmed by the CERN-SPS beam test and also investigated by Monte-Carlo simulations. New telemetry system using a commercial satellite of iridium, power supply by solar batteries, and automatic level control using CPU have successfully been developed and operated during the flight. We have collected 5.7 × 10 3 events over 100 GeV including nearly 100 candidates of primary electrons.

A balloon-borne superconducting submillimeter-wave limb-emission sounder (BSMILES) was developed to observe thermal emission lines from stratospheric minor constituents. BSMILES carries a 300-mm-diameter offset parabolic antenna, a 624-639-GHz superconductor-insulator-superconductor (SIS) receiver, a three-axis fiber-optical gyroscope, and an acousto-optical spectrometer. BSMILES was launched from the Pacific Coast of Japan. All systems operated properly and emission line spectra of stratospheric gases, such as O/sub 3/, HCl, HO/sub 2/, and O/sub 3/ isotopes were measured. The system noise temperature in double sideband (DSB) during the flight was less than 460 K over the observing bandwidth with a best value of 330 K that is 11 times as large as the quantum limit (11h/spl nu//k/sub B/). After the observation, the gondola splashed down in the Pacific Ocean and was retrieved. Almost all instruments were waterproofed, and it has been proved that they are reusable.

Polar patrol balloon experiments were carried out at Syowa Station in Antarctica from 2002 to 2004. Two balloons were launched for the purpose of observing phenomena in the polar atmosphere and one was done for the observation of high energy cosmic electrons. We developed a new housekeeping system including communication device using the Iridium satellite network, an auto-level controller driven by a new program for keeping the flight altitude, and a power management system for solar cells combined with secondary batteries. Two balloons for studying phenomena in the Antarctic atmosphere launched on January 13, 2003 made flights for 18 days and 25 days, respectively. All the housekeeping system worked well during the flights as we expected. Based on these experiments, we adjusted parameters for the altitude control system and the power management system. We launched a balloon for the cosmic electron observation on January 4, 2004. It flew 13 days around the Antarctica with the perfect operation of the onboard housekeeping system. We hope that fruitful scientific results will be obtained from these long-duration flights.

Development of a balloon to fly at higher altitudes is one of the most attractive challenges in scientific balloon technologies. After reaching the highest record setting balloon altitude of 53.0 km using the 3.4 μm film in 2002, we tried to make a thinner balloon film. In 2003, we developed a forming die and an air-ring and succeeded in forming a film with a thickness of 3.0 μm and a width of 220 cm. Using this film, we manufactured a balloon with a volume of 5000 m3 and succeeded in flying the balloon up to an altitude of 46.0 km. We then searched for a good combination of resins to make a thinner and wider film and obtained films with widths of 280 cm, and a thickness of 3.0 μm at first, and then 2.8 μm. In 2004, we performed balloon experiments making a 30,000 m3 balloon with the 3.0 μm film and a 5000 m3 balloon with the 2.8 μm film. Both balloons were well manufactured and reached the highest altitudes of 50.7 and 42.6 km, respectively.

Launching a large balloon in a limited launching field is a long standing problem in Japan. The largest balloon ever launched successfully was 200,000 m3 in volume. It was launched in 1973. A larger balloon with a volume of 500,000 m3 was tried later, but it burst during the ascending phase. For launching balloons with a large lift exceeding 500 kg, the conventional static launching method had the most serious problem with possible damage to the polyethylene film of the balloon caused by the holding mechanism. After that, we had developed a new static launching method to launch balloons with a total lift of 1.0 ton. For launching a large balloon with a total lift above 1.5 ton, the new static launching method had a weak point in that if there was an air bubble in the folded part of the balloon, it may puncture the balloon as it is pushed by a spool. To avoid this problem, we developed a semi-dynamic launching method in 1999 using a launcher fixed to the ground leaving a freedom of rotation around the vertical axis. We have launched some balloons using the method and have gradually enriched our experience in using this system. In 2003, we successfully launched a balloon with a volume of 500,000 m3 by using the method. This balloon was made of polyethylene films with a thickness of 20 μm and it is the largest balloon ever launched in Japan.

