Mars Pathfinder was the first completed mission Mars Pathfinder was the first completed mission in NASAs Discovery Program of low-cost, rapidly in NASAs Discovery Program of low-cost, rapidly developed planetary missions with highly focused developed planetary missions with highly focused sci-ence goals. With a development time of only three ence goals. With a development time of only three years and a total cost of $265 million, Pathfinder was years and a total cost of $265 million, Pathfinder was
originally designed originally designed as a technology as a technology demonstration of a demonstration of a way to deliver an way to deliver an instrumented lander instrumented lander and a free-ranging and a free-ranging robotic rover to the robotic rover to the surface of the red surface of the red planet. Pathfinder planet. Pathfinder not only not only accom-plished this goal but plished this goal but also returned an also returned an unprecedented unprecedented amount of data and amount of data and outlived its primary outlived its primary design life. design life. Pathfinder used Pathfinder used an innovative an innovative method of directly method of directly entering the entering the Martian Martian atmos-phere, assisted by a phere, assisted by a parachute to slow parachute to slow its descent through its descent through
the thin Martian atmosphere and a giant system of the thin Martian atmosphere and a giant system of airbags to cushion the impact. It was the first time airbags to cushion the impact. It was the first time this airbag technique had been used. After the entry this airbag technique had been used. After the entry vehicle entered M
vehicle entered Marsars atmosphere from atmosphere from its interplane-its interplane-tary trajectory, it successfully completed a tary trajectory, it successfully completed a 4-1/2-minute sequence of complex and
minute sequence of complex and precisely timedprecisely timed
events, ending in a touchdown which left all systems events, ending in a touchdown which left all systems intact.
intact.
The landing site, an ancient flood plain in
The landing site, an ancient flood plain in MarsMars northern hemisphere known
northern hemisphere known as Ares Vas Ares Vallis, is allis, is amongamong the rockiest parts of Mars. It was chosen because the rockiest parts of Mars. It was chosen because sci-entists believed it to entists believed it to be a relatively safe be a relatively safe surface to land on surface to land on and one which and one which con-tained a wide tained a wide vari-ety of rocks
ety of rocks
deposited during a deposited during a catastrophic flood. catastrophic flood. In the event early in In the event early in Mars
Mars historyhistory, sci, sci--entists believe that entists believe that the flood plain was the flood plain was cut by a volume of cut by a volume of water the size of water the size of North Americas North Americas
Great Lakes in Great Lakes in about two weeks. about two weeks.
The lander, The lander, for-mally named the mally named the Carl Sagan Carl Sagan
Memorial Station Memorial Station following its following its suc-cessful touchdown, cessful touchdown, and the rover, and the rover, named Sojourner after American civil rights crusader named Sojourner after American civil rights crusader Sojourner Truth, both outlived their design lives Sojourner Truth, both outlived their design lives the lander by nearly three times, and the rover by the lander by nearly three times, and the rover by 1212 times.
times.
From the landing on July 4, 1997, to the final data From the landing on July 4, 1997, to the final data transmission on September 27, 1997,
transmission on September 27, 1997, Mars PathfinderMars Pathfinder
Mars Pathfinder
Mars Pathfinder
N
NA
AS
SA
A F
Fa
ac
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s
National Aeronautics and National Aeronautics and Space Administration Space Administration
Jet Propulsion Laboratory Jet Propulsion Laboratory California Institute of Technology California Institute of Technology Pasaden
returned 2.3 billion bits of information, including returned 2.3 billion bits of information, including more than 16,500 images from the lander and 550 more than 16,500 images from the lander and 550 images from the rover, as well as more
images from the rover, as well as more than 15 chem-than 15 chem-ical analyses of rocks and soil and extensive data on ical analyses of rocks and soil and extensive data on winds and other weather factors. Findings from the winds and other weather factors. Findings from the investigations carried out by scientific instruments on investigations carried out by scientific instruments on both the lander and the rover suggest that Mars was at both the lander and the rover suggest that Mars was at one time in its past warm and wet, with water existing one time in its past warm and wet, with water existing in its liquid state and a thicker atmosphere.
in its liquid state and a thicker atmosphere. Overall, the Pathfinder mission was a
Overall, the Pathfinder mission was a great suc-great suc-cess, providing scientists with large amounts o
cess, providing scientists with large amounts of data,f data, pioneering many new technologies, and pioneering many new technologies, and demonstrat-ing the feasibility of developdemonstrat-ing, designdemonstrat-ing launchdemonstrat-ing ing the feasibility of developing, designing launching and operating a planetary mission according to
and operating a planetary mission according to NASAs new faster, better, cheaper philosophy. NASAs new faster, better, cheaper philosophy.
Mission Overview Mission Overview
Mars Pathfinder was launched atop a
Mars Pathfinder was launched atop a Delta II-Delta II-7925 launch
7925 launch vehicle from Cape Canaveral Air Stationvehicle from Cape Canaveral Air Station in Florida on
in Florida on December 4, 1996. The launch vehicleDecember 4, 1996. The launch vehicle
included a Star 48 solid rocket as the third-stage included a Star 48 solid rocket as the third-stage booster.
booster.
