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Blog Category: Measurement and calibration

NIST Goes the Distance for the Olympics

NIST technician Christopher Blackburn uses a microscope to precisely align a retroreflector over the center of a hash mark on a measuring tape. Photo credit: Bruce Borchardt

In yet another Olympian feat of measurement, researchers at Commerce's National Institute of Standards and Technology (NIST) recently calibrated a tape that will be used to measure out the distance of this summer's Olympic marathon—a distance of 26 miles 385 yards—to 1 part in 1,000.

Measurement is a vital aspect of the Olympic Games. Officials measure the height of jumps, the speed of races, and the mass of weights to determine who wins a medal and who goes home. The marathon is no different. Because of the difficulties in measuring out the distance, the International Association of Athletic Federations (IAAF) only recognized best times and didn't begin awarding world records for marathons until 2004 when a method using a device called a Jones Counter was officially recognized as sufficiently accurate.

Developed by a father-son duo in the early 1970s, the Jones Counter is a simple geared device that counts the revolutions of a bicycle wheel. To calibrate the device, course measurers lay out a calibrated measuring tape at least 30 meters in length. Once they have determined the number of revolutions that equal that distance—and a couple of successively longer distances—they follow painstaking procedures for laying out the rest of the course. The measurements, which can take hours to complete, will ensure that the shortest distance a runner will run will be at least the required distance and no more than about 40 meters over, corresponding to an error of about one part in 1,000.  Full story

NIST/CU 'Star Comb' Joins Quest for Earthlike Planets

Infrared starlight (three solid band) by comparing the missing light to a laser frequency comb reference "ruler" (sets of bright vertical bars indicating precise wavelengths, which increase from left to right).  Credit: CU/NIST/Penn State

If there is life on other planets, a laser frequency comb developed at Commerce's National Institute of Standards and Technology (NIST) may help find it.

Such a comb—a tool for precisely measuring frequencies, or colors, of light—has for the first time been used to calibrate measurements of starlight from stars other than the Sun. The good results suggest combs will eventually fulfill their potential to boost the search for Earth-like planets to a new level.

The comb was transported to the Texas mountains to calibrate a light analyzing instrument called a spectrograph at the Hobby-Eberly telescope. A University of Colorado Boulder (CU) astronomer and Pennsylvania State University students and astronomers collaborated on the project.

“The comb worked great,” says NIST physicist Scott Diddams. “In a few days, it enabled measurement precision comparable to the very best achieved in the same wavelength range with much more established techniques—and we hope the comb will do much better as the new technique is perfected.”

The NIST comb calibrated measurements of infrared starlight. This type of light is predominantly emitted by M dwarf stars, which are plentiful in Earth’s part of the galaxy and might have orbiting planets suitable to life.