Spirit (rover)

''Spirit'', also known as MER-A (Mars Exploration Rover – A) or MER-2, is a Mars robotic rover, active from 2004 to 2010. ''Spirit'' was operational on Mars for sols or 3.3 Martian years ( days; '). It was one of two rovers of NASA's Mars Exploration Rover Mission managed by the Jet Propulsion Laboratory (JPL). Spirit landed successfully within the impact crater Gusev on Mars at 04:35 Ground UTC on January 4, 2004, three weeks before its twin, ''Opportunity'' (MER-B), which landed on the other side of the planet. Its name was chosen through a NASA-sponsored student essay competition. The rover got stuck in a "sand trap" in late 2009 at an angle that hampered recharging of its batteries; its last communication with Earth was on March 22, 2010.

The rover completed its planned 90-sol mission (slightly less than 92.5 Earth days). Aided by cleaning events that resulted in more energy from its solar panels, ''Spirit'' went on to function effectively over twenty times longer than NASA planners expected. ''Spirit'' also logged of driving instead of the planned , allowing more extensive geological analysis of Martian rocks and planetary surface features. Initial scientific results from the first phase of the mission (the 90-sol prime mission) were published in a special issue of the journal ''Science''.

On May 1, 2009 (5 years, 3 months, 27 Earth days after landing; 21 times the planned mission duration), ''Spirit'' became stuck in soft sand. This was not the first of the mission's "embedding events" and for the following eight months NASA carefully analyzed the situation, running Earth-based theoretical and practical simulations, and finally programming the rover to make extrication drives in an attempt to free itself. These efforts continued until January 26, 2010, when NASA officials announced that the rover was likely irrecoverably obstructed by its location in soft sand,
though it continued to perform scientific research from its current location.

The rover continued in a stationary science platform role until communication with ''Spirit'' stopped on March 22, 2010 (sol ).September 30 – October 5, 2010 Spirit Remains Silent at Troy
NASA. October 5, 2010. JPL continued to attempt to regain contact until May 24, 2011, when NASA announced that efforts to communicate with the unresponsive rover had ended, calling the mission complete. A formal farewell took place at NASA headquarters shortly thereafter.

Mission overview

The primary surface mission for ''Spirit'' was planned to last at least 90 sols. The mission received several extensions and lasted about 2,208 sols. On August 11, 2007, ''Spirit'' obtained the second longest operational duration on the surface of Mars for a lander or rover at 1282 Sols, one sol longer than the Viking 2 lander. Viking 2 was powered by a nuclear cell whereas ''Spirit'' is powered by solar arrays. Until ''Opportunity'' overtook it on May 19, 2010, the Mars probe with longest operational period was Viking 1 that lasted for 2245 Sols on the surface of Mars. On March 22, 2010, ''Spirit'' sent its last communication, thus falling just over a month short of surpassing Viking 1's operational record. An archive of weekly updates on the rover's status can be found at the ''Spirit'' Update Archive.

''Spirit's'' total odometry is .

Objectives

The scientific objectives of the Mars Exploration Rover mission were to:

* Search for and characterize a variety of rocks and soils that hold clues to past water activity. In particular, samples sought will include those that have minerals deposited by water-related processes such as precipitation, evaporation, sedimentary cementation or hydrothermal activity.
* Determine the distribution and composition of minerals, rocks, and soils surrounding the landing sites.
* Determine what geologic processes have shaped the local terrain and influenced the chemistry. Such processes could include water or wind erosion, sedimentation, hydrothermal mechanisms, volcanism, and cratering.
* Perform calibration and validation of surface observations made by Mars Reconnaissance Orbiter instruments. This will help determine the accuracy and effectiveness of various instruments that survey Martian geology from orbit.
* Search for iron-containing minerals, identify and quantify relative amounts of specific mineral types that contain water or were formed in water, such as iron-bearing carbonates.
* Characterize the mineralogy and textures of rocks and soils and determine the processes that created them.
* Search for geological clues to the environmental conditions that existed when liquid water was present.
* Assess whether those environments were conducive to life.