During the
During the spacecraftspacecrafts seven-month journey s seven-month journey toto Mars, four trajectory correction maneuvers fine-tuned Mars, four trajectory correction maneuvers fine-tuned its flight path. NASAs Deep Space Network of giant its flight path. NASAs Deep Space Network of giant dish antennas provided the
dish antennas provided the two-way communicationstwo-way communications link for command, tracking and
link for command, tracking and telemetry operations.telemetry operations. Except for some difficulty with two of the
Except for some difficulty with two of the space- space-craft
crafts five Sun s five Sun sensors early in the sensors early in the flight, all criticalflight, all critical spacecraft subsystems performed as expected.
spacecraft subsystems performed as expected. At 1:42 p.m
At 1:42 p.m. PDT. PDT on June 30, 1997, ton June 30, 1997, the flighhe flightt team commanded the spacecraft to switch into team commanded the spacecraft to switch into itsits mode for entry, descent and landing on Mars. On July mode for entry, descent and landing on Mars. On July 3, 1997, at about 4 a.m. PDT, the spacecraft passed 3, 1997, at about 4 a.m. PDT, the spacecraft passed into the sphere of Mars
into the sphere of Mars gravitational inflgravitational influence. Earlyuence. Early on July 4, 1997, Pathfinder was heading for its
on July 4, 1997, Pathfinder was heading for its approximately 100- by 200-kilometer (60- by approximately 100- by 200-kilometer (60- by 120-mile) landing ellipse.
mile) landing ellipse. The sequence of
The sequence of entryentry, descent and , descent and landing eventslanding events was as follows: release of the cruise stage (34 minutes was as follows: release of the cruise stage (34 minutes
Wind Sensor Wind Sensor
Wind Socks Wind Socks
Imager for Mars Imager for Mars Pathfinder (IMP) Pathfinder (IMP)
Instrument Electronics Instrument Electronics Assemblies
Assemblies Alpha ProtonAlpha Proton
X-ray Spectrometer X-ray Spectrometer ASI/MET ASI/MET Accelerometers Accelerometers Thermocouples Thermocouples Rover Rover Atmospheric Structure Instrument
Atmospheric Structure Instrument and Meteorology Package
and Meteorology Package (ASI/MET) (ASI/MET) Solar Panel Solar Panel Low-Gain Low-Gain Antenna Antenna High-Gain High-Gain Antenna Antenna Solar Panel Solar Panel Solar Panel Solar Panel
prior to landing),
prior to landing), entry into Maentry into Marsrs upper atmosphereupper atmosphere (4 minutes to landing),
(4 minutes to landing), deployment of the 11-meterdeployment of the 11-meter--diameter (36-foot) parachute (2 minutes to landing), diameter (36-foot) parachute (2 minutes to landing), release of the heat shield, release of the lander from release of the heat shield, release of the lander from the backshell and descent of the
the backshell and descent of the lander on a 20-meterlander on a 20-meter (65 foot) tether, acquisition of altitude
(65 foot) tether, acquisition of altitude information byinformation by the radar altimeter
the radar altimeter, inflation of the , inflation of the airbags (8 secondsairbags (8 seconds to landing), firing of
to landing), firing of the rocket-assisted decelerationthe rocket-assisted deceleration engines, cutting of the tether, and free-fall of the engines, cutting of the tether, and free-fall of the lan-der to the Martian surface.
der to the Martian surface.
The airbag-cushioned lander hit Martian soil The airbag-cushioned lander hit Martian soil atat 10:07 a.m. PDT
10:07 a.m. PDT on July 4, 1997, at on July 4, 1997, at a speed of 14a speed of 14 meters per second (31 miles per hour). Measuring 5.8 meters per second (31 miles per hour). Measuring 5.8 meters (19 feet) in diameter, it bounced like a giant meters (19 feet) in diameter, it bounced like a giant beach ball about 15 times, as high as 15 meters (50 beach ball about 15 times, as high as 15 meters (50 feet), before coming to rest 2-1/2
feet), before coming to rest 2-1/2 minutes later aboutminutes later about 1 kilometer (six-tenths of a mile) from the point of 1 kilometer (six-tenths of a mile) from the point of initial impact. The landing coordinates were 19.13 initial impact. The landing coordinates were 19.13 degrees north latitude, 33.22 degrees west
degrees north latitude, 33.22 degrees west longitude,longitude, in the boulder-strewn Ares Vallis flood plain.
in the boulder-strewn Ares Vallis flood plain. Fortuitously
Fortuitously, the lander came to rest right , the lander came to rest right side up onside up on its base petal, thereby eliminating the need for the its base petal, thereby eliminating the need for the spacecraft to right itself while deploying its petals. spacecraft to right itself while deploying its petals.
An antenna mounted on one of the landers petals An antenna mounted on one of the landers petals
sent confirmation back to Earth
sent confirmation back to Earth that Pathfinder hadthat Pathfinder had landed. Approxim
landed. Approximately 90 minutes ately 90 minutes after landing, engi-after landing, engi-neering data received by the flight team indicated that neering data received by the flight team indicated that Pathfinder had fully deployed its petals and was
Pathfinder had fully deployed its petals and was awaiting sunrise on Mars to begin its mission. The awaiting sunrise on Mars to begin its mission. The lander came to rest about 20 kilometers (12 miles) lander came to rest about 20 kilometers (12 miles) southwest of its targeted landing spot and was resting southwest of its targeted landing spot and was resting on the surface at a very slight tilt of about 2.5
on the surface at a very slight tilt of about 2.5 degrees.
degrees.
Pathfinders first transmission via the
Pathfinders first transmission via the landerslanders low-gain antenna was received on time at 2:07 p.m. low-gain antenna was received on time at 2:07 p.m. PDT
PDT on July 4, 1997, or on July 4, 1997, or sol 1 (a Marsol 1 (a Martian daytian day, or, or sol, is 24 hours, 37 minutes). The transmission sol, is 24 hours, 37 minutes). The transmission con-tained preliminary inform
tained preliminary information about the health of ation about the health of thethe spacecraft and rover; the spacecrafts orientation on spacecraft and rover; the spacecrafts orientation on the surface; data about
the surface; data about its entryits entry, descent and , descent and landing;landing; and a first look
and a first look at the density and temperatures of theat the density and temperatures of the Martian atmosphere.
Martian atmosphere.
Pathfinders first transmission via its high-gain Pathfinders first transmission via its high-gain antenna, beginning at 4:
antenna, beginning at 4:28 p.m. PDT28 p.m. PDT the same daythe same day,, returned to Earth the first images taken by
returned to Earth the first images taken by the lan-the lan-ders camera, including a color mosaic of the
ders camera, including a color mosaic of the boulder- boulder-strewn Ares Vallis flood plain. Some of the images strewn Ares Vallis flood plain. Some of the images revealed that one of the airbags had
revealed that one of the airbags had not fully retract-not fully
retract-Solar Panel Solar Panel Alpha Proton Alpha Proton X-ray Spectrometer X-ray Spectrometer Rocker-Bogie Rocker-Bogie Mobility System Mobility System
Warm Electronics Box Warm Electronics Box
Cameras/ Cameras/ Lasers Lasers Antenna Antenna Material Material Adherence Adherence Experiment Experiment
ed, and was obstructing opening of one of the rover ed, and was obstructing opening of one of the rover ramps.
ramps.
