This week has been perhaps the busiest to date for the MSL team, with a series of milestones for the project being reached one after another which pretty much complete the initial characterisation phase of the mission (phases 1a and 1b). These have included the first firings of the rover’s laser system, an initial stretching of the instrument-laden robot arm and Curiosity’s first drive.
On Sol 13 (19th August), the mission team carried out the first test firings of the ChemCam laser at a surface object. The inaugural target was a small rock some 7 centimetres (3 inches) across which scientists christened “Coronation” to mark the event, but which was previously designated N165. It had been selected as it presented a relatively flat surface to the rover.
The test firing lasted some 10 seconds, during which the rock was struck by 30 pulses from the laser system, each pulse delivering more than a million watts of power for about five billionths of a second to a tiny spot on the surface of the rock, vaporising it into plasma. Light from the plasma was captured by ChemCam’s telescope and fed via fibre-optics to the rover’s three spectrometers for analysis.
The results were far better than anticipated, prompting ChemCam Deputy Project Scientist Sylvestre Maurice of the Institut de Recherche en Astrophysique et Planetologie (IRAP) in Toulouse, France, to comment, “It’s surprising that the data are even better than we ever had during tests on Earth, in signal-to-noise ratio. It’s so rich, we can expect great science from investigating what might be thousands of targets with ChemCam in the next two years.”
This was followed-up with a further series of firings on Sol 16 at some of the rocks exposed by the motors of the Descent Stage as it hovered in “skycrane” mode to lower the rover onto the surface of Gale Crater. Here the laser was fired some 50 times at three targets in the exposed rocks, which were also photographed by ChemCam’s RMI.
On Sol 14 Curiosity finally got to give her arm a bit of a stretch. The 2.1-metre (7 foot) long arm includes a 60-centimetre (2 ft) diameter “hand” called the Turret, which contains a range of scientific instruments and tools essential to the mission, including a dedicated camera (the Mars Hand Lens Imager, or MAHLI), a drill system, a scoop for collecting Martian soil (“fines”), and an Alpha-particle X-ray Spectrometer (APXS).
In this initial manoeuvre, the arm was raised, extended and rotated to use all five of its joints prior to it being stowed once more in preparation for Curiosity’s first drive. The manoeuvre marks the first step in calibrating the arm’s movements and preparing it for science operations. Further tests of the arm and its equipment load will take place over the next several weeks, but the system is unlikely to be fully commissioned until around mid-October.
Wriggle and Roll
Sol 15 saw Curiosity ready herself for her first drive on Mars. The front and rear wheels of the rover are all steerable, making Curiosity extremely manoeuvrable (it can turn 360-degrees on the spot); key to her being able to turn are the actuators controlling the movement of each of these wheels. So, prior to attempting its first drive, mission engineers wanted to ensure the actuators were functioning correctly and to this end, Curiosity wiggled her wheels back and forth to confirm the actuators were working, her Navam recording the results.
With the actuators successfully tested, commands were uploaded to Curiosity overnight between Sol 15 and Sol 16, specifying the route of her first, short drive on Mars. This was a modest manoeuvre which occurred on Sol 16, intended to confirm the actuators are turning her wheels properly and that her navigation system is updating correctly. In it, Curiosity rolled forward some 4.5 metres (14.5 feet), turned through 120-degrees in a clockwise direction and then reversed a further 2.5 metres (8 feet), coming to rest some 6 metres (20 feet) from its landing point. In all the drive took some five minutes, including a number of stops in which the rover imaged its wheels using the Navcam system, and was followed by a further 10 minutes in which additional images were captured.
“It is good to renew one’s wonder. Space travel has again made children of us all.” – Ray Bradbury, The Martian Chronicles
Author Ray Bradbury not only wrote wonderful science fiction and fantasy, he was an ardent supporter of NASA and a frequent visitor at JPL. Sadly, he passed away in June of 2012. On August 22nd, the day Bradbury would have been 92 years old, NASA approved a request from the mission team to call Curiosity’s landing point Bradbury Landing in his memory.
