The high-fidelity re-entry break-up simulation software SCARAB (SpaceCraft Atmospheric Re-entry and Aerothermal Break-up) is currently being upgraded with new models for aerothermodynamics and material ablation. The capabilities of SCARAB are extended to improve the support of Design-for-Demise (D4D) methodology modelling and uncertainty quantification. A set of newly implemented features for the so-called measurement evaluation support (MES) provide the functionality to rebuild static flow conditions of wind tunnel experiments and Computational Fluid Dynamics (CFD) simulations and extend the SCARAB re-entry simulation with options for fixed attitude and reference trajectory input. The new models implemented are validated with recent data from wind tunnel experiments, re-entry observations and CFD, using the new MES capabilities. This paper provides an overview on the new SCARAB models and extended functionality.

The concern about the on-ground risk caused by spacecraft fragments surviving atmospheric re-entry has significantly grown during the past decade, resulting in numerous activities of the space community like re-entry simulation tool development, improvement, and validation, as well as research for design-for-demise (D4D). The purpose of the first group is to increase the confidence in numerical re-entry risk predictions, while the second activity aims to develop new spacecraft design techniques which are likely to improve the demise behavior significantly.

In recent studies thermospheric densities and cross-winds have been derived from linear acceleration measurements of the gradiometer on board the GOCE satellite. Our current work is aimed at analyzing also the angular accelerations, in order to improve the thermosphere density and wind data by allowing for the estimation of more unknown parameters. On this poster an overview is provided of the modeling efforts involved in isolating the aerodynamic torque. The intermediate result is a comparison of modeled and measured torques. Each box contains a plot of the torque from a specific source, compared to the measured torque, on October 16th, 2013. A short description of the model for each torque is also provided.

Today, there is little knowledge on the attitude state of decommissioned intact objects in Earth orbit. Observational means have advanced in the past years, but are still limited with respect to an accurate estimate of motion vector orientations and magnitude. Especially for the preparation of Active Debris Removal (ADR) missions as planned by ESA’s Clean Space initiative or contingency scenarios for ESA spacecraft like ENVISAT, such knowledge is needed. ESA's “Debris Attitude Motion Measurements and Modelling” project (ESA Contract No. 40000112447), led by the Astronomical Institute of the University of Bern (AIUB), addresses this problem. The goal of the project is to achieve a good understanding of the attitude evolution and the considerable internal and external effects which occur. To characterize the attitude state of selected targets in LEO and GTO, multiple observation methods are combined. Optical observations are carried out by AIUB, Satellite Laser Ranging (SLR) is performed by the Space Research Institute of the Austrian Academy of Sciences (IWF) and radar measurements and signal level determination are provided by the Fraunhofer Institute for High Frequency Physics and Radar Techniques (FHR). The In-Orbit Tumbling Analysis tool (ιOTA) is a prototype software, currently in development by Hyperschall Technologie Gottingen GmbH (HTG) within the framework of the project. ιOTA will be a highly modular software tool to perform short-(days), medium-(months) and long-term (years) propagation of the orbit and attitude motion (six degrees-of-freedom) of spacecraft in Earth orbit. The simulation takes into account all relevant acting forces and torques, including aerodynamic drag, solar radiation pressure, gravitational influences of Earth, Sun and Moon, eddy current damping, impulse and momentum transfer from space debris or micro meteoroid impact, as well as the optional definition of particular spacecraft specific influences like tank sloshing, reaction wheel behaviour, magnetic torquer activity and thruster firing. The purpose of ιOTA is to provide high accuracy short-term simulations to support observers and potential ADR missions, as well as medium-and long-term simulations to study the significance of the particular internal and external influences on the attitude, especially damping factors and momentum transfer. The simulation will also enable the investigation of the altitude dependency of the particular external influences. ιOTA's post-processing modules will generate synthetic measurements for observers and for software validation. The validation of the software will be done by cross-calibration with observations and measurements acquired by the project partners.

