For the future planetary exploration of the world ---What "NOZOMI" left with us---

"NOZOMI" was installed with fifteen observation means. During five years' unexpected staying in heliocentric orbit after the mishap of several times of the earth swing-by in 1998, the probe conducted a number of scientific observations partly for the purpose of checking up the equipments. Among them, there is the first observation in the world.

"Two-shot image of earth with moon", which attracted public attention was taken by Mars imaging camera (MIC). It was taken as a check operation of MIC, and may not be so valuable from Mars specialist point of view, it gave deep impressions to a lot of people. It was really a souvenir picture of Japanese first planetary explorer.

And the rear side of moon also was taken for the first time in Japanese mission.

Ultraviolet Imaging Spectrometer (UVS) successfully observed hydrogen Lyman-alpha line in interplanetary space. Lyman-alpha line emitted from the sun is dispersed by neutral hydrogen atom drifting in interplanetary space to cause glittering in there. It reminds us of the beautiful blue sky of earth made with dispersing of sunlight by particles of surrounding atmosphere of earth. Where does this hydrogen come from? Its source is so-called "interstellar wind" which is the stream of materials in Galaxy.

The interstellar wind is ionized by the ultraviolet from the sun and solar wind energy when it approaches the sun. The ionized hydrogen no longer scatters Lyman-alpha. The interstellar wind now with lower density due to ionization moves toward downstream.

Therefore, the hydrogen Lyman-alpha is lighter in the direction from where interstellar wind blows (upstream), and darker in the opposite direction (downstream).

The distribution map of Lyman-alpha observation enables detailed research into the property of solar wind which causes the variation of Lyman-alpha.

Charged particles (plasma) streams out constantly from ionosphere of earth. Plasma is usually captured in and around earth by magnetic field, so unless there occurs extensive disturbance in magnetic flux, plasma cannot escape into space. Cold plasma originated from ionosphere has been understood that it is kept below the altitude of magnetic line about four times, on the average, as high as radius of earth above equator. 90% of captured plasma is hydrogen ion and nearly all of the rest is helium ion. Helium ion disperses extreme ultraviolet rays emitted by the sun. "NOZOMI" succeeded in observing, by capturing this dispersed light with the Extreme Ultraviolet Telescope (XUV), the sphere in question from outside for the first time in the world. It has been revealed by "NOZOMI" observation that much more volume of helium ion than expected is streaming out from this region.

Dust Counter (MDC) began its observation just after the launch, and continued to observe the velocity and mass of dusts around earth and interplanetary space. Since the first detection on July 11, 1998, approx. 100 dusts were detected during the 4 year observation. Most of them are thought to have originated from asteroid and comets on Keplerian orbit around the sun, but some of them are clearly of extra-solar system origin. Among the dusts detected in 1999, four of them at least came from outside of our solar system. As the velocity vectors of two of them coincides with the relative velocity vector of our solar system to surrounding interstellar gas, they can be said to have come from interstellar gas. This detection of dusts of extra-solar system origin in near-earth region is one of the most important results done by "NOZOMI".