Mars Polar Lander


Mars Polar Lander
Mars Polar Lander
Mars Polar Lander - artist depiction.png
Artist depiction of Mars Polar Lander on Mars.
Operator NASA / JPL
Major contractors Martin Marietta
Mission type Lander
Orbital insertion date Year-Month-Day Hour:Minute:Second UTC
Launch date 1999-01-03 20:21:10 UTC
(12 years, 10 months and 11 days ago)
Launch vehicle Delta II 7425
Launch site Space Launch Complex 17A
Cape Canaveral Air Force Station
Mission duration (failure in transit)
Last contact on day 334
1999-12-03 20:00:00 UTC
Landing site Ultimi Scopuli, 76°S 195°W / 76°S 195°W / -76; -195 (Mars Polar Lander) (projected)
COSPAR ID 1999-001A
Homepage Mars Polar Lander Website
Mass 290 kilograms (640 lb)
Power 200 W
(Solar array / NiH2 battery)

The Mars Polar Lander, also referred to as the Mars Surveyor '98 Lander, was a 290-kilogram robotic spacecraft lander, launched by NASA on January 3, 1999, to study the soil and climate of Planum Australe, a region near the south pole on Mars, as part of the Mars Surveyor '98 mission. However, on December 3, 1999, after the descent phase was expected to be complete, the lander failed to reestablish communication with Earth. It was determined the most likely cause of the mishap was an improperly ceased engine firing prior to the lander touching the surface, causing the lander to impact at a high velocity.

Contents

Mission background

History

As part of the intended goals of the Mars Surveyor '98 mission, a lander was sought as a way to gather climate data from the ground in conjunction with an orbiter. It was suspected that a large quantity of frozen water may exist under a thin layer of dust at the south pole. If that were true, then why does it differ from the Martian north pole, a region suspected to contain much less frozen water. In planning Mars Polar Lander, the potential water content in the Martian south pole was the strongest determining factor for choosing a landing location.[1]

The primary objectives of the mission included:[2]

  • Land on the layered terrain in Mars’ south polar region.
  • Search for evidence related to ancient climates and more recent periodic climate change.
  • Give a picture of the current climate and seasonal change at high latitudes and, in particular, the exchange of water vapor between the atmosphere and ground.
  • Search for near-surface ground ice in the polar regions, and analyze the soil for physically and chemically bound carbon dioxide and water.
  • Study surface morphology (forms and structures), geology, topography and weather of the landing site.

Deep Space 2 Probes

Mars Polar Lander carried two, small, identical impactor probes known as Deep Space 2 A and B. The probes were intended to impact the surface with a high velocty at approximately 73°S 210°W / 73°S 210°W / -73; -210 (Deep Space 2), to penetrate the Martian soil and study the subsurface composition up to a meter in depth. However, after entering the Martian atmosphere, attempts to contact the probes failed.[1]

Spacecraft design

The spacecraft measured 3.6 meters wide and 1.06 meters tall with the legs and solar arrays fully deployed. The base was primarily constructed with an aluminum honeycomb deck, composite graphite epoxy sheets forming the edge, and three aluminum legs. During landing, the legs were to deploy from stowed position with compression springs and absorb the force of the landing with crushable, aluminum honeycomb inserts in each leg. On the deck of the lander, a small thermal, Faraday cage enclosure housed the computer, power distribution electronics and batteries, telecommunication electronics, and the Capillary Pump Loop Heat Pipe (LHP) components which maintained operable temperature. Each these components included redundant units in the event that one may fail.[1][3][4]

Attitude control and propulsion

While traveling to Mars, the Cruise Stage was three-axis stabilized with four hydrazine monopropellant reaction engine modules, each including a 22-newton trajectory correction maneuver thruster for propulsion and a 4-Newton reaction control system thruster for attitude control. Orientation of the spacecraft was obtained using redundant Sun sensors, star trackers, and inertial measurement units.[3]
During descent, the lander used three clusters of pulse modulated engines, each containing four 266-Newton hydrazine monopropellant thrusters. Altitude during landing was provided by a doppler radar system and an Attitude and Articulation Control subsystem (AACS) controlled the attitude to ensure the spacecraft landed at the optimal azimuth to maximize solar collection and telecommunication with the lander.[1][3][4]
The lander was launched with two hydrazine tanks containing 64 kilograms of propellant and pressurized using helium. Each spherical tank was located the underside of the lander and provided propellant during the cruise and descent stages.[1][3][4]

