Space Detection Research Articles

MODULATION OF GALACTIC ELECTRONS IN THE HELIOSPHERE DURING THE UNUSUAL SOLAR MINIMUM OF 2006–2009: A MODELING APPROACH

The last solar minimum activity period, and the consequent minimum modulation conditions for cosmic rays, was unusual. The highest levels of Galactic protons were recorded at Earth in late 2009 in contrast to expectations. A comprehensive model was used to study the proton modulation for the period from 2006 to 2009 in order to determine what basic processes were responsible for solar modulation during this period and why it differs from proton modulation during previous solar minimum modulation periods. This established model is now applied to studying the solar modulation of electron spectra as observed for 80 MeV–30 GeV by the PAMELA space detector from mid-2006 to the end of 2009. Over this period the heliospheric magnetic field had decreased significantly until the end of 2009 while the waviness of the heliospheric current sheet decreased moderately and the observed electron spectra increased by a factor of ~1.5 at 1.0 GeV to ~3.5 at 100 MeV. In order to reproduce the modulation evident from seven consecutive semesters, the diffusion coefficients had to increase moderately while maintaining the basic rigidity dependence. It is confirmed that the main diffusion coefficients are independent of rigidity below ~0.5 GV, while the drift coefficient had to be reduced below this value. The 2006–2009 solar minimum epoch indeed was different than previously observed minima, at least since the beginning of the space exploration era. This period could be called diffusion-dominated as was also found for the modulation of protons.

Space detectors for gamma rays (100 MeV–100 GeV): From EGRET to Fermi LAT

The design of spaceborne high-energy (E>100MeV) γ-ray detectors depends on two principal factors: (1) the basic physics of detecting and measuring the properties of the γ rays; and (2) the constraints of operating such a detector in space for an extended period. Improvements in technology have enabled major advances in detector performance, as illustrated by two successful instruments, EGRET on the Compton Gamma Ray Observatory and LAT on the Fermi Gamma-ray Space Telescope. L'architecture des détecteurs spatiaux de rayons gamma de hautes énergies (E>100MeV) dépend de deux facteurs principaux : (1) les principes physiques de base permettant la détection et la mesure des propriétés des rayons gamma et (2) les contraintes de fonctionnement de tels détecteurs dans l'espace sur de longues durées. Les progrès techniques ont permis des avancées majeures concernant les performances des détecteurs telles qu'illustrées par les deux instruments que sont EGRET à bord du Compton Gamma Ray Observatory et LAT à bord du Fermi Gamma-ray Space Telescope.

Physics Goals and Status of JEM-EUSO and its Test Experiments

The JEM-EUSO mission aims to explore the origin of the extreme energy cosmic rays (EECRs) through the observation of air-shower fluorescence light from space. The superwide- field telescope looks down from the International Space Station onto the night sky to detect UV photons (fluorescence and Cherenkov photons) emitted from air showers. Such a space detector offers the remarkable opportunity to observe a huge volume of atmosphere at once and will achieve an unprecedented statistics within a few years of operation. Several test experiments are currently in operation: e.g., one to observe the fluorescence background from the edge of the Atmosphere (EUSO-Balloon), or another to demonstrate on ground the capability of detecting air showers with a EUSO-type telescope (EUSO-TA). In this contribution a short review on the scientific objectives of the mission and an update of the instrument definition, performances and status, as well as status of the test experiments will be given.

