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RE: The Opportunity rover

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Reports indicate that NASAs Opportunity rover on Mars has malfunctioned due to the failure of two of its most important instruments, thus halting research work.
The instruments that have broken down are the rovers rock grinding tool and its infrared spectrometer.
The rock grinding tool on Opportunity is having problems with one of its encoders which monitors the brush that clears away rock dust produced by the grinder. The encoders also tell the rovers computers whether the grind head is moving or not. The grinding tools help the rovers study the interior of rocks by cutting away the surface.

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Image taken by the Opportunity rover on Sol 1351.

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Credit NASA

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OPPORTUNITY UPDATE: Rover Finds Way to Brush Rock Surfaces Despite Setbacks - sol 1343-1348, Nov 13, 2007:

Opportunity is still parked in front of the rock layer known as "Smith" inside Victoria Crater. The rover has now lost two encoders that operate motors on the rock abrasion tool during the grinding and brushing of surfaces. Science team members and engineers have been working in test beds and computer sequencing rooms to devise creative ways of using the rock abrasion tool without the grind and revolve encoders.
On sol 1347 (Oct. 7, 2007), they achieved their goal when Opportunity successfully completed a new, seek-scan procedure. Using this technique, the rover locates a rock surface by simultaneously spinning its grind teeth and wire brush while also extending toward the rock surface. Normally, the rock abrasion tool software monitors the safe operation of the grind or brush using the two encoders, which detect stalls that can occur during grinding and encoding. In the event of a stall, the encoders measure the z-axis position (the point where the rock abrasion tool contacts the rock surface). Without the encoders, engineers must rely on current limits and contact switches to know when grind teeth come into contact with a rock surface.
Opportunity followed a command to run both the grind and revolve motors along with a parallel command to move in toward the rock surface. When the rock abrasion tool made contact with the surface, contact switches disengaged, ending the activity. The following day, sol 1348 (Oct. 8, 2007), the science team directed the rover to retract the rock abrasion tool 1 millimetre and brush the surface. The brushing proceeded as planned!
Grind testing will continue next week using a rock abrasion tool with new grind bits on a surrogate rover on Earth in preparation for grinding new targets on Smith.
Opportunity is also scheduled to test communications next week with NASA's Mars Reconnaissance Orbiter. This test, along with other tests conducted recently with the European Space Agency's Mars Express orbiter, are demonstrations of the capability to conduct UHF communications in preparation for next year's arrival of the Phoenix lander.
Opportunity's solar array energy has been approximately 670 watt-hours (100 watt-hours is the amount of energy needed to light a 100-watt bulb for one hour) per sol with atmospheric dust opacity, known as tau, of 0.87.

Sol-by-sol summary:
In addition to morning uplinks directly from Earth via the rover's high-gain antenna, evening downlinks to Earth via the Odyssey orbiter at UHF frequencies, standard measurements of atmospheric dust with the panoramic and navigation cameras, and surveys of the horizon with the panoramic camera, Opportunity completed the following activities:

Sol 1343 (Nov. 3, 2007): Opportunity ran diagnostic tests of the rock abrasion tool and collected compositional data from Smith using the Mössbauer spectrometer. The rover relayed data overnight to Odyssey.

Sol 1344: Opportunity continued to acquire compositional data from Smith with the Mössbauer spectrometer and scanned the sky for clouds with the navigation camera. Opportunity took full-colour images, using all 13 filters of the panoramic camera, of a rock target known as "Jin," and took panoramic camera images of Smith and the rock layer known as "Lyell."

Sol 1345: Opportunity continued the compositional analysis of Smith with the Mössbauer spectrometer and monitored dust on the camera mast. The rover acquired colour images using all 13 filters of the panoramic camera of a rock target dubbed "Gressly," scanned the sky for clouds, and took thumbnail images of the sky with the panoramic camera.

Sol 1346: Opportunity ran more diagnostic tests of the rock abrasion tool, placed the Mössbauer spectrometer back on Smith, and collected 11 hours' worth of compositional data with the instrument. The rover acquired a mosaic of images of Lyell as well as spot images of the sky with the panoramic camera.

Sol 1347: Opportunity completed a seek-scan procedure with the rock abrasion tool (during which the rover locates a rock surface by simultaneously spinning its grind teeth and wire brush while extending toward the rock surface). In addition, Opportunity took panoramic camera images of Lyell, measured atmospheric argon with the alpha-particle X-ray spectrometer, relayed data to the Odyssey orbiter overnight, and scanned the sky for clouds with the navigation camera.

