Sometimes the chain of measurement traceability—the unbroken series of links between a calibrated instrument and the official standard maintained by the National Institute of Standards and Technology (NIST)—can get pretty long. But 250 million kilometers is remarkable, even for NIST.
That's the current distance between the Curiosity rover on Mars and the temperature labs in Gaithersburg, Md., where the calibration process began for several small but critically important temperature sensors that monitor the rover's power generator.
"They're all hand-made and hand-customized," says Chris Albert of Sensing Devices Inc. (SDI) in Lancaster, Pa., which designed the sensors to specifications. "Each one has to be calibrated, and each one has to have NIST traceability."
So Albert brought the company's master reference thermometer to the NIST laboratories to have it calibrated according to the International Temperature Scale of 1990, the worldwide standard for equipment calibration.
Read the full story, "PML Goes to Mars: Far-Out Thermal Calibration."