NASA sought evidence of life on Mars, beginning with the question of whether the Martian environment was ever suitable for life. Life forms known to science require water, so the history of water on Mars is a critical piece of knowledge. Although the Mars Exploration Rovers did not have the ability to detect life directly, they offered very important information on the habitability of the environment during the planet's history.

Design and construction

''Spirit'' (and its twin, ''Opportunity'') are six-wheeled, solar-powered robots standing high, wide and long and weighing . Six wheels on a rocker-bogie system enabled mobility over rough terrain. Each wheel had its own motor. The vehicle was steered at front and rear and was designed to operate safely at tilts of up to 30 degrees. The maximum speed was ; , although the average speed was about . Both ''Spirit'' and ''Opportunity'' have pieces of the fallen World Trade Center's metal on them that were "turned into shields to protect cables on the drilling mechanisms".

The solar arrays generated about 140 watts for up to four hours per Martian day (sol) while rechargeable lithium ion batteries stored energy for use at night. ''Spirit's'' onboard computer used a 20 MHz RAD6000 CPU with 128 MB of DRAM, 3 MB of EEPROM, and 256 MB of flash memory. The rover's operating temperature ranged from . Radioisotope heater units provided a base level of heating, assisted by electrical heaters when necessary. A gold film and a layer of silica aerogel provided insulation.

Communications depended on an omnidirectional low-gain antenna communicating at a low data rate and a steerable high-gain antenna, both in direct contact with Earth. A low-gain antenna was also used to relay data to spacecraft orbiting Mars.

Science payload

The science instruments included:

* Panoramic Camera (Pancam) – examined the texture, color, mineralogy, and structure of the local terrain.
* Navigation Camera (Navcam) – monochrome with a higher field of view but lower resolution, for navigation and driving.
* Miniature Thermal Emission Spectrometer (Mini-TES) – identified promising rocks and soils for closer examination, and determined the processes that formed them.
* Hazcams, two B&W cameras with 120 degree field of view, that provided additional data about the rover's surroundings.

The rover arm held the following instruments:

* Mössbauer spectrometer (MB) MIMOS II – used for close-up investigations of the mineralogy of iron-bearing rocks and soils.
* Alpha particle X-ray spectrometer (APXS) – close-up analysis of the abundances of elements that make up rocks and soils.
* Magnets – for collecting magnetic dust particles.
* Microscopic Imager (MI) – obtained close-up, high-resolution images of rocks and soils.
* Rock Abrasion Tool (RAT) – exposed fresh material for examination by instruments on board.

Mission timeline

2004

The ''Spirit'' Mars rover landed successfully on the surface of Mars on 04:35 SCET on January 4, 2004. This was the start of its 90-sol mission, but solar cell cleaning events would mean it was the start of a much longer mission, lasting until 2010.

Landing site: ''Columbia'' Memorial Station

''Spirit'' was targeted to a site that appears to have been affected by liquid water in the past, the crater Gusev, a possible former lake in a giant impact crater about from the center of the target ellipse at .

After the airbag-protected landing craft settled onto the surface, the rover rolled out to take panoramic images. These give scientists the information they need to select promising geological targets and drive to those locations to perform on-site scientific investigations. The panoramic image below shows a slightly rolling surface, littered with small rocks, with hills on the horizon up to away. The MER team named the landing site "''Columbia'' Memorial Station," in honor of the seven astronauts killed in the Space Shuttle ''Columbia'' disaster.

"Sleepy Hollow," a shallow depression in the Mars ground at the right side of the above picture, was targeted as an early destination when the rover drove off its lander platform. NASA scientists were very interested in this crater. It is across and about north of the lander.

