A path towards low-cost, high-accuracy orbital object monitoring

In an increasingly crowded space environment, precise predictions of space object trajectories are of paramount importance in order to avoid collisions and unnecessary evasive manoeuvres. Laser-optical range measurements are a promising approach to attain the high quality input data required for good predictions. However, while laser ranging to space debris objects is possible and has been demonstrated by several observatories, the technique requires expensive, high-power lasers and large aperture telescopes, to detect the faint diffuse reflections from the surface of the targets. Therefore, we propose to routinely equip satellites, rocket bodies and potential mission related debris with small laser retroreflectors. With these, precise position measurements can be obtained much more easily, not only during the operational phase, but also after the mission. Such equipment could possibly be mandated by regulatory bodies like number plates in road vehicles. However, if the additional impact and cost of the technology is small enough, satellite owners and operators may even choose to include retroreflectors in their designs voluntarily and for their own benefit. This seems especially likely in the case of large constellations, in which a precise tracking of defunct satellites is of great importance to protect the other objects in the constellation. In this contribution we will present recent developments at DLR Stuttgart to facilitate a more wide-spread introduction of this technology. The miniSLR system is a small, fully automated laser ranging ground station that can be used to track and range to objects equipped with retroreflectors. It is completely integrated in a box of 120 cm x 180 cm footprint and can be transported to a remote observation site after full integration and testing at the home institution. If produced in a small series, it may become the backbone of a global low-cost satellite laser ranging network for space traffic monitoring services. Furthermore, new types of retroreflectors are currently under development, which may allow a unique identification of space objects using laser ranging. In combination, these technologies can contribute to a more controlled and thus safer space environment

The MSW effect in a fluctuating matter density

We consider the effect on matter-enhanced neutrino flavor transformation of a randomly fluctuating, delta-correlated matter density. The fluctuations will produce a distribution of neutrino survival probabilities. We find the mean and variance of the distribution for the case of solar neutrinos, and discuss the possibility of placing a limit on solar density fluctuations using neutrino data.Comment: 20 LaTeX pages plus 24 Postscript figures; submitted to Phys. Rev. D; also available at http://nucth.physics.wisc.edu/preprints/mad-nt-96-01.tar.g

Challenges in the implementation of the EAACI AIT guidelines:A situational analysis of current provision of allergen immunotherapy

Purpose:The European Academy of Allergy and Clinical Immunology (EAACI) has produced Guidelines on Allergen Immunotherapy (AIT). We sought to gauge the preparedness of primary care to participate in the delivery of AIT in Europe.Methods:We undertook a mixed-methods, situational analysis. This involved a purposeful literature search, and two surveys: one to primary care clinicians and the other to a wider group of stakeholders across Europe.Results:The 10 papers identified all pointed out gaps or deficiencies in allergy care provision in primary care. The surveys also highlighted similar concerns, particularly in relation to concerns about lack of knowledge, skills, infrastructural weaknesses, reimbursement policies and communication with specialists as barriers to evidence-based care. Almost all countries (92%) reported the availability of AIT. In spite of that, only 28% and 44% of the countries reported the availability of guidelines for primary care physicians and specialists, respectively. Agreed pathways between specialists and primary care physicians were reported as existing in 32-48% of countries. Reimbursement appeared to be an important barrier as AIT was only fully reimbursed in 32% of countries. Additionally, 44% of respondents considered accessibility to AIT and 36% stating patient costs were barriers.Conclusions:Successful working with primary care providers is essential to scaling-up AIT provision in Europe, but to achieve this the identified barriers must be overcome. Development of primary care interpretation of guidelines to aid patient selection, establishment of disease management pathways and collaboration with specialist groups are required as a matter of urgency

Conceptual Study on Laser Networks for Near‐Term Collision Avoidance for Space Debris in the Low Earth Orbit

Due to the increasing amount of space debris, several laser‐based concepts for orbit modification have been proposed in the recent years. Since the sparse availability of pulsed lasers with high energy (> 10 kJ) seems to render laser‐ablative debris nudging for collision avoidance into a solution only for the long run, alternative options which can be realized earlier are mandatory to counter the rapidly increasing number of space debris in low Earth orbit. In this regard, high‐power CW lasers (> 10 kW) have been proposed in the past for debris nudging by photon pressure. With momentum coupling being 3 – 4 orders of magnitude lower than in the case of laser ablation, this might appear as a poor alternative at first glance, but the opposite is the case when a greater number of laser stations are combined forming an international network for laser tracking and momentum transfer (LTMT). From this viewpoint, we report on our findings on photon momentum transfer to space debris from our work performed under the conceptual study LARAMOTIONS (SSA P3‐SST‐XV) funded by the European Space Agency (ESA) in the framework of ESA’s Space Situational Awareness Program. Commercial availability of high power CW lasers allows for the setup of a network of relatively cost‐efficient laser stations in the next decade. Such an LTMT network would serve for both momentum transfer to space debris as well as for high precision laser tracking as a prerequisite for conjunction alert assessment and high‐power laser beam pointing. Depending on the network size, geographical distribution of stations, orbit parameters and remaining time to conjunction, multi‐pass irradiation enhances the efficiency of photon momentum coupling by 1 – 2 orders of magnitude and has the potential to eventually yield a promisingly significant reduction of the collision rate in low Earth orbit

