Rocket astronomy

(astronomy) The discipline comprising measurements of the electromagnetic radiation from the sun, planets, stars, and other bodies, of wavelengths that are almost completely absorbed below the 150-mile (250-kilometer) level, by using a rocket to carry instruments above 150 miles to measure these phenomena.

The discipline that makes use of sounding rockets that fly near-vertical paths carrying scientific instruments to altitudes ranging from 25 to more than 900 mi (40 to 1500 km). Altitudes up to 30 mi (48 km) can be reached by balloons, so sounding rockets are typically used for higher altitudes in order to measure emissions from the Sun or other celestial sources that do not penetrate the Earth's atmosphere. Sounding rockets do not achieve orbital velocity; after completion of the launch phase, the payload follows a ballistic trajectory that permits 5–15 min of data taking before reentry. See also Rocket.

In comparison with experiments launched on satellites, rockets offer the advantages of simplicity, relatively frequent access to launch opportunities, a shorter time scale from conception to reality, lower cost, and recoverability of the payload and the possibility of postflight instrument calibration, refurbishment, and reflight. Major disadvantages are short observing time, localized coverage, and size and weight restrictions on payloads. See also Satellite astronomy.

Scientific rocket programs focus on the disciplines of aeronomy, magnetospheric physics, meteorology, and material sciences, as well as astronomy and astrophysics. The ability to carry out vertical profile measurements of relevant atmospheric parameters at heights of 25–125 mi (40–200 km) is essential in many of these scientific disciplines. To the extent that the Sun influences or controls conditions in the upper atmosphere and magnetosphere of the Earth, there is a strong connection between solar astronomy and the more local research areas. See also Aeronomy; Ionosphere; Magnetosphere.

The emission from the solar corona is dominated by ultraviolet and x-ray photons. During the late 1950s and early 1960s, techniques were developed for focusing x-rays and thereby providing direct imaging of the corona. These early studies revealed the highly structured nature of the atmosphere, with approximately semicircular loops of hot plasma outlining the shape of the underlying magnetic field, which confines the hot gas. Among the notable advances in coronal studies from rockets has been the development of a new technique for x-ray imaging: the use of multilayer coatings for enhanced x-ray reflectivity. See also Sun; X-ray astronomy; X-ray telescope.

Observations of nonsolar sources from sounding rockets are hindered by the low intensity of the emission and the problem of pointing the payload at the source during the flight.