Sol 1348 (Nov. 8, 2007): Plans called for Opportunity to complete an encoder-less brush of the surface of Smith, acquire microscopic images of Smith, place the alpha-particle X-ray spectrometer on Smith, and study composition of Smith with the spectrometer. The rover was to take panoramic camera images of "Cabo Frio," a promontory at the rim of Victoria Crater. Opportunity was to acquire full-colour images, using all 13 filters of the panoramic camera, of a layered rock target known as "Brongniart."

Odometry:
As of sol 1348 (Nov. 8, 2007), Opportunity's total odometry remained at 11,584.32 metres.

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Image taken by the Opportunity rover on Sol 1344

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Credit NASA

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OPPORTUNITY UPDATE: Opportunity Prepares for Arrival of Phoenix While Exploring "Victoria Crater" - sol 1329-1335, Nov 06, 2007:

Opportunity is healthy and receiving an average of 685 watt-hours of energy from the solar arrays (that's enough energy to run a 100-watt lightbulb for almost 7 hours). On sol (Martian day) 1327 (Oct. 18, 2007), the rover backed away from the "Steno" rock layer inside "Victoria Crater" to move within reach of the "Smith" rock layer a few meters deeper into the crater. However, the rover terminated the drive earlier than planned when stereo images in the visual odometry system, which enables the rover to use computer smarts to compare stereo images and accurately determine the rover's location, failed to line up properly. Opportunity re-pointed the cameras, acquired new stereo images for visual odometry, and completed the drive to Smith on sol 1329 (Oct. 20, 2007).
On Sol 1330 (Oct. 21, 2007), Opportunity supported a communications test on behalf of the Phoenix mission that demonstrated that large data sequences could be sent from Earth via the European Space Agency's Mars Express orbiter. The test involved multiple transmissions that were reassembled successfully on board by Opportunity. The rover recognised and received all four data sequences.
On sol 1332 (Oct. 23, 2007), Opportunity began a campaign that included acquiring a stereo (3D) microscopic image mosaic of Smith as well as compositional data about the rock outcrop. The following day, Sol 1333 (Oct. 24, 2007), Opportunity took panoramic camera images of a target known as "Sharp" -- a sequence of fine rock layers -- at different times of day to determine how the images were affected by changes in illumination. The day after that, sol 1334 (Oct. 25, 2007), Opportunity completed the first of a two-step process for brushing the surface of Smith. Plans called for Opportunity to finish the brushing sequence over the weekend, on sol 1336 (Oct. 27, 2007).

Sol-by-sol summary:
In addition to standard observations that included measurements of atmospheric dust with the panoramic and navigation cameras, surveys of the sky and ground with the miniature thermal emission spectrometer, and transfers of data to Earth via the Odyssey orbiter, Opportunity completed the following activities:

Sol 1329 (Oct. 20, 2007): Opportunity took pre-drive, full-colour, panoramic camera images of a two-toned rock target known as "Sedgwick" as well as images of "Cape Verde," a rock promontory. The rover stowed the robotic arm and drove to Smith. Opportunity then acquired post-drive images with the hazard avoidance cameras, rearward - and forward-looking images with the navigation camera, and unstowed the robotic arm. The next morning, Opportunity took thumbnail images of the sky with the panoramic camera.

Sol 1330: Opportunity used the navigation camera to survey surfaces in the rover's shadow to characterise the brightness of the sky as well as dust on the camera itself. After the overhead pass of the Odyssey spacecraft, the rover spent 7 hours measuring atmospheric argon using the alpha-particle X-ray spectrometer. In the evening, Opportunity communicated with Mars Express at UHF frequencies. The next morning, the rover surveyed the horizon with the panoramic camera.

Sol 1331: After measuring atmospheric dust, Opportunity took a nap until 2:30 p.m. local Mars time. The rover surveyed the sky with the panoramic camera while continuing to monitor atmospheric dust. In the morning, Opportunity acquired full-colour images, using all 13 filters of the panoramic camera, of iron-bearing particles accumulated on the rover's external magnets. The rover also monitored dust accumulation on the mast.

Sol 1332: Opportunity acquired a panel of stereo microscopic images of Smith, including extra images to improve the signal-to-noise ratio (eliminate random interference) resulting from dust accumulation on the microscopic imager. The rover placed the alpha-particle X-ray spectrometer on Smith, acquired panoramic camera images of a rock layer called "Lyell," and, after communicating with Odyssey, acquired data from Smith with the alpha-particle X-ray spectrometer. The next morning, the rover surveyed the sky, took spot images of the sky, and surveyed the horizon with the panoramic camera.

