Pathfinder will be the first U.S. spacecraft to land on Mars since the two Vikings arrived in 1976. Pathfinder is likely to be joined on the Mars surface in 1997 by two landers and two penetrators of the Russian Mars 96 mission. A unique feature of Pathfinder will be its Microrover, a small vehicle which can range up to a few tens of meters away from the spacecraft and examine the composition of surrounding rocks and soils.
Pathfinder is planned for launch aboard a Delta II rocket sometime between December 1996 and January 1997. The spacecraft will be on a direct course from the Kennedy Space Center in Florida to the Martian surface. Landing is planned for July 4, 1997, nearly 21 years after the Viking landings.
Pathfinder will land during the Martian night. Just before the spacecraft impacts the surface, giant airbags will inflate to cushion the landing. After the spacecraft comes to rest on the surface, the airbags will deflate and three solar panels will unfold. These panels are arranged in a way that will allow the spacecraft to be flipped over if it should land upsidedown. The solar panels will begin providing power to the spacecraft as soon as the sun comes up that first morning on Mars.
The primary objective for Pathfinder is to demonstrate a low-cost approach for cruise, descent, and an upright landing systems to place a payload on the Martian surface in a safe and operational configuration.The lander also carries the microrover which will test mobility for small rovers on Mars. The microrover will also examine the condition and configuration of the Pathfinder landing craft to assess how well the landing system performed.
The scientific objectives include examination of the composition of rocks and soils in the vicinity of the lander.The mission will characterized surface morphology and geology, acquire elemental composition information, and obtain atmospheric measurements such as temperature, pressure, and wind velocity. The lander is shaped like a tetrahedron. The tetrahedron consists of four similarly-shaped triangular panels. All lander equipment except the solar arrays and rover are attached to a single center panel. The other three panels are attached to the edges of the center panel. These three panels can move in a way that would flip the lander into an upright position if it should land upside-down. The lander is designed to last a minimum of 30 days on the Martian surface. It's instruments are described further below.
The microrover has 6 wheels and a mass of about 10 kg. It is about 65 cm long by 45 cm wide and 32 cm high. The rover will allow scientists to examine rocks that would otherwise be out of reach from a fixed lander. The rover will also be able to look at the lander and check out its condition.
The microrover carries the Alpha Proton X-ray Spectrometer (APXS) experiment. It also has two small monochrome cameras which act as "eyes" for navigating the rover around the landscape. These imagers can see objects about one millimeter in size and may allow scientists a close-up view of the texture of rocks found at the landing site. The rover is expected to function for a minimum of 7 days, but hopefully will last 30 or more days on the Martian surface.
The two cameras provide operators on Earth with a stereo view of the area in front of the rover. The rover is commanded from Earth, but most of its activity relies on capabilities programed into the onboard computer. The 6 wheels can respond independently to conditions in rough terrain.
There are three major science experiments aboard Pathfinder, and each has a variety of scientific goals. For example, the imaging system can obtain multispectral images of the surface and atmosphere, thus allowing estimation of how much dust is in the air and what types of rocks might be present. The imaging system will also look at a wind sock experiment, allowing determination of wind velocity above the surface. The imaging system may also be able to monitor changes in weather, particularly cloud cover, and can also be used to plan the work of the microrover. The Primary Investigator of this instrument is Peter Smith of UA's Lunar and Planetary Lab.
The experiments aboard Pathfinder will provide information about the element abundance, iron-bearing minerals, and atmospheric properties during descent and on the surface. These instruments and the science objectives they represent will provide us with a new, fresh view of the Red Planet from its surface. The project is required to have a cost of less than $150 Million, have a fast schedule (less than three years from new start to launch), and achieve a set of significant but focused engineering, science, and technology objectives.