SU‐E‐T‐35: A General Fill Factor Definition Serving to Characterise the MLC Misalignment Detection Capabilities of Two‐Dimensional Detector Arrays

Purpose:To present a general definition of the fill factor realistically characterizing the “field coverage”, i.e. the MLC misalignment detection capabilities of a detector array.Methods:According to Gago‐Arias et al.1 the fill factor of a 2D array is defined as the ratio of the area enclosed by the FWHM of the fluence response function KM(x) of a single detector and its cell area defined by the detector spacing. More generally ‐ accounting also for the possible overlap between FWHM's of neighboured detectors ‐ the fill factor is here defined as that fraction of the sum of the detector cell areas in which a defined MLC misalignment is detectable when the induced percentage signal changes exceed a detection threshold d. Ideally the generalized fill factor may reach 100 %. With user code EGS_chamber and a 2 MeV photon slit beam 0.25 mm wide, both types of the fill factor were calculated for an array with total cell area 100 cm2 for chamber widths 1–9 mm, using =1mm, d=5%.Results:For single chamber width 5 mm, fill factors were 0.49 (FWHM) and 0.61 (generalized). For chamber width 2 mm the FWHM fill factor was 0.13 whereas the generalized fill factor was 0.32. For chamber widths above 7 mm, the FWHM fill factor exceeds unity, and the general fill factor is exactly 1.00.Conclusions:An updated fill factor definition is introduced which, as a generalization of the FWHM‐based definition, more closely estimates the performance of small array chambers and gives a realistic value in the case of overlapping sensitive areas of neighboured chambers.

TU-F-CAMPUS-T-02: Vernier Picket Fence Test: A Non-Imaging Method to Localize the Radiation Isocenter with Submillimeter Accuracy

Purpose: The purpose of this study is to propose a new non-imaging method to localize the radiation isocenter with submillimeter accuracy. Methods: The Vernier picket fence (VPF) is a multileaf collimator (MLC) picket fence sequence in which the fence spacing is 1/N smaller than the detector spacing of the QA phantom, where N is the magnification factor, typically set to 10 or 20. Similar to reading a Vernier caliper, the user can easily achieve the resolution of 1/N of the detector spacing by visually inspecting the maximum signal. To achieve higher accuracy, a Gaussian model was used to interpolate the peak position, which can fall between adjacent detectors. In two separate tests, precise MLC offsets and imprecise couch offsets were applied to a 2D detector array (MapCheck, Sun Nuclear Corp., Melbourne, Florida) to introduce setup errors. Two vertical VPF fields were delivered with collimator angles at 0° and 90° to detect the lateral and longitudinal setup errors, respectively. For a rotational QA phantom, an additional lateral VPF field is needed to detect the vertical setup error for three-dimensional capabilities. Results: With N set to 20 and a detector spacing of 5 mm for MapCheck, the resolution of the VPF's visual analysis is 0.25 mm. With the Gaussian interpretation, the VPF can achieve an accuracy of 0.02 mm, as shown by the MLC offset test. The couch offset test measured the couch hysteresis and demonstrated that the setup error detected by the VPF differed from the ExacTrac™ (Brainlab AG, Feldkirchen, Germany) optical tracking by 0.055 mm in the lateral direction and 0.041 mm in the longitudinal direction on average. The VPF was also shown to be feasible in the vertical direction as well. Conclusion: This study verified the VPF as a non-imaging method to localize the radiation isocenter with submillimeter accuracy. Funding is in part by the Portland Chapter of the Achievement Rewards for College Scientists. The content is solely the responsibility of the authors, and does not necessarily represent the official views of the sponsors. The authors declare no conflict of interest.

SU‐E‐P‐24: Simplified EDW Profile Measurements Using Two Commonly Available Detector Arrays

Purpose:Enhanced dynamic wedge (EDW) profiles are needed as part of the commissioning of a treatment planning system. This work compares the acquisition of EDW profiles using a linear diode array (LDA) with two commonly used detector arrays available in the clinics, with the goal of identifying the simplest approach for these measurements.Methods:The measurements of EDW profiles were performed on a Varian TrueBeam linear accelerator for 6, 10, and 18 MV photon beams for all seven wedge angles at four depths. The measurements were done using the LDA 99 in Blue Phantom2 (IBA Dosimetry), and IC Profiler and MapCHECK2 (Sun Nuclear) in solid water phantoms. The water phantom was set up at 100 cm SSD, whereas the two other devices were set up at 75 cm due to the size limitations of the devices. The largest possible field size was used. The average and maximum percentage differences were examined within the central 90% of the field and in the penumbra.Results:Dose profiles measured with IC Profiler were in a good agreement with LDA 99 data. The average percentage difference within the field did not exceed 0.5% for all energies. MapCHECK2 measurements matched well with LDA 99 for 10 and 18 MV (within 0.3%) with discrepancies of up to 1.4% observed for the 6 MV beam. The maximum percentage differences for both devices in the penumbra exhibited larger variations than LDA 99 results due to differences in detector spacing and high dose gradient, as expected.Conclusion:Common linac QA devices such as IC Profiler or MapCHECK2 provide EDW beam profile data of reasonable accuracy as compared to measurements performed using a linear diode array in a water phantom, saving the expense and time involved in acquiring and setting up a LDA.