Sol 1333: Opportunity took panoramic camera images of both Sharp and Lyell. After transmitting data to Odyssey, the rover resumed collecting data from Smith with the alpha-particle X-ray spectrometer. The next morning, the rover took thumbnail images of the sky, spot images of the sky, and surveyed the horizon with the panoramic camera.

Sol 1334: Opportunity positioned the rock abrasion tool on Smith (the first step of the process for brushing the surface) and acquired panoramic camera images of rock targets known as "Kuenen" and "Lapworth." The next morning, the rover surveyed the sky with the panoramic camera, monitored dust accumulation on the rover mast assembly, and took spot images of the sky with the panoramic camera.

Sol 1335 (Oct. 26, 2007): Plans called for Opportunity to acquire panoramic camera image mosaics of Lyell, including specific targets known as "Lyell South" and a custom mosaic of a target called "Lyell Top." The rover was also to acquire panoramic camera images of a rock target known as "Conybeare." The following morning, the rover was to take thumbnail images of the sky and survey the horizon with the panoramic camera.

Odometry:
As of sol 1332 (Oct. 23, 2007), Opportunity's total odometry was 11,584 metres.

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Image taken by the Opportunity rover on Sol 1341

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OPPORTUNITY UPDATE: Opportunity Studies Rock Composition and Changes in Atmosphere - sol 1316-1321, Nov 05, 2007:

Though atmospheric dust has returned to nearly pre-dust storm levels, Opportunity's solar arrays are still dustier than before the storm, keeping power levels about 200 watt-hours lower than pre-storm levels. Opportunity continues to generate solar power levels of more than 600 watt-hours per Martian day, or sol (100 watt-hours is the amount of energy required to light a 100-watt bulb for one hour), with the help of wind-related cleaning of the solar panels. The spacecraft is healthy.
Opportunity has been studying the so-called "bathtub ring," a light band of rock that appears to circle Victoria Crater partway below the surface. Scientists think the band may be the remains of the original surface of Meridiani Planum before a meteor blasted out the crater. The ring itself appears to have three layers, originally dubbed "alpha," "beta" and "gamma" after the first three letters of the Greek alphabet, but now renamed "Steno," "Smith" and "Lyell," in honour of pioneering geologists of the 17th and 18th centuries.
Opportunity is to complete studies of Steno after grinding a hole into the rock surface with the rock abrasion tool and acquire a final set of observations that include measurements with the Mössbauer spectrometer.
The two spectrometers on Opportunity provide different kinds of information. The alpha-particle X-ray spectrometer is a general-purpose spectrometer that helps determine the chemical composition of the rocks. The Mössbauer spectrometer is specifically designed to study iron-bearing minerals, which are abundant on Mars and give the planet its red-orange colour. Both spectrometers rely on radioactive energy sources but the one in the Mössbauer spectrometer has a shorter half-life. That means it gets weaker faster. As a result, Mössbauer integrations now take longer, typically as many as 60 hours to acquire useful data. The rover acquires the observations over several sols.
To conserve battery power, which relies on sunlight as a source of energy, Opportunity sleeps at night. Opportunity happens to have a heater stuck in the "on" position that draws additional power. Mechanical thermostats added to the mission just before it was launched in 2003 prevent the heater from running during the daytime. But the heater continues to draw power at night.
Scientists plan to move Opportunity to a second spot on Steno for continued investigation. Before moving, Opportunity must stow the robotic arm. If the stow is successful, plans call for the rover to back uphill and aim high to compensate for potential slip on the steep slope of Victoria Crater before driving forward.
Plans also call for the rover to measure atmospheric argon. Argon is a trace gas in the Martian atmosphere, comprising about 1.6 percent (the bulk of the Martian atmosphere is carbon dioxide, the same gas that gives soft drinks their fizz). Argon is one of the noble gases, so named because they don't react chemically with other substances. It is always a gas. Water, on the other hand, can be a gas (water vapour), a liquid (cloud, mists, and rain), or a solid (ice, snow, sleet, and hail). Water can also bind physically or chemically to other substances in the air, such as dusts and soots, smog, and acid rain.
Because argon is always in one physical state (a gas) that is unadulterated by other substances, it can be used as a barometer. When atmospheric pressure is high, there's more argon in the field of view. When it's low, there's less argon. Measurements of the gas with the alpha-particle X-ray spectrometer track changes in Mar's atmospheric pressure as a result of changes in global energy flows, dust storms, and Mars' position relative to the Sun.
On sol 1320 (Oct. 11, 2007), Opportunity is scheduled to take a series of nine microscopic images within a minute or two at exactly the same spot. By adding the pixels (picture elements), engineers can reduce the amount of "noise" -- random, microscopic overexposures or underexposures -- within the image. Such noise is a constant in nature. By combining the pixels, engineers can average out the noise to reveal details and fine texture that would otherwise be obscured.