First color image

To the right is the first color image derived from images taken by the panoramic camera on the Mars Exploration Rover ''Spirit''. It was the highest resolution image taken on the surface of another planet. According to the camera designer Jim Bell of Cornell University, the panoramic mosaic consists of four pancam images high by three wide. The picture shown originally had a full size of 4,000 by 3,000 pixels. However, a complete pancam panorama is even 8 times larger than that, and could be taken in stereo (i.e., two complete pictures, making the resolution twice as large again.) The colors are fairly accurate. (For a technical explanation, se
colors outside the range of the human eye
)

The MER pancams are black-and-white instruments. Thirteen rotating filter wheels produce multiple images of the same scene at different wavelengths. Once received on Earth, these images can be combined to produce color images.

Sol flash memory management anomaly

On January 21, 2004 (sol ), ''Spirit'' abruptly ceased communicating with mission control. The next day the rover radioed a 7.8 bit/s beep, confirming that it had received a transmission from Earth but indicating that the craft believed it was in a fault mode. Commands would only be responded to intermittently. This was described as a very serious anomaly, but potentially recoverable if it were a software or memory corruption issue rather than a serious hardware failure. ''Spirit'' was commanded to transmit engineering data, and on January 23 sent several short low-bitrate messages before finally transmitting 73 megabits via X band to ''Mars Odyssey''. The readings from the engineering data suggested that the rover was not staying in sleep mode. As such, it was wasting its battery energy and overheating – risk factors that could potentially destroy the rover if not fixed soon. On sol 20, the command team sent it the command SHUTDWN_DMT_TIL ("Shutdown Dammit Until") to try to cause it to suspend itself until a given time. It seemingly ignored the command.

The leading theory at the time was that the rover was stuck in a "reboot loop". The rover was programmed to reboot if there was a fault aboard. However, if there was a fault that occurred during reboot, it would continue to reboot forever. The fact that the problem persisted through reboot suggested that the error was not in RAM, but in either the flash memory, the EEPROM, or a hardware fault. The last case would likely doom the rover. Anticipating the potential for errors in the flash memory and EEPROM, the designers had made it so that the rover could be booted without ever touching the flash memory. The radio itself could decode a limited command set – enough to tell the rover to reboot without using flash. Without access to flash memory the reboot cycle was broken.

On January 24, 2004 (sol ) the rover repair team announced that the problem was with ''Spirits flash memory and the software that wrote to it. The flash hardware was believed to be working correctly but the file management module in the software was "not robust enough" for the operations the ''Spirit'' was engaged in when the problem occurred, indicating that the problem was caused by a software bug as opposed to faulty hardware. NASA engineers finally came to the conclusion that there were too many files on the file system, which was a relatively minor problem. Most of these files contained unneeded in-flight data. After realizing what the problem was, the engineers deleted some files, and eventually reformatted the entire flash memory system. On February 6 (sol ), the rover was restored to its original working condition, and science activities resumed.Planetary Blog

First intentional grinding of a rock on Mars

For the first intentional grinding of a rock on Mars, the ''Spirit'' team chose a rock called " Adirondack". To make the drive there, the rover turned 40 degrees in short arcs totaling . It then turned in place to face the target rock and drove four short moves straightforward totaling . Adirondack was chosen over another rock called "Sashimi", which was closer to the rover, as Adirondack's surface was smoother, making it more suitable for the Rock Abrasion Tool (aka "RAT").

''Spirit'' made a small depression in the rock, in diameter and deep. Examination of the freshly exposed interior with the rover's microscopic imager and other instruments confirmed that the rock is volcanic basalt.

Humphrey rock

On March 5, 2004, NASA announced that ''Spirit'' had found hints of water history on Mars in a rock dubbed "Humphrey". Raymond Arvidson, the McDonnell University Professor and chair of Earth and Planetary Sciences at Washington University in St. Louis, reported during a NASA press conference: "If we found this rock on Earth, we would say it is a volcanic rock that had a little fluid moving through it." In contrast to the rocks found by the twin rover ''Opportunity'', this one was formed from magma and then acquired bright material in small crevices, which look like crystallized minerals. If this interpretation holds true, the minerals were most likely dissolved in water, which was either carried inside the rock or interacted with it at a later stage, after it formed.

