In-Flight Reconfiguration with System-On-Module Based Architectures for Science Instruments on Nanosatellites

For science payloads on nanosatellite missions, there is a great interest in cost-effective, reliable and state-of-the-art computing performance. Highly integrated system architectures combine reconfigurable System-on-Chip (SoC) devices, memory and peripheral interfaces in a single System-on-Module (SoM) and offer low resource requirements regarding power and mass, but moderate to high processing power capabilities. The major advantages of these architectures are flexibility, (re)programmability, modularity and module reuse. However, it is a challenge to use SoM with COTS based memories devices in a radiation sensitive environment. In order to achieve these requirements, mitigation measures, such as the use of redundant or alternative memory devices and in-flight reconfiguration, are important in terms of reliability. Reprogramming strategies e.g. partial dynamic reconfiguration and scrubbing techniques are published in the past. With a remote sensing instrument for atmospheric temperature measurements using a SRAM-based Xilinx Zynq-7000 SoM, we combine some of these techniques with supervisor circuits to select the boot image from alternative memory devices. The approach distinguishes between programmable logic and processing system reconfiguration, and enables in-flight firmware updates in the case of Single Event Effect (SEE) hazards or changing measurement conditions

In-situ estimation of ice crystal properties at the South Pole using LED calibration data from the IceCube Neutrino Observatory

The IceCube Neutrino Observatory instruments about 1 km3 of deep, glacial ice at the geographic South Pole using 5160 photomultipliers to detect Cherenkov light emitted by charged relativistic particles. A unexpected light propagation effect observed by the experiment is an anisotropic attenuation, which is aligned with the local flow direction of the ice. Birefringent light propagation has been examined as a possible explanation for this effect. The predictions of a first-principles birefringence model developed for this purpose, in particular curved light trajectories resulting from asymmetric diffusion, provide a qualitatively good match to the main features of the data. This in turn allows us to deduce ice crystal properties. Since the wavelength of the detected light is short compared to the crystal size, these crystal properties do not only include the crystal orientation fabric, but also the average crystal size and shape, as a function of depth. By adding small empirical corrections to this first-principles model, a quantitatively accurate description of the optical properties of the IceCube glacial ice is obtained. In this paper, we present the experimental signature of ice optical anisotropy observed in IceCube LED calibration data, the theory and parametrization of the birefringence effect, the fitting procedures of these parameterizations to experimental data as well as the inferred crystal properties.</p

Design and Performance of the mDOM Mainboard for the IceCube Upgrade

About 400 mDOMs (multi-PMT Digital Optical Modules) will be deployed as part of the IceCube Upgrade Project. The mDOM’s high pressure-resistant glass sphere houses 24 PMTs, 3 cameras, 10 flasher LEDs and various sensors. The mDOM mainboard design was challenging due to the limited available volume and demanding engineering requirements, like the maximum overall power consumption, a minimum trigger threshold of 0.2 photoelectrons (PE), the dynamic range and the linearity requirements. Another challenge was the FPGA firmware design, dealing with about 35 Gbit/s of continuous ADC data from the digitization of the 24 PMT channels, the control of a high speed dynamic buffer and the discriminator output sampling rate of about 1GSPS. High-speed sampling of each of the discriminator outputs at ~1 GSPS improves the leading-edge time resolution for the PMT waveforms. An MCU (microcontroller unit) coordinates the data taking, the data exchange with the surface and the sensor readout. Both the FPGA firmware and MCU software can be updated remotely. After discussing the main hardware blocks and the analog frontend (AFE) design, test results will be shown, covering especially the AFE performance. Additionally, the functionality of various sensors and modules will be evaluated

