Cs. armady 14, 160 00 Prague, Czech Republic

The instrument 2SD [tu:esdi:] (Space Dosimetry System Demonstrator)

The instrument 2SD [tu:esdi:] (Space Dosimetry System Demonstrator) is composed of two detectors:

  • SXRM (SpacepiX Radiation Monitor)
  • SXM (Soft X-ray Monitor)

The SXRM is a radiation monitor based on the revolutionary SpacePix2 ASIC. It can be used for a wide range of space radiation monitoring applications and was developed in cooperation between esc Aerospace and FNSPE CTU (Czech Technical University) in Prague. It is designed for long-term orbital missions of up to 15 years on GEO, MEO, LEO and interplanetary missions. It has been developed to be compliant with European Space Agency (ESA) requirements for radiation hardness and has been fully ESA qualified. The device is designed as a space environment awareness monitor for communication, navigation and Earth observation satellites. It will monitor the space weather radiation component. SXRM is sensitive to electrons and protons from the van Allen belt and heavy ions from the galactic cosmic rays. It detects individual particles and was designed to operate even in a dynamic range of solar particle events with fluxes of up to 106 protons cm2s-1. The SXRM uses pattern recognition techniques in 5 detection layers, interleaved with energy absorbers in a telescopic configuration, to cover a large particle energy range.

The SXM detector is designed for the measurement of the flux and spectrum of soft X-rays photons, emitted during transient events in the Solar magnetosphere, such as X-ray flares during magnetic reconnection. The SXM uses the specialized X-CHIP-03-SXR ASIC with a dynamic range optimized for soft X-ray photon measurement.

The SpacePix2 detection chip is a radiation-resistant monolithic pixel ionizing radiation detector developed at the FNSPE CTU in 180 nm SoI CMOS process for space dosimetry and charged particle detection. SpacePix2 measures approximately 4×5.5 mm2 and contains 4096 pixels arranged in a matrix of 64×64 pixels. The dynamic range is extended using a technique of backside pulse digitization and has a range of five orders of magnitude, making it capable to characterize particles from low-energy electrons to high-energy heavy ions of galactic cosmic rays. Its small dimensions, low power consumption, simple interfacing and large dynamic make it ideal for mass deployment in space situation awareness applications.

The 2SD instrument is based on the second generation esc Aerospace on-board computer and data processing board escOBC2™, and includes an additional interface and power board for the detectors. The escOBC2™ is an upgraded version of the escOBC™. The board is featuring a state-of-the-art 32-bit processor based on 45nm technology and 0.5 MB of radiation immune MRAM memory for critical system data and 128 MB of flash mass storage for mission or scientific data. The product is compatible with the standard Cubesat PC104 form factor and features a main connector compatible with most of the Cubesat boards. The Communication with subsystems can be established via UART, CAN, SPI, I2C or discrete lines. For safety reasons the escOBC2™ is equipped with an independent HW watchdog to prevent system hangs and current&voltage monitors.

The solar radiation is detected using the pixel chip XChip03SXR. The insight of each sensor is shielded by a thin titanium foil to protect against photons and low-energy particles.

Technical parameters

2SD instrument features

  • Dimensions 90 x 96 x 45 mm3, mass 300 g
  • Operating temperature range -40 °C to +65 °C
  • Average power consumption ~150 mW (peak 550 mW)
  • Powering from 3.3V and 5V rails
  • Communication via CAN interface


  • In-flight SW updates
  • Internal storage for data
  • Configurable sampling rate, thresholds and exposure time (shutter open)
  • Several data products available: Raw data frames, reconstructed clusters, particle tracklets and summary histograms

SXRM detector features

  • Designed for charged particle energy and species determination
  • Pattern recognition techniques and partial reconstruction of particle trajectory
  • Supports operational modes of radiation imaging, clustering, tracking and LET histogram
  • Alert capability in the event of elevated radiation
  • Energy ranges for particle species
  • 0.5-10 MeV (electrons)
  • 2-200 MeV (protons)
  • 0.5-100 MeVcm2mg-1 (heavy ions).

SXM detector features

  • Sensitive to photons in energy range 4 to 20 keV.
  • Maximal X-ray flux of 105 photons cm2s-1
  • Charged particle discrimination functionality
  • Data products include raw frames, X-ray flux and spectra