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Mars Climate Orbiter/Mars Polar Lander
Mission Overview

Mars Surveyor Program

The National Aeronautics and Space Administration (NASA) has initiated a long-term systematic program of Mars exploration, the Mars Surveyor Program (MSP). The highest priority scientific objectives of this program are to:

The common thread of these objectives is water: past and present sources and sinks; exchanges between subsurface, surface and atmospheric reservoirs; and the change of volatiles over time.

The goal of the Mars Surveyor Program is to carry out low-cost missions, each of which provides important, focused, scientific return, and which will in sum constitute a major element of the scientific exploration of Mars. A series of lander and orbiter spacecraft are being launched at each favorable Mars launch opportunity, which occur approximately every 26 months. In 1997 the Mars Surveyor Program launched the Mars Global Surveyor (MGS), which together with the launch of the Discovery Program's Mars Pathfinder lander, initiated the new era of Mars exploration.

In the 1998-1999 launch opportunity, the Mars Surveyor Program successfully launched the following spacecraft, which are now in flight to Mars:

The Mars Polar Lander also carries two New Millennium Program (NMP) microprobes as the Deep Space 2 (DS2) Mission. These probes will separate from Mars Polar Lander prior to its entry into the Martian atmosphere, then fall through the atmosphere (without parachutes or rockets to slow their entry) and crash into the surface, with the probe forebodies penetrating up to a meter deep into the Mars surface. The short-lived DS2 probes will be located approximately 100 km further north (equatorward) of the Mars Polar Lander touchdown point and will themselves search for the presence of subsurface water ice and attempt to characterize subsurface soil thermal properties. Thus, complementary data will be obtained by the Deep Space 2 and Mars Polar Lander surface packages (and by Mars Climate Orbiter and Mars Global Surveyor). Future missions will culminate in the return of samples of Martian rocks and soil to Earth. The focus of the Mars Surveyor 98 element of the Mars Surveyor Program is to advance our understanding of the volatile and climate history of Mars through systematic mapping of the Mars seasonal cycles of weather, dust, water and carbon dioxide by remote sensing from orbit and through exploration in situ at a landed site on the layered terrain near the Martian south pole.

Mars Climate Orbiter/Mars Polar Lander
Project Objectives

Mars Climate Orbiter Mission Overview


The Mars Climate Orbiter was launched aboard a Delta 7425 in December 1998, and arrives at Mars in September 1999. Once the Delta 3rd stage burn is complete, the assembly is despun using a yo-yo despin device. After separation from the 3rd stage, the spacecraft's solar panels are deployed and pointed to the sun, and initial acquisition achieved by the Deep Space Network (DSN). During inner cruise, contact with Earth is maintained via the Medium Gain Antenna.

Approximately 15 days after launch, the largest trajectory correction maneuver is executed, which removes launch vehicle injection errors and adjusts the spacecraft's Mars approach aimpoint. Up to 3 additional small maneuvers may be required during the remainder of cruise to direct the spacecraft to the proper aimpoint for Mars orbit insertion. All cruise maneuvers are performed with the hydrazine thrusters. As the geocentric distance increases during cruise, communications moves to the high gain antenna.

At Mars arrival, in September, 1999, the Orbiter's main engine is used to propulsively insert the spacecraft into an elliptical capture orbit. This bipropellant engine burn lasts approximately 16 minutes, until all the loaded oxidizer is exhausted. One minute later, an additional maneuver is executed by the hydrazine thrusters, if needed, to reduce the orbit period further. The resulting capture orbit is expected to have a period no greater than 29 hours, and a periapse altitude of 160 km. A maneuver to lower periapse in preparation for aerobraking occurs at the first apoapse of the final capture orbit. Over the next two months, the energy of the orbit is reduced via successive passes through the atmosphere of Mars, controlled by small trim maneuvers near apoapse. At aerobrake termination, two maneuvers transfer the Orbiter to its final, frozen, near sun-synchronous mapping orbit, at a descending node of approximately 4 PM. This occurs some time prior to Mars Polar Lander arrival in December 1999.