Also on its
Also on its first day on Mars, Sojourner, whichfirst day on Mars, Sojourner, which was programmed to communicate with the lander was programmed to communicate with the lander asas frequently as every 10 minutes, was not completing frequently as every 10 minutes, was not completing full sentences in its
full sentences in its transmissions to the lander. Thistransmissions to the lander. This communication problem which engineers communication problem which engineers conclud-ed was the result of a problem with the modem on the ed was the result of a problem with the modem on the lander used to communicate with the rover was lander used to communicate with the rover was solved the next day.
solved the next day.
After receiving hundreds of new images of the After receiving hundreds of new images of the Ares V
Ares Vallis outflow channel, the allis outflow channel, the flight team spent flight team spent thethe rest of sol 1 retracting the airbag obstructing the rover rest of sol 1 retracting the airbag obstructing the rover ramp. On the night of July 5, late in the second
ramp. On the night of July 5, late in the second Martian day
Martian day, or sol , or sol 2, Sojourner stood up 2, Sojourner stood up to its fullto its full height of 30 centimeters (1 foot) and rolled down the height of 30 centimeters (1 foot) and rolled down the landers rear ramp, which was tilted at 20
landers rear ramp, which was tilted at 20 degreesdegrees from the surface, well within the
from the surface, well within the limits of safelimits of safe deployment.
deployment. Sojourner then Sojourner then positioned its positioned its primaryprimary science instrument, an alpha proton X-ray science instrument, an alpha proton X-ray spectrome-ter (APXS), face-down in the Martian soil to take 10 ter (APXS), face-down in the Martian soil to take 10 hours of measurements overnight.
hours of measurements overnight.
On sol 3, Sojourner performed two science On sol 3, Sojourner performed two science exper-iments:
iments: a soil meca soil mechanics experiment hanics experiment designed todesigned to demonstrate how the rover
demonstrate how the rovers wheels and mobility sys-s wheels and mobility sys-tem operate on the Martian surface; and a trip
tem operate on the Martian surface; and a trip of of about 36 centimeters (1.2 feet) to a rock nicknamed about 36 centimeters (1.2 feet) to a rock nicknamed Barnacle Bill, against which Sojourner placed the Barnacle Bill, against which Sojourner placed the APXS overnight to gather data on its composition. APXS overnight to gather data on its composition.
Over the course of the next 2-1/2 months, Over the course of the next 2-1/2 months,
Sojourner collected data on an additional 14 rocks Sojourner collected data on an additional 14 rocks including those
including those nicknamed Ynicknamed Yogi and Scooby ogi and Scooby Doo Doo and on nearby
and on nearby soils. soils. It also perfIt also performed a numormed a number of ber of technology experiments designed to provide
technology experiments designed to provide informa- informa-tion that will improve future planetary rovers. These tion that will improve future planetary rovers. These experiments included terrain geometry reconstruction experiments included terrain geometry reconstruction from lander/rover imaging, basic soil mechanics by from lander/rover imaging, basic soil mechanics by studying wheel sinkage, path reconstruction by dead studying wheel sinkage, path reconstruction by dead reckoning and track images, and vision sensor reckoning and track images, and vision sensor perfor-mance. Additional Sojourner experiments studied mance. Additional Sojourner experiments studied vehicle performance, rover thermal
vehicle performance, rover thermal conditions, effec-conditions, effec-tiveness of the radio link, and material abrasion by tiveness of the radio link, and material abrasion by sensing the wear on different thicknesses of paint on a sensing the wear on different thicknesses of paint on a rover wheel.
rover wheel.
The last successful data transmission
The last successful data transmission cycle fromcycle from Pathfinder was
Pathfinder was completed at completed at 3:23 a.m. 3:23 a.m. PDTPDT onon
September 27, 1997, which was sol 83 of the mission. September 27, 1997, which was sol 83 of the mission. A
A final signal wfinal signal without any spacecithout any spacecraft data wraft data wasas received on Oc
received on October 7. tober 7. The Pathfinder team The Pathfinder team attempt-
attempt-ed to reestablish contact with the spacecraft for ed to reestablish contact with the spacecraft for sever-al months until March 1998, but were unable to
al months until March 1998, but were unable to regain contact.
regain contact. Although the cause of Although the cause of the loss of the loss of com- com-munication with the lander may never be known, munication with the lander may never be known, engineers suspected that
engineers suspected that depletion of the depletion of the spacecraftspacecraftss battery and a drop in
battery and a drop in the operating temperature of thethe operating temperature of the spacecraft, which was kept warm by the battery, were spacecraft, which was kept warm by the battery, were to blame.
to blame. (The battery (The battery was only designed twas only designed to operateo operate for one month.)
for one month.) The rover had cThe rover had completed an ompleted an APXSAPXS study of a rock nicknamed Chimp when it was last study of a rock nicknamed Chimp when it was last heard from.
heard from. Assuming that the lander Assuming that the lander was not func-was not func-tioning after the loss of signal, it is assumed that the tioning after the loss of signal, it is assumed that the rover would have gone into a contingency mode rover would have gone into a contingency mode with-in a few days --
in a few days -- either circling the lander repeatedlyeither circling the lander repeatedly or standing in
or standing in place, awaplace, awaiting instructions. iting instructions. TheThe Pathfinder mission was
Pathfinder mission was declared officially concludeddeclared officially concluded in March 1998.
in March 1998.
