Japan Exploring Our Solar System . . .

Hope Went Astray On The Way To Mars

Satellites     Rockets     Surveying the Moon     Exploring Planets

Japan's interplanetary probe Nozomi arrives at Mars in 2004, in this artist's view. The unsuccessful probe was Japan's fourth deep space mission.
Japan, the fourth nation ever to send a satellite to Earth orbit, became the third nation ever to send a spacecraft to Mars when it blasted off a probe then called Planet-B from Japan's Kagoshima Space Center on the southern island of Kyushu on July 4, 1998.

While on its way to Mars, Planet-B was renamed Nozomi which means Hope. It did arrive in the vicinity of Mars in December 2003, but ground controllers back on Earth were unable to direct it into orbit around the Red Planet. It flew on by and was lost in a useless orbit around the Sun.

Here's what went wrong along the way to Mars:

A bumpy road. Unfortunately, an out-of-control thruster necessitated an heroic rescue effort, which lead Nozomi around the Sun on its way to the Red Planet. That meant arrival at Mars would be four years later than originally planned.

In addition, Nozomi suffered a further setback in 2002 when one of its communication systems was knocked out by a massive outburst of energy from the Sun on April 21.

Then, as it approached Mars five years behind schedule and low on fuel, the spacecraft's heating system broke down and had to be brought back to life to prevent its fuel from freezing up. As Nozomi moved away from the Sun, it cooled to a point where its fuel could freeze. That left the probe unable to fire its thrusters to slow down and drop into orbit around Mars.

At that point, spaceflight experts gave the robot probe only a 50 percent chance of entering Mars orbit successfully and carrying out its assignment.

The flight plan. The $88 million (11 billion yen) Nozomi was launched from a pad in the southwestern prefecture (state) of Kagoshima on July 4, 1998, to probe the atmospheric movements and topography of Mars, as well as measure solar winds.

After launch in 1998, the robot science explorer went into a looping orbit around Earth, which took it out and around the Moon. Nozomi completed two swings by the Moon to establish its final trajectory to Mars. The swing-by technique helped the probe gather speed for the trip to Mars.

Nozomi originally was to have arrived at the Red Planet at the end of 1999.

Once the spacecraft reached Mars, it was to have been placed in a highly elliptical or "egg-shaped" orbit stretching from a low of 93-186 miles out to about 17,000 miles above the planet's surface.

What went wrong? Nozomi made a first gravity-assist flyby of the planet Earth on September 24, 1998. Following a second Earth flyby on December 18, 1998, a thruster on the spacecraft stuck open and much fuel was wasted. Nozomi did not receive sufficient acceleration boost to reach orbit around Mars.

Controllers at Japan's Institute of Space and Astronautical Sciences (ISAS) ordered the thrusters to burn in a correctional manuever on Dec. 21, 1998. However, that did not leave enough fuel for Nozomi to be able to slow itself down later as it entered Mars orbit.

The situation looked bleak and called for an extraordinary effort to save Nozomi.

How they fixed it. Ground controllers in Japan radioed orders to the spacecraft, assigning it a new flight plan.

Now it would make three trips around the Sun and two additional Earth flybys. They hoped those gravity assists from the Sun and Earth would give Nozomi just the right speed for entering Mars orbit by 2004, without requiring much thruster fuel.

If it had worked, Nozomi's new orbital path around Mars would have been elliptical, ranging from a low of 93 miles out to a high of 31,620 miles.

ISAS researchers said they believed the spacecraft's science instruments would work properly after the four year delay. A benefit of the longer flight, they said, would be extra time to collect and send back data on the solar wind in interplanetary space.

Then the radio went down. Nozomi suffered a setback in 2002 when one of its communication systems was knocked out by a massive outburst of energy from the Sun on April 21.

Such powerful solar flares are well known on Earth where they sometimes cause radio and electrical disruptions.

Japan's Education Ministry, which oversaw the program, expected it would take six months to fix the communication problem. Fortunately, the probe's computer controls were not damaged so engineers on Earth were able to repair the spacecraft by remote control. The probe was able to continue on a course that would take it to Mars by 2004.

The probe completed speed-boosting flybys of Earth in December 2002 and June 2003.

Unfortunately, there was insufficient fuel left when the spacecraft reached Mars. Controllers in Japan could not direct it into an orbit around Mars. Nozomi flew on by into a useless orbit around the Sun.

Nozomi's Martian Studies
Nozomi was designed to perform long-term studies of the upper Martian atmosphere and ionosphere, and its interaction with the solar wind.

The low-altitude portion of the orbit would have been used for remote sensing of the lower atmosphere and surface, and for direct measurements of upper atmosphere and ionosphere.