Capturing the sounds of an urban greenspace

Acoustic data can be a source of important information about events and the environment in modern cities. To date, much of the focus has been on monitoring noise pollution, but the urban soundscape contains a rich variety of signals about both human and natural phenomena. We describe the CitySounds project, which has installed enclosed sensor kits at several locations across a heavily used urban greenspace in the city of Edinburgh. The acoustic monitoring components regularly capture short clips in real-time of both ultrasonic and audible noises, for example encompassing bats, birds and other wildlife, traffic, and human. The sounds are complemented by collecting other data from sensors, such as temperature and relative humidity. To ensure privacy and compliance with relevant legislation, robust methods render completely unintelligible any traces of voice or conversation that may incidentally be overheard by the sensors. We have adopted a variety of methods to encourage community engagement with the audio data and to communicate the richness of urban soundscapes to a general audience

Stereoscopic Light Curve Analysis of Space Debris Objects

As an object in orbit rotates, the amount of sunlight which it reflects towards Earth varies. When measured by an observer on the ground, these perceived changes in brightness are know as a light curve. The shape of a light curve is determined, in part, by the attitude and rotation state of the object but also depends on a great many other parameters. Research into how useful information might be recovered from an object’s light curve is an active area of research. If solved it would have important implications in the fields of orbit propagation and active space debris removal. One possible route to better understanding light curves is through stereoscopic observation, where two observers simultaneously measure the brightness changes from different vantage points. This thesis documents the planning and execution of a collaborative campaign of stereoscopic light curve acquisition between the German Aerospace Center’s Institute of Technical Physics and Institute for Planetary Research. In these experiments, the light curves of space debris objects in MEO were observed using a pair of telescopes separated by a baseline of 1595 km. These two observatories being, the Uhlandshöhe Forschungsobservatorium (UFO) in Stuttgart, Germany and the Centro Astronómico Hispano-Alemán (CAHA) in Almeriá province, Spain. Also documented is the complete development of Raxus Prime 2.0, a program for performing the analysis and simulation of stereoscopic light curves. An early attempt at estimating the spin state of space debris objects from stereoscopic light curves using Raxus Prime 2.0 is detailed

Concept for a new minimal SLR system

To improve the global coverage of SLR measurements and to keep up with the growing number of missions, new SLR stations will be needed around the world. However, local scientific communities often find it hard to acquire the funding necessary to deploy and operate a conventional SLR station. German Aerospace Center is currently developing a new minimal SLR system with the goal to improve this situation. The miniSLR system is fully integrated in a box smaller than 2x2x1.5 metres and consists of only a minimal set of devices indispensable for standard SLR operation. A simple design and the use of standard components keep the investment costs at a minimum and facilitate on-site maintenance. Transmitter and receiver telescopes are located on the two sides of a direct drive Alt-Az mount. The detector package and the laser system are installed on the mount itself to avoid a coudé path. The 100 kHz laser ranging technology developed for the Stuttgart SLR station is used here as well and allows for a small yet powerful laser that can be integrated on the mount. A 19 inch rack contains all other components, such as the control PC, event timer and the time source. The whole system is fully sealed and air-conditioned. Completely automatic operation is envisaged to reduce running costs and operation in remote areas. This contribution will present the current status of the design and first hardware tests

Spectral Light Curve Simulation for Parameter Estimation from Space Debris

Characterisation of space debris has become a fundamental task to facilitate sustainable space operations. Ground-based surveillance provides the means to extract key attributes from spacecraft. However, signal inversion attempts are generally under-constrained, which is why an increase in measurement channels through multispectral observations is expected to benefit parameter estimation. The current approach to simulating space debris observation at the Institute of Technical Physics of the German Aerospace Centre (DLR) in Stuttgart relies on monochromatic images taken from the POV-Ray render engine to form light curve signals. Rendered scenes are generated based on the location of an observer by propagating a target’s orbit and rotation. This paper describes the simulation of spectral light curves through the extension of DLR’s Raxus Prime simulation environment. Light reflections are computed using the Mitsuba2 spectral render engine, while atmospheric attenuation is accounted for by the radiative transfer library libRadTran. A validation of the simulator was achieved using multispectral measurements, carried out at the Uhlandshöhe research observatory in Stuttgart. Measured and synthetic data were found to be in agreement based on an RMS error <1% of the total measured signal count. Further, simulated spectral products were used to determine a target’s surface material composition and rotation state and examine aspects of laser ranging to non-cooperative targets