Category: Other Worlds and Tech

Curiosity is once more moving forwards – by going backwards.

Since crossing the “Dingo Gap” sand dune, the rover has been on terrain dubbed “Moonlight Valley” which is far smoother than has been encountered in recent travels, exactly as the mission team would hope would be the case. Nevertheless, precautionary measures are still being used to offer Curiosity’s aluminium wheels some additional relief after a routine inspection of them revealed some had suffered much greater wear and tear than had been anticipated crossing some very rugged terrain.

While the damage to the wheels is not an immediate threat to the rover, mission planners were aware it could happen, and so have been considering various alternatives to minimise further undue wear. One of these alternatives involves the rover proceeding by driving backwards.

Theoretically, the design of the rover means that it can make forward progress either by driving with its front end (mounting the robot arm and science turret), or with its rear end, the large RTG cooling system, facing the direction of travel. However, the technique has never been fully tested on Mars, only having being tried over any significant distance using Curiosity’s Earth-based test bed twin; but with much smoother terrain now before the rover, mission managers were eager to discover how well Curiosity could drive when travelling backwards.

“We wanted to have backwards driving in our validated toolkit because there will be parts of our route that will be more challenging,” said mission Project Manager Jim Erickson at  NASA’s Jet Propulsion Laboratory, Pasadena, California. To this end, on Tuesday February 18th, Sol 647 of the mission, Curiosity covered just over 100 metres (329 feet) whilst driving backwards, a traverse which was also the first long trek the rover has made in more than three months, bringing the total distance it has driven since arriving on Mars in August 2012 to some 5.21 kilometres (3.24 miles).

With the reverse driving now proven, Curiosity is set to resume its primary mission, which will see it make its way to an area previously referred to as “KMS-9”, comprising three different terrain / rock types offer a relatively dust-free area, and which has now been renamed “Kimberley” after a region in north-western Australia noted for its ancient, exposed rocks.

Following the February 18th drive, Curiosity faced a 1.1 kilometre curving trek to reach “Kimberley”. Once there, the rover will stop there to conduct further science activities, including gathering further rock samples using the turret-mounted drill. At the same time, mission managers will use orbital imagery to select the preferred route the rover will be instructed to take in order to continue onwards to its primary destination: the lower slopes of “Mount Sharp”.

“We have changed our focus to look at the big picture for getting to the slopes of Mount Sharp, assessing different potential routes and different entry points to the destination area,” Erickson said, commenting on the need to reassess the route. “No route will be perfect; we need to figure out the best of the imperfect ones.”

It is not clear how long the rover will remain at “Kimberley” once it arrives there; part of this decision will likely only be made once the rover have been able to survey the area for itself.

MSL reports in this blog

Images and video courtesy of NASA / JPL.

Last time around, I mentioned that the Curiosity team was looking at alternative routes to get the rover down to the crossing-point for the start of its explorations of “Mount Sharp” at the centre of Gale Crater and, more immediately, to a target of interest for further science studies.

The desire to seek alternative routes came as a result of periodic examinations of Curiosity’s aluminium wheels revealing they’d suffered more wear and tear during recent traverses of very rough terrain than had been anticipated. While not a threat to the rover, mission managers would still prefer to lessen the impact of the rover’s southerly transit over what has proven exceptionally rugged ground.

At the time of writing that last update, planners were considering taking Curiosity over a sand dune roughly a metre (3 feet) in height sitting between two rocky scarps, as the terrain beyond the dune, dubbed “Dingo Gap”, appeared to be markedly less rough. While a little more circuitous than a direct-line drive, crossing the dune would still allow the rover to get to its next target for taking samples, a rocky outcrop dubbed “KMS-9″.

While other routes were under consideration as well, it was decided to take Curiosity “Dingo Gap” after it had been ordered to drive up to the base of the dune and take a peep directly over the top of the mound to get a detailed view of the land on the other side. The rover actually made the crossing  on Sol 535 (February 6th), and a series of nine black-and-white images captured by the rear hazard-avoidance cameras (Hazcams) were later strung together to form a short video of the crossing.