In the Polar Patrol Balloon (PPB) project, two balloons named PPB-8 and -10 were launched in rapid succession to form a cluster of balloons during their flight on January 13, 2003, from Syowa Station, Antarctica. In order to make the two-dimensional images for auroral X-rays and to obtain the energy spectra of auroras with energy range from 30 keV to 778 keV, the same instruments for hard X-rays were installed on PPB-8 and -10, respectively. These detection systems observed several auroral X-ray events during the flight. In particularly on January 25, 2003, strong auroral events were detected at about 0919 UT by PPB-10 and at 0927 UT by PPB-8. The aurora observed by PPB-10 was observed after about 8 min by PPB-8 located a 650 km west of PPB-10. The energy spectra of the bright aurora at 0919 UT and 0927 UT for PPB-10 and -8 is obtained as E0 = (78+-5) keV and (70+-5) keV, respectively.

The Sanriku Balloon Center (SBC), which belongs to the Institute of Space and Astronautical Science, was built in 1971. The launching field of SBC was 140 m in length and 20 m in width. In Japan, the balloon launching method that we have been using since 1971 is a kind of static launching method. In 1998, we extended the launching field 20 m in length and created a new launcher at this point. We have recently developed a “semi-dynamic” launching method. This newly developed launcher is different from the launcher used in the dynamic launching method, it is fixed to the ground creating freedom of rotation around the vertical axis. It is also possible for the launcher to lift up a payload to a height of 5 m from the ground. We succeeded in launching the first test balloon by using this new launching method on September 6, 1999. Utilizing the new launching machine, it became possible to launch a balloon with a volume of 1,000,000 m 3 and a total lift of 2 tons, even in Japan.

The balloon group at the Institute of Space and Astronautical Science (ISAS) has studied to develop high altitude balloons that could reach an altitude of more than 40 km with a light payload in order to meet the requirements of observations at extremely high altitudes. In 1999, we developed a ultra thin balloon film with a thickness of 3.4 μm. It is synthesized with a new catalyst, metallocene, and has a ultimate strength of ∼650 kg/cm 2 at −80°C. Using the film, we made the first balloon with 1,000 m 3 in volume and 2.6 kg in weight. We launched the balloon from Sanriku Balloon Center on September 1, 1999 and it successfully reached an altitude of 37.1 km. In 2000, we prepared the second balloon with 5,000 m 3 in volume with 6.8 kg in weight. It was launched on June 7, 2000 and it successfully reached an altitude of 43.0 km. Such light weight balloons are planned to be used for scientific studies in near future.

We report experimental results obtained by the emulsion chambers on board of the long duration balloon. We have been carrying out the trans-Siberian-continental balloon flight since 1995, and the results from 1995 to 1996 experiments are presented here. Total exposure of these two years amounts to 231.5 m 2 h at the average altitude of ∼32 km. The energy range covers 10–500 TeV for proton-primary, 3–70 TeV/n for helium-primary, and 1–5 TeV/n for Fe-group ( Z =26–28), though statistics of heavy components is not yet enough. Our preliminary data show that the spectra of the proton and the helium have nearly the same power indices ∼2.80, while those of heavier ones become gradually harder as the mass gets heavier, for instance the index is ∼2.70 for CNO-group and ∼2.55 for Fe-group. It is remarkable that a very high energy proton with multi-PeV is detected in 1995 experiment, and the estimated flux of this event coincides with a simple extrapolation from the energy spectrum with the power index 2.8 observed in the range 10–500 TeV. It indicates that there is no spectral break at around 100 TeV, in contrast to the maximum energy predicted by the current shock-wave acceleration model. This evidence requires some modification on the acceleration and/or propagation mechanism. Also we present all-particle spectrum and the average primary mass in the energy range 20–1000 TeV/particle. Our preliminary data show no drastic change in mass composition over the wide energy range, at least up to 1 PeV/particle, though the statistics is not yet enough to confirm it concretely. The flight performance and the procedure of the analysis, particularly the energy determination methods and the detection efficiency calculation are also given.

