TES News

August 1994, Volume 3, No. 3

Thermal Emission Spectrometer Project Mars Global Surveyor Space Flight Facility Department of Geology, Arizona State University Box 871404, Tempe, Arizona 85287-1404, U.S.A.

Key Decisions for '96 Mars Missions

Mars Global Surveyor Contractor Chosen

Mars Global Surveyor cleared major hurdles during the Summer of 1994. On July 8th, NASA chose Martin Marietta Technologies, Inc. of Denver, Colorado, to build the small, light-weight orbiter for a November 1996 launch. Martin Marietta announced that it would begin construction immediately. At the same time, the U.S. Congress began to make decisions about the Fiscal Year 1995 NASA budget, which is expected to include funds for Mars Global Surveyor.

Mars Global Surveyor is to be launched aboard a McDonnell Douglas Delta II rocket from the Kennedy Space Center around November 3, 1996. It will reach Mars in September 1997, and begin mapping in late January 1998. Mars Global Surveyor will be the first in what is planned to be a series of small spacecraft to be sent to Mars between 1996 and 2006. Mars Global Surveyor will carry five of the instruments that were aboard the lost Mars Observer, including the Thermal Emission Spectrometer (TES) which is controlled from Arizona State University. While Martin Marietta builds the spacecraft "bus," the individual science instruments are being assembled elsewhere. For example, the new TES will come from the Hughes Santa Barbara Research Center in Goleta, California. (continued below)

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Mars Global Surveyor. The innovative spacecraft design by Martin Marietta of Denver, Colorado, is shown in this artist's conception. The diagram shows Mars Global Surveyor during an aerobraking maneuver. The twin solar panels on each side of the spacecraft are used as shields to protect the science instruments while at the same time slowing the spacecraft as the thin upper atmosphere creates a drag on the vehicle.

The Thermal Emission Spectrometer (TES) instrument, a project directed by Dr. Philip Christensen of Arizona State Univeristy, is next to a long, white cannister which forms the high resolution camera system. The TES will measure infrared energy to help determine the mineral composition of Mars. The camera on Mars Global Surveyor will be able to image objects as small as 2 meters. Also aboard the spacecraft is a laser altimeter to measure the Martian topography.

NASA and the Jet Propulsion Laboratory (JPL; operated in Pasadena, CA, by the California Institute of Technology) conducted an industry competition to select the contractor for Mars Global Surveyor. Performance objectives called for a low mass, polar-orbiting spacecraft that would cost under $155 million. At least two other companies bid on the contract. To use less fuel, the Martin Marietta spacecraft will use a technique called aerobraking to slow the vehicle and put it in the proper orbit. Aerobraking has never been tried at Mars before. The Venus probe Magellan was successfully slowed via aerobraking during experimental tests in 1993; but this was done after, not before, the spacecraft had met all of its primary science objectives.

The NASA budget for Fiscal Year 1995 (which runs from October 1, 1994, to September 30, 1995) is still being resolved. In May 1994 the House of Representatives authorization committee designed a NASA budget that did not include funding for Mars Global Surveyor. However, in early June the House appropriations committee recommended a $14 billon budget for NASA, including full funding for Mars Global Surveyor. The full House of Representatives approved this budget in late June. In mid-July, the Senate appropriations committee recommended a $14.4 billion NASA budget, which was approved by the full Senate in early August. As of this writing, the House and Senate authorization bills had not been voted upon. In late August or early September, the two houses are expected to meet in conference committees to work out the differences between their bills.

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Mars Pathfinder and its microrover will land on the Red Planet in July 1997. Pathfinder will be joined September 1997, by the orbiting spacecraft Mars Global Surveyor.

Mars Pathfinder Landing Site Chosen

Mars Pathfinder is set to land at the junction of two giant flood channels, Ares and Tiu, on July 4, 1997. The spacecraft will land at night. Once the sun comes up, Pathfinder's IMP camera system, built by a team at the University of Arizona in Tucson, will begin to photograph the landscape. Also during this first day, Pathfinder's microrover will be deployed to begin probing the composition of rocks brought to the site by massive floods many millions of years ago. The rover will bear the name of a famous heroine (from literature, history, or mythology) chosen by children and young adults born after the last U.S. spacecraft landed on Mars in 1976 (see below).