Communications

During the cruise stage, communications with the spacecraft were conducted over the X band using a medium-gain, horn-shaped antenna and redundant solid state power amplifiers. For contingency measures, a low-gain omni-directional antenna was also included.[1]
The lander was originally intended to communicate data through the failed Mars Climate Orbiter via the UHF antenna. With the orbiter being lost on September 23, 1999, the lander would still be able to communicate directly to the Deep Space Network through the Direct-To-Earth (DTE) link, an X band, steerable, medium-gain, parabolic antenna located on the deck. Alternatively, Mars Global Surveyor could be used as a relay using the UHF antenna at multiple times each Martian day; however the Deep Space Network could only receive data from and not send commands to the lander using this method. Communicating using the medium-gain antenna provided a 12.6-KB/s link and the UHF relay provided 128-KB/s uplink. Communications with the spacecraft would be limited to one-hour events, constrained by heat-buildup that would occur in the amplifiers; the number of communication events would also be constrained by power limitations.[1][2][3][4]

Power

During cruise, the Cruise Stage included two gallium arsenide solar arrays to power the radio system and maintain power to the batteries in the lander which kept certain electronics warm.[1][3]
After descending to the surface, the lander was to deploy two, 3.6-meter wide gallium arsenide solar arrays, located on either side of the spacecraft. Another two auxilary solar arrays are located on the side to provide additional power for a total of an expected 200 watts and approximately 8-9 hours of operating time per day.[1][3]
While the Sun would not have set below the horizon during the primary mission, too little light would have reached the solar arrays to remain warm enough for certain electronics to continue functioning. To avoid this problem, a 16-amp-hour nickel hydrogen battery was included to be recharged during the day and used to power the heater for the thermal enclosure at night. This solution also was expected to limit the life of the lander. As the Martian days would grow colder in late summer, too little power would be supplied to the heater to avoid freezing, resulting in the battery also freezing and signaling the end of the operating life for the lander.[1][3][4]

Scientific instruments

Mars Descent Imager (MARDI)
Mars Polar Lander - MARDI instrument photo - mardi.jpg

Mounted to the bottom of the lander, the camera was intended to capture thirty images as the spacecraft descended to the surface. The images acquired would be used to provide geographic and geologic context to the landing area.[5]


Stereo Surface Imager (SSI)
Mars Polar Lander - SSI instrument photo - ssi closeup s.jpg

Using a pair of charge coupled devices (CCD), the stereo panoramic camera was mounted to a one-meter tall mast and would aid in the Thermal Evolved Gas Analyzer and determining areas of interest for the Robotic Arm. In addition, the camera would be used to estimate the column density of atmospheric dust, the optical depth of aerosols, and slant column abundances of water vapor using narrow-band imaging of the Sun.[6]

  • Principal investigator: David Paige / UCLA / University of Arizona (website)
  • reincorporated on Phoenix

Light Detection and Ranging (LIDAR)
Mars Polar Lander - LIDAR instrument photo - mpl lidar.gif

The laser sounding instrument was intended to detect and characterize aerosols in the atmosphere up to three kilometers above the lander. The instrument operated in two modes: active mode using an included laser diode and acoustic mode using the Sun as the light source for the sensor.

-In active mode, the laser sounder was to emit 100-nanosecond pulses at a wavelength of 0.88-micrometer into the atmosphere, and then record the duration of time to detect the light scattered by aerosols. The duration of time required for the light to return could then be used to determine the abundance of ice, dust and other aerosols in the region.
-In acoustic mode, the instrument measures the brightness of the sky as lit by the Sun and records the scattering of light as it passes to the sensor.[7]
  • Principal investigator: Viacheslav Linkin / IKI/RSA

Robotic Arm (RA)
Mars Polar Lander - RA instrument photo - arm.png

Located on the front of the lander, the Robotic Arm is a meter-long aluminum tube with an elbow joint and an articulated scoop attached to the end. The scoop was intended to be used to dig into the soil in direct vicinity of the lander. The soil could then be analyzed in the scoop with the Robotic Arm Camera or transferred into the Thermal Evolved Gas Analyzer.[6]

  • Principal investigator: David Paige / UCLA (website)
  • reincorporated on Phoenix

Robotic Arm Camera (RAC)
Mars Polar Lander - RAC instrument photo.png

Located on the Robotic Arm, the charge coupled camera includes 2 red, 2 green, and 4 blue lamps to illuminate soil samples for analysis.[6]


Meteorological Package (MET)
Mars Polar Lander - MET instrument photo - mettop.png

Several instruments related to sensing and recording weather patterns, were included in the package. Wind, temperature, pressure and humidity sensors were located on the Robotic Arm and two deployable masts: a 1.2-meter 'main' mast, located on top of the lander and a 0.9-meter secondary 'submast' that would deploy downward to acquire measurements close to the ground.[6]