During the Mars Polar Lander's 3-month surface mission, the Orbiter provides command and data relay support, and also performs a limited amount of orbital science. Upon completing this Lander support phase in February 2000, the Orbiter starts its mapping phase, during which systematic daily global sounding of the atmosphere and imaging of the surface is performed for one Mars year (687 days). The nadir-mounted science payload consists of a Pressure Modulator Infrared Radiometer (PMIRR) and the Mars Color Imager (MARCI). Once the mapping mission is complete, the Orbiter will be available as a communication relay for future Mars landers for up to 3 additional years. Upon completion of its relay mission, the Orbiter may perform a maneuver or be placed in a low- drag attitude to satisfy orbit lifetime requirements.

Additional details on the Orbiter's mission may be found in the Mission Plan and Databook.

Mars Polar Lander Mission Overview


The Mars Polar Lander was launched on a Delta 7425 in January 1999, and arrives at Mars in December 1999. As with the Orbiter, burnout of the Delta's 3rd stage is followed by yo-yo despin of the entire stack, followed by spacecraft separation. After separation, the solar panels are deployed and pointed to the sun, and initial acquisition achieved by the DSN. Throughout cruise, contact is maintained via the medium gain antenna, and the solar panels remain pointed at the sun (with a small offset in inner cruise). Approximately 15 days after launch, the largest trajectory correction maneuver is executed. Depending on the size of the maneuver, it may be necessary to divide this into two smaller maneuvers. Up to 4 additional small maneuvers may be needed during the remainder of cruise, including a contingency maneuver seven hours before entry, for final control of the entry angle and landing footprint. Near simultaneous tracking of the approaching Lander and an orbiter at Mars (either the Mars Climate Orbiter or Mars Global Surveyor) is planned, to support precision approach navigation.

Minutes before atmospheric entry, the cruise stage, which supported the Lander during its interplanetary journey, is separated from the protective aeroshell containing the Lander. Shortly after separation, two New Millennium Microprobes deploy themselves from the discarded cruise stage, and enter and land independently from the Mars Polar Lander. During entry, the Mars Polar Lander is slowed by a Mars Pathfinder-heritage aeroshell and parachute. Unlike Mars Pathfinder, the Mars Polar Lander uses thrusters to perform a controlled, propulsive landing. The Mars Descent Imager (MARDI) collects images of the surface during descent.

The targeted landing site is on the southern polar layered terrain, between 74S and 78S, less than 1000 km from the South pole. This area underlies the seasonal advance and retreat of the South polar ice cap, and may contain clues to the climatic history of Mars. Landing occurs during Spring in the southern hemisphere of Mars. The first landed day's activities include all deployments [solar panels, steerable medium gain antenna, and payload masts], functional checkout, establishment of communications, and time critical science activities. The Lander is equipped with a UHF relay for downlink to Earth via the Mars Climate Orbiter and/or Mars Global Surveyor, and command uplink from Earth via the Mars Climate Orbiter. A direct to Earth link is also available via the medium gain antenna, for backup commanding and data return.

Instruments used by the Lander on the surface include the Mars Volatiles and Climate Surveyor (MVACS) instrument suite, which performs in situ investigations to address the science theme "Volatiles and Climate History" on Mars, and a LIDAR instrument supplied by the Russian Space Agency. MVACS includes meteorology, imaging, and soil composition experiments. A robotic arm is used to dig a trench and collect soil samples for analysis. Investigations include a search for near-surface ice and possible surface records of cyclic climate change, and a study of physical processes key to the seasonal cycles of water, carbon dioxide and dust on Mars. The Lander is expected to operate on the surface for approximately three months.

Additional details on the Lander's mission can be found in the Mission Plan and Databook.

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