TH-CD-304-10: A Method for Correcting Ion Recombination Effects in OCTAVIUS 1000 SRS Measurements

Purpose: PTW's Octavius 1000 SRS array performs IMRT QA measurements with liquid filled ionization chambers to allow closer detector spacing and higher resolution. Increased density of liquid relative to air, leads to increased ion recombination effects, which are proportional to dose/pulse experienced at the detectors. During IMRT QA, dose/per pulse will vary across the array, leading to varying collection efficiencies. Magnitudes of recombination effects were investigated and a method was developed to correct them in QA measurements. Methods: The OCTAVIUS 1000 SRS was used to measure different IMRT plans using varying dose/pulse and results were normalized to air filled chamber measurements to obtain collection efficiencies. Regression analysis was performed to relate collection efficiency to dose/pulse. Matlab software was developed to correct IMRT QA measurements using these correlations. Measurements were performed on a Truebeam equipped with high-definition MLC, using 6MV and 10FFF RapidArc plans. Plans were measured in the OCTAVIUS 4D system, which measures dose in time intervals. Dose/time was converted to dose/pulse using pulse repetition information. Collection efficiency to dose/pulse correlations were used to correct measured dose. 3D gamma analysis was performed on plans with and without corrections. Results: Liquid filled ionization chamber collection efficiency correlated linearly to dose/pulse with slopes of 2.15%/(mGy/pulse) for 6MV and 5.74%/(mGy/pulse) for 10FFF. After corrections, average gamma pass rates improved by [0.02%,0.06%,0.24%] for 6MV and [0.19%,0.54%,2.01%] for 10FFF using [3%/3mm,2%/2mm,1%/1mm] criteria. Maximum changes in gamma pass rates were [0.1%,0.3%,0.5%] for 6MV and [0.4%,0.8%,5.1%] for 10FFF using [3%/3mm,2%/2mm,1%/1mm] criteria. Conclusion: OCTAVIUS 1000 SRS ion recombination effects have little effect on 6MV measurements. However, the effect is larger for higher dose/pulse unflattened beams when using tighter gamma tolerances, as is common for SRS/SBRT. This researched was supported by PTW.

Towards a gravitational wave observatory designer: sensitivity limits of spaceborne detectors

The most promising concept for low frequency (millihertz to hertz) gravitational wave observatories are laser interferometric detectors in space. It is usually assumed that the noise floor for such a detector is dominated by optical shot noise in the signal readout. For this to be true, a careful balance of mission parameters is crucial to keep all other parasitic disturbances below shot noise. We developed a web application that uses over 30 input parameters and considers many important technical noise sources and noise suppression techniques to derive a realistic position noise budget. It optimizes free parameters automatically and generates a detailed report on all individual noise contributions. Thus one can easily explore the entire parameter space and design a realistic gravitational wave observatory. In this document we describe the different parameters, present all underlying calculations, and compare the final observatory’s sensitivity with astrophysical sources of gravitational waves. We use as an example parameters currently assumed to be likely applied to a space mission proposed to be launched in 2034 by the European Space Agency. The web application itself is publicly available on the Internet at http://spacegravity.org/designer. Future versions of the web application will incorporate the frequency dependence of different noise sources and include a more detailed model of the observatory’s residual acceleration noise.