The only objective left unfinished at the The only objective left unfinished at the timetime communications was lost was completion of a communications was lost was completion of a high-resolution 360-degree image of the landing site resolution 360-degree image of the landing site nick-named the Super Pan, of which 83 percent was named the Super Pan, of which 83 percent was received on
received on Earth. Earth. Other complete Other complete panoramas hadpanoramas had already been received.
already been received.
Mars Mars
One of five planets known to the ancients, Mars is One of five planets known to the ancients, Mars is known as the
known as the red planet because of its red planet because of its reddish colorreddish color.. At times it is the third brightest planet, after Venus At times it is the third brightest planet, after Venus and Jupiter. Mars was named by the Romans
and Jupiter. Mars was named by the Romans for theirfor their god of war.
god of war.
The fourth planet from the Sun, Mars is about 1.5 The fourth planet from the Sun, Mars is about 1.5 times farther from the Sun than Earth is. Radio times farther from the Sun than Earth is. Radio sig-nals take between 2-1/2 and 20 minutes to travel one nals take between 2-1/2 and 20 minutes to travel one way between Earth and Mars. Mars revolves
way between Earth and Mars. Mars revolves aroundaround the Sun once every 687
the Sun once every 687 Earth days, and its day, orEarth days, and its day, or sol, is slightly longer than Earths, at 24 hours sol, is slightly longer than Earths, at 24 hours 3737 minutes. Because
minutes. Because MarsMars axis tilts at 25.19 degraxis tilts at 25.19 degreesees (Earth
(Earths polar tilt is s polar tilt is 23.43 degrees), it has Earth-like23.43 degrees), it has Earth-like seasonal changes.
seasonal changes. Mars
Mars diameter is 6,780 kildiameter is 6,780 kilometers (4,217 mileometers (4,217 miles),s), about half the size of Earth but twice the size of about half the size of Earth but twice the size of Earth
Earths Moon. Marss Moon. Mars mass is 1/10th that of Earth, andmass is 1/10th that of Earth, and its gravity is 38 percent as
its gravity is 38 percent as strong as Earths. Mars hasstrong as Earths. Mars has an elliptical orbit; its distance from the Sun ranges an elliptical orbit; its distance from the Sun ranges from 206.7 million kilometers (128.4 million miles) from 206.7 million kilometers (128.4 million miles) to 249.2 million kilometers (154.8
to 249.2 million kilometers (154.8 million miles),million miles), with an average distance of
with an average distance of 227.7 million kilometers227.7 million kilometers (141.5 million miles). No planet-wide magnetic field (141.5 million miles). No planet-wide magnetic field has been detected on Mars, although localized ancient has been detected on Mars, although localized ancient
remnant fields have been detected in various regions remnant fields have been detected in various regions by the orbiting
by the orbiting Mars Global Surveyor.Mars Global Surveyor. Mars
Mars atmosphere is composeatmosphere is composed chiefly of cad chiefly of carbonrbon dioxide (95.3 percent), nitrogen (2.7 percent) and dioxide (95.3 percent), nitrogen (2.7 percent) and argon (1.6 percent), with traces of oxygen, carbon argon (1.6 percent), with traces of oxygen, carbon monoxide and
monoxide and water vapor. Surface atmospheric pres-water vapor. Surface atmospheric pres-sure on Mars is less than 1/100th that of Earths sure on Mars is less than 1/100th that of Earths aver-age atmospheric pressure; its
age atmospheric pressure; its surface temperaturesurface temperature averages -53
averages -53 C (-64C (-64 F), varying F), varying from -128 from -128 C (-199 F)C (-199 F) during polar night to 27 C (80 F) during midday near during polar night to 27 C (80 F) during midday near the equator when Mars is at its closest point in orbit the equator when Mars is at its closest point in orbit around the Sun.
around the Sun.
The highest point on Mars is Olympus Mons, a The highest point on Mars is Olympus Mons, a huge shield volcano more than 27 kilometers (16 huge shield volcano more than 27 kilometers (16 miles) high and 600 kilometers (370 miles) across, miles) high and 600 kilometers (370 miles) across, covering about the
covering about the same area as Arizona. The Martiansame area as Arizona. The Martian canyon system known as Valles Marineris is the
canyon system known as Valles Marineris is the largest and deepest known canyon in our solar largest and deepest known canyon in our solar sys-tem. About 5 to 10 kilometers (3 to 6 miles) deep, tem. About 5 to 10 kilometers (3 to 6 miles) deep, 100 kilometers (60 miles) wide and extending for 100 kilometers (60 miles) wide and extending for more than 4,000 kilometers (2,500
more than 4,000 kilometers (2,500 miles), it dwarfsmiles), it dwarfs Americas Grand Canyon.
Americas Grand Canyon. Mars
Mars two irregularly two irregularly shaped moons are the largershaped moons are the larger Phobos (fear), 28 by 20 kilometers (17 by 12
Phobos (fear), 28 by 20 kilometers (17 by 12 miles); and the smaller Deimos (terror), 16 by miles); and the smaller Deimos (terror), 16 by 1010 kilometers (10 by 6
kilometers (10 by 6 miles). miles). Both are named fBoth are named for theor the sons of the Greek god of war.
sons of the Greek god of war.
Earlier missions to Mars began with the Mariner Earlier missions to Mars began with the Mariner flybys of the 1960s. In
flybys of the 1960s. In 1965, the first successful flyby1965, the first successful flyby of Mars, Mariner 4, provided the
of Mars, Mariner 4, provided the first closeup imagesfirst closeup images of another planet. Along with the 1969
of another planet. Along with the 1969 Mariner 6 andMariner 6 and 7 flybys, it provided images of
7 flybys, it provided images of a moonlike planeta moonlike planet pocked with impact craters. In 1971,
pocked with impact craters. In 1971, Mariner 9Mariner 9 orbiter provided evidence of dry flood channels and orbiter provided evidence of dry flood channels and volcanism on Mars.
volcanism on Mars.
