Aerospace Instruments Onboard Radiation Belt Storm Probes

Aerospace-developed instruments will play a central role in the two-year NASA mission to study the Van Allen radiation belts around Earth. Called the Radiation Belt Storm Probes (RBSP) mission, the space segment consists of two identical spacecraft, launched by an Atlas 401 rocket from Cape Canaveral on Aug. 30. Each spacecraft carries the same complement of instruments, which includes five built by The Aerospace Corporation.

The RBSP mission is part of NASA’s Living With a Star Geospace program to explore fundamental processes that operate throughout the solar system, in particular those that generate hazardous space weather effects near the Earth and phenomena that could affect solar system exploration. RBSP is designed to help understand the sun’s influence on Earth and near-Earth space by studying the planet’s radiation belts on various scales of space and time.

The instruments on the two RBSP spacecraft will provide the measurements needed to characterize and quantify the processes that produce relativistic ions and electrons. They will measure the properties of charged particles that comprise the Earth’s radiation belts and the plasma waves that interact with them, the large-scale electric fields that transport them, and the magnetic field that guides them. Understanding the radiation belt environment and its variability has extremely important practical applications in the areas of spacecraft operations, spacecraft and spacecraft system design, mission planning, and astronaut safety.

The Aerospace instruments aboard the RBSP spacecraft are of two designs. The first is the Magnetic Electron Ion Spectrometer (MagEIS). Measurements from MagEIS are central to the RBSP science objective of understanding the sources and losses of the outer Van Allen radiation belt electrons. These electrons are responsible for the hazard of spacecraft charging and dominate the total ionizing dose in many orbits. The MagEIS instruments use a permanent magnetic field and arrays of silicon solid-state detectors to measure magnetospheric electron energy, intensity, and arrival direction. This instrumental method is the most accurate way to measure electrons in space because of their tendency to scatter once they interact with matter. MagEIS is based upon flight experience from Aerospace-built magnetic spectrometers, beginning with the Orbiting Vehicle (OV) 3-3 mission that was launched in August 1966.  

The second instrument is a Relativistic Proton Spectrometer (RPS). RPS extends the scientific capability of the RBSP mission to include the highest-energy trapped protons in the inner Van Allen radiation belt. The inner belt protons can cause single-event effects in microelectronics and dominate the total ionizing dose under thick shielding. RPS uses silicon solid-state detectors and a Cherenkov radiation system to measure proton energy, intensity, and arrival direction. RPS benefits from prior Aerospace experience with similar techniques that were first employed in the inner Van Allen belt on the OV1-20P mission in 1972.  Each RPS also includes two Teledyne microdosimeters (developed under the Aerospace Technical Investment Program) to monitor total ionizing dose on RBSP. There is one RPS sensor on each of the RBSP vehicles.