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Goddard Space Flight Center

Astrophysics Science Division | Sciences and Exploration

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Advanced
Cosmic Ray
Composition
Experiment for the
Space
Station

ACCESS Instruments

ACCESS instruments To capture a wide variety of cosmic rays, the ACCESS instrument is equipped with two detectors, each utilizing a different technique that capitalizes on the unique properties of particular types of cosmic rays. For example, some cosmic rays are more common than others; some are faster and more energetic.

    dot The top ACCESS instrument is a detector called the Transition Radiation Detector (TRD -- in green and metallic gold on the diagram at right), used to analyze cosmic rays with charges of +4 to +26, or lithium to iron. The TRD employs a state-of-the-art version of technology first developed in the 1960s and 1970s. The detector measures the velocity (related to the energy) of the cosmic rays, and is sometimes referred to as the "velocity" module.

    dot Underneath the TRD is the calorimeter (at the bottom, in red), which will analyze hydrogen, helium, and a limited number of heavier cosmic rays. These cosmic rays have high energies compared to their light size, which the calorimeter can detect. For this reason, the detector is called the "energy" module.