"Wind speed and direction is measured by a nine-element hot wire array wind sensor mounted on the main mast and a two-element wind sensor mounted on the submast. Three fast thermocouple assembly temperature sensors are mounted at different heights on the main mast. Two temperature sensors are also located on the submast and one on the elbow joint of the robotic arm. A soil temperature probe on a 15 cm fiberglass tube is mounted on the back of the robotic arm scoop and can be pushed into the ground by the arm. A barocap atmospheric pressure sensor is located inside the Payload Electronics Box. A tunable diode 2.656 and 2.729 micrometer laser is mounted on the main mast to measure the abundance of atmospheric water and carbon dioxide and to measure the isotopic ratios carbon-13/carbon-12 and oxygen-18/oxygen-16 in atmospheric carbon dioxide, and deuterium/hydrogen and oxygen-18/oxygen-16 in atmospheric water."[6]

  • Principal investigator: David Paige / UCLA (website)
  • reincorporated on Phoenix

Thermal and Evolved Gas Analyzer (TEGA)
Mars Polar Lander - TEGA instrument photo.png

The instrument was intended to measure abundances of water, water ice, adsorbed carbon dioxide, oxygen, and volatile-bearing minerals in surface and subsurface soil samples collected and transferred by the Robotic Arm.

To do this, materials placed onto a grate inside one of the eight ovens, would be heated and vaporized at 1000 °C. The Evolved Gas Analyzer would then record measurements using a spectrometer and an electrochemical cell. For calibration, an empty oven would also be heated during this process for differential scanning calorimetry. The difference in the energy required to heat each oven would then indicate concentrations of water ice and other minerals containing water or carbon dioxide.[6]

  • Principal investigator: David Paige / UCLA (website)
  • reincorporated on Phoenix

Mars Microphone
Mars Polar Lander - Mars Microphone instrument photo - microphone.jpg

The microphone was intended to be the first instrument to record sounds on another planet. Primarily composed of a microphone generally used with hearing aids, the instrument was expected to record sounds of blowing dust, electrical discharges and the sounds of the operating spacecraft in either 2.6-second or 10.6-second, 12-bit samples.[8]

  • Principal investigator: Louis Friedman / SSL Berkeley / The Planetary Society (website)
  • reincorporated on Phoenix

Images of the spacecraft
Annotated diagram of the Mars Polar Lander spacecraft
Annotated diagram of the Mars Polar Lander spacecraft. 
The spacecraft in stowed position just prior to encapsulation
The spacecraft in stowed position just prior to encapsulation. 
Testing performed at the Spacecraft Assembly and Encapsulation Facility
Testing performed at the Spacecraft Assembly and Encapsulation Facility 
The Mars Polar Lander entry capsule, just prior to being mounted to the Star 48 upper stage
The Mars Polar Lander entry capsule, just prior to being mounted to the Star 48 upper stage. 

Mission profile

Timeline of observations

Date Event

1999-01-03
Spacecraft launched at 20:21:10 UTC
1999-12-03
1999-12-03
2000-01-17
Mission declared a loss. No further attempts to contact.

Launch and trajectory

Mars Polar Lander was launched on January 3, 1999, at 20:21:10 UTC by the National Aeronautics and Space Administration from Space Launch Complex 17B at the Cape Canaveral Air Force Station in Florida, aboard a Delta II 7425 launch vehicle. The complete burn sequence lasted for 47.7 minutes after a Thiokol Star 48B solid-fuel third stage booster placed the spacecraft into an 11 month, Mars transfer trajectory at a final velocity of 6.884 kilometers per second with respect to Mars. During cruise, the spacecraft was stowed inside an aeroshell capsule and was powered and communicated with Earth with the a segment known as the cruise stage.[1][2][3]

Diagram of the configured positions of Mars Polar Lander within a Delta II launch vehicle
Launch configuration diagram. 
Launch photo of Mars Polar Lander being lifted into space by a Delta II launch vehicle
Launch photo of Mars Polar Lander aboard a Delta II launch vehicle. 
Diagram of the interplanetary trajectory of Mars Polar Lander
Diagram of the interplanetary trajectory of Mars Polar Lander. 

Landing encounter with Mars

Cruise configuration diagram of Mars Polar Lander.
Cruise configuration
Diagram of landing prodedures of Mars Polar Lander as it would pass through the atmosphere and land on the surface.
Landing procedure
Map of the region targeted for landing by the Mars Polar Lander.
Landing region
Mars Polar Lander enterted the Martian atmosphere with an aeroshell for protection from atmospheric friction.

