What is a MISR orbit?
The Terra platform that carries MISR and other scientific instruments flies at an altitude of 705 km above sea level on a sun-synchronous orbit. It revolves once around the planet in 98.88 minutes and thus completes about 14.5 revolutions per day. In the context of MISR data exploitation, each complete revolution is called an orbit, and orbits are consecutively numbered from launch. The number of the orbit is thus directly related to the time span since launch. In practice, since MISR is an optical sensor that measures the reflectance of the Earth in the solar spectral range, it is acquiring useful data only while the Terra platform is over the illuminated (day) side of the planet, i.e., during one half of the complete orbit or a bit less. Of course, the Earth itself keeps turning around its own axis while Terra proceeds on its orbit. As a result, when Terra completes an orbit and initiates the next one, it actually flies over quite different regions. The orbit number thus also indicat
