 Artist's depiction of theMars Polar Lander on the Martian surface | |
| Names | Mars Surveyor '98Lander |
|---|---|
| Mission type | Mars lander |
| Operator | NASA /JPL |
| COSPAR ID | 1999-001A |
| SATCATno. | 25605 |
| Website | science.nasa.gov |
| Mission duration | 334 days Mission failure |
| Spacecraft properties | |
| Manufacturer | Martin Marietta |
| Launch mass | 290 kg (640 lb)[1] |
| Power | 200 Wsolar array andNiH 2 battery |
| Start of mission | |
| Launch date | 20:21:10, January 3, 1999 (UTC) (1999-01-03T20:21:10Z) |
| Rocket | Delta II 7425–9.5 D-265 |
| Launch site | Cape Canaveral Air Force Station SLC-17A |
| Contractor | Boeing |
| End of mission | |
| Disposal | Communication failure after landing |
| Declared | January 17, 2000 (2000-01-17) |
| Last contact | 20:00, December 3, 1999 (UTC) (1999-12-03T20:00:00Z) |
| Mars impact(failed landing) | |
| Impact date | ~20:15 UTCERT, December 3, 1999 |
| Impact site | Ultimi Scopuli,76°S195°W / 76°S 195°W /-76; -195 (Mars Polar Lander) (projected) |
| Mars impactor | |
| Spacecraft component | Deep Space 2 |
 Mars Surveyor 98 mission logo | |
TheMars Polar Lander, also known as theMars Surveyor '98 Lander, was a 290-kilogramuncrewed spacecraftlander launched byNASA on January 3, 1999, to study thesoil andclimate ofPlanum Australe, a region near the south pole onMars. It formed part of theMars Surveyor '98 mission. On December 3, 1999, however, after the descent phase was expected to be complete, the lander failed to reestablish communication with Earth. A post-mortem analysis determined the most likely cause of the mishap was premature termination of the engine firing prior to the lander touching the surface, causing it to strike the planet at a high velocity.[2]
The total cost of the Mars Polar Lander was US$165 million. Spacecraft development cost US$110 million, launch was estimated at US$45 million, and mission operations at US$10 million.[3]
As part of theMars Surveyor '98 mission, a lander was sought as a way to gather climate data from the ground in conjunction with an orbiter.NASA suspected that a large quantity of frozen water may exist under a thin layer of dust at the south pole. In planning the Mars Polar Lander, the potential water content in the Martian south pole was the strongest determining factor for choosing a landing location.[4] A CD-ROM containing the names of one million children from around the world was placed on board the spacecraft as part of the "Send Your Name to Mars" program designed to encourage interest in the space program among children.[5]
The primary objectives of the mission were to:[6]
The Mars Polar Lander carried two small, identicalimpactor probes known as "Deep Space 2 A and B". The probes were intended to strike the surface with a high velocity at approximately73°S210°W / 73°S 210°W /-73; -210 (Deep Space 2) to penetrate theMartian soil and study the subsurface composition up to a meter in depth. However, after entering the Martian atmosphere, attempts to contact the probes failed.[4]
Deep Space 2 was funded by theNew Millennium Program, and their development costs was US$28 million.[3]
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 aluminumhoneycomb deck, compositegraphite-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 thermalFaraday cage enclosure housed the computer, power distribution electronics and batteries, telecommunication electronics, and the capillary pumploop heat pipe (LHP) components, which maintained operable temperature. Each of these components included redundant units in the event that one may fail.[4][1][7]
While traveling to Mars, the cruise stage was three-axis stabilized with fourhydrazinemonopropellant reaction engine modules, each including a 22-newton trajectory correction maneuver thruster for propulsion and a 4-newton reaction control system thruster forattitude control (orientation). Orientation of the spacecraft was performed using redundantSun sensors,star trackers, andinertial measurement units.[1]
During descent, the lander used three clusters of pulse-modulated engines, each containing four 266-newton hydrazine monopropellant thrusters. Altitude during landing was measured by aDoppler radar system, and an attitude and articulation control subsystem (AACS) controlled the attitude to ensure the spacecraft landed at the optimalazimuth to maximize solar collection and telecommunication with the lander.[4][1][7]
The lander was launched with two hydrazine tanks containing 64 kilograms of propellant and pressurized withhelium. Each spherical tank was located at the underside of the lander and provided propellant during the cruise and descent stages.[4][1][7]
During the cruise stage, communications with the spacecraft were conducted over theX band using a medium-gain, horn-shaped antenna and redundant solid state power amplifiers. For contingency measures, a low-gain omnidirectional antenna was also included.[4]
The lander was originally intended to communicate data through the failedMars Climate Orbiter via theUHF antenna. With the orbiter lost on September 23, 1999, the lander would still be able to communicate directly to theNASA 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. The direct-to-Earth medium-gain antenna provided a 12.6-kbit/sreturn channel, and the UHF relay path provided a 128-kbit/s return channel. 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.[4][6][1][7]
The cruise stage included twogallium arsenidesolar arrays to power the radio system and maintain power to the batteries in the lander, which kept certain electronics warm.[4][1]
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 auxiliary solar arrays were located on the side to provide additional power for a total of an expected 200 watts and approximately eight to nine hours of operating time per day.[4][1]