With the crossing made, Curiosity is set to travel to “KMS-9”, something over half a kilometre away, and which comprises three different terrain / rock types offer a relatively dust-free area for examination and further drilling operations. The area is one of the number of potential “waypoints” identified from orbit that missions scientists hope will help provide greater insight in the soil, rock and climatic conditions which may have once existed around “Mount Sharp” and help build up a clearer picture of changes in conditions which may have occurred within the region through which the rover is travelling.

Continue reading “Crossing the divide and looking homeward” →

The progress of NASA’s Curiosity rover on Mars has slowed somewhat in January, the rover having covered around 265 metres (865 feet) in the month, bringing the total distance Curiosity has travelled since arriving on Mars in august 2012 to some 4.89 kilometres (3.04 miles).

Part of the reason for the slow-down has been due to the recent traverse of considerably rougher terrain during the rover’s trek towards its encounter with “Mount Sharp” having resulted in somewhat more wear-and-tear of the aluminium wheels than had perhaps been anticipated.

While not of a serious concern – the rover can function with quite substantial damage having being done to the wheels – the mission team has nevertheless been looking for ways and means for the rover’s progress to continue at a reasonable pace, but without exposing the wheels to excessively rugged terrain.

Most recently, this has involved examining a possible gateway to a smoother route down to the point at which they plan to commence explorations of “Mount Sharp’s” lower slopes.  This gateway is a 1-metre (3-ft) high sand dune sitting between two rocky scarps. Dubbed “Dingo Gap”, the dune appears to provide access to a smoother route heading south-west and towards the rover’s ultimate destination.

“The decision hasn’t been made yet, but it is prudent to go check,” said Jim Erickson, NASA’s project manager for Curiosity. on January 28th. “We’ll take a peek over the dune into the valley immediately to the west to see whether the terrain looks as good as the analysis of orbital images implies.” The orbital images he referred to came from the High Resolution Imaging Science Experiment (HiRISE) camera on NASA’s Mars Reconnaissance Orbiter, while the “closer look” actually took place on January 30th.

In addition to using alternative routes, the drive team has also been evaluating possible driving techniques that might help reduce the rate of wheel punctures, such as driving backwards or using four-wheel drive instead of six-wheel drive. This may help is situations where some of the wheel damage may have resulted from the force of the rear wheels pushing the middle or front wheels against sharp rocks, rather than simply the weight of the rover driving over the rocks.

As a result of the slow-down, JPL are considering introducing some evening and weekend drives into the February drive schedule.

More Drilling

As well as providing a route southwards, Dingo Gap may also allow the rover easier access to its next waypoint on the journey, where it is expected to carry out further drilling and sample-gathering activities. The site, identified as “KMS-9” is around 800 metres (half-a-mile) from Curiosity’s current position when measured in a straight line – but that is over rugged terrain the mission team would potentially avoid if possible.

The drilling site has been imaged from orbit, and holds significant appeal to the mission team, as Katie Stack, a science team collaborator explained. “At KMS-9, we see three terrain types exposed and a relatively dust-free surface. This area is appealing because we can see terrain units unlike any that Curiosity has visited so far. One unit has striations all oriented in a similar direction. Another is smooth, without striations. We don’t know yet what they are. The big draw is exploration and seeing new things.”

“KMS-9” won’t be the first rocky area examined by Curiosity in 2014. On January 15th, the rover examined a rock dubbed “Harrison”, which revealed linear crystals with feldspar-rich composition.

Earth-side Tests

At the same time as the efforts to select a candidate route have been underway, other members of the team have been carrying out further tests to validate capabilities for the rover to drill for rock samples on the kind of slopes it will likely encounter when exploring and climbing “Mount Sharp”.

In particular, the tests have been focused on the drill mechanism’s ability to withstand damage as a result of slippage when the rover is parked on a sloping surface. So far, results have shown that the drill mechanism can withstand slippage of around 5 centimetres (2 inches) in the rover’s position without any real damage occurring. Such slippage could be induced through a number of circumstances, including the angle of slope, cumulative damage to the wheels which may impact their ability to grip the surface beneath them, and material on the surface which may also impact the rover’s ability to sustain a solid grip on underlying rock.

Continue reading “Dunes, rocks, comets and dust” →