While Curiosity Takes the Spotlight, Opportunity Keeps Working Backstage

This is one of the first images that the Mars Science Laboratory rover Curiosity took of itself upon touching down on the Red Planet. Photo Credit: NASA / JPL

Everyone is ecstatic that the newest Mars rover, the Mars Science Laboratory, or Curiosity, has landed safely and begun returning data, but that doesn’t mean that NASA’s other Mars rover is retiring.

The last Mars Exploration Rover, Opportunity, is continuing to explore its region of Mars.

Opportunity was one of two Mars Exploration Rovers, the other being Spirit.

The two rovers were launched from Cape Canaveral Air Force Station on Delta II rockets in June and July of 2003. Spirit landed on January 3, 2004 at Gusev Crater and Opportunity landed on January 24, 2004 at Meridiani Planum.

Launch of MER-1
The first Mars Exploration Rover, Spirit, launches aboard a Delta II rocket from Cape Canaveral Air Force Station in June 2003. Photo Credit: NASA

The rovers carried five science instruments with a total mass of 5 kg. The instruments were the Pancam, the Microscopic Imager, the Miniature Thermal Emission Spectrometer, a Mossbauer Spectrometer, and an Alpha Particle X-ray Spectrometer (APXS).

The Pancam is a stereo camera mounted on the top of the rovers’ masts and is the primary way for scientists to see the rovers’ environment. The Microscopic Imager is a CCD attached to a microscope and is used to examine rock and soil samples close-up.

The three spectrometers are designed to determine the make-up of samples.

The MER rovers were meant to last just 90 sols (a Martian day) before their solar panels were covered in dust and left unable to generate enough power to sustain the rovers.

Opportunity Self Portrait 2007
This image was taken by Opportunity using its Pancam to illustrate the amount of dust that had accumulated on its solar panels after 3 years on Mars. Image Credit: NASA/JPL-Caltech/Cornell

But Spirit and Opportunity surprised everyone. They lasted far beyond their original “warranty period,” as the rover team called it. In fact, they lasted so long that Opportunity claimed the title of longest operational probe on the surface of Mars; it surpassed the Viking 1 landers’ record of six years and 116 days on May 20, 2010.

But the rovers’ did have one vulnerability: they relied on solar panels to get power. As the rovers traveled, dust gathered on the solar panels and reduced the amount of sunlight reaching the photovoltaic array, and thus the power the panels could make. This weakness turned out not to be as severe as NASA originally expected, but it has somewhat limited the operations of the rovers. Spirit regularly had to stop driving and take a position to point its solar panels northward to cope with the reduced sunlight available as the Martian winter set in at Spirit’s location.

Unfortunately, Spirit became stuck in a patch of soft ground in April 2010 and was unable to orient itself in time for winter, and had its last communication with Earth on March 22, 2010. Before it finally ceased functioning, Spirit had traveled 7.7 km over the course of 2210 sols, radically surpassing the original expectations of at total drive of 100 m and 90 sols.

Opportunity Self Portrait 2011
This image was captured by the Opportunity rover in 2011 to illustrate the amount of dust that had accumulated on its solar panels after 7 years on Mars. Image Credit: NASA/JPL-Caltech/Cornell

Opportunity’s location closer to the equator allowed it to continue mobile science operations through its local winter period. It benefited from wind clearing off the dust on its solar panels, increasing the available power.

However, the dust had continued to accumulate on the rover, and this winter, starting in December 2011, it had to remain stationary to conserve power. It spent the winter resting at a site its operators called Greely Haven. While it was stationary, it did not stop doing science. It used its stationary position to its advantage and conducted radio science that might reveal more about the interior of Mars. It resumed mobile operations in May 2012.

Once it got back on its “feet,” Opportunity continued exploring Endeavour Crater, a massive crater 22 km in diameter that intrigues scientists.

Three Generations of Rovers
A group shot of NASA’s three Mars rovers: Sojourner, MER, and MSL. The Sojourner rover was about the size of a microwave and weighed 11 kg. The MER rovers weighed 185 kg and carried 5 kg of science instruments. MSL weighs 3900 kg in total and carries 75 kg of science instruments. Photo Credit: NASA/JPL-Caltech

As of August 7, Opportunity has driven 34.6 km and been on Mars for 3035 sols.

But, after missing a launch opportunity in 2009 and running hundreds of millions of dollar over-budget, the Mars Science Laboratory has finally landed on Mars.

MSL, or Curiosity, carries 10 science instruments with a total mass of 75 kg. For comparison, the MER rovers weighed 185 kg each, and their science instruments weighed only 5 kg.

While Curiosity approached Mars and began its entry, descent, and landing sequence, Opportunity had to reduce its activity level for a period of nine days to allow Curiosity to make maximum use of the Deep Space Network, NASA’s method of communicating with deep space probes. During these nine days, starting August 2, Opportunity made APXS measurements of a rock sample, took Pancam images and made daily atmospheric opacity measurements.

Whim Creek
This image was taken by Opportunity’s Pancam on Sol 3032 of its mission (August 4) and the area is called “Whim Creek” by the rover’s operators. Image Credit: NASA/JPL-Caltech

But Opportunity’s contribution to Curiosity’s landing was just to sit still and keep quiet while Curiosity took the spotlight. On July 31 the rover tested a method of communicating directly with Earth via UHF radio that might be used during Curiosity’s mission.

But now that Curiosity is safely on the ground and getting ready for regular operations, Opportunity will get its share of DSN time again. The mission team plans to begin driving Opportunity again any day now.

An image from Opportunity’s forward Hazcam showing Opportunity’s arm holding its APXS instrument up to a target called Rushall1 by the rover’s operators. Photo Credit: NASA/JPL-Caltech


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