M. Fujii

Venus balloons at low altitudes

Abstract The Venus balloons are one of the most important vehicles to explore the dynamics and composition of Venusian atmosphere and several feasibility studies have been reported. /1/,/2/ We here propose the balloons at low altitude of 10 to 20 km floating below the cloud in the Venus atmosphere, which will make it possible to perform the study of the Venus atmosphere at low altitude together with a direct observation of the Venus surface. The atmospheric pressure is 20 to 40 atm. at this altitude, and the temperature is as high as 300°C to 400°C. The balloons proposed here are of the spherical shape of super pressure type filled by the Helium gas. The balloons are made of thin Ti alloy or reinforced by CFRP, and have capabilities to carry the payloads of weights of several kg. This type of the balloon has several merits on the weight considerations over the normal inflatable balloons with gas containers and its inlet systems.

The improvement of the static launch method in Japan

Abstract 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.

Energy determination of the cascade shower by means of a new type of emulsion chamber with diffuser module

Abstract An account is given of a new type of emulsion chambers which have been in our use since 1997 in our RUNJOB program (RUssia–Nippon JOint Balloon-program). Each chamber is equipped with an additional “diffuser module” placed under the usual set of modules. We have made the experiments using 4 cm thick diffuser modules composed of several photo-sensitive layers (X-ray films and/or nuclear emulsion plates) sandwiched with spacers. The result is as follows. Even in the case where the path length of only 6 radiation lengths is available within the calorimeter module placed above, the visible energy sum is determined with an accuracy better than σ∼0.2 for a group of electromagnetic cascade showers induced by a proton of energy up to several tens of TeV, or by an iron nucleus of energy up to one hundred TeV. If the available path length in the calorimeter module is 9 radiation lengths, we can estimate the energy sum up to ∼100 TeV within an accuracy of σ∼0.2 for a proton-induced cascade shower group. It means that the use of our new-type emulsion chamber can reduce the detector payload dramatically, which is essentially important for the high-energy cosmic-ray observations made on board the vehicles such as balloons, satellites and so on.

First results obtained by RUNJOB campaign

Abstract 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.

Automatic control of balloon altitude

Abstract An ascentmeter with a sensitivity of 1 cm/s was applied to the automatic control of balloon altitudes. In the flight tests made in 1980 and 1981, the automatic control system was successfully operated to keep a balloon altitude constant during sunset or to descend a balloon with a constant speed.

A model experiment of the Venus balloon

Abstract In order to explore the dynamics and composition of the Venus atmosphere, characteristics of several types of Venus balloons have been investigated. Vapor of a suitable liquid in the balloon gives buoyancy in the carbon dioxide atmosphere of Venus. In this case the phase transition of vapor to liquid occurs as the temperature changes with the altitude within the Venus atmosphere. Thus, the phase transition of vapor to liquid in the balloon works to stabilize the balloon altitude. A model experiment testing the phase transition balloon in a water vessel with an appropriate temperature gradient and some results obtained with this model experiment are described.