Echtzeitsystem für Phasenrücksetzanalysen und Neuro-Rückkopplungen am MEG

Modern medical imaging systems like Magnetic Resonance Tomography (MRT), Positron Emission Tomography (PET), Single Photon Emission Computed Tomography, Electroencephalography (EEG), or Magnetoencephalography (MEG) are used for the investigation of complex brain functions and their localization. In MEG magnetic fields outside the brain, caused by electrical currents due to the neural activity within the brain, can be measured with high temporal resolution [Cohen03], [Mamivuo95], [Hamlainen93]. In the field of neuroscience the MEG is e.g. used to analyze rhythmic brain activity under stimulation. Based on the high temporal resolution of the MEG simultaneously active neural populations may be identified. These measurements are commonly used in both, research and clinical applications. Existing MEG systems acquire the signals from a huge number of sensors, pre-process the signals measured by the magnetic field sensors and store them for later offline analysis. Neither instantaneous analysis of the measured data, visualization and localization of the electrical sources nor feedback stimulation is facilitated. But, these features would open up new desirable MEG applications. Real time feedback stimulation of the measured and reconstructed brain activity would be very helpful in order to scientifically explore methods for the manipulation of synchronization processes in brain. For this, a data acquisition system for a 148 channel MEG, capable of online reconstruction of the cerebral current density distribution, phase analysis and realtime feedback stimulation has been developed. The developed system is designed as an add-on for an existing BTi MAGNES-2500WH MEG. The usage of a optical splitter allows the utilization of the given fibre optic interface for parallel data acquisition of the new system. Therefore the new MEG-Online system does not affect the original MEG, but adds realtime functionality for feedback experiments and online data analysis, reconstruction and visualization. The realized hardware concept is based on three different signal processing units. The combination of the FPGA, DSP and PC architecture (hybrid system) provides sufficient computational power to fulfil the requirements. In particular, the reconstruction of the current densities of up to 10 voxels can be done within 1 ms. The developed PCI bus add-on hardware is based on a FPGA and DSP design, using the benefits from both hardware architectures. This hybrid technology board enables a standard PC to handle all time critical calculations for the realtime data acquisition, reconstruction of a cerebral current course and feedback signal generation. This enables realtime stimulations based on acquired signals or a reconstructed cerebral current time course. The 3D reconstruction and visualization of the 3-dimensional volume data is done by the PC, which hosts the powerful DAQ and pre-processing board. The control of the whole online system, the online analysis, i.e. the reconstruction of the current densities of all voxels, the phase resetting analysis and finally the visualisation is done on the PC. A user friendly application software for experiment control, data analysis and visualization has been developed. Filters, phase analysis, spectrum analysis and reconstruction algorithms are implemented. The acquired or processed data and volume sets can be saved to the hard disc for further analysis with standard packages

Dark current performance of an analog SiPM array under irradiation with cold neutrons

Research on novel approaches concerning scintillation based solid-state detectors to be used in small angle neutron scattering (SANS) experiments [1] has been triggered through low world-wide availability of the 3He gas [2], which has been the detection material of choice for most neutron detection tasks. The active area sizes of such detectors might vary between 1 m² (sometimes smaller) and 30 m² or more, depending on the instrument design. It is reasonable to stress the enormous readout and data rate concerned complexities accompanying a pixelated solid-state approach for SANS scintillator detectors, if a single “pixel” size of some mm² is considered in neutron detectors with active areas of several tens of square meters. Nevertheless, in SANS instruments requiring active areas up to 1 m², the approach based on an indirect detection of impinging cold and thermal neutrons via pixelated scintillator detectors, where the size of each “pixel” would be defined only by the dispersion of visible photons produced within the overlying scintillator material, this approach becomes feasible. An interesting candidate for the photodetector part in these detectors could be an array of analog silicon photomultipliers (SiPM). It would yield the possibility of single photon counting, low power consumption, a space resolution of at least 3×3 mm² (or less), and the possibility of acceptable photodetection performance even in presence of high magnetic fields. The main risk defined so far for using this technology in SANS scintillation detectors is their performance in hard radiation environments: in this case, under the irradiation of thermal or cold neutrons. We investigated the dark signal and breakdown voltage performances of a 12x12 array of SensL Series C SiPMs with an active area of 3x3 mm² under irradiation with cold neutrons (lambda = 5 Å, and the main neutron flux of 108 n·s-1cm-2) up to a dose of 2×1012 n·cm-2. The SiPM detectors were at all times fully operational, and the measurements were performed in-situ.[1] D. L. Price and K. Sköld "Introduction to Neutron Scattering", Methods in Experimental Physics, Volume 23, Part A, pp. 1–97, Academic Press (1986)[2] U.S. Government Accountability Office (GAO). Neutron Detectors. Alternatives to using helium-3. Technology assessment. Report to Congressional Requesters, GAO—11-753 (2011