If you got in a car, took it out on the highway and drove without stopping for 642 years, you will have driven the equivalent of the distance Curiosity traveled to get to Mars. Many millions of kilometres away, the incredible machine sits on the surface of this dusty, alien planet (see the previous post for the story of how it got there).
At 899kg, 2.9m long, 2.7m wide, and 2.2m high, it’s the size of a car too. It’s powered by a radioisotope thermoelectric generator which will give it 125 to 100 watts over its expected 14 year lifetime (the power output slowly degrades over time). Imagine if you could leave your car headlights on for 14 years and still have power left over!
The R.T.G. works by converting heat from the decay of plutonium into electricity via the use of thermocouples. The waste heat this produces is piped around the vehicle to protect its systems from the extreme cold Mars can drop to; −127 °C at its minimum for the landing site. The generator also charges 2 lithium ion batteries used boost its power output during certain operations.
It has two computers onboard, but not used simultaneously; one is configured as a backup. The core speed of the RAD750 CPU is only about 200mhz, which does not seem impressive at first, but it is specially designed to withstand extreme temperatures and radiation (unlike Earth, Mars does not have a geomagnetic field to protect it from cosmic radiation). An ordinary cpu would not survive long in such an environment.
Communication is possible either directly with Earth, or via the Mars orbiters. Using the orbiters is the preferred method, since they have more powerful transmitters. When transmitting to Earth directly, bandwidth is about 4 kilobytes per second, about the same as an old-school dialup modem connection. Transmitting via the orbiters however, can enable speeds of 250k/s when using the Mars Reconnaissance orbiter, or 32k/s with the Odyssey orbiter. However, their orbits are such that they can only communicate with the rover for about 8 minutes per day.
The wheels use what is called the rocker-bogie suspension system. Doubling as landing gear, each 50cm diameter wheel is individually actuated and geared. The front and back wheels can also be independently steered to allow the vehicle to be turned in place. The tread used is actually a binary code; it says “JPL” (Jet Propulsion Laboratories) which also doubles as a method of judging the distance traveled by the rover – the cameras count how many ‘JPL’s’ are left on the ground behind it as it goes. The vehicle should be able to clear obstacles 65cm in height, and undergo a tilt of up to 50 degrees without overturning!
What really sets the Curiosity apart from the other rovers is its scientific instruments, including a fricken laser, which was fired today!
The image may be slightly misleading, the laser is in the infra-red spectrum, not the visible red spectrum as it appears. Still cool though.
The laser is part of the ChemCam system. It works by targeting a rock or soil sample up to 7 metres away and vapourizing a small part of it with a million watts of power for around 5 billionths of a second, turning it into a glowing plasma. By analyzing the spectrum of light given off, it can be determined exactly what elements the sample was made of!
Other impressive instruments include:
- The Mars Hand Lens Imager (MAHLI), which is basically a microscope on a robotic arm that can take high detail microscopic images
- Alpha Particle X-ray Spectrometer (APXS), a device which can irradiate samples with alpha particles (helium nuclei) and from the resulting X-rays which are emitted, determine the chemical composition
- Chemistry and Mineralogy (CheMin), this instrument will drill into rock, gathering some of the fine powder produced, and deposit the sample into a inlet at the top of the vehicle. Then, using X-ray powder diffraction and fluorescence, determine the mineral composition of the sample.
- Sample analysis at Mars (SAM), will test for organic compounds from both the atmosphere and solid samples
- Radiation assessment detector (RAD), Along with measuring radiation on Mars, this instrument also characterized the broad spectrum of the radiation environment inside the spacecraft during its journey, with the goal of determining what the radiation shielding needs would be for future human explorers.
- Dynamic Albedo of Neutrons (DAN), used for measuring levels of hydrogen/ice/water near the surface
- Mars Descent Imager (MARDI), the camera which filmed this and this, and mapped the surrounding terrain and landing location.
All of these instruments almost guarantee some very exciting discoveries will be made!
Coming in a future post – Curiosity: What now? The mission