In 1976, the Viking 1 and 2 missions each sent an In 1976, the Viking 1 and 2 missions each sent an orbiter and lander to
orbiter and lander to Mars. The VMars. The Viking landers moni-iking landers moni-tored the weather, detected nitrogen in the
tored the weather, detected nitrogen in the atmosphereatmosphere for the first time and analyzed soil samples near the for the first time and analyzed soil samples near the landing sites, finding no evidence for the presence of landing sites, finding no evidence for the presence of life. The Vi
life. The Viking missions king missions also established that also established that MarsMars has channels that were probably cut by
has channels that were probably cut by ancient rivers.ancient rivers. Nearly two decades later, the Mars Observer orbiter Nearly two decades later, the Mars Observer orbiter
was lost while preparing to enter Martian orbit in was lost while preparing to enter Martian orbit in August 1993.
August 1993.
Spacecraft Spacecraft
At launch, the Mars Pathfinder spacecraft At launch, the Mars Pathfinder spacecraft
weighed 894 kilograms (1,973 pounds), including its weighed 894 kilograms (1,973 pounds), including its
cruise stage platform, heat shield, back shell, solar cruise stage platform, heat shield, back shell, solar panels, propulsion system, low- and
panels, propulsion system, low- and high-gain anten-high-gain anten-nas, lander, rover, parachute, airbags and 94 nas, lander, rover, parachute, airbags and 94 kilo-grams (207 pounds) of fuel. It stood 1.5 meters (5 grams (207 pounds) of fuel. It stood 1.5 meters (5 feet) tall and measured 2.65 meters (8.5
feet) tall and measured 2.65 meters (8.5 feet) in diam-feet) in diam-eter. During interplanetary cruise, 2.5 square meters eter. During interplanetary cruise, 2.5 square meters (27 square feet) of gallium arsenide s
(27 square feet) of gallium arsenide solar cells provid-olar cells provid-ed the 178 watts
ed the 178 watts of electrical power required by theof electrical power required by the spacecraft.
spacecraft.
Upon entry into the Martian atmosphere, the entry Upon entry into the Martian atmosphere, the entry vehicle weighed 584 kilograms (1,288 pounds). Upon vehicle weighed 584 kilograms (1,288 pounds). Upon landing, and after airbag deflation, the Pathfinder landing, and after airbag deflation, the Pathfinder lan-der weighed 370 kilograms (816 pounds). The der weighed 370 kilograms (816 pounds). The pyra-mid-shaped lander stood about 0
mid-shaped lander stood about 0.9 meter (3 feet) tall,.9 meter (3 feet) tall, with three triangular-shaped sides, or petals, hinged to with three triangular-shaped sides, or petals, hinged to the base platform.
the base platform.
Each petal was covered with solar cells
Each petal was covered with solar cells a totala total area of 2.8 square meters (30 square feet) that area of 2.8 square meters (30 square feet) that sup-plied up to 1,200 watt-hours of power to the lander plied up to 1,200 watt-hours of power to the lander for daytime operations and to charge the silver zinc for daytime operations and to charge the silver zinc batteries for nighttime use.
batteries for nighttime use. When unfolded and lying
When unfolded and lying flat, the lander mea-flat, the lander mea-sured 2.75 meters (9 feet) across,
sured 2.75 meters (9 feet) across, with the mast-with the mast-mounted camera standing about 1.5
mounted camera standing about 1.5 meters (5 feet)meters (5 feet) above the ground.
above the ground.
The lander was controlled by a
The lander was controlled by a derivative of thederivative of the commercially available IBM RAD6000
commercially available IBM RAD6000 computercomputer,, radiation-hardened to survive the flight. The computer radiation-hardened to survive the flight. The computer featured a
featured a computing speedcomputing speed of 20 million of 20 million instructionsinstructions per second and 128 megabytes of dynamic random per second and 128 megabytes of dynamic random access memory for storage of flight software and access memory for storage of flight software and engineering and science data, including images and engineering and science data, including images and rover infor
rover information. mation. Six megabytSix megabytes of es of non-volatilenon-volatile memory stored flight software and
memory stored flight software and time-criticatime-critical data.l data.
Soj
Sojournournerer RovRoverer
The Pathfinder rover was named
The Pathfinder rover was named after Sojournerafter Sojourner Truth, an African-A
Truth, an African-American crusader who merican crusader who lived dur-lived dur-ing the U.S. Civil War era and traveled throughout the ing the U.S. Civil War era and traveled throughout the country advocating the rights of all people to
country advocating the rights of all people to be free.be free. The name Sojourner, which means traveler, was the The name Sojourner, which means traveler, was the winning entry in a year-long competition in which winning entry in a year-long competition in which students 18 years and younger submitted essays students 18 years and younger submitted essays onon the historical accomplishments of a heroine of the historical accomplishments of a heroine of theirtheir choosing.
choosing.
The microwave-oven-sized rover weighed about The microwave-oven-sized rover weighed about 10.6 kilograms (23 pounds), plus about 5 kilograms 10.6 kilograms (23 pounds), plus about 5 kilograms (11 pounds) of mounting and
(11 pounds) of mounting and deployment equipment.deployment equipment. Once deployed, the rover measured about 65 Once deployed, the rover measured about 65
centime-ters (2 feet) long by
ters (2 feet) long by 48 centimeters (1.5 feet) wide by48 centimeters (1.5 feet) wide by 30 centimeters (1 foot) tall. By
30 centimeters (1 foot) tall. By comparison, duringcomparison, during the cruise to Mars, Sojourner was folded in its the cruise to Mars, Sojourner was folded in its stowage space and measured only
stowage space and measured only 18 centimeters (718 centimeters (7 inches) tall.
inches) tall.
The rovers maximum traveling speed on Mars The rovers maximum traveling speed on Mars was 1 centimeter per second
was 1 centimeter per second (2 feet per minute). It(2 feet per minute). It was powered by a
was powered by a 0.25-square-meter (1.9-square0.25-square-meter (1.9-square--foot) solar ar
foot) solar array on its top surray on its top surface. face. Non-rechargeableNon-rechargeable lithium thionol chloride
lithium thionol chloride D-cell-sized batteries provid-D-cell-sized batteries provid-ed limitprovid-ed storprovid-ed
ed limited stored powerpower..