The development of high altitude balloons will enrich many areas of scientific observation. A high altitude balloon fabricated using improved technology with thin Winzen polyethylene films has been flown in the upper atmosphere. A light weight balloon carrying small instruments can reach an altitude higher than 40 km. In contrast to sounding rockets, the balloon-borne experiment provides a unique opportunity to stay at a high altitude for more than a few hours at low cost. We have developed methods for fabricating large balloons for scientific observation and have also established a new belt sealer and successful launching system. In January 27, 1997, a thin-film balloon with a volume of 120,000 m 3 , carrying a payload of 11.8 kg, reached an altitude of 50.2 km which is the highest balloon altitude ever in Japan. This shows that a thin-film balloon is suitable for high altitude observations and can fill the gap between satellite and conventional balloon altitudes.

We report experimental results obtained by using a wide-gap type emulsion chamber flown in the first Japanese-Russo joint balloon project, called RUNJOB ( RU ssia- N ippon JO int B alloon-program). Two balloons were launched from Kamchatka in July 1995, and both were recovered successfully near the Volga River. The exposure time was 130 hours for the first flight and 168 hours for the second. The mean ceiling altitude, in both flights, was 32 km corresponding to 10 g/cm 2 . Total area of the emulsion chamber was 0.8 m 2 , and the thickness 0.385 and 2.28 collision m.f.p.'s for vertically incident proton- and iron-primaries, respectively. We detected 381 showers using Fuji-#200-type X-ray film; of these 174 showers were due to atmospheric secondary γ-rays, and the rest 207 came from nuclear components. The energy range covers 20∼200 TeV for proton-primary, 3∼30 TeV/nucleon for helium-primary, and 0.7∼5 TeV/nucleon for iron-primary. We give the energy spectra for various elements (proton, helium, …, iron) as well as the all-particle spectrum and the average mass of the cosmic-ray primaries.

We describe a new Low Altitude Space Communication System (LASCOS), which was completed in 1996 by the Institute of Space and Astronautical Science in Japan. This system consists of a mobile balloon tracking and receiving station and networks which connect them to the Sanriku Balloon Center in Iwate Municipality and the Institute of Space and Astronautical Science (ISAS) in Kanagawa Municipality. This station and the SBC receiving station are connected via telephone lines, i. e. an Integrated Services Digital Network (ISDN) or an analog communication network. Balloon trajectory monitoring, telecommand transmission operation and telemetry data acquisition can be done from any computer terminal through the LASCOS. LASCOS has built-in flexibility to adapt to a foreign balloon station. The number of individuals necessary to operate it minimum. LASCOS will be used for long range tracking and balloon expedition. We present the results of its first test with an actual balloon flight.

For a new balloon material, we have been studying the properties of an EVAL (Ethylene-Vinyl-ALcohol) film during a part of few years. The EVAL film is a product of Kurare Plastic Company, and has mechanical properties similar to that of a Mylar film. Besides this strong mechanical strength, we found that the EVAL film has several characteristics which seems to be suitable for the balloon material. Those are: 1. 1. Sandwiched EVAL films laminated by polyethylene films can be heat-sealed, 2. 2. Gas leakage through the EVAL film is extremely low, and for Helium gas, it is almost 100 times less than that of a Mylar film, 3. 3. The EVAL film is transparent in the optical band, while it efficiently absorbs the infrared radiation from the earth. In 1997, we have carried out a test flight from the Sanriku Balloon Center using a small balloon with a volume of 1000 m 3 . The balloon reached an altitude of 22 km successfully and showed a maximum burst pressure of 2.1 g/cm 2 . In this paper, basic properties of the EVAL film and performance of the test balloon are described.

