ISS Radiation Hardware Description

Source: International Space Station Familiarization, Mission Operations
Directorate, Space Flight Training Division, July 31, 1998

14.5.1.3 Radiation Hardware

Tissue Equivalent Proportional Counter

The Tissue Equivalent Proportional Counter (TEPC) measures and stores accumulated
radiation spectra. The TEPC includes a detector and spectrometer (Figure 14-9). During
Increment 1, the TEPC interfaces with the MEC for data storage and downlink. After Flight 5A,
TEPC data is transferred via the CHeCS 1553B bus for telemetry to the ground. The TEPC uses
ISS power and must be connected to a CHeCS designated power/data port for data downlink.
The TEPC operates continuously, requiring relocation by the crew weekly. The Tissue
Equivalent Proportional Counter (TEPC) is secured to ISS nodes and modules via seat track
fittings or Velcro.

Personal Dosimeters

Personal dosimeters are worn continuously by each crewmember throughout the increment.
Similar personal dosimeters are worn by space shuttle and NASA/Mir crewmembers. The small,
passive dosimeters are analyzed postflight to determine the radiation exposure of the
crewmember throughout the mission.

The Intravehicular-Charged Particle Directional Spectrometer (IV-CPDS) measures the flux
of all trapped, secondary, and galactic cosmic rays as a function of time, energy, and direction
internal to the ISS (Figure 14-10). Data from the IV-CPDS is transferred via the CHeCS 1553B
bus for telemetry to the ground. The IV-CPDS is relocated by the crew weekly This may
involve only rotating the instrument, since measurements are taken unidirectionally.

Extravehicular-Charged Particle Directional Spectrometer
The Extravehicular-Charged Particle Directional Spectrometer (EV-CPDS) measures the flux
of all trapped, secondary, and galactic cosmic rays as a function of time, energy, and direction
external to the ISS. The EV-CPDS is composed of three Intravehicular-Charged Particle
Directional Spectrometers (IV-CPDSs), each facing a different direction (Figure 14-11).

The EV-CPDS is contained in an Extravehicular Activity/Extravehicular Robotics removable
avionics box mounted to the S-0 truss. The EV-CPDS is mounted preflight and arrives on Flight
8A attached to the S-0 truss segment. An EVA is required to position the EV-CPDS properly.
Data is transferred via the CHeCS 1553B bus for telemetry to the ground. The EV-CPDS is the
only CHeCS component located external to the ISS.