Speaker
Mr
Arlindo Marques
(EFACEC)
Description
Radiation monitors are a crucial instrument in every space mission, since they can provide vital information for all the spacecraft instruments safety, with respect to radiation flux, energies and doses.
EFACEC radiation monitors were built taken into consideration the ability to discriminate particles and energies, improving counting rate and withstand orbits e.g. GEO and interplanetary space.
The physical concept and instrument performances were simulated in GEANT4 and calibrated under electron, proton radiation beams in several particle accelerators: PSI (Switzerland), KVI (Netherlands), UCL (Louvain-La-Neuve), in order to study and refine design parameters to obtain the instrument maximum science return and performances.
MCNPX displacement damage simulations were performed to assess Mercury solar particles impact and secondaries. Results allow instrument particle fluence improvement seen around the Solar system innermost planet.
EFACEC’s radiation monitors architecture is based on silicon detectors, with aluminium and tantalum absorbers, measuring the deposited energy as the particles travel along the stack.
Particle reconstruction, type and energy, are processed in “real time” just after the particle ended its path along the stack, by energy cut method through parameterised LUT, updatable in flight. Default LUT of the instrument was defined based on the radiation test data correlated with GEANT4 simulations, for the different ranges and particles type.
Design also includes a Radfet for TID measurement up to 50kRad.
Two different test modes were integrated into the instruments to allow in flight calibration and LUT tune. One test mode is dedicated to validate the integrity of the digital part of the instrument with respect to the recognition process through pre-defined and known signatures and the other is optimized to verify the analogue chain of the system by use of known stimulus and determination of system drifts, if existing.
MFS architecture allows a particle and energy discrimination between protons (1 – 120MeV in 10 bins), electrons (0.45 – 7MeV in 7 bins), alphas (5 – 400MeV in 10 bins), nuclear species (1 – 50MeV/mg/cm2 LET in 10 bins) and a counting rate of 1e7 #/cm2/s. It provides histograms and housekeeping data with a temporal resolution from 1miute to 32minutes, programmable by TC.
MFS has an envelope of 257.3x120.0x108.0mm3, mass of 2.914kg, power consumption of 5W (average) and less than 50bps link budget.
MFS is on-board of Alphasat satellite and starts its operation in the last trimester of 2013. First results of MFS shows a shape consistent with expected results and processing data and calibration review have started.
BERM is a direct evolution of the MFS for Bepicolombo mission with improved characteristics and direct connection to the spacecraft host computer, while MFS was connected to CTTB getting from it power and commands.
BERM allows a particle and energy discrimination between protons (1 – 200MeV in 8 bins), electrons (0.3 – 10MeV in 5 bins), nuclear species (1 – 50MeV/mg/cm2 LET in 5 bins) and a counting rate of 1e7 #/cm2/s. It provides histograms and housekeeping data with a temporal resolution of 30s.
BERM has an envelope of 174.8x120.0x107.0mm3, mass of 2.143kg, power consumption of 5W (average) and less than 50bps link budget.
Communications with the host computer uses MIL-STD-1553, for housekeeping and science packets.
BERM is currently finishing its environmental qualification tests and shall be integrated into the Bepicolombo MPO during May of 2014.
Preliminary radiation calibration test was performed at PSI and results are in line with expected performance and MFS results.
EFACEC radiation monitors can fly in missions from near Earth orbit to the vicinity of Mercury. Future missions in between those extreme environments could be also addressed as around Venus planet.
EFACEC radiation monitors are evolving and it is expected to have better performance, lighter, less power and outer solar system environments, in the near future.
With this aim, RADEM is now starting with a goal of being a 1L, 1kg, 2.2W instrument. RADEM will include three detector heads, one for Protons and Heavy Ions, another for Electrons and a third one for electrons directionality. System goals are foreseen to be achieved by means of a new improved custom ASIC, evolved from the developed radiation monitors.
While MFS and BERM used FPGA’s for operations control, RADEM will be based on a microcontroller. Software will update as required a configurable anti-coincidence logic embedded in the front-end ASICs; test modes with availability of its RAW data are foreseen in very specific operating modes.
Space-wire will be used to communicate with the JUICE spacecraft host computer.
Primary author
Mr
Arlindo Marques
(EFACEC)
Co-authors
Mr
Adolfo Aguilar
(Aguilar Aerospace SL)
Mr
Joao Costa Pinto
(EFACEC)
