Image right: Artist's Concept of Mars Odyssey Orbiter at Mars

The Mars Odyssey Orbiter was launched from the Kennedy Space Center on April 7, 2001 using a Delta II launch vehicle, and it reached Mars on October 24, 2001. Once it was captured in Mars orbit, an aerobraking technique was employed which used the Martian atmosphere to slow the spacecraft and adjust it to a circular science orbit with an altitude of about 400 km. The orbit adjustment process ended in January 2002, and the science mapping began in February of that same year. The primary science mission will continue through August 2004, and the mission itself will extend for more than a full Martian year (two-and-a-half Earth years).

Mars is extremely vulnerable to the effects of space radiation primarily because it does not have a global magnetic field like that of the Earth to shield if from solar energetic particle events (SEP) and galactic cosmic radiation (GCR). In addition, Martian atmosphere is less than 1% as thick as that of the Earth. Radiation protection for crew members in this environment poses a significant challenge to spacecraft design for manned missions. The focus of MARIE is to determine the galactic cosmic ray energy spectra during the maximum of the 24th solar cycle, and to study the dynamics of solar energetic particle events and their radial dependence during both the cruise phase and the orbit phase around Mars.

Image left: Launch of Mars Odyssey Orbiter, April 7, 2001

Galactic cosmic radiation provides a steady source of high-energy particles that is primarily responsible for stochastic effects such as cancer and central nervous system damage. The dose contribution from GCR is inversely correlated to solar activity; the higher the solar activity, the lower the dose contribution from GCR. The solar energetic particle events occur sporadically during 3 years preceding and 4 years following solar maximum, and they lead to sharp, short-term increases in dose and dose rate. SEP events are directly correlated to solar activity, and they can lead to acute effects, such as nausea and even death. GCR particles are more difficult to shield against than those from SEP events. Because their energies are much higher than for particles resulting from SEP events, small uncertainties in dose projections can lead to a nearly exponential increase in the required shielding mass for a given level of acceptable risk to the crew. Consequently, direct measurements of radiation levels (including the relative contributions of protons, neutrons, and heavy ions) and of Martian atmospheric characteristics are a pre-requisite for any human mission.

MARIE measures particles with energies which fall in the range of 15 MeV to 500 MeV per nucleon (proton or neutron in the nucleus of an atom). Radiation particles which are harmful to humans fall mostly in this energy range because they possess enough energy to damage human DNA. Particles with energies above 500 MeV per nucleon threshold pass through the human body so quickly that there is not enough time to transfer their energy into the surrounding tissue.

The data gathered from MARIE is combined into an energy spectrum which describes how many particles at what energy level were present when the measurement was made. The data is being compared against the best available radiation environment and transport models, and these models are being improved for subsequent use. The data will be used to provide key inputs for the engineering of spacecraft in order to better protect human crews for interplanetary missions from space radiation.

NASA, Lockheed-Martin, and Battelle coordinated the development of MARIE at the Johnson Space Center. Battelle developed the CPU, power boards, and detector boards. Lockheed-Martin was responsible for the development of the position sensor devices, instrument packaging, system integration, software development, and certification of the instrument for flight. NASA/JSC provided the project management and coordination.

Image right: Dr. Gautam Badhwar

Dr. Gautam Badhwar was the principal investigator for the MARIE experiment and the Senior Scientist for Space Radiation at JSC until his death in August of 2001. The MARIE experiment is the result of Dr. Badhwar's vision to characterize the specific aspects of Martian near-space radiation environment. He proposed the experiment to the Odyssey project, and the instrument was developed under his guidance. Dr. Badhwar had a PhD in Physics from the University of Rochester, Rochester, NY. He had over 150 articles and publications to his credit, and he was internationally known as an expert in the field of space radiation.

MARIE science team members include:
Frank Cucinotta, NASA/JSC
Cary Zeitlin, Lawrence Berkeley National Laboratory
Claude Chambellan, NASA/JSC
Tim Cleghorn, NASA/JSC
Paul Delaune, NASA/JSC
Jeff Bahr, Lockheed-Martin
Terry Byers, Lockheed-Martin
Bob Dunn, Lockheed-Martin
Joel Flanders, Lockheed-Martin
Fadi Riman, Lockheed-Martin
Prem Saganti, Lockheed-Martin