On April 14, 2004, NASA announced an opportunity for researchers to propose science investigations for the Mars Science Laboratory (MSL) mission. Eight months later, the agency announced selection of eight investigations. In addition, Spain and Russia would each provide an investigation through international agreements. The instruments for these ten investigations make up the science payload on the Curiosity rover.
The ten instruments on Curiosity have a combined mass of 165 pounds. Curiosity carries the instruments plus multiple systems that enable the science payload to do its job and send home the results. Key systems include six-wheeled mobility, sample acquisition and handling with a robotic arm, navigation using stereo imaging, a radioisotope power source, avionics, software, telecommunications, and thermal control.
Curiosity is 10 feet long (not counting its arm), 9 feet wide, and 7 feet high at the top of its mast, with a mass of 1,982 pounds, including the science instruments. Curiosity’s mechanical structure provides the basis for integrating all of the other rover subsystems and payload instruments.
Curiosity’s mobility subsystem is a scaled-up version of what was used on the three earlier Mars rovers: Sojourner, Spirit, and Opportunity. Six wheels all have driver motors, and the four corner wheels all have steering motors. Each front and rear wheel can be independently steered, allowing the vehicle to turn in place, as well as to drive in arcs. The suspension is a rocker-bogie system, enabling Curiosity to keep all its wheels in contact with the ground, even on uneven terrain. Curiosity’s wheels are aluminum and 20" in diameter. They have cleats for traction and structural support. Curving titanium spokes give springy support.
The rover has a top speed on flat, hard ground of about 1.5 inches per second. However, under autonomous control with hazard avoidance, the vehicle achieves an average speed of less than half that.
Arm and Turret
The Robot Arm (RA) is a five-degrees-of-freedom manipulator used to place and hold the turret-mounted devices and instruments on rock and soil targets, as well as manipulate the turretmounted sample processing hardware.
The science instruments on the arm’s turret are the Mars Hand Lens Imager (MAHLI) and the Alpha Particle X-ray Spectrometer (APXS). The other tools on the turret are components of the rover’s Sample Acquisition/Sample Processing and Handling (SA/SPaH) subsystem: the Powder Acquisition Drill System (PADS), the Dust Removal Tool (DRT), and the Collection and Handling for In-situ Martian Rock Analysis (CHIMRA) device.
The SA/SPaH subsystem is responsible for the acquisition of rock and soil samples from the Martian surface, and the processing of these samples into fine particles that are then distributed to the analytical science instruments SAM and CheMin. The SA/SPaH subsystem is also responsible for the placement of the two contact instruments, APXS and MAHLI, on rock and soil targets. SA/SPaH also includes drill bit boxes, the Organic Check Material (OCM), and an observation tray, which are all mounted on the front of the rover, and inlet cover mechanisms that are placed over the SAM and CheMin solid sample inlet tubes on the rover top deck.
The Powder Acquisition Drill System is a rotary percussive drill to acquire samples of rock material for analysis. It can collect a sample from up to 2" beneath a rock’s surface. The drill penetrates the rock and powders the sample to the appropriate grain size for use in SAM and CheMin. If the drill bit becomes stuck in a rock, the drill can disengage from that bit and replace it with a spare. The Dust Removal Tool is a metal-bristle brushing device used to remove the dust layer from a rock surface or to clean the rover’s observation tray.