Accuracy Analysis of Freeway Traffic Speed Estimation Based on the Integration of Cellular Probe System and Loop Detectors

Traffic speed estimation is a fundamental task for traffic management centers and a critical element of intelligent transportation systems. For this purpose, various sensors are used to collect traffic speed information. The cellular probe system is gaining market penetration and becomes a newly effective and practical traffic speed measurement technique. In this article, the handoff system, one type of cellular probe technology, is used for speed detection. However, the handoff coverage size is usually variable and consecutive handoff points are usually far apart on a freeway. To improve the accuracy of speed estimation, this article proposes a travel-time-based method to aggregate the estimation results of the cellular probe system and loop detectors. For the purpose of a rigorous analysis, data are generated from microscopic simulation models of virtual one-direction freeway segments under various traffic conditions. Thus, the correlations between estimation accuracy and handoff distance, traffic condition, and the number of loop detectors are evaluated and analyzed. The results show that best performance is achieved with the shortest handoff distance. The aggregation of estimated speeds from cellular probe system and loop detectors can improve the speed estimation accuracy by taking advantage of each sensor if the space of loop detectors is more than 500 m. Also, an increasing number of loop detectors will improve the accuracy. Furthermore, the improvement of integration accuracy is much better under free flow conditions than under congested conditions.

Gravitational waves from a particle in circular orbits around a rotating black hole to the 11th post-Newtonian order

We compute the energy flux of the gravitational waves radiated by a particle of mass |$\mu$| in circular orbits around a rotating black hole of mass |$M$| up to the 11th post-Newtonian order (11PN), i.e. |$v^{22}$| beyond the leading Newtonian approximation where |$v$| is the orbital velocity of the particle [L. Blanchet, Living Rev. Relativity 5, 3 (2002)]. By comparing the PN results for the energy flux with high-precision numerical results in black hole perturbation theory, we find the region of validity in the PN approximation becomes larger with increasing PN order. If one requires the relative error of the energy flux in the PN approximation to be less than |$10^{-5}$|⁠, the energy flux at 11PN (4PN) can be used for |$v\lessapprox 0.33$| (⁠|$v \lessapprox 0.13$|⁠). The region of validity can be further extended to |$v\lessapprox 0.4$| if one applies a resummation method to the energy flux at 11PN. We then compare the orbital phase during a two-year inspiral from the PN results with the high-precision numerical results. We find that, for late (early) inspirals when |$q\le 0.3$| (⁠|$q\le 0.9$|⁠), where |$q$| is the dimensionless spin parameter of the black hole, the difference in the phase is less than 1 (⁠|$10^{-4}$|⁠) rad and hence these inspirals may be detected in the data analysis for space detectors such as eLISA|$/$|New Gravitational wave Observatory by the PN templates. We also compute the energy flux radiated into the event horizon for a particle in circular orbits around a non-rotating black hole at 22.5PN, i.e. |$v^{45}$| beyond the leading Newtonian approximation, which is comparable to the PN order derived in our previous work for the energy flux to infinity at 22PN.