The six-wheel, rocker-bogie suspension system The six-wheel, rocker-bogie suspension system provided a great degree of stability and provided a great degree of stability and obstacle-crossing capability for obstacle-crossing the
crossing capability for crossing the uneven Martianuneven Martian surface. The aluminum wheels, which could move surface. The aluminum wheels, which could move independently of each other, were 13
independently of each other, were 13 centimeters (5centimeters (5 inches) in diameter, with stainless steel tread and inches) in diameter, with stainless steel tread and cleats for traction. Sojourner was able to
cleats for traction. Sojourner was able to scale boul-scale boul-ders higher than 20 centimeters (about 8 inches). ders higher than 20 centimeters (about 8 inches).
The rover carried two
The rover carried two finger-sized black-and-finger-sized black-and-white cameras in front, a color camera in back, an white cameras in front, a color camera in back, an alpha proton X-ray spectrometer (APXS) for alpha proton X-ray spectrometer (APXS) for deter-mining the elemental composition of rocks and soil, mining the elemental composition of rocks and soil, and a set
and a set of experimentsof experiments for testing mfor testing material aaterial adher- dher-ence and wheel abrasi
ence and wheel abrasion. Aon. A laser system worked inlaser system worked in conjunction with the two
conjunction with the two forward cameras to detectforward cameras to detect and avoid obstacles.
and avoid obstacles.
The robotic rover capable of autonomous The robotic rover capable of autonomous navi-gation and performance of tasks
gation and performance of tasks communicatedcommunicated with Earth via
with Earth via the lander. Sojourners control systemthe lander. Sojourners control system was built around an
was built around an Intel 80C85 computer processor,Intel 80C85 computer processor, with a computing speed of 100,000 instructions per with a computing speed of 100,000 instructions per second and 500 kilobytes of random access memory second and 500 kilobytes of random access memory mass storage.
mass storage.
Science Instruments Science Instruments
The payload of
The payload of science instruments carried aboardscience instruments carried aboard Pathfinder included the
Pathfinder included the landers camera, the atmos-landers camera, the atmos-pheric structure instrument/meteorology package and pheric structure instrument/meteorology package and the rovers alpha proton X-ray spectrometer.
the rovers alpha proton X-ray spectrometer.
q
qThe landersThe landers ImaImagerger forfor MarMars s PathPathfindfinderer
(IMP) camera was a stereo imaging system with (IMP) camera was a stereo imaging system with colorcolor capability provided by a set of
capability provided by a set of selectable filterselectable filters fors for each of the two camera channels. It was
each of the two camera channels. It was developed bydeveloped by a team led
a team led by the University of Arizona at Tucson,by the University of Arizona at Tucson, with contributions from Lockheed Martin Corp.; with contributions from Lockheed Martin Corp.; MaxMax Planck Institute
Planck Institute for Aeronomyfor Aeronomy, , Katlenberg-Katlenberg-Lindau,Lindau, Germany; Technical University of Braunschweig, Germany; Technical University of Braunschweig, Germany; and the Orsted
Germany; and the Orsted LaboratoryLaboratory, Niels Bohr, Niels Bohr
Institute for Astronomy, University of
Institute for Astronomy, University of Copenhagen,Copenhagen, Denmark. The principal investigator was
Denmark. The principal investigator was DrDr. Peter. Peter Smith.
Smith.
In addition to imaging the surface, the camera In addition to imaging the surface, the camera provided stereo images used to navigate the rover provided stereo images used to navigate the rover. . AA number of atmospheric investigations were also number of atmospheric investigations were also car-ried out us
ried out using the ing the imagerimager. Aerosol opacity was mea-. Aerosol opacity was mea-sured periodically by imaging the Sun through two sured periodically by imaging the Sun through two narrow-band filters. Dust particles in the atmosphere narrow-band filters. Dust particles in the atmosphere were characteri
were characterized by observing Phobos, one zed by observing Phobos, one of of Mars
Mars moons, at night, as wmoons, at night, as well as the Sun during tell as the Sun during thehe day. Water vapor abundance was measured by day. Water vapor abundance was measured by imag-ing the Sun through filters in the water vapor ing the Sun through filters in the water vapor absorp-tion band and in
tion band and in the spectrally adjacent continuum.the spectrally adjacent continuum. A
A magnetic magnetic properties investiproperties investigation was gation was includedincluded as part of the imaging investigation.
as part of the imaging investigation. AA set of magnetsset of magnets of different field strengths was mounted in a variety of different field strengths was mounted in a variety of locations around the
of locations around the landerlander. Images taken over the. Images taken over the duration of the lander mission were used to determine duration of the lander mission were used to determine the accumulation of magnetic species in the the accumulation of magnetic species in the wind-blown dust. Multispectral images of these
blown dust. Multispectral images of these accumula- accumula-tions may be used to
tions may be used to differentiadifferentiate among likely mag-te among likely mag-netic minerals.
netic minerals.
The imaging investigation also included the The imaging investigation also included the observation of wind direction and speed, using wind observation of wind direction and speed, using wind socks that were located at various heights on a socks that were located at various heights on a 1-meter-t
meter-tall (40-inch) mast. The all (40-inch) mast. The wind socks wind socks werewere imaged repeatedly by the imager; orientations of imaged repeatedly by the imager; orientations of thethe wind socks were measured in the images to determine wind socks were measured in the images to determine the wind velocity at three different heights above the the wind velocity at three different heights above the surface. This information was then used to
surface. This information was then used to estimateestimate the aerodynamic roughness of the surface in the vicin the aerodynamic roughness of the surface in the vicin--ity of the lander and
ity of the lander and to determine the variation into determine the variation in wind speed with height.