On December 3, 1999, Mars Polar Lander encountered Mars while mission operators began preparing for landing operations. At 14:39:00 UTC, the cruise stage was jettisoned, beginning a planned communication dropout until the spacecraft had touched down on the surface. Six minutes prior to atmospheric entry, a programmed 80-second thruster firing turned the spacecraft to the proper entry orientation, with the heat shield oriented to absorb the intense, 1650 °C heat that would be generated as the descent capsule passed through the atmosphere. Traveling at 6.9 kilometers per second, the entry capsule entered the Martian atmosphere at 20:10:00 UTC and was expected to land in the vicinity of 76°S 195°W / 76°S 195°W / -76; -195 (Mars Polar Lander) in a region known as Planum Australe. Communication was expected to be reestablished with the spacecraft at 20:39:00 UTC after having landed. However, no communication attempt was successful with the spacecraft.[1][2][3]

The Phoenix lander has subsequently completed most of the objectives of Mars Polar Lander, carrying several of the same or derivative instruments. Phoenix landed successfully on May 25, 2008.

Intended operations

Traveling at approximately 6.9 kilometers/second and 125 kilometers above the surface, the spacecraft entered the atmosphere and was initially decelerated by using a 2.4 meter ablation heat shield, located on the bottom of the entry body, to aerobrake through 116 kilometers of the atmosphere. Three minutes after entry, the spacecraft had slowed to 496 meters per second signaling an 8.4-meter, polyester parachute to deploy from a mortar followed immediately by heat shield separation and MARDI being powered on, while 8.8 kilometers above the surface. The parachute further slowed the speed of the spacecraft to 85 meters per second when the ground radar began tracking surface features to detect the best possible landing location. When the spacecraft had slowed to 80 meters per second, one minute after parachute deployment, the lander separated from the backshell and began a powered descent while 1.3 kilometers aloft. The powered descent was expected to have lasted approximately one minute, bringing the spacecraft 12 meters above the surface. The engines were then shut off and the spacecraft would expectedly fall to the surface and land at 20:15:00 UTC near 76°S 195°W in Planum Australe.[1][2][3][4]

Lander operations were to begin five minutes after touchdown, first unfolding the stowed solar arrays followed by orienting the medium-gain, Direct-To-Earth antenna to allow for the first communication with the Deep Space Network. At 20:39:00 UTC, a 45-minute transmission was to be broadcast to Earth, transmitting the expected thirty landing images acquired by MARDI and signaling a successful landing. The lander would then power down for six hours to allow the batteries to charge. On the following days, the spacecraft instruments would be checked by operators and science experiments were to begin on December 7 and last for at least the following 90 Martian Sols, with the possibility of an extended mission.[1][2][3][4]


Communications loss

On December 3, 1999, at 14:39:00 UTC, the last telemetry from Mars Polar Lander was sent, just prior to cruise stage separation and the subsequent atmospheric entry. No further signals were received from the spacecraft. Attempts were made by Mars Global Surveyor, to photograph the area the lander was believed to be. An object was visible and believed to possibly be the lander; however, subsequent imaging performed by Mars Reconnaissance Orbiter resulted in the identified object to be incorrect. Mars Polar Lander remains lost.[9][10]

The cause of the communication loss is not known. However, the Failure Review Board concluded that the most likely cause of the mishap was a software error that incorrectly identified vibrations, caused by the deployment of the stowed legs, as surface touchdown.[11] The resulting action by the spacecraft was the shutdown of the descent engines, while still likely 40 meters above the surface. Although it was known that leg deployment could create the false indication, the software's design instructions did not account for that eventuality.[12]

In addition to the premature shutdown of the descent engines, the Failure Review Board also assessed other potential modes of failure.[13] Lacking substantial evidence for the mode of failure, the following possibilies could not be excluded:

  • Surface conditions exceed landing design capabilities.
  • Loss of control due to dynamic effects.
  • Landing site not survivable.
  • Backshell/parachute contacts lander.
  • Loss of control due to center-of-mass offset.
  • Heatshield fails due to micrometeoroid impact.

The failure of the Mars Polar Lander took place two and a half months after the loss of the Mars Climate Orbiter. Inadequate funding and poor management have been cited as underlying causes of the failures.[14] According to Thomas Young, chairman of the Mars Program Independent Assessment Team, the program "was under funded by at least 30%."[15]

Quoted from the report[13]

"A magnetic sensor is provided in each of the three landing legs to sense touchdown when the lander contacts the surface, initiating the shutdown of the descent engines. Data from MPL engineering development unit deployment tests, MPL flight unit deployment tests, and Mars 2001 deployment tests showed that a spurious touchdown indication occurs in the Hall Effect touchdown sensor during landing leg deployment (while the lander is connected to the parachute). The softwarelogic accepts this transient signal as a valid touchdown event if it persists for two consecutive readings of the sensor. The tests showed that most of the transient signals at leg deployment are indeed long enough to be accepted as valid events, therefore, it is almost a certainty that at least one of the three would have generated a spurious touchdown indication that the software accepted as valid.

