Observation of interplanetary and interstellar dust particles by Mars Dust Counter (MDC) on board NOZOMI

Abstract The Mars Dust Counter (MDC) is an impact-ionization dust detector on board the Japanese Mars mission NOZOMI, which was launched on 1998-07-04. It is an improved type of MDC-HITEN and MDC-BREMSAT and has three detection channels (electron, iron, and neutral) to discriminate noise signals from impact signals. The main aim of the MDC is to measure dust particles around Mars and reveal the distribution of the predicted Martian ring or torus of dust from Phobos and Deimos. On 1998-07-13, the MDC detected the first impact signal. On 1998-11-18, NOZOMI encountered the Leonids meteoroid stream. The MDC detected two dust impacts, but directional analysis showed that those particles probably did not belong to the Leonids. The NOZOMI orbital plan was changed; Mars insertion was postponed to be on 2004-01-01. By the end of 1999, MDC had detected more than 40 particles, including at least three — maybe five - particles of interstellar origin. Between 1999 and 2003, MDC-NOZOMI can thus continuously measure interplanetary dust.