Sol-by-sol summary:
In addition to daily observations that included measurements of atmospheric dust with the panoramic and navigation cameras, surveys of the sky and ground with the miniature thermal emission spectrometer, and transfers of data to Earth via the Odyssey orbiter, Opportunity completed the following activities:

Sol 1316 (Oct. 6, 2007): Opportunity acquired stereo microscopic images of Steno, studied the rock's composition with the alpha-particle X-ray spectrometer, and checked for drift (changes with time) in the miniature thermal emission spectrometer.

Sol 1317: Opportunity acquired data from Steno using the Mössbauer spectrometer, went into a mini-deep sleep, and checked for drift in the miniature thermal emission spectrometer.

Sol 1318: Opportunity restarted the Mössbauer spectrometer for continued observation of Steno for 24 hours. The rover took thumbnail images of the sky and a mosaic of images of a target known as "Dolomieu" using the panoramic camera. The rover checked for drift in the miniature thermal emission spectrometer.

Sol 1319: Plans called for Opportunity to restart the Mössbauer spectrometer for 11 hours of observation of Steno and acquire images with the panoramic camera as well as check for drift in the miniature thermal emission spectrometer. The rover was to wake up at 11:20 p.m. local Mars time to turn off the Mössbauer spectrometer before returning to a mini-deep sleep. The following morning, Opportunity was to take thumbnail images of the sky with the panoramic camera and scan the sky for clouds with the navigation camera.

Sol 1320: Plans called for Opportunity to take microscopic images of a hole ground into the surface of Steno with the rock abrasion tool and spend 23 hours observing the same surface with the Mössbauer spectrometer. Opportunity was also slated to acquire full-colour images, using all 13 filters of the panoramic camera, of a target known as "Arduino" and survey the horizon and take thumbnail images of the sky with the panoramic camera.

Sol 1321 (Oct. 12, 2007): Plans called for Opportunity to stow the robotic arm, bump backward a short distance, take images with the hazard avoidance camera along the way as well as navigation camera images after the drive, and acquire panoramic camera images of the work volume reachable by the robotic arm. The rover was to acquire post-drive images with the navigation camera, unstow the robotic arm, measure atmospheric argon with the alpha-particle X-ray spectrometer, monitor dust on the rover mast, and check for drift in the miniature thermal emission spectrometer.

Odometry:
As of sol 1321 (Oct. 12, 2007), Opportunity's total odometry remained at 11,572.94 metres.

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OPPORTUNITY UPDATE: Opportunity Studies "Bathtub Ring" In "Victoria Crater" - sol 1301-1308, Nov 01, 2007:

Opportunity is healthy, with energy levels ranging from about 450 watt-hours to 475 watt-hours (100 watt-hours is the amount of electricity needed to light a 100-watt bulb for one hour).
Recently, Opportunity was temporarily unable to send scientific data to Earth because the Odyssey orbiter experienced a computer crash and went into "safing" mode. While in safing mode, the spacecraft shuts off unnecessary power loads, orients itself for maximum sunlight to the solar arrays, switches to communication modes most likely to receive commands from Earth, and basically stops all unnecessary activity while waiting for the folks back home to fix it and put it back in service.
While in safing mode, Odyssey did not send communications from either Mars rover. Opportunity continued to collect as much science as possible while waiting for Odyssey to be fixed.
After Odyssey was back in service, Opportunity began making up for lost time. Following a series of "toe dips," during which the rover drove a short way into "Victoria Crater" and backed out again, then drove a little farther and backed out again, Opportunity began examining the crater's interior.
Victoria Crater is interesting because it affords a chance to study rock layers down to a depth of about 70 meters below the surrounding surface. The modern surface isn't the original surface -- it has been altered by an incoming meteor. When a meteor strikes, it throws up a huge amount of debris that falls back around the crater and creates an "ejecta blanket." This blanket is thickest near the crater rim and thinnest farther away from the crater.
Below Victoria's raised rim is a light-coloured band nicknamed the "bathtub ring." Scientists hypothesise that this band is the dividing line between the original surface and the ejecta blanket above it. Opportunity has now reached this area -- but not without difficulty.
To reach the ring, Opportunity drove across a slope of about 25 degrees, nearly the maximum allowable tilt for the rover. The rover approached the ring on sol 1302 (Sept. 22, 2007) and then partially drove and partially slipped into closer position. On sol 1305 (Sept. 25, 2007), the rover unstowed the robotic arm and began studying the rocks that make up the top, or "Alpha," layer of the ring. Below that are two more layers, known as "Beta" and "Gamma," respectively.
Halfway through the last short drive of about 20 centimetres, Opportunity automatically stopped when the rover violated the tilt limit. As a result, the rover drove laterally about 10 centimetres and then slid downslope 10 centimetres. Subsequent analysis suggested that one of the downslope wheels rolled off a slight curb, producing a jolt that caused the rover to slip. Images showed that the rover had stopped on a hard outcrop of rock rather than sand or soil and was unlikely to slip farther.
Given the steep slope, Opportunity was extremely careful about moving the robotic arm. Before placing it on Alpha Layer, Opportunity moved the arm out, to the left, and to the right, while also checking for any vehicle motion with both the inertial measurement unit and cameras. The first rock target was dubbed "Steno."
Opportunity continued to conduct untargeted remote sensing by, among other things, measuring Tau, or atmospheric opacity, several times each Martian day, or sol. Now that the dust storms are over, the dust is settling. How fast it settles is of both scientific and engineering interest because it affects solar energy levels. Opportunity also periodically checked deposition and movement of dust on the panoramic camera mast assembly and solar arrays. This provides data for estimating wind directions and speeds, dust particle sizes, and dust composition.
Opportunity performed two "Quick Fine Attitude" checks. These are calibration activities that compensate for drift, or changes in time, in the inertial measurement unit. The unit uses gyroscopes and accelerometers to estimate the rover's motion, from which its position can be calculated. However, the gyroscopes show a slight change in attitude while the rover is still. (Older, mechanical gyroscopes drifted because of friction; newer, electronic gyroscopes drift for more complex reasons.)
The attitude checks compute where the sun should be based on the current time and the rover's movement and then compares this to the actual location of the sun in images from the panoramic camera. The difference forms the basis of the attitude correction for the rover.

