As other nations launch their stake in this year's wave of Mars exploration, Japan has its own mission that is chugging toward the Red Planet despite encountering a rocky journey.

An artist's concept of the Nozomi spacecraft at Mars. Credit: ISAS

Launched almost five years ago in July 1998, the spacecraft has faced more than its share of troubles. But in spite of that, ground controllers have guided Nozomi onto the right course that should see it arrive in Martian orbit either at the end of this year or early in 2004.

Project officials told Spaceflight Now there are still several alternatives for an exact date to enter orbit around Mars. Those time frames range from mid-December of 2003 to early January of next year.

Nozomi's troubles began in December 1998 during an Earth fly-by that was to send the craft onto a trajectory to arrive at Mars in October 1999.

The spacecraft's thrusters were to fire to assist in the swing-by, but a stuck valve and subsequent maneuvers left Nozomi with too little propellant to properly inject itself into orbit around Mars at the scheduled arrival time.

The Nozomi team was forced to develop an alternate trajectory that met both fuel and scientific constraints. Using two more Earth fly-by's, the new path will see the craft get to Mars at about year's end.

The first close approach to Earth was successful last December, while the final gravity-assist maneuver is scheduled for June 19 as Nozomi flies by Earth for the final time.

Once controllers finally seemed to refine the trajectory, other issues began plaguing Nozomi. The probe's S-band transmitter stopped working, so scientists now only use the spacecraft's X-band instrument for communications downlinks.

Also, a large solar flare that bombarded Nozomi left part of its power system offline. Ground team members will conduct an extensive recovery operation of the failed power system between July and October in advance of Mars arrival.

Once at Mars, Nozomi -- which means "hope" in Japanese -- will train its instruments on the Martian upper atmosphere to study its interaction with the solar wind. Other objectives include looking at the magnetic field around the Red Planet and imaging the surface of Mars and its two natural satellites.