A sounding rocket, sometimes called a research rocket, is an instrument-carrying rocket designed to take measurements and perform scientific experiments during its sub-orbital flight. The rockets are used to carry instruments from above the surface of the Earth, the altitude generally between weather balloons and satellites (the maximum altitude for balloons is about and the minimum for satellites is approximately ). Certain sounding rockets, such as the Black Brant X and XII, have an apogee between ; the maximum apogee of their class. Sounding rockets often use military surplus rocket motors. NASA routinely flies the Terrier Mk 70 boosted Improved Orion lifting payloads into the region between .