August/September 1992, Volume 1, No. 2
Thermal Emission Spectrometer Project Mars Observer Space Flight Facility Department of Geology, Arizona State University Box 871404, Tempe, Arizona 85287-1404, U.S.A.
The rocks and minerals that occur on the surface of Mars represent only a tiny fraction of the total volume of the planet, but their properties provide very important clues to a wide range of questions regarding the nature, timing, and duration of geologic and climatic events which have shaped the Red Planet. The composition and particle sizes of martian surface materials can be used to study the history of erosion, transport, and deposition of surface sediments and provide a potential record of planetary climate change. The composition of the surface also provides important constraints upon the mineralogy of the martian crust and mantle, which in turn are used to decipher the geologic evolution of the planet. Despite visits by 15 U.S. and U.S.S.R. spacecraft over the past 27 years, the mineralogic composition of Mars remains largely unknown.
The Thermal Emission Spectrometer (TES) is one of seven experiments aboard the Mars Observer spacecraft. The TES will provide direct measurements of the surface mineralogy of Mars. The TES is designed to systematically map the surface from orbit at a resolution of 3 km (1.9 miles). The TES will completely map the planet once every 188 days, each orbit will give a strip of data 9 km (5.6 miles) wide from pole to pole. TES observations will also examine the amount of dust suspended in the atmosphere and provide important information about surface temperatures, particle sizes, and give a detailed look at how and when dust, carbon dioxide, and water-ice clouds form. The TES will obtain detailed observations on the composition, growth, and retreat of the polar ice caps.
The Mars Observer Spacecraft. Note the location of the Thermal Emission Spectrometer.
The TES consists of three subsections: (1) a Michelson interferometer, which obtains detailed infrared spectra between wavelengths of 6 and 50 microns; (2) a solar reflectance detector, which measures the brightness of light reflected off the martian surface; and (3) a radiance detector which provides an independent measure of martian surface temperatures.
The TES was built under contract from NASA by the Hughes Santa Barbara Research Center (SBRC) in Goleta, California. The project involved more than 100 staff and engineers over a period of 6 years and about 170 person-years of effort. Following calibration tests at SBRC in the Summer and Fall of 1991, the TES was delivered to the General Electric Astro Space Division near Princeton, New Jersey, where it was mounted on the Mars Observer spacecraft. Mars Observer will launch from the Kennedy Space Center, Florida, in September 1992.
(For more information and pictures of TES being built and calibrated, see the slide set, "The Story of TES." K.S.E., 29-Jan.-94)The Principal Investigator for the TES project is Dr. Philip R. Christensen, Professor of Geology at Arizona State University. The Principal Investigator for each Mars Observer instrument is responsible for the control of the instrument and receipt of data at the investigator's home institution. The TES will be commanded from the Mars Observer Space Flight Facility at Arizona State University.
TABLE 1: TES Science Team
The TES Science Team is composed ot individual from across the United States who have worked previously on the Mariner, Viking, and Voyager projects. The TES team also involves a group of Participating Scientists, including two from Russia.
The variety of remote sensing instruments employed in the study of Earth and the Solar System utilize different portions of the electromagnetic spectrum, depending upon the scientific objectives being addressed. For example, the Magellan spacecraft uses radar to penetrate clouds and map the surface of Venus, while Landsat uses visible and near infrared wavelengths to monitor land use and the health of vegetation on Earth. The TES measures emitted infrared light between 6 and 50 microns. These wavelengths are the best for the identification of different types of rocks and minerals. Each mineral type has its own distinct infrared signature, thus allowing the opportunity to map their abundances on the martian surface. Examples of mineral spectra are shown in the figure below.
Thermal infrared spectra of common minerals (Click on Icon to see a good representation).
Text prepared by:T.E. Montoya and K.S. Edgett
Original Text: August 1992 Hypertext Version: January 29, 1994