The more distant parts of the orbit around Mars would have allowed instruments to probe the ions and neutral gas escaping from the Red Planet, which interact with the charged-particle "wind" blowing outward from the Sun. Ionization of the upper atmospheric gas by solar radiation produces the charged-particle atmosphere (ionosphere) that acts as an obstacle to the solar wind.

This radiation produces species of gas not seen in Mars' lower atmosphere, such as nitric oxide, or dissociates the atmosphere into single atomic species, such as atomic oxygen. If these neutral or ionized species possess enough energy, they can escape the gravitational pull of Mars, resulting in a net atmospheric loss. Measurements of lighter species such as atomic hydrogen and deuterium also can provide clues about the evolution of the Martian atmosphere.

More like Venus. Mars has little or no intrinsic magnetic field to interact with this process, making it more like Venus in this respect than Earth.

The upper atmosphere of Venus and its solar wind environment had been studied for almost fourteen years by the U. S. Pioneer Venus Orbiter spacecraft from a similar, highly elliptical orbit. Nozomi carried an insturment, known as NMS, which was a state-of-the-art enhancement of the Pioneer Venus mass spectrometer. It weighed only six pounds. To conserve space and weight, electronic items such as transistors and integrated circuits were removed from their outer casings and placed in larger packages called hybrid circuits.

Dust storms. Data from previous Mars exploration spacecraft such as Mariner 9 indicate that dust storms near the surface can heat the lower atmosphere and increase the gas density in the upper atmosphere where Nozomi would have made its measurements. Meanwhile, the U.S. Mars Climate Orbiter carries an instrument called the Pressure Modulated Infrared Radiometer, which will provide complementary information on the lower atmosphere and its response to dust storms.

Nozomi's Objectives
The main objective was to investigate the motion and structure of the upper atmosphere of the planet Mars. To do that, 14 instruments were on board the spacecraft. The observations by Nozomi would have included:

  • Magnetic field of Mars
    Scientists are not sure if Mars has a magnetic field or not. Nozomi would have measured precisely the Martian magnetic field.

  • Atmosphere of Mars
    Nozomi would have investigated the composition and structure of the atmosphere with ultraviolet remote-sensing detectors. A small mass-analyzer would have been used to study the composition of the the ionosphere.

  • Plasma in the Ionosphere of Mars
    Nozomi would have studied the components, structure, temperature and plasma waves within the ionosphere with detectors.

  • Pictures of Mars and its Moons
    A small camera would have snapped pictures of Martian weather and its two moons -- Phobos and Deimos. Those images would have helped scientists understand how sandstorms and clouds are generated on Mars and the planet's polar icecaps grow and decay.

  • Dust Rings around Mars
    Scientists suggest there may be a dust-ring along the orbit of Phobos. By using the dust counter aboard Nozomi, they may have been able to discover if it exists.
None of these instruments now will benefit Mars scientists.

Science instruments
Nozomi carried 14 instruments for scientific research at Mars. Those science packages of equipment were supplied by:
  • Japan
  • United States, NASA and Johns Hopkins University
  • Canada, Calgary University
  • Germany, Munich Technical University
  • France, space agency CNES
  • Sweden.
Spectrometer. One of the instruments from the United States was the Neutral Mass Spectrometer and Ultra Stable Oscillator (NMS) provided by NASA to measure the gas composition of the upper atmosphere of Mars.

The Neutral Mass Spectrometer would have enabled researchers to measure the chemical composition of the upper atmosphere of Mars on a global scale, which had not been done before.

Previous upper atmospheric composition measurements were done in only two locations as NASA's Viking landers entered the Martian atmosphere on July 20 and Sept. 3, 1976.

Precise clock. Another U.S. instrument package was a radio science experiment. That hardware was built for NASA by the Johns Hopkins University Applied Physics Laboratory in Laurel, Maryland. The ultra-precise signals generated by the oscillator would have served as a very accurate clock to enable analysis of the Martian atmosphere and might have helped guide the spacecraft in its orbit around the Red Planet.

M-5 Rocket
The spacecraft was built by the Nippon Electric Corporation and was launched on one of Japan's M-5 rockets – a launcher that had been designed to expand Japan's launch capability to the inner planets and beyond.

The Nozomi project was managed by ISAS and the Japanese Ministry of Education. ISAS personnel operated the spacecraft and its instruments. Flight operations were conducted from Sagamihara Spacecraft Operations Center.

Information on NMS and the NASA portion of the Nozomi mission is at the Laboratory for Atmospheres at NASA's Goddard Space Flight Center in Greenbelt, Maryland.