The Polar Patrol Balloon No. 6 (PPB#6) observed quasi-periodic pulsations of bremsstrahlung X-rays (E 30∼120 keV) in the daytime of 0855 UT (0914 MLT) ∼ 1630 UT (1614 MLT) on January 5, 1993, near Syowa Station, Antarctica (L∼6). The X-ray pulsations near the noon (1208:00 UT (1216 MLT) ∼ 1225:04 UT (1232 MLT)) include a period of about 260 sec, which corresponds to Pc 5 magnetic pulsations. It was found that at Syowa Station and Tjornes, Iceland, which are both pair locations of the geomagnetic conjugacy, the X-ray pulsations are in correlation with the ULF-D pulsations. Also the Tjornes VLF (2 kHz) pulsations correlated well with the X-ray pulsations of the period corresponding to Pc 5. It is probable that the VLF- and ULF-associated X-rays or precipitating energetic electrons in the vicinity of the L ∼ 6 shell are in synchronization with the electron-cyclotron resonance. Lastly, the so-called ballooning-mirror instability (the BMI) is a candidate to explain the compressional MHD waves that occur during the short time interval (1216 MLT ∼ 1232 MLT) in which the experimental results were interpreted.

Balloons made of thin films have been frequently used to observe high altitude winds. Such a balloon is also useful to perform some scientific observations now performed by sounding rockets. Since this balloon is lighter than a normal balloon, it can easily reach an altitude more than 40km with a payload less than 10 kg. A ceiling altitude of 48.7 km was achieved by the new balloon with a volume of 30,000m 3 in a test flight in 1995. We need to reduce mechanical stress by attaching an exhaust duct especially for a thin polyethylene balloon. Three types of exhaust ducts were tested in flights in 1995. We have confirmed good performance of the thin polyethylene balloon. The launching device for the high altitude balloon is also described.

A convection enhancement event was observed with the Polar Patrol Balloon #4 which was launched at Syowa Station on December 26,1992. This event occurred during 1700-1900 UT on December 28,1992,when the balloon located in the afternoon sector of the sub-auroral zone. During this period, the amplitude of the southward electric field (E_S) increased from about 20mV/m to 50mV/m and then decreased to 20mV/m again. The northward component of the magnetic field variation (B_H) also increased from 200nT to 600nT, and then decreased to about 100nT. The maximum time of E_S lagged about 12 min after the B_H maximum time (t_). We could estimate the height integrated ionospheric electric conductivity from these horizontal electric field and magnetic field data. Before t_ Hall conductivity (σ_H) was about two times greater than Pedersen conductivity (σ_P), and after t_ σ_H decreased monotonously to become smaller than σ_P, while σ_P maintained a nearly constant value. Around t_ both σ_H and σ_P were enhanced by about 1.5 times in about 10min, and energetic particle precipitation was observed with the on-board X-ray counter. We could summarize this event as follows : there was stable enough particle precipitation to maintain σ_H before t_ : As E_S increased, the ionospheric Hall current increased, and B_H increased. Around t_ a large quantity of particles precipitated above the balloon, ionospheric conductivities and Hall current reached a maximum value, and thus the B_H reached a maximum value. After t_ σ_H and B_H decreased because the energy spectrum of the precipitation became softer, while E_S continued to increase. E_S reached a maximum value about 12min after t_. From the ground-based data in the southern and northern hemispheres and also satellite IMF data, it was concluded that this event was not an isolated disturbace confined just around the balloon location, but was a global feature of the ionospheric convection variation corresponding to the IMF fluctuation.

The Polar Patrol Balloon (PPB#6) aimed at studying the elemental and isotopic composition of galactic cosmic rays, solar energetic particles cosmic gamma ray bursts and auroral X-rays, and was launched from Syowa Station Antarctica, by the 34th Japanese Antarctic Research Expedition on 5 Jan 1993. The balloon moved westward by 1.5 circumpolar rounds over Antarctica covering 6–13g/cm 2 atmospheric depth and 63°S–70°S geographic latitude. A total of 584 hours of observations was obtained. The balloon trajectory, the observing system and preliminary results of spectra and global distribution of cosmic radiation and auroral X-rays were described.

