|Illustrations courtesy NASA|
The initial excitement and pride over the Mars Curiosity rover's inventive descent to the Martian surface has given way to continuous, methodical scientific exploration using a variety of sensors and instrumentation. The cameras get most of the press, with their stunning panoramic views and occasional amusing curious sightings. But science is a patient discipline, and experiments which peel back the layers of Mars' composition and history are underway each day now.
Performance and reliability are essential for all research and industrial applications, but the prospect of a service call more than hundreds of millions of kilometers away poses special challenges, so it was critical for every component of the Curiosity rover to have proven reliability and robust performance. We are thrilled that PI and PI miCos products are not only part of the rover's instrumentation package but already performing important science on Mars.
"Only through curiosity can we discover opportunities, and only by gambling can we take advantage of them."award-winning PICMA® low-voltage ceramic actuators have been the gold standard for reliability in nanopositioning and are the heart of PI's nanopositioning stage products since their introduction several years ago. They are the heart of our nanopositioning equipment. NASA's testing of these actuators validated their performance over 100 billion cycles, which aided their qualification for use as the foundation for the Chemistry & Mineralogy (CheMin) instrument, now hard at work in Gale Crater.
Sixteen PICMA actuators operate a precision oscillatory material delivery system feeding transmissive X-ray diffraction and fluorescence spectrometry experiments. Thirty-two sample chambers (including five containing fixed references) are arrayed around a sample wheel; the chambers are arranged in pairs with a PICMA actuator coupling each pair. The actuators are used to load sample powder into the chambers and to unload it once metrology is concluded. Clearly, their reliability is crucial to the mission's success. Metrology is performed during the Martian night so that the CCD sensor can be efficiently cooled. This rover never sleeps!
While the PICMA actuators are hard at work performing spectrometry on Martian mineral samples, another experiment called ChemCam is busy performing the first interplanetary Laser Induced Breakdown Spectrometry (LIBS). This all-optical, non-contact technique utilizes a powerful, pulsed infrared laser to induce optical emission from interesting samples. The visible, sparking flash that results from each laser pulse is evaluated by a fiber-coupled spectrometer, with chemometric analysis providing the material breakdown of the sample.
One key advantage of this methodology is that the geologic sample being tested can be a distance from the rover. But it requires exacting control of the optical focus, and that's where a space-qualified variant of the PI miCos MT Series stage comes in. This high-precision stepper-motor stage axially translates the secondary mirror of the telescope which collects the optical return from the sample while providing imaging information to place the sample within geologic context.
The shocks and vibration of launch and landing necessitated that every component in the stage from the stepper motor to the crossed roller bearings be validated and optimized to eliminate the possibility of failure or degradation. The autofocus process places stringent demands on the stage's performance-- resolution, backlash, trajectory quality and stability are all crucial for responsive and predictable operation and reliable data. The wide temperature excursions to which the stage was to be exposed in flight and on the Martian surface added significantly to the challenge. Modeling and thermal compensation technologies and sophisticated vacuum-compatible components, coatings and lubricants were utilized. This specialized variant of the commercial-off-the-shelf (COTS) stage passed all preflight tests and validated the cost-containment strategy of leveraging COTS designs.
Of course, performance, reliability and cost-effectiveness have their place here on Earth as well. Contact your local PI sales engineer for the finest products and applications advice in the solar system.