Bonneville crater

On sol March 11, 2004, ''Spirit'' reached Bonneville crater after a journey. This crater is about across with a floor about below the surface. JPL decided that it would be a bad idea to send the rover down into the crater, as they saw no targets of interest inside. ''Spirit'' drove along the southern rim and continued to the southwest towards the Columbia Hills.

''Spirit'' reached Missoula crater on sol 105. The crater is roughly across and deep. Missoula crater was not considered a high priority target due to the older rocks it contained. The rover skirted the northern rim, and continued to the southeast.
It then reached Lahontan crater on sol 118, and drove along the rim until sol 120. Lahontan is about across and about deep. A long, snaking sand dune stretches away from its southwestern side, and ''Spirit'' went around it, because loose sand dunes present an unknown risk to the ability of the rover wheels to get traction.

Columbia Hills

''Spirit'' drove from Bonneville crater in a direct line to the Columbia Hills. The route was only directly controlled by the engineers when the terrain was difficult to navigate; otherwise, the rover drove in an autonomous mode. On sol 159, ''Spirit'' reached the first of many targets at the base of the Columbia Hills called West Spur. Hank's Hollow was studied for 23 sols. Within Hank's Hollow was the strange-looking rock dubbed " Pot of Gold". Analysing this rock was difficult for ''Spirit'', because it lay in a slippery area. After a detailed analysis with the AXPS-and the Mößbauer instrument it was detected that it contains hematite. This kind of rock can be built in connection with water.

As the produced energy from the solar panels was lowering due to the setting Sun and dust the Deep Sleep Mode was introduced. In this mode the rover was shut down completely during the night in order to save energy, even if the instruments would fail. The route was selected so that the rover's panels were tilted as much as possible towards the winter sunlight.

From here, ''Spirit'' took a northerly path along the base of the hill towards the target Wooly Patch, which was studied from sol 192 to sol 199. By sol 203, ''Spirit'' had driven southward up the hill and arrived at the rock dubbed "Clovis". Clovis was ground and analyzed from sol 210 to sol 225. Following Clovis came the targets of Ebenezer (Sols 226–235), Tetl (sol 270), Uchben and Palinque (Sols 281–295), and Lutefisk (Sols 296–303). From Sols 239 to 262, ''Spirit'' powered down for solar conjunction, when communications with the Earth are blocked. Slowly, ''Spirit'' made its way around the summit of Husband Hill, and at sol 344 was ready to climb over the newly designated "Cumberland Ridge" and into " Larry's Lookout" and "Tennessee Valley". ''Spirit'' also did some communication tests with the ESA orbiter ''Mars Express'' though most of the communication was usually done with the NASA orbiters ''Mars Odyssey'' and ''Mars Global Surveyor''.

2005

Driving up to Husband Hill

''Spirit'' had now been on Mars for one Earth year and was driving slowly uphill towards the top of Husband Hill. This was difficult because there were many rocky obstacles and sandy parts. This led frequently to slippage and the route could not be driven as planned. In February, ''Spirits computer received a software update in order to drive more autonomously. On sol 371, ''Spirit'' arrived at a rock named "Peace" near the top of Cumberland Ridge. ''Spirit'' ground ''Peace'' with the RAT on sol 373. By sol 390 (mid-February 2005), ''Spirit'' was advancing towards "Larry's Lookout", by driving up the hill in reverse. The scientists at this time were trying to conserve as much energy as possible for the climb.

''Spirit'' also investigated some targets along the way, including the soil target, "Paso Robles", which contained the highest amount of salt found on the red planet. The soil also contained a high amount of phosphorus in its composition, however not nearly as high as another rock sampled by ''Spirit'', "Wishstone". One of the scientists working with ''Spirit,'' Dr. Steve Squyres, said of the discovery, "We're still trying to work out what this means, but clearly, with this much salt around, water had a hand here".

Image:Pot of gold-Close-med.jpg, Pot of Gold rock
Image:Gusev - Colina Husband.jpg, ''Spirits traverse up