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[[File:Marspathrov.jpg|thumb|''Sojourner'' at JPL]]
''Sojourner'' was an experimental vehicle whose main mission was to test in the Martian environment technical solutions that were developed by engineers of the NASA research laboratories.<ref name="Matijevic2" /> It was necessary to verify whether the design strategy followed had resulted in the construction of a vehicle suitable for the environment it would encounter, despite the limited knowledge of it. Careful analysis of the operations on Mars would make it possible to develop solutions to critical problems identified and to introduce improvements for subsequent planetary exploration missions. One of the mission's main aims was to prove the development of "faster, better and cheaper" spacecraft was possible. Development took three years and cost under $150 million for the lander, and $25 million for the rover; development was faster and less costly than all previous missions.
<!--Particularly innovative aspects were the semi-automatic navigation and locomotion systems. The effects of Martian dust on the [[photovoltaic panel]]s that powered the lander and the rover were not known with certainty
These objectives required careful selection of the landing site to balance the technical requests with the scientific ones.<ref name="landing site">{{cite journal|first1=M.P. |last1=Golombek | first2=R.A. |last2= Cook| first3= H.J. |last3= Moore| first4= T.J. |last4= Parker |title=Selection of the Mars Pathfinder landing site |journal=J. Geophys. Res. |volume=102 | number=E2 |pages=3967–3988 |year=1997 |doi=10.1029/96JE03318|bibcode=1997JGR...102.3967G |doi-access=free }}</ref> A large plain was needed for the probe to land and rocky terrain to verify the rover's systems. The choice fell on [[Ares Vallis]] in [[Chryse Planitia]], which is characterized by alluvial-looking rock formations. Scholars believed the analysis of the rocks, which lie in what appears to be the outlet of a huge drainage channel, could have confirmed the past presence of liquid water on the surface of Mars and provide details of the surrounding areas, from which the rocks were eroded.<ref name="landing site" /><ref name=Golombek97>{{cite journal |title=Overview of the Mars Pathfinder Mission and Assessment of Landing Site Predictions |journal=Science |year=1997 |volume=278 |number=5344 |pages=1743–1748 |first=M.P. |last=Golombek |doi=10.1126/science.278.5344.1743 |pmid=9388167 |bibcode=1997Sci...278.1743G |doi-access=free }}</ref>
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The Wheel Abrasion Experiment (WAE) was designed to measure the abrasive action of Martian soil on thin layers of aluminum, nickel, and platinum, and thus deduce the grain size of the soil at the landing site. For this purpose, 15 layers—five of each metal—were mounted on one of the two central wheels with a thickness between 200 and 1000 [[ångström]], and electrically isolated from the rest of the rover. By directing the wheel appropriately, sunlight was reflected towards a nearby [[Photocell|photovoltaic sensor]]. The collected signal was analyzed to determine the desired information.<ref name=Deposits>{{cite journal| author=The Rover Team |title=Characterization of the Martian Surface Deposits by the Mars Pathfinder Rover, Sojourner |journal=Science |year=1997 |volume=278 | number=5344 |pages=1765–1768 |doi=10.1126/science.278.5344.1765|bibcode=1997Sci...278.1765M |doi-access=free }}</ref> For the abrasive action to be significant on the mission schedule, the rover was scheduled to stop at frequent intervals and, with the other five wheels braked, force the WAE wheel to rotate, causing increased wear.<ref name=Ferguson>{{cite journal| author=D.C. Ferguson |title=Evidence for Martian electrostatic charging and abrasive wheel wear from the Wheel Abrasion Experiment on the Pathfinder Sojourner rover |journal=J. Geophys. Res. |volume=104 | number=E4 |pages=8747–8789 |year=1999 |doi=10.1029/98JE02249 |bibcode=1999JGR...104.8747F }}</ref> Following the WAE experiment on Mars, attempts were made to reproduce the effects observed in the laboratory.<ref name="Ferguson" />
The interpretation of the results proposed by Ferguson ''et al''. suggests the soil at the landing site is made up of fine-grained dust of limited hardness with a grain size of less than 40
=== Materials Adherence Experiment ===
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File:Rover movie sol10 S0050F with Yogi.gif|Rover near Yogi, sol 10.
</gallery>
{{Wide image|
{{Wide image|Mars Pathfinder Presidential Panorama.jpg|1200px|Various images of the ''Sojourner'' shot by the lander have been composited into the 360 degree Presidential Panorama. Since the camera's position was consistent, it is thus possible to see these images of the rover in the context of the entire landscape. This provides a visual scale for understanding the sizes and distances of rocks surrounding the lander as well as a record of the travels of the rover. Several of the rover images were captured in full color. The rest were colorized using color sampled from those frames.<ref>{{cite web |title=Presidential Panorama |url=https://mars.nasa.gov/MPF/ames/ames-rovers.html |website=mars.nasa.gov |publisher=NASA |access-date=30 August 2021 |archive-date=23 June 2021 |archive-url=https://web.archive.org/web/20210623060402/https://mars.nasa.gov/MPF/ames/ames-rovers.html |url-status=live }}{{PD-notice}}</ref>}}
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