FACT SHEET: MARS OBSERVER February 1992 A NASA mission to study the surface, atmosphere, interior and magnetic field of Mars for a full Martian year is being readied at the Jet Propulsion Laboratory (JPL) for a 1992 Titan III launch. Mars Observer will use a new class of spacecraft derived from Earth-orbiter designs. These missions will be of modest cost and are intended to explore objects of the inner solar system such as Venus, the Moon, Mars and near-Earth asteroids and comets. Mars Observer will continue NASA's exploration of the red planet, which began with the Mariner 4 mission in l964-65, and continued with Mariners 6 and 7 in l969 and Mariner 9 in l97l-72. This program reached a peak with the Viking orbiters and landers of l975-82. The Soviet Union in 1988 also sent spacecraft to orbit Mars and visit its inner satellite Phobos. The Mariners and Vikings provided a wealth of data about Mars. New global studies of the planet's geology and atmosphere are expected to give scientists even more information about the planet's evolution. One subject of particular interest is the role that water once played on Mars. While there is no liquid water on the surface of Mars now, the Mariner and Viking missions found ample evidence that liquid flowed there long ago. Scientists also want to compare the planetary neighbors Venus, Earth and Mars. Data from Mars Observer may help scientists understand why Venus, the Earth and Mars have evolvedto be such different planets. Mars Observer will use the expendable commercial Titan III launch vehicle. In September l992, a Titan III will carry Mars Observer and its booster into Earth orbit. From there, the Transfer Orbit Stage will boost the spacecraft into an interplanetary orbit leading to Mars. After an ll-month cruise, Mars Observer will arrive at the red planet and be placed in a large elliptical orbit. Then the orbit will be carefully adjusted through several intermediate steps, taking several months, until the spacecraft circles above Mars about every two hours. This mapping orbit will be sun- synchronized, so that sunlight will be at the same angle (early afternoon directly below the spacecraft) on the day side throughout the mission. The scientific mission will last for one Martian year (almost 669 Mars days, or 687 Earth days). This will allow Mars Observer to examine the planet through the four seasons. Mars Observer's science objectives are to: * Determine the global elemental and mineralogical character of the surface material; * Define the global topography and gravitational field; * Establish the nature of the magnetic field; * Determine the time and space distribution, abundance, sources and sinks of volatile material and dust over a seasonal cycle; * Explore the structure and aspects of the circulation of the atmosphere. Scientific investigations have been selected by NASA to carry out studies to meet those objectives. Mars Observer carries seven instruments: * A gamma-ray spectrometer will measure the abundance of elements (uranium, thorium, potassium, iron and silicon, for example) on the surface of Mars. William V. Boynton of the University of Arizona is the team leader. The instrument is managed by NASA's Goddard Space Flight Center and was built by the Martin Marietta Astronautics Group. * A thermal-emission spectrometer will map the mineral content of surface rocks, frosts and the composition of clouds. Philip R. Christensen of Arizona State University is the principal investigator. The Santa Barbara Research Center is the instrument contractor. * A line-scan camera will make low-resolution images of Mars on a daily basis for studies of the climate, and medium- and high-resolution images of selected areas to study surface geology and interactions between the surface and the atmosphere. Michael C. Malin of Malin Space Science Services is principal investigator. The instrument was built by the California Institute of Technology. * A laser altimeter will determine the topographic relief of the Martian surface. David E. Smith of NASA's Goddard Space Flight Center is the principal investigator. The instrument was built by the Goddard Space Flight Center. * A pressure-modulator infrared radiometer will measure dust and condensates in the atmosphere, as well as profiles of temperature, water vapor and dust opacity as they change with latitude, longitude and season. Daniel J. McCleese of JPL is the principal investigator. The instrument was built by JPL. * A radio-science investigation will use the spacecraft radio with an ultrastable oscillator built by the Applied Physics Laboratory of Johns Hopkins University to measure atmospheric refractivity as it varies with altitude to determine the temperature profile of the atmosphere, and will use tracking data to measure the gravity field of Mars. G. Leonard Tyler of Stanford University is the team leader. * A magnetometer and electron reflectometer will determine the nature of the magnetic field of Mars, and its interactions