NOZOMI Succeeds in Earth Swingby

The Mars explorer NOZOMI launched on July 4, 1998, is now cruising in interplanetary orbit, targeting the insertion to the Mars orbit at the end of 2003. On December 21, 2002, the explorer came close to Earth and successfully implemented the earth swingby. The time of its nearest approach to Earth was at about 4:37 p.m. with a distance of approx. 30,000 km. This marked NOZOMI’s return home after a long absence. At it’s furthest point, it was 360 million km away from Earth. Unfortunately, when NOZOMI was approaching Earth, we were unable to see it from Japan. By this swingby, the explorer deviated a little from the ecliptic plane and shifted to the trajectory passing the north of Earth.

After encountering a large solar flare involving coronal mass ejections on April 21, 2002, that damaged equipment and caused its power system to malfunction, NOZOMI has been unable to send telemetry. Scientific observation during the cruising phase was therefore cancelled. But the ranging function for orbit determination and command receiving are normal. In addition, by adopting an ingenious technique that makes use the NOZOMI’s onboard autonomous capability and substituting ON/OFF beacon radio waves for telemetry, we are able to implement attitude and orbital control. At present we are analyzing in detail the cause of the failure and searching for countermeasures for recovery.

NOZOMI will execute the earth swingby again on June 19, 2003, and enter into cruising orbit inside the ecliptic plane. At the end of this year, the explorer will be ready to enter into the Mars orbit.

January 17, 2003