DOSimetry TELescopes (DOSTEL) is designed to measure time-dependent fluence rates of charged particles and their corresponding dose rates and linear energy transfer (LET) spectra. The experiment uses two sensor types: planar Silicon detectors (PIPS) and PIN diodes.Principal Investigator(s)
University of Kiel, Kiel, , Germany
German Aerospace Center (DLR), Cologne, , Germany
European Space Agency (ESA)Sponsoring Organization
Information PendingResearch Benefits
Information PendingISS Expedition Duration:
October 2007 - October 2009Expeditions Assigned
16,17,18,19/20Previous ISS Missions
Small Radiation Telescope for measuring the radiation environment.
The detector unit uses five Silicon sensors for measurements. The detector telescope head is built up by two PIPS detectors and one PIN diode. The other two PIN diodes are fixed to the one print board and mounted towards the other two directions.
Each detector is connected to an independent analogue signal section consisting of a charge sensitive amplifier (CSA) with 2pF integrating capacitor followed by a two-step pulse amplifier (PA1, PA2) and two peak detectors. For noise reduction purpose, two RC-filters with equal individual time constants of 1micro-second are included in each detector signal line. Together with a multiplexed 8-bit ADC this design allows a pulse height analysis of the detector signals with different resolution for the low and high energy deposit region.The power requirement is +/-5 Volt for the CSAs and 70 Volt detector bias voltage (high impedance, less than 1microA per detetor). The selection of the sensor is controlled by the software and the power and data lines are switched via a multiplexer on the main board.
The main component of the digital section is the HC711 8-bit microcontroller. This circuit controls detector unit selection, data sampling, preliminary analysis and data reduction, internal intermediate storage and data transfer to the external main storage. The internal clock will be synchronized to mission elapsed time in order to correlate the measurement to orbit positions.
Data products are time dependent fluence rates of charged particles and their corresponding dose rates. The instrument will continuously monitor temporal variation of the charged particle count rate, the dose rate, charged particle and LET spectra. Two modes of operation will be performed: Mode 1) single detector mode for dose measurements in the individual detectors and for the measurement of particle and LET spectra in the range 0.1 to 200 keV microm, Mode 2) single event mode.
In the normal operational mode, Mode 1, DOSTEL integrates the measured spectra for certain time periods. The count rates and dose rates are also stored in the memory for given time periods. As the count rate exceeds a given threshold DOSTEL switches to shorter periods to get a higher resolution during the SAA crossings. As soon as the count rate falls below another threshold DOSTEL switches back to normal orbital integration periods. The spectra measured during the stay in the region of the SAA are stored separately. After the integration period for the spectra is achieved the data block is copied from the RAM to the Flash-Memory. This data block contains the spectra, the time profile of the measured count rate and additional information about the instruments status. The integration time is adjusted automatically to include the time between two cosmic ray equator crossings for the integration of the spectra.
Mode 2 is the single event mode of DOSTEL. Every Trigger produces six bytes of data. Every 100s a time tag is stored to get time information. With this time information count rate profiles and spectral profiles can be generated by processing the data.This mode produces large amount of data and will only be activated during limited time periods. Mode 1 is the instrument mostly used mode. To switch between modes a command message is needed from EuTEF. In case of power loss, DOSTEL starts in the mode running before power loss.
Information PendingEarth Applications
Information PendingOperational Protocols
DOSTEL has no separate experiments, its task is to continuously monitor the radiation behind a low shielding during the whole mission. Real time control is not required. The DOSTEL operation modes for launch and in-orbit are connected directly to the EuTEF operation modes. Switching will be performed between "single detector mode" and "single event mode". The latter will be used for about 1 day per month Once powered the instrument is fully activated and operating. Science data acquisition from DOSTEL will be performed by DHPU every 20 seconds, with a maximum data amount of 740 byte per data set, which is 3Mbyte per day. The gathered data shall be send by the EuTEF DHPU to ground once a day.