wind speed with height. Because the VBecause the Viking landersiking landers had wind sensors at only one height, such a vertical had wind sensors at only one height, such a vertical wind profile has never been measured on Mars. This wind profile has never been measured on Mars. This new knowledge will help to develop and modify new knowledge will help to develop and modify theo-ries for how dust and sand particles are lifted into the ries for how dust and sand particles are lifted into the Martian atmosphere by winds, for example. Because Martian atmosphere by winds, for example. Because erosion and deposition of wind-blown materials have erosion and deposition of wind-blown materials have constituted such an important geologic process on the constituted such an important geologic process on the surface of Mars, the results of the wind sock surface of Mars, the results of the wind sock experi-ment will be of interest to geologists as well as ment will be of interest to geologists as well as atmospheric scientists.
atmospheric scientists.
q
q TheTheAtmospheric Structure Instrument andAtmospheric Structure Instrument and Meteorology Package
Meteorology Package (ASI/MET) was an engineer-(ASI/MET) was an engineer-ing subsystem that acquired atmospheric information ing subsystem that acquired atmospheric information during the descent of the lander through the Martian during the descent of the lander through the Martian atmosphere and during the entire
Alvin Seiff of San Jose State University, San Jose, Alvin Seiff of San Jose State University, San Jose, CA, was the instrument definition team leader. Dr. CA, was the instrument definition team leader. Dr. John T
John T. Schofield of JPL. Schofield of JPL was team leader for the scwas team leader for the sci- i-ence team that used the data
ence team that used the data acquired by the package.acquired by the package. Data acquired during the entry and descent of Data acquired during the entry and descent of thethe lander permitted reconstruction of profiles of lander permitted reconstruction of profiles of atmos-pheric density, temperature and pressure from pheric density, temperature and pressure from alti-tudes in excess of 120 kilometers (75 miles) from the tudes in excess of 120 kilometers (75 miles) from the surface.
surface.
The accelerometer portion of the atmospheric The accelerometer portion of the atmospheric structure instrument was designed to
structure instrument was designed to measure acceler-measure acceler-ations over a wide variety of ranges from the micro-G ations over a wide variety of ranges from the micro-G accelerations experienced upon entering the
accelerations experienced upon entering the atmos- atmos-phere to the peak deceleration and landing events phere to the peak deceleration and landing events inin the range of 30 to 50 Gs.
the range of 30 to 50 Gs.
The package also included several sensors on the The package also included several sensors on the lander to measure pressure, temperature and wind. lander to measure pressure, temperature and wind. They recorded weather at the landing site throughout They recorded weather at the landing site throughout the mission.
the mission.
q
qThe roversThe rovers Alpha Proton X-rayAlpha Proton X-ray Spectrometer
Spectrometer (APXS) was designed to determine the(APXS) was designed to determine the elements that make up the rocks and soil on Mars. It elements that make up the rocks and soil on Mars. It was a derivative of instruments flown on the Soviet was a derivative of instruments flown on the Soviet V
Vega and Phobos ega and Phobos missions and identical to missions and identical to the unitthe unit that flew on the Russian Mars 96 landers, which that flew on the Russian Mars 96 landers, which were lost shortly after launch. Thanks to the
were lost shortly after launch. Thanks to the mobilitymobility provided by the Mars
provided by the Mars Pathfinder roverPathfinder rover, the APXS not, the APXS not only took measurements of the Martian dust but, only took measurements of the Martian dust but, more importantly, permitted analysis of rocks in the more importantly, permitted analysis of rocks in the landing area. The alpha and proton portions were landing area. The alpha and proton portions were pro-vided by the
vided by the Max Planck Institute for Max Planck Institute for ChemistryChemistry,, Mainz, Germany. The X-ray spectrometer portion was Mainz, Germany. The X-ray spectrometer portion was provided by the University of Chicago. Dr. Rudolph provided by the University of Chicago. Dr. Rudolph Rieder of the Max
Rieder of the Max Planck Institute for Chemistry wasPlanck Institute for Chemistry was principal investigator; co-investigators were
principal investigator; co-investigators were DrDr..
Thanasis Economou of the University of Chicago and Thanasis Economou of the University of Chicago and Dr. Heinrich Wanke of the Max Planck Institute for Dr. Heinrich Wanke of the Max Planck Institute for Chemistry.
Chemistry.
The instrument was able to measure the amounts The instrument was able to measure the amounts of all elements present (except hydrogen and helium) of all elements present (except hydrogen and helium) which make up more than about 1/10th of 1 percent which make up more than about 1/10th of 1 percent of the mass of the sample rock or soil. The of the mass of the sample rock or soil. The spectrom-eter worked by bombarding a rock or soil sample with eter worked by bombarding a rock or soil sample with alpha particles charged particles equivalent to the alpha particles charged particles equivalent to the nucleus of a helium atom, consisting of two protons nucleus of a helium atom, consisting of two protons and two neutrons. The sources of the particles were and two neutrons. The sources of the particles were small pieces of the radioactive element curium-244 small pieces of the radioactive element curium-244 onboard the instrument. In some cases, the alpha onboard the instrument. In some cases, the alpha par-ticles interacted with the rock or soil sample by
ticles interacted with the rock or soil sample by
bouncing back; in other cases, they caused
bouncing back; in other cases, they caused X rays orX rays or protons to be generated.
protons to be generated.
The backscattered alpha particles, X rays, and The backscattered alpha particles, X rays, and protons that made it back into the detectors of the protons that made it back into the detectors of the instrument were counted, and their energies were instrument were counted, and their energies were measured. The number of particles counted at each measured. The number of particles counted at each energy level is related to the abundance of various energy level is related to the abundance of various elements in the rock or
elements in the rock or soil sample, and the soil sample, and the energiesenergies are related to the types of elements present in
are related to the types of elements present in thethe sample.
sample. AA high-quality analyhigh-quality analysis requires about 10sis requires about 10 hours of instrument operation while the rover is hours of instrument operation while the rover is sta-tionary and may be done at any time of day or night. tionary and may be done at any time of day or night.
Maj
Majoror ScieScience Resultnce Resultss
q
qChemical analyses returned by Mars PathfinderChemical analyses returned by Mars Pathfinder indicate that some rocks at the landing
indicate that some rocks at the landing site appear tosite appear to be high in
be high in silica, suggesting differentiasilica, suggesting differentiated parentted parent materials.
materials. These rocks are distincThese rocks are distinct from the met from the mete- te-orites found on Earth that are thought to be of orites found on Earth that are thought to be of Martian origin.