Measurement‐guided volumetric dose reconstruction for helical tomotherapy

It was previously demonstrated that dose delivered by a conventional linear accelerator using IMRT or VMAT can be reconstructed — on patient or phantom datasets — using helical diode array measurements and a technique called planned dose perturbation (PDP). This allows meaningful and intuitive analysis of the agreement between the planned and delivered dose, including direct comparison of the dose‐volume histograms. While conceptually similar to modulated arc techniques, helical tomotherapy introduces significant challenges to the PDP formalism, arising primarily from TomoTherapy delivery dynamics. The temporal characteristics of the delivery are of the same order or shorter than the dosimeter's update interval (50 ms). Additionally, the prevalence of often small and complex segments, particularly with the 1 cm Y jaw setting, lead to challenges related to detector spacing. Here, we present and test a novel method of tomotherapy‐PDP (TPDP) designed to meet these challenges. One of the novel techniques introduced for TPDP is organization of the subbeams into larger subunits called sectors, which assures more robust synchronization of the measurement and delivery dynamics. Another important change is the optional application of a correction based on ion chamber (IC) measurements in the phantom. The TPDP method was validated by direct comparisons to the IC and an independent, biplanar diode array dosimeter previously evaluated for tomotherapy delivery quality assurance. Nineteen plans with varying complexity were analyzed for the 2.5 cm tomotherapy jaw setting and 18 for the 1 cm opening. The dose differences between the TPDP and IC were 1.0%±1.1% and 1.1%±1.1%, for 2.5 and 1.0 cm jaw plans, respectively. Gamma analysis agreement rates between TPDP and the independent array were: 99.1%±1.8% (using 3% global normalization/3 mm criteria) and 93.4%±7.1% (using 2% global/2 mm) for the 2.5 cm jaw plans; for 1 cm plans, they were 95.2%±6.7% (3% G/3) and 83.8%±12% (2% G/2). We conclude that TPDP is capable of volumetric dose reconstruction with acceptable accuracy. However, the challenges of fast tomotherapy delivery dynamics make TPDP less precise than the IMRT/VMAT PDP version, particularly for the 1 cm jaw setting.PACS number: 87.55Qr

The RPC space resolution with the charge centroid method

RPC detectors were originally developed to exploit the very good intrinsic time resolution of the plane geometry and have been used as muon trigger in most of their high energy physics applications, disregarding the detector space resolution. Due to the high luminosity of future colliders, new experiments will be very demanding in terms of momentum selection of the muon spectrometer. For this reason, trigger detectors will be required to have a sub-millimeter space resolution as well as a sub-nanosecond time resolution. RPCs are good candidates for these applications, as it can be shown that they have excellent intrinsic space resolution, while the actual results depend mostly on the front-end electronics performance. Here we present a beam test carried out on a small size RPC. The results are consistent with a space resolution of ∼ 130 μm.

Cavity-enhanced laser cooling for Yb^3+-doped fluoride crystal using a low-power diode laser

A diode laser with a power of 178 mW is used to pump a 2.2% (wt.) Yb3+-doped YLiF4 crystal in an optical extracavity, and a resonant cavity-enhanced laser cooling for Yb3+-doped fluoride crystal is proposed and demonstrated. The pump laser enhancement factor so far obtained is up to 8.6 with the resonant cavity. Given that 82% of incident laser power is absorbed, the cooling efficiency is calculated as 1.08% and the temperature drop is 12.3 K/W. Accordingly, the combination of the diode laser—featuring low cost, long life, small weight, compact volume, and low power consumption—and the simple resonant cavity for laser cooling of solids is promising in some important applications in optical refrigeration of space sensors and detectors, etc.

Poster — Thur Eve — 17: In‐phantom and Fluence‐based Measurements for Quality Assurance of Volumetric‐driven Adaptation of Arc Therapy

During volumetric modulated arc therapy (VMAT) of head and neck cancer, some patients lose weight which may result in anatomical deviations from the initial plan. If these deviations are substantial a new treatment plan can be designed for the remainder of treatment (i.e., adaptive planning). Since the adaptive treatment process is resource intensive, one possible approach to streamlining the quality assurance (QA) process is to use the electronic portal imaging device (EPID) to measure the integrated fluence for the adapted plans instead of the currently‐used ArcCHECK device (Sun Nuclear). Although ArcCHECK is recognized as the clinical standard for patient‐specific VMAT plan QA, it has limited length (20 cm) for most head and neck field apertures and has coarser detector spacing than the EPID (10 mm vs. 0.39 mm). In this work we compared measurement of the integrated fluence using the EPID with corresponding measurements from the ArcCHECK device. In the past year nine patients required an adapted plan. Each of the plans (the original and adapted) is composed of two arcs. Routine clinical QA was performed using the ArcCHECK device, and the same plans were delivered to the EPID (individual arcs) in integrated mode. The dose difference between the initial plan and adapted plan was compared for ArcCHECK and EPID. In most cases, it was found that the EPID is more sensitive in detecting plan differences. Therefore, we conclude that EPID provides a viable alternative for QA of the adapted head and neck plans and should be further explored.