Pathfinder will launch in December 1996, and is designed to test new engineering concepts for Mars landings. In particular, the lander uses giant airbags, much like those found in automobiles, to cushion the impact when it reaches the Martian surface. The design may be adopted for other Mars landings planned for the Mars Surveyor program, which is expected to launch one or more spacecaft to the Red Planet in 1996, 1998, 2001, 2003, and 2005. Pathfinder will also test the capabilities of a small rover, the first of its kind sent to Mars. Robotic rovers have only been used previously on the Moon in the 1970's by the Soviet Union.

The choice of a landing site for Pathfinder was not an easy one. Engineers constrained the landing site to be within 5 degrees of 15 degrees North latitude and below 0 km elevation. In July 1997, Mars will be in Northern Summer, and 15 North will get the most sunlight. Maximum sunlight is critical because Pathfinder, unlike the Vikings of 1976, will use solar power to operate.

Dr. Matthew Golombek, Project Scientist for Pathfinder at JPL, convened a meeting at the Lunar and Planetary Institute in Houston, Texas, April 18-19, 1994, which brought together the Mars science community to discuss landing sites.

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Pathfinder is well-suited for examining the composition of rocks and soil at its landing site. The microrover carries an instrument which uses protons and x-rays to estimate chemical composition, and the IMP provides multispectral images which will also give clues about rock composition. After the April 1994, Houston meeting, the Pathfinder scientists met several times before mid-June, when they finally settled on a landing site. Four sites were actually chosen, with the first being of the highest priority.

The Ares-Tiu site (19.5 N, 32.8 W) is expected to provide a "grab bag" of rock types brought down by massive floods that originated in the cratered highlands and lava flows to the south. This site is near the orignal Viking 1 site (19.5 N, 34 W) that was rejected in June 1976 as being too dangerous for landing. If the Pathfinder engineers determine that the new landing site is likewise dangerous (using Earth-based radar data to be obtained in early 1995), then the #2 site is south of Trouvelot Crater (approx. 10 to 17 N, 11 to 20 W). The Trouvelot site is not a flood channel but would provide samples of ancient highlands rock plus dark, wind-blown sand. Dark sand is known to occur on Mars but was not seen at either of the 1976 Viking lander sites. If both the #1 and #2 sites prove dangerous when examined with the 1995 radar observations, the #3 (18.8 N, 52 W) and #4 (13.5 N, 53 W) sites are associated with deposits formed by another vast flood channel system known as Maja Valles.

Russian Mars Missions Delayed to '96, '98

Earlier this summer, Russia and its international partners decided to postpone the Mars 94 mission to a 1996 launch, and the Mars 96 mission moved to 1998. The new Mars 96 will have two landers and two penetrators; Mars 98 will have a rover. The 1996 landers carry a U.S. experiment to test oxidants in the soil.

K-12 Education Opportunities

The Arizona Mars K-12 Education Program provides an opportunity for students and educators to experience a "piece" of the space program. Teachers may arrange student visits to the TES facility by contacting the ASU Undergraduate Admissions Office at (602) 965-2622. The facility can also be "visited" by computer over the Internet using the NCSA Mosaic browse tool. Our URL is: http://marsed.asu.edu Teacher workshops are held at ASU in February and August. For information, call (602) 965-1790.

Name the Pathfinder Microrover

Pathfinder's microrover needs a name. Choose the name of a heroine from mythology, fiction, or history (not living). You must be born after January 1, 1976. Deadline is March 1, 1995. Contact: The Planetary Society, 65 N. Catalina Ave., Pasadena, CA 91106; (818) 793-5100.

Recent Mars Articles

A new TES News is available every 3 months. This 
newsletter may be copied for educational purposes. Supported by NASA Grants NAGW 
943 and NAGW 3923. Please share or recycle this document. Text and Typesetting 
by: K. S. Edgett Reviewed by: 
M. Presley and D. Wakefield 
Figures Courtesy: NASA / Jet Propulsion Laboratory 
Original Text:  August 8, 1994
Hypertext:  August 9, 1994