Martian origin.
q
qThe identification of rounded pebbles and cob-The identification of rounded pebbles and cob-bles on the ground, and sockets and pebcob-bles in some bles on the ground, and sockets and pebbles in some rocks, suggests conglomerates that formed in
rocks, suggests conglomerates that formed in runningrunning water
water, during a warmer past , during a warmer past in which liquid in which liquid waterwater was stable.
was stable.
q
q Some rocks at the landing site appear groovedSome rocks at the landing site appear grooved and fluted, suggesting abrasion by
and fluted, suggesting abrasion by sand-sized parti-sand-sized parti-cles. Dune-shaped deposits were also found in a cles. Dune-shaped deposits were also found in a trough behind the area of the landing site known as trough behind the area of the landing site known as the Rock Garden, indicating the presence of sand. the Rock Garden, indicating the presence of sand.
q
q The soil chemistry of the landing The soil chemistry of the landing site appearssite appears to be similar to that of the Viking 1 and 2 landing to be similar to that of the Viking 1 and 2 landing sites, suggesting that the soil may be
sites, suggesting that the soil may be a globallya globally deposited unit.
deposited unit.
q
q Radio tracking of Mars Pathfinder provided a Radio tracking of Mars Pathfinder provided a precise measure of the landers location and Mars precise measure of the landers location and Mars pole of r
pole of rotation. otation. This in turn This in turn suggested that thesuggested that the radius of the planets central metallic core is greater radius of the planets central metallic core is greater than 800 miles (1,300 kilometers) but less than than 800 miles (1,300 kilometers) but less than rough-ly 1,250 miles (2,000
ly 1,250 miles (2,000 kilometers).kilometers).
q
qAirborne dust is magnetic with Airborne dust is magnetic with each particleeach particle about 3
about 3 microns in diameter. Interpretations suggestmicrons in diameter. Interpretations suggest the magnetic mineral is maghemite, a
the magnetic mineral is maghemite, a very magneticvery magnetic form of iron oxide, which may have
form of iron oxide, which may have been freeze-driedbeen freeze-dried on the particl
on the particles as a stain or es as a stain or cement. cement. The iron mayThe iron may have been leached out of materials in the
have been leached out of materials in the planetplanetss crust by an active water cycle.
crust by an active water cycle.
q
q Whirlwinds called dust devils were imaged andWhirlwinds called dust devils were imaged and frequently measured by temperature, wind and frequently measured by temperature, wind and
pres-sure sensors.
sure sensors. Observations suggested Observations suggested that these that these gustsgusts are a mechanism for mixing dust into the atmosphere. are a mechanism for mixing dust into the atmosphere.
q
q Imaging revealed early morning water iceImaging revealed early morning water ice clouds in the
clouds in the lower atmosphere, which evaporate aslower atmosphere, which evaporate as the atmosphere warms.
the atmosphere warms.
q
qAbrupt temperature fluctuations were recordedAbrupt temperature fluctuations were recorded in the morning, suggesting that the atmosphere is in the morning, suggesting that the atmosphere is warmed by the planets surface, with heat convected warmed by the planets surface, with heat convected upwards in small eddies.
upwards in small eddies.
q
qThe weather was similar to The weather was similar to weather encoun-weather encoun-tered by V
tered by Viking 1; there were rapid iking 1; there were rapid pressure and tem-pressure and tem-perature variations, downslope winds at night and perature variations, downslope winds at night and light winds
light winds in general. Temin general. Temperatures at the peratures at the surfacesurface were about 18 F (10 C) warmer than those measured were about 18 F (10 C) warmer than those measured by Viking 1.
by Viking 1.
q
qThe atmosphere was a The atmosphere was a light yellowish-brownlight yellowish-brown color due to fine dust mixed in the lower atmosphere, color due to fine dust mixed in the lower atmosphere, as was seen by Viking. Particle size and shape as was seen by Viking. Particle size and shape esti-mates and the amount of water vapor in the mates and the amount of water vapor in the atmos-phere are also
phere are also similar to Viking observations.similar to Viking observations.
q
q Scientists were able to use Viking images at a Scientists were able to use Viking images at a scale generally greater than 1
scale generally greater than 1 kilometer (0.6 mile) perkilometer (0.6 mile) per pixel, along with analysis of similar geography on pixel, along with analysis of similar geography on Earth, to correctly predict a rocky plain safe for Earth, to correctly predict a rocky plain safe for land-ing and rovland-ing with a variety of rocks deposited by ing and roving with a variety of rocks deposited by catastrophic floods.
catastrophic floods.
Project/Program Management Project/Program Management
Mars Pathfinder was managed for NASAs Mars Pathfinder was managed for NASAs Office of Space Science, Washington, D.C., by the Jet Office of Space Science, Washington, D.C., by the Jet Propulsion Laboratory
Propulsion Laboratory, a division , a division of the California of the California Institute of Technology.
Institute of Technology. At NASA
At NASA Headquarters, KeHeadquarters, Kenneth Wnneth W.. Ledbetter was program manager and Joseph
Ledbetter was program manager and Joseph BoyceBoyce was program scientist.
was program scientist.
At JPL, the position of project manager was At JPL, the position of project manager was held successively by Anthony J. Spear and Brian K. held successively by Anthony J. Spear and Brian K. Muirhead, who also served as
Muirhead, who also served as flight system managerflight system manager.. Project scientist was Dr. Matthew Golombek.
Project scientist was Dr. Matthew Golombek. Richard A. Cook was mission
Richard A. Cook was mission operations manager,operations manager, John B. Wellma
John B. Wellman was science and n was science and instruments manag-instruments manag-er, Dr. Jacob R. Matijevic was rover manager and er, Dr. Jacob R. Matijevic was rover manager and Allan Sacks was ground
Allan Sacks was ground system managersystem manager..
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