Mro-launch qxp

Mars Climate Sounder will study water vapor, dust, ices and temperatures in Mars'

atmosphere. It will assess how they vary with altitude, map how they are distributed

around the planet, and monitor their changes from day to night and from season to

season. The results will aid understanding of the atmosphere's structure and circula-

tion, thus the planet's weather and climate. The instrument looks both toward the hori-

zon and straight down, in a broadband visible and in several thermal infrared channels.

Looking toward the horizon, it can observe the atmosphere in vertical slices, assessing

each 5-kilometer-thick (3-mile-thick) section from the surface to an altitude of 80 kilo-

meters (50 miles). The resulting atmospheric profiles from different areas around the

planet can be combined into daily, three-dimensional global weather maps for both

daytime and nighttime.

Mars Climate Sounder is one of the instruments serving the mission's global-monitor-

ing research mode. One goal for researchers using it is to examine how solar energy

interacts with the atmosphere and the surface. The measurements will also serve

understanding of how the atmosphere moves water around the planet seasonally and

the give and take between the surface and the atmosphere in quantities of water and

dust. One area of regional focus is the polar regions, where measurements of the

amount of solar energy absorbed by the surface ice can be used to estimate the

amount of carbon dioxide that is exchanged between the atmosphere and the surface

during the Martian year.

The Mars Climate Sounder instrument will address the scientific goals of an earlier,

much heavier instrument that flew on the ill-fated Mars Observer and Mars Climate

Orbiter spacecraft. It uses a pair of telescopes with apertures of 4 centimeters (1.6

inches). They are mounted in a cylinder in a yoke frame articulated so that, without

repositioning the spacecraft, the telescopes can point sideways to the horizon and to

space, down onto the planet, or at calibration targets attached to the yoke. Detectors

record the intensity of radiation in nine channels or bands of the electromagnetic spec-

trum. One channel covers visible and near-infrared frequencies from 300 to 3,000

nanometers (0.3 to 3 microns). The other eight channels are in the thermal infrared

part of the spectrum, from 12 to 50 microns. 

Principal investigator for the Mars Climate Sounder is Dr. Daniel McCleese of NASA's

Jet Propulsion Laboratory, Pasadena, Calif., and JPL provided the instrument to the

mission.

The orbiter's Shallow Subsurface Radar will probe beneath Mars' surface to find

and map underground layers of ice, rock and, if present, liquid water. The information

will come from the patterns of reflected radio waves transmitted by the instrument. The

instrument will search to a depth of up to one kilometer (0.6 mile), with the actual

depth of penetration depending on the composition of the upper crust of Mars. It will be

able to distinguish between layers of different composition or physical state (e.g., liquid

water) as thin as 10 meters (33 feet).

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The Shallow Subsurface Radar is a regional-survey instrument. Researchers will use it

to follow up on the discovery by Mars Odyssey that the top layer of ground in many

parts of Mars holds substantial quantities of hydrogen, believed to be in the form of

water ice. The Odyssey instruments provided information about the top meter (3 feet)

of ground. This radar will allow scientists to determine whether the ice-bearing material

extends much deeper, helping scientists discern whether the ice content results from

an equilibrium with the Martian atmosphere of today or persists as a remnant of a

much thicker ice layer formed long ago. The instrument can distinguish icy layers from

water-bearing layers. If the instrument does find any underground water, those sites

could become landing-site candidates for future Mars rovers or human exploration.

Researchers also plan to use the Shallow Radar for mapping the distribution of buried

channels, studying the internal structure of Mars' ice caps, checking for liquid water

underneath the ice caps, and examining the extent and relative depths of rock layers in

selected regions. The structure of the upper crust may be very complex and so the use

of surface observations may be critical to the proper interpretation of the radar data.

Thus, areas like the Meridiani Planum region surrounding the rover Opportunity's

research area are high-priority targets for radar mapping to see how far the surface

layers with their water-related minerals extend laterally beneath the surface. 

The instrument will transmit "chirps" lasting 85 milliseconds each at radio frequencies

from 15 megahertz to 25 megahertz (wavelengths of about 15 meters or 50 feet in free

space) with 10 watts of power. In most cases, it will operate on the night side of the

planet. Compared with the only other ground-penetrating radar instrument ever to orbit

Mars, the Mars Advanced Radar for Subsurface and Ionospheric Sounding on the

European Space Agency's Mars Express, the instrument on Mars Reconnaissance

Orbiter will focus on shallower layers and have higher resolution. The Shallow

Subsurface Radar's antenna will extend five meters (16 feet) to each side of the

spacecraft. It is stowed in a folded-up configuration for launch and will not be deployed

until after aerobraking has been completed. During the mission's two-year primary sci-

ence phase, investigations with the Shallow Subsurface Rader are expected to return

more data than the entire NASA Magellan mission, which mapped 99 percent of the

surface of Venus with an orbiting radar instrument in the early 1990s.

The Italian Space Agency (ASI) selected Alenia Spazio, Rome, as the prime contractor

for the Shallow Subsurface Radar and selected Dr. Roberto Seu of the University of

Rome La Sapienza as the principal investigator for the instrument's science team. The

Italian Space Agency provided the Shallow Subsurface Radar to NASA as a facility sci-

ence instrument, with Dr. Seu as team leader. As part of this international collaboration,

NASA selected a team of U.S. co-investigators, led by Dr. Roger Phillips of Washington

University, St. Louis, to support Dr. Seu's team.

Two additional facility science investigations will use spacecraft subsystems to conduct

scientific investigations of Mars.

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