This paper reports on the application of uncertainty quantification methods to the prediction of the survivability of satellites re-entering the Earth atmosphere. Aleatory as well as epistemic parameters were varied. Parametric variation, Monte-Carlo, and Polynomial chaos expansion methods were applied. The re-entry code used was SCARAB. For the uncertainty quantification analysis this code was coupled with the DAKOTA software. Two satellites were modelled: a 2U CubeSat, representing the class of very light spececraft to study the demise characteristics, and a generic test satellite representing the class of medium-sized spacecraft, to study the ground impact uncertainty.

The data processing and the resulting data set are unique in several ways: GOCE uses an ion thruster to compensate for thermospheric drag, in order to maintain its orbit at a very low mean altitude of 270 km. This means that the most important acceleration data source for density retrieval is the thruster activation data. This information is combined with cross-track accelerometer measurements from GOCE’s Electrostatic Gravity Gradiometer instrument to derive crosswind speeds. The nearly sun-synchronous dawn-dusk orientation of the orbit is also unique for high-resolution acceleration-derived thermosphere measurements.

Since the begin of space flight activities more than 32,000 tones of payloads, rocket bodies, and mission-related objects were injected into orbit, of which some 5,500 tons are still in space today. The major share of the mass has decayed and re-entered into the atmosphere, mostly in an uncontrolled manner. Such uncontrolled re-entries may lead to elevated risk levels, either due to hazardous payloads (e.g. the reactor core of Cosmos 954 in Jan. 1978), or due to large masses (e.g. Skylab-1 in July 1979, and Salyut-7 in Feb. 1991). Over the past years, Space Agencies worldwide have established individual space debris mitigation guidelines, and they are presently working towards an international set of guidelines in the frame of the Inter-Agency Space Debris Coordination Committee (IADC). All of these guidelines request a de-orbit of space systems from low-Earth orbits (LEO) at their end of operational life. Such direct or reduced-lifetime deorbits are necessary to conserve the long-term stability of the LEO debris environment. Since the reduced-lifetime de-orbits ultimately lead to uncontrolled re-entries (typically within 25 years), some of the guidelines also address the tolerable risk on ground. The present paper outlines procedures, which are used by the European Space Agency (ESA) to predict uncontrolled re-entries, to forecast surviving parts of an entry object, and to assess the resulting casualty risk for the population in the entry ground swath. For re-entry events with partial control (e.g. Skylab-1), and for events with full control of the spacecraft (e.g. Mir) strategies will be outlined which minimize the on-ground risk for a given orbit inclination, or which alternatively maximize the total tolerable cross-section of survivor objects for an acceptable risk level. It will be briefly explained how such assessment procedures are reflected in ESA’s Space Debris Mitigation Handbook, in a European Code of Conduct for Space Debris Mitigation, and in an ESA software for Debris Risk Assessment and Mitigation Analysis (DRAMA).

The introduction of debris mitigation measures, and subsequent mitigation standards, is recognised as a vital step to preserve the near Earth orbital region for future use. To this end, ESA and national space agencies in Europe have drafted a European Code of Conduct for Space Debris Mitigation. To enable ESA space programmes to assess their compliance with the recommendations in this Code of Conduct, a new software model has been conceived - the Debris Risk Assessment and Mitigation Analysis (DRAMA) tool. This tool has been developed by a European team under ESA contract. DRAMA is composed of five individual software applications collected under a common graphical user interface. The individual applications have been designed and developed to address different aspects of debris mitigation. They enable an assessment of collision avoidance manoeuvres, collision flux and damage statistics, disposal manoeuvres at end-of-life, re-entry survival and re-entry risk analysis. Each of these tools provides the user of DRAMA with numerical and graphical results suitable for determining the debris risk posed to their mission and assessing the effectiveness of their end-of-life strategy. In this way, the tool can provide a basic compliant / non-compliant answer, in respect of the European Code of Conduct recommendations, for the operational and disposal phases of a mission.