The software—intended to ignore touchdown indications prior to the enabling of the touchdown sensing logic—was not properly implemented, and the spurious touchdown indication was retained. The touchdown sensing logic is enabled at 40 meters altitude, and the software would have issued a descent engine thrust termination at this time in response to a (spurious) touchdown indication.

At 40 meters altitude, the lander has a velocity of approximately 13 meters per second, which, in the absence of thrust, is accelerated by Mars gravity to a surface impact velocity of approximately 22 meters per second (the nominal touchdown velocity is 2.4 meters per second). At this impact velocity, the lander could not have survived."

See also

References

  1. ^ a b c d e f g h i j k l m n "1998 Mars Missions Press Kit" (PDF) (Press release). NASA. 1998. http://www.jpl.nasa.gov/files/misc/mars98launch.pdf. Retrieved 2011-03-12. 
  2. ^ a b c d e f "Mars Polar Lander/Deep Space 2 Press Kit" (PDF) (Press release). NASA. 1999. http://www.jpl.nasa.gov/files/misc/mpl-ds2hq.pdf. Retrieved 2011-03-12. 
  3. ^ a b c d e f g h i j k l "Mars Polar Lander". NASA/National Space Science Data Center. http://nssdc.gsfc.nasa.gov/nmc/masterCatalog.do?sc=1999-001A. Retrieved 2011-03-12. 
  4. ^ a b c d e f g "MPL: Lander Flight System Description". NASA / JPL. 1998. http://lunar.ksc.nasa.gov/mars/msp98/lander/bus.html. Retrieved 2011-03-12. 
  5. ^ "Mars Descent Imager (MARDI)". NASA/National Space Science Data Center. http://nssdc.gsfc.nasa.gov/nmc/experimentDisplay.do?id=1999-001A-02. Retrieved 2011-03-17. 
  6. ^ a b c d e f "Mars Volatiles and Climate Surveyor (MVACS)". NASA/National Space Science Data Center. http://nssdc.gsfc.nasa.gov/nmc/experimentDisplay.do?id=1999-001A-01. Retrieved 2011-03-17. 
  7. ^ "Light Detection and Ranging (LIDAR)". NASA/National Space Science Data Center. http://nssdc.gsfc.nasa.gov/nmc/experimentDisplay.do?id=1999-001A-03. Retrieved 2011-03-17. 
  8. ^ "Mars Microphone". NASA/National Space Science Data Center. http://nssdc.gsfc.nasa.gov/nmc/experimentDisplay.do?id=1999-001A-04. Retrieved 2011-03-17. 
  9. ^ Editors (6 May 2005). "Mars Polar Lander Found at Last?". Sky and Telescope. http://skyandtelescope.com/news/article_1509_1.asp. Retrieved 2009-04-22. 
  10. ^ "Release No. MOC2-1253: Mars Polar Lander NOT Found". Mars Global Surveyor / Mars Orbiter Camera. NASA/JPL/Malin Space Science Systems. 17 October 2005. http://www.msss.com/mars_images/moc/2005/10/17/. Retrieved 2009-04-22. 
  11. ^ [1] Youtube - NASA 3: Mission Failures
  12. ^ Nancy G. Leveson. The Role of Software in Recent Aerospace Accidents. http://sunnyday.mit.edu/accidents/issc01.pdf. 
  13. ^ a b "Report on the Loss of the Mars Polar Lander and Deep Space 2 Missions". Jet Propulsion Laboratory. 22 March 2000. ftp://ftp.hq.nasa.gov/pub/pao/reports/2000/2000_mpl_report_1.pdf. 
  14. ^ Thomas Young (14 March 2000). Mars Program Independent Assessment Team Summary Report. Draft #7 3/13/00. House Science and Technology Committee. http://www.spaceref.com/news/viewpr.html?pid=1444. Retrieved 2009-04-22. 
  15. ^ Jeffrey Kaye (14 April 2000). "NASA in the Hot Seat" (transcript). NewsHour with Jim Lehrer (PBS). http://www.pbs.org/newshour/bb/science/jan-june00/nasa_4-14.html. Retrieved 2009-04-22. 

Further reading

External links


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