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-ampere-hournickel–hydrogen battery was included to be recharged during the day and 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.[4][1][7]
| Timeline of observations | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
Mars Polar Lander was launched on January 3, 1999, at 20:21:10 UTC by theNational Aeronautics and Space Administration fromSpace Launch Complex 17B at theCape Canaveral Air Force Station in Florida, aboard aDelta II 7425–9.5 launch vehicle. The complete burn sequence lasted for 47.7 minutes after aThiokolStar 48B solid-fuel third stage booster placed the spacecraft into an 11-month, Mars transfer trajectory at a final velocity of 6.884 km/s (4.278 mi/s) with respect to Mars. During cruise, the spacecraft was stowed inside anaeroshell capsule and a segment known as thecruise stage provided power and communications with Earth.[4][6][1]
The target landing zone was a region near thesouth pole of Mars, calledUltimi Scopuli, because it featured a large number ofscopuli (lobate or irregularscarps).[citation needed]
On December 3, 1999,Mars Polar Lander arrived at Mars and mission operators began preparations for landing. At 14:39:00 UTC, the cruise stage was jettisoned, which began a planned communication dropout to last 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 theheat shield positioned to absorb the 1,650 °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 theMartian atmosphere at 20:10:00 UTC, and was expected to land in the vicinity of76°S195°W / 76°S 195°W /-76; -195 (Mars Polar Lander) in a region known asPlanum Australe. Reestablishment of communication was anticipated for 20:39:00 UTC, after landing. However communication was not reestablished, and the lander was declared lost.[4][6][1]
Traveling at approximately 6.9 km/s (4.3 mi/s) and 125 km (78 mi) above the surface, the spacecraft entered the atmosphere and was initially decelerated by using a 2.4 meterablationheat shield, located on the bottom of the entry body, toaerobrake through 116 km (72 mi) of the atmosphere. Three minutes after entry, the spacecraft had slowed to 496 m/s (1,630 ft/s), signaling an 8.4-meterpolyester parachute to deploy from a mortar, followed immediately by heat shield separation and MARDI powering on while 8.8 km (5.5 mi) above the surface. The parachute further slowed the speed of the spacecraft to 85 m/s (280 ft/s) when the ground radar began tracking surface features to detect the best possible landing location and determine the vertical speed via the Doppler effect for thrust control.
When the spacecraft had slowed to 80 m/s (260 ft/s), one minute after parachute deployment, the lander separated from the backshell and began a powered descent at 1.3 km (0.81 mi) aloft. Vertical speed was intended to drop to 2.4 meters per second at 12 m height and then be constant until touchdown. Below 40 meters, the radar would become unreliable by raised dust and was switched off already at that height; for the final seconds, the thrust would be controlled by inertial sensors. A function to switch off the thrust immediately at touchdown was also armed at 40 meters. Touchdown was expected at 20:01 UTC, given as 20:15 ″Earth-received time″.[4][6][1][7]
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 NASA Deep Space Network. A 45-minute transmission was to be broadcast to Earth containing 30 landing images acquired by MARDI. Arrival of that signal of a successful landing was expected at 20:39 UTC. 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 90Martian Sols, with the possibility of an extended mission.[4][6][1][7]
On December 3, 1999, at 14:39:00 UTC, the lasttelemetry fromMars 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 theMars Global Surveyor to photograph the area in which the lander was believed to be. An object was visible and believed to be the lander. However, subsequent imaging in September 2005 resulted in the identified object being ruled out.Mars Polar Lander remains lost.[13][14]
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.[15] 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.[16]
In addition to the premature shutdown of the descent engines, the Failure Review Board also assessed other potential modes of failure.[2] Lacking substantial evidence for the mode of failure, the following possibilities could not be excluded:
The failure of the Mars Polar Lander took place two and a half months after the loss of theMars Climate Orbiter. Inadequate funding and poor management have been cited as underlying causes of the failures.[17] According to Thomas Young, chairman of the Mars Program Independent Assessment Team, the program "was under funded by at least 30%."[18]
| Quoted from the report[2] |
|---|
"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 theHall Effect touchdown sensor during landing leg deployment (while the lander is connected to the parachute). The software logic 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." |
Planum Australe, which served as the exploration target for the lander and the twoDeep Space 2 probes,[19] would in later years be explored by European Space Agency'sMARSIS radar, which examined and analyzed the site from Mars' orbit.[20][21][22][23]
| Rovers |  | |
|---|---|---|
| Landers | ||
| Memorial sites | ||
| Sample depots | ||
| Other | ||
† indicates a mission failure (no significant data returned from the surface). | ||
| Active |
|  .jpg) .jpg) | |||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|
| Past |
| ||||||||||
| |||||||||||
| Future |
| ||||||||||
| |||||||||||
| Exploration |
| ||||||||||
Missions are ordered by launch date. Sign† indicates failure en route or before intended mission data returned.‡ indicates use of the planet as agravity assist en route to another destination. | |||||||||||