Influence of light source-detector spacing on shape of probability density functions of scattering angles in laser Doppler flowmetry.

Analytical models, describing laser Doppler flowmetry and its derived applications, are based on fundamental assumptions of photon scattering angles. It is shown by means of Monte Carlo simulations that, even in the case these assumptions are correct, the presence of a specific source-detector configuration may bias the shape of the probability density functions describing scattering angle behavior. It is found that these biased shapes are generated by selective filtering of photons induced by a particular source-detector configuration. In some specific cases, this phenomenon might invalidate laser Doppler analytical models.

Cosmic Gamma-Ray Spectroscopy

AbstractPenetrating gamma-rays require complex instrumentation for astronomical spectroscopy measurements of gamma-rays from cosmic sources. Multiple-interaction detectors in space combined with sophisticated post-processing of detector events on ground have lead to a spectroscopy performance which is now capable to provide new astrophysical insights. Spectral signatures in the MeV regime originate from transitions in the nuclei of atoms (rather than in their electron shell). Nuclear transitions are stimulated by either radioactive decays or high-energy nuclear collisions such as with cosmic rays. Gamma-ray lines have been detected from radioactive isotopes produced in nuclear burning inside stars and supernovae, and from energetic-particle interactions in solar flares. Radioactive-decay gamma-rays from 56Ni directly reflect the source of supernova light. 44Ti is produced in core-collapse supernova interiors, and the paucity of corresponding 44Ti gamma-ray line sources reflects the variety of dynamical co...

Dynamic engagement of human motion detectors across space-time coordinates.

Motion detection is a fundamental property of the visual system. The gold standard for studying and understanding this function is the motion energy model. This computational tool relies on spatiotemporally selective filters that capture the change in spatial position over time afforded by moving objects. Although the filters are defined in space-time, their human counterparts have never been studied in their native spatiotemporal space but rather in the corresponding frequency domain. When this frequency description is back-projected to spatiotemporal description, not all characteristics of the underlying process are retained, leaving open the possibility that important properties of human motion detection may have remained unexplored. We derived descriptors of motion detectors in native space-time, and discovered a large unexpected dynamic structure involving a >2× change in detector amplitude over the first ∼100 ms. This property is not predicted by the energy model, generalizes across the visual field, and is robust to adaptation; however, it is silenced by surround inhibition and is contrast dependent. We account for all results by extending the motion energy model to incorporate a small network that supports feedforward spread of activation along the motion trajectory via a simple gain-control circuit.

Continuous‐time spatially explicit capture–recapture models, with an application to a jaguar camera‐trap survey

SummaryMany capture–recapture surveys of wildlife populations operate in continuous time, but detections are typically aggregated into occasions for analysis, even when exact detection times are available. This discards information and introduces subjectivity, in the form of decisions about occasion definition.We develop a spatiotemporal Poisson process model for spatially explicit capture–recapture (SECR) surveys that operate continuously and record exact detection times. We show that, except in some special cases (including the case in which detection probability does not change within occasion), temporally aggregated data do not provide sufficient statistics for density and related parameters, and that when detection probability is constant over time, our continuous‐time (CT) model is equivalent to an existing model based on detection frequencies. We use the model to estimate jaguar density from a camera‐trap survey and conduct a simulation study to investigate the properties of a CT estimator and discrete‐occasion estimators with various levels of temporal aggregation. This includes investigation of the effect on the estimators of spatiotemporal correlation induced by animal movement.The CT estimator is found to be unbiased and more precise than discrete‐occasion estimators based on binary capture data (rather than detection frequencies) when there is no spatiotemporal correlation. It is also found to be only slightly biased when there is correlation induced by animal movement, and to be more robust to inadequate detector spacing, while discrete‐occasion estimators with binary data can be sensitive to occasion length, particularly in the presence of inadequate detector spacing.Our model includes as a special case a discrete‐occasion estimator based on detection frequencies, and at the same time lays a foundation for the development of more sophisticated CT models and estimators. It allows modelling within‐occasion changes in detectability, readily accommodates variation in detector effort, removes subjectivity associated with user‐defined occasions and fully utilizes CT data. We identify a need for developing CT methods that incorporate spatiotemporal dependence in detections and see potential for CT models being combined with telemetry‐based animal movement models to provide a richer inference framework.