with the solar wind. Mario H. Acuna of NASA's Goddard Space Flight Center is the principal investigator. The magnetometer was built by Goddard Space Flight Center and the electron reflectometer by the French Centre National d'Etudes Spatiales. Six investigations that cross over the lines of specific scientific disciplines will examine overlapping interests. They are: * Geosciences. Michael H. Carr, U.S. Geological Survey. * Surface-atmosphere interactions. Bruce M. Jakosky, University of Colorado. * Atmosphere and climatology. James B. Pollack, NASA's Ames Research Center. * Polar atmospheric sciences. Andrew P. Ingersoll, California Institute of Technology. * Surface weathering. Raymond A. Arvidson, Washington University. * Surface processes and Geomorphology. Laurence A. Soderblom, U.S. Geological Survey. In addition to the spacecraft-based scientific program, Mars Observer will participate in an ambitious international Mars investigation through an agreement with France and the Commonwealth of Independent States (CIS). This participation is the Mars Balloon Relay Experiment. The CIS Mars '94 mission will deploy balloon-borneinstrument packages in the atmosphere of Mars. During their operating lifetime, they will transmit data to a CIS orbiter and to the Mars Observer spacecraft. Special equipment on the Mars Observer spacecraft, supplied by the Centre Nationale d'Etudes Spatiales, will receive the balloon data. Mars Observer's camera will format the balloon measurements (as if they were a digital picture) for storage and later transmission to Earth, where they will be converted back into balloon instrument readings. The Mars Observer spacecraft design is based on those of General Electric communications satellites and defense mapping satellites, modified for the Mars mission. At launch, antenna and instrument booms and solar arrays are folded close to the spacecraft bus, which is box-shaped and approximately 2.9 by 2.9 by 3.2 meters (9.5 by 9.5 by 10.5 feet) in size. The main communications antenna is raised on a 6-meter (20-foot) boom to clear the 3.7-by-6.5-meter solar array, which is fully unfolded only after the spacecraft reaches its mapping orbit around Mars. Most electronic subsystems use proven designs from previous satellite applications. The total spacecraft mass after launch and injection is about 2500 kilograms (5500 pounds). The Deep Space Network, a worldwide system of antenna and space communication stations operated for NASA by JPL, will provide tracking and data acquisition for the Mars Observer mission. Mission operations for Mars Observer and other planetary observers will be conducted in a new multimission facility, the JPL Advanced Multimission Operations System. During the more than three years of the mission, scientists and experimenters will be able to participate from their home institutions via electronic links to the operations center. At the home institution of each principal investigator or team leader, a science operations planning computer will provide the scientist with as much control of the instrument and experiment as feasible within operational, resource and security constraints. Each principal investigator or team leader will devise the proper sequences for operating the instrument. At the operations center, the sequences will be checked for authenticity and proper operation, and transmitted to the spacecraft via the Deep Space Network. Scientific data from the spacecraft will be routed to the science operations computer at the investigator's institution for analysis. JPL will maintain a project database to provide access to all data, both as received and as reduced, for all Mars Observer investigators. The cost of design, development and fabrication has been minimized by using existing spacecraft designs developed for Earth-orbiting satellite missions. Engineering modifications and the addition of science instruments have transformed the Earth- orbiter design into a spacecraft capable of traveling to and conducting experiments at other bodies in the inner solar system. JPL manages Mars Observer for the Solar System Exploration Division of NASA's Office of Space Science and Applications. JPLhas designed and will conduct the mission. The Astro Space Division of General Electric in East Windsor, N.J., is the spacecraft contractor. NASA's Lewis Research Center will supply the Titan III launch vehicle through a commercial launch services contract with Martin Marietta Commercial Titan, Inc., Denver, Colo. NASA's Marshall Space Flight Center will supply the upper stage to propel Mars Observer out of Earth orbit. That stage is the Transfer Orbit Stage (TOS), developed by Orbital Sciences Corporation (OSC) of Vienna, Va., as a privately financed venture. OSC's contractor for the stage is Martin Marietta Astronautics Group, Denver. Mars Observer's project manager is David D. Evans; Dr. Arden Albee of the California Institute of Technology is the project scientist. 2/11/92 JHW