Almost all of Curiosity’s on-board science systems are now active, with the exception of SAM, (Sample Analysis at Mars) a suite of instruments designed to analyse organics and gases from both atmospheric and solid samples, and CheMin (Chemistry and Mineralogy instrument), designed to identify and measure the abundances of various minerals on Mars. So far, all of the science instruments have functioned flawlessly apart from rover’s wind sensor. A part of the Remote Environment Monitoring System (REMS) – Curiosity’s weather station – this is mounted on the rover’s mast, but is only returning partial or degraded data. Engineers believe it may have been struck by stones thrown up by the Descent Stage rocket motors, damaging some of its wiring, and are attempting to see if a workaround for the problem can be found.
Sol 11 saw the Dynamic Albedo of Neutrons (DAN) experiment, a system comprising units mounted on either side of the rover, start making initial measurements of the ground under Curiosity. DAN is designed to determine the amount of hydrogen – an indicator of water – trapped in the Martian soil, and will be used extensively when the rover is on the move to map changes in the water content of the soil down to about one metre (3.3 feet) below the surface.
Descent Stage Crash Imaged?
On August 17th, JPL released two side-by-side images captured by Curiosity’s left rear Hazard Avoidance Camera (Hazcam) shortly after the rover arrived safely on the surface of Mars.
Both images appear murky due to the cover intended to protect the lens from dirt and dust thrown up by the descent engines still being in place at the time they were captured. However, in centre of the image on the left, taken just a couple of minutes after landing, there is what appears to be cloud of debris being thrown into the air. The image on the right, taken 45 minutes later, shows no such cloud, confirming it is not a smear on the camera’s protective cover. This has led mission managers to believe the cloud in the left image is the result of the Descent Stage crashing into Mars. The bright areas at the top of both images are light saturation due to the camera facing towards the late afternoon sun.
What Next for Curiosity?
With the rover’s first drive now complete, Curiosity is now in what is called the “intermission phase” of the mission. Originally, this was a period of time allotted to completing further check-out work on some of the science experiments and on-board systems. However, mission planners have decided to extend this phase for a few additional days, and have set the following primary goals for the period:
- Complete initial commissioning of SAM, which will undergo two separate days of tests in when its pumps will be turned on, allowing it to draw-in samples of the Martian atmosphere for analysis
- Undertake check-outs on the Mastcam’s advanced capabilities, including its ability to produce long-range 3D images
- Complete further characterisations tests on ChemCam to determine how well the optics are aligned and the sensitivity of the spectrometers
- Examine the scours created by the Descent Stage’s rocket motors in greater detail using Mastcam, ChemCam and DAN, which will likely involve the rover manoeuvring around Bradbury Landing.
Following the intermission period, at around the end of the month, Curiosity will be ordered to start its first long-range traverse, which will take it some 400 metres (1300 feet) to the South-east to a region dubbed Glenelg. This is of interest to mission scientists as it marks the junction of three terrain types.
During the traverse it is hoped that the rover will encounter an area of Martian fines suitable for testing the robot arm’s scoop and to allow the check-out of SAM and CheMin to be completed using samples gathered by the scoop. If a suitable area is found, the rover will stop for several weeks while the sample gathering and analysis systems are thoroughly checked-out. This pause may also see check-outs carried out on APXS and MAHLI (although they may be checked-out sooner, if suitable targets present themselves).
If all goes according to plan, Curiosity should arrive at Glenelg in October, and will likely remain their through November, performing a wide range of tasks, including the first use of the drill system mounted on the robot arm turret.
“Straighten-up and Fly Right!”
During it’s descent through the Martian atmosphere, Curiosity used a downward-pointing camera, the Mars Descent Imager, or MARDI, to capture over 1,000 images of the rover’s landing. On August 21st, JPL released the following video, voiced by Adam Steltzner, the man in charge of the mission’s EDL phase, which feature the EDL animation from NASA’s Eyes on the Solar System coupled with images captured by MARDI. The video is best watched full screen, with the image quality set to 720p via the gear cog in the video window.
Additionally, YouTube user The Andorion has put together a film of the landing using some 680 high-resolution images from MARDI. note this footage is inverted when compared to the official JPL video above. The video is best watched full screen, with the image quality set to Original via the gear cog in the video window.
The name of Curiosity’s first destination – Glenelg – is an intentional palindrome, designed to reflect the fact that the rover will visit the area twice, both coming and going. It’s also, and coincidentally, the name of a town in the Scottish highlands.
All images courtesy of NASA / JPL. YouTube video courtesy of The Andorion.