A Polar Patrol Balloon observation of cosmic ray protons (E ≥ 100 MeV) was carried out in Antarctica, also energetic X-ray (E = 30-120 keV) observations of auroral, solar and/or cosmic origins as well. The Polar Patrol Balloon No. 6 (PPB≠6) was launched from Syowa Station on January 5, 1993 and drifted westward by 1.5 circumpolar rounds over Antarctica, covering 6-13 g/cm2 atmospheric depth and 63°S-70°S geographic latitude. A total of 584 hours of observations was obtained. During the period, data telemetry and balloon tracking were performed by a multi-ID ARGOS system, through which the all data were acquired every 30 seconds. A preliminary report of fluxes and spatial distributions of cosmic ray protons and auroral X-rays is presented. Some features of the results are summarized as follows. 1) Proton fluxes measured in the polar cusp region still reveal a progressive increase at higher latitudes above the cosmic-ray latitude knee. 2) The differential energy spectrum of cosmic ray protons measured near the solar minimum is consistent with observations in 1967 and 1977. 3) Distinct enhancements of auroral X-rays were often observed, particularly dominant in the magnetic local dayside time.

Trans-oceanic flights between Japan and China have been successfully carried out for three years (from 1986 to 1988), and nine balloons were launched from Kyusyu Island toward China. Although two flights were terminated due to balloon problems during ascending phase, seven balloons reached China successfully and those payload were recovered in the inland of China. During the long duration flights lasting for more than ten hours, the scientific objectives were accomplished by the scientists of both countries in collaboration and many useful data could be obtained.

We have improved the static launch method in the Sanriku Balloon Center (SBC). The motivation of the improvement is to reduce the shock for the scientific instruments during launching and to increase the ability of launching heavier payloads. In the new launch method, the entire balloon train is extended vertically before launch. We have found that the launch condition in the new system is satisfactory, for both lowering shock while launching and maintaining stability of the payload, when the balloon lift is equally divided to the launch rope and the payload suspension rope. Under the new launch method, a payload of more than 1000 kgs has been successfully launched with the launching shock of about 0.3G.

A balloon observation of auroral X-rays has been carried out by using two types of X-ray imagers. The first is a new type of imager consisting of a two-dimensional 5×5 matrix array of Si(Li) semiconductor detectors whereas the other is a one-dimensional array of 8 NaI(Tl) scintillation detectors. Both are pinhole camera type imagers. The balloon carrying these imagers was launched from Abelver, Norway, on July 5, 1985, and flew westward over Iceland. Near the location of L=5.2 at the geomagnetic midnight during a geomagnetic substorm, temporal variations of auroral X-ray images were observed with 3-s time intervals by the Si(Li) imager. These images were confirmed simultaneously by the NaI(Tl) imager. A time sequence of the auroral X-ray images did not show a stable arc structure, but rather a localized small-scale structure with rapid time variation. The present observation suggests that localized intermittent precipitations of energetic electrons with energies of several tens keV occurred in the post-break-up phase of an auroral substorm. It is fully possible that localized energetic electron precipitations are due to the localized field-aligned electric field.

A balloon-borne superconducting submillimeter-wave limb-emission sounder was developed to measure stratospheric molecules. It carries a 300 mm-diameter offset parabolic antenna, a 620-650 GHz heterodyne SIS receiver, and an acousto-optical spectrometer. Tsys(DSB) is less than 460 K at 624-639 GHz with a best value of 330 K(11 hv/kB). BSMILES was launched from Japan in 2003 and 2004. All systems operated properly and emission line spectra of O3, CIO, HO, HO2 etc. were measured. After the observations, the gondola splashed on the Pacific Ocean and was retrieved.

We have developed a balloon-borne superconducting submillimeter-wave limb-emission sounder (BSMILES) to determine vertical profiles of stratospheric minor constituents like ozone and a number of key species related to ozone destruction by observing thermal emission lines from these molecules. BSMILES carries a 624-652 GHz superconductor-insulator-superconductor (SIS) receiver with the system noise temperature of 330-460 K in double sideband (DSB) during the flight. BSMILES flight experiments were conducted on August 30, 2003 and September 7, 2004 from the Pacific Coast of Japan. The system operated properly and spectra of O/sub 3/, ClO, HCl, HO/sub 2/, O/sub 3/ isotopes were successfully measured. After the observation, the gondola splashed down in the Pacific Ocean and was retrieved.