Microparticle impact calibration of the Arrayed Large-Area Dust Detectors in INterplanetary space (ALADDIN) onboard the solar power sail demonstrator IKAROS

The Arrayed Large-Area Dust Detectors in INterplanetary space (ALADDIN) is an array of polyvinylidene fluoride (PVDF) based dust detectors aboard the solar power sail demonstrator named IKAROS (Interplanetary Kite-craft Accelerated by Radiation Of the Sun). The total sensor area of ALADDIN (0.54m2) is the world׳s largest among the past PVDF-based dust detectors. IKAROS was launched in May 2010 and then ALADDIN measured cosmic dust impacts for 16 months while orbiting around between 0.7 and 1.1 AU. The main scientific objective of ALADDIN is to reveal number density of ≥10-μm-sized dust in the zodiacal cloud with much higher time-space resolution than that achieved by any past in-situ measurements. The distribution of ≥10-μm-sized dust can be also observed mainly with the light scattering by optical instruments. This paper gives the scientific objectives, the instrumental description, and the results of microparticle impact calibration of ALADDIN conducted in ground laboratories. For the calibration tests we used Van de Graaf accelerators (VdG), two-stage light gas guns (LGG), and a nano-second pulsed Nd:YAG laser (nsPL). Through these experiments, we obtained depolarization charge signal caused by hypervelocity impacts or laser irradiation using the flight spare of 20-μm-thick PVDF sensor and the electronics box of ALADDIN. In the VdG experiment we accelerated iron, carbon, and silver microparticles at 1–30km/s, while in the LGG experiment we performed to shoot 100׳s-μm-sized particles of soda-lime glass and stainless steel at 3–7km/s as single projectile. For interpolation to ≥10-μm size, we irradiated infrared laser at the energy of 15–20mJ directly onto the PVDF sensor. From the signal analysis, we developed a calibration law for estimation of masses of impacted dust particles. The dynamic range of ALADDIN corresponds from 9×10−14kg to 2×10−10kg (4−56μm in diameter at density of 2.0g/cm3) at the expected impact velocity of 10km/s at 1 AU on the IKAROS inbound orbit. It was found that ALADDIN has ability to measure spatial densities of interplanetary dust particles larger than 10μm in size by setting the sensor threshold to an output voltage of 1V.

Electrical signatures of hypervelocity impact plasma with applications in in-situ particle detection

Hypervelocity impacts of micrometeoroid and space debris particles can produce a highly transient plasma cloud that shows a spectrum of distinct electrical phenomena ranging from charge production to electrostatic field and electromagnetic wave generation. The coupling of these effects to electrical probes can be used as a means of in-situ debris detection to monitor the polluted orbits around the Earth. In the past, some detectors were built mainly for the detection of natural dust populations in space, such as a long heritage of charge collection detectors. In addition, several radio astronomy and ambient plasma instruments that were not specifically dedicated to particle detection revealed impact-induced anomalies during interplanetary missions. Most of them were explained by the interaction of electrically sensitive probes with free charges produced upon impact. For the application in low Earth orbits, one needs to take into account, that the man-made debris population differs from natural populations in many regards, as does the plasma environment between interplanetary space and in orbits close to Earth. The paper at hand gives a summary of detectors with flight heritage and devises a first concept for in situ space debris detectors in low Earth orbit by exploiting past experience with dust detectors in deep space.