A test target is a common feature on interplanetary landing craft such as the Viking Lander and Mars Exploration Rovers.
The target is usually a visible marker or plate on the exterior of the vehicle within sight of the lander's imaging system (usually a CCD camera). The target possesses samples of primary colors and a grey scale. The camera uses this much like a photographer would use a chip chart on Earth; the color samples allow the camera to compensate for white balance and contrast. The target provides a visual reference as well, so that the initial orientation of the camera can be fixed.
On the Mars Exploration Rover, the target was designed with a pillar elevated above the main surface, so that it could be used as a sundial.
Famous quotes containing the words test and/or target:
“He who has never failed somewhere, that man can not be great. Failure is the true test of greatness. And if it be said, that continual success is a proof that a man wisely knows his powers,—it is only to be added, that, in that case, he knows them to be small.”
—Herman Melville (1819–1891)
“All of women’s aspirations—whether for education, work, or any form of self-determination—ultimately rest on their ability to decide whether and when to bear children. For this reason, reproductive freedom has always been the most popular item in each of the successive feminist agendas—and the most heavily assaulted target of each backlash.”
—Susan Faludi (20th century)