Sol-by-sol summary:
In addition to daily observations that included frequent measurements of atmospheric dust with the panoramic and navigation cameras, surveys of the sky and ground with the miniature thermal emission spectrometer, and checks for drift (changes with time) in the miniature thermal emission spectromeer, Opportunity completed the following activities:

Sol 1301 (Sept. 21, 2007): Opportunity acquired panoramic camera images of the foreground, checked for drift in the miniature thermal emission spectrometer, checked the operation of the spectrometer, and surveyed the rover's external calibration target with the spectrometer. Before going into a deep sleep, the rover surveyed the horizon at low sun with the panoramic camera. The next morning, Opportunity monitored dust on the rover mast.

Sol 1302: Opportunity stowed the robotic arm, drove toward Alpha Layer, acquired images with the hazard avoidance cameras just prior to and after completing the drive, and completed a "quick fine attitude" update to confirm the rover's exact location. The rover unstowed the robotic arm, acquired post-drive images with the navigation camera, and acquired panoramic camera images of the work volume (the area reachable by instruments on the robotic arm). After that, Opportunity went into a deep sleep.

Sol 1303: Opportunity assessed the external calibration target with the miniature thermal emission spectrometer, recalibrated the panoramic camera, and spent six hours measuring atmospheric argon with the alpha-particle X-ray spectrometer. The rover went into a mini-deep sleep.

Sol 1304: Opportunity surveyed the external calibration target with the miniature thermal emission spectrometer, recalibrated the panoramic camera, and went into a deep sleep. The next morning, the rover took spot images of the sky with the panoramic camera.

Sol 1305: Opportunity stowed the robotic arm, bumped (drove a short distance) to Alpha Layer, and acquired penultimate and ultimate images with the hazard avoidance cameras. The rover completed a "quick fine attitude" check, acquired panoramic camera images of the work volume, unstowed the robotic arm, and acquired post-drive navigation camera images. Opportunity recalibrated the panoramic camera and went into a deep sleep.

Sol 1306: Opportunity acquired data from the external calibration target with the miniature thermal emission spectrometer and recalibrated the panoramic camera.

Sol 1307: Opportunity completed a "quick fine attitude" check, conducted a safety test with the robotic arm, acquired left-eye images of the alpha-particle X-ray spectrometer with the panoramic camera, and acquired stereo images of Steno with the microscopic imager. The rover placed the alpha-particle X-ray spectrometer on Steno and, after relaying data to Odyssey and recalibrating the panoramic camera, collected data from Steno with the spectrometer for 12 1/2 hours.

Sol 1308 (Sept. 28, 2007): After the usual dust monitoring and imaging activities as well as data relays to Odyssey, Opportunity went into a deep sleep.

Odometry:
As of sol 1308 (Sept. 28, 2007), Opportunity's total odometry was 11,572.94 metres.

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Cape Verde