著者人数: 19名, 資料番号: SA1002820000

著者人数：21名, 資料番号: SA1000962000

著者人数：19名, 資料番号: SA1000927000

This report presents the spatial distributions of auroral X-rays obtained by the balloon flight named AZCO-C1,which was launched from Norway in July 1985. A time sequence of auroral X-ray images were derived by using a set of three NaI (T1) scintillation counters for each of the three different energy channels : 22-35,35-55 and 55-88keV. The precipitation region of energetic particles and its modulations with time were well demonstrated, though the X-ray enhancements were only three times the background flux.

A balloon observation of auroral X-rays has been carried out by using two kinds of X-ray imagers, i.e., a newly developed imager with 5×5 matrix array of Si(Li) semiconductor detectors (SSD's) and another one with one-dimen-sional array of 8 NaI (Tl) scintillation counters. Each of these two imagers has a pinhole collimator, which gives a resolution angle of 15°at the central detector (counter). The lower limits of X-ray energy measurable are 37 and 22keV for the SSD and NaI(Tl) imagers, respectively. The balloon carrying these imagers was launched from Abelver, Norway at 2117 UT on July 5,1985 and was flown toward lceland. An enhancement of auroral X-ray flux was observed in the location of L=5.2 at ∿ 2334 MLT near the geomagnetic midnight, during a geomagnetic substorm. Temporal variation of two-dimensional auroral X-ray images was derived with 3 s time resolution from SSD imager data. Also, another imager of NaI(Tl) counters confirmed the SSD results. It is shown that a sequence of auroral X-ray images obtained by two imagers are not like a stable arc structure but a localized structure with a rapid time variation. The present results suggest that localized intermittent precipitations of energetic electrons with several tens keV or greater are possible.

A new static-launch method that we have developed as an improvement of our former method is described. The key procedure is to extend a whole balloon vertically upon the launcher before release, with squeezing the top bubble of the balloon by a soft collar. The new method improved the capability for heavier payload significantly. In 1981, 15 balloons, ranging from 5,000 m 3 to 50,000 m 3 in volume with a total lift from 150 kg to 650 kg, were launched by this new method successfully.

A system for microgravity experiments by using a stratospheric balloon has been planned and developed in ISAS since 1978. A rocket-shaped chamber mounting the experiment apparatus is released from the balloon around 30 km altitude. The microgravity duration is from the release to opening of parachute, controlled by an on-board sequential timer. Test flights were performed in 1980 and in 1981. In September 1983 the first scientific experiment, observing behaviors and brain activities of fishes in the microgravity circumstance, have been successfully carried out. The chamber is specially equipped with movie cameras and subtransmitters, and its release altitude is about 32 km. The microgravity observed inside the chamber is less than 2.9 × 10 −3 G during 10 sec. Engineering aspects of the system used in the 1983 experiment are presented.

We carried out electron observations with balloons to investigate acceleration and propagation of electrons in the universe. We developed BETS (Balloon-borne Electron Telescope with Scintillation fibers) for electron observations in Sanriku. We obtained electron energy spectrum from 10 to 100 GeV with it. At higher energies, the energy spectrum of electron might show some structure caused by nearby sources like the Vela supernova remnant. In order to observe the energy spectrum above 100 GeV, we needed a thicker calorimeter and a longer observation time. We developed PPB-BETS (Polar Patrol Balloon-BETS) by improving BETS to carry out a long duration ballooning in Antarctica. Energy spectrum of electrons from 100 to 1000 GeV was obtained by a successful fight for 13 days. The arrival direction of electrons seems to be consistent with isotropic distribution for the data taken with PPB-BETS, although we need better statistics to make it clear. We have a future plan to make an observation of electrons and gam...