Most spacecraft or rocket bodies re-entering the Earth's atmosphere, controlled or uncontrolled, do not demise completely during re-entry. Fragments of these re-entry objects survive and reach the ground where they pose a risk to people. Re-entry tools have been developed all over the world in order to calculate the destruction processes and to assess the resulting ground risk. This paper describes the NASA re-entry analysis tools DAS (Debris Assessment Software) and ORSAT (Object Re-entry Survival Analysis Tool), and the ESA tools SCARAB (Spacecraft Atmospheric Re-entry and Aero-thermal Breakup) and SESAM (Spacecraft Entry Survival Analysis Module). Results calculated with these tools are compared in order to identify the major differences. Final recommendations are given in order to improve these tools and to minimize the identified differences.

The Debris Risk Assessment and Mitigation Analysis (DRAMA) tool, developed by a European team under ESA contract, has been designed to enable space programmes to assess their compliance with the European Code of Conduct for Space Debris Mitigation. DRAMA is composed of five individual software applications collected under a common graphical user interface. The individual applications have been designed and developed to address different aspects of debris mitigation - collision avoidance manoeuvres, collision flux and damage statistics, disposal manoeuvres at end-of-life, re-entry survival and re-entry risk analysis. These tools provide the DRAMA user with numerical and graphical results suitable for determining the debris risk posed to their mission and assessing the effectiveness of their end-of-life strategy. The tool also provides a basic compliant / noncompliant answer, in respect of the European Code of Conduct, for the operational and disposal phases of a mission. This paper demonstrates the capabilities of the ESA DRAMA model, describing its concept and purpose, and providing an overview of the individual software tools and graphical user interface that form DRAMA.

ATV (Automated Transport Vehicle) is one of ESA!s most ambitious contributions to the International Space Station (ISS). It is launched by Axiane-5, it is controlled by the control center (ATV-CC) located in Toulouse in CNES premises, it performs an automatic rendezvous and docking with the ISS, it supplies cargo and propulsive support to the ISS during an attached phase that can last up to six months. The ATV shall after its nominal mission de-dock from the International Space Station and conduct a controlled re-entry into the atmosphere. During this re-entry ATV is supposed to bum up with the requirement that the possible ground risk due to surviving fragments remains below the accepted limits. In a first ESA study the destructive re-entry of ATV has been already analyzed with SCARAB. This study considered two re-entry cases and it included also the analysis of tank bursting. In this study only the influence of liquid mass loss due to tank bursting was analyzed. In order to analyze additional consequences of tank bursting, which might be explosions, an additional study was initiated by ESA. Within this study, jointly conducted by CNES and HTG, four different re-entry scenarios of ATV have been used. In order to treat explosions and the associated influence on the possible ground risk the following methods have been developed as supporting tools for SCARAB:Assessment of explosion likelihood by monitoring all events during re-entry, which contribute to an explosion environment and to explosion initiationAn explosion model, based on NASA's EVOLVE 4, which matches the material specific mass budget of ATVA fast object oriented re-entry analysis tool, which allows too track the enormous amounts of fragments, generated by an explosion, till demise and or ground impactThis paper will outline these developments in detail and analysis results will be presented.

The lifetime of objects in low Earth orbits is limited due to the atmospheric drag, which will finally cause their re-entry into the Earth's atmosphere. Generally, these objects demise, but surviving fragments of heavy re-entry objects can cause a non-negligible risk to the ground population. The current re-entry rate is about 1, 100 tons per year or about 3 tons per day, respectively. Many objects have re-entered and landed near residences, and one person was hit with a light piece of debris and fortunately was not injured.This paper will describe the main re-entry analysis tools which are currently used by NASA and ESA. The different modeling and analysis approaches will be outlined and compared, and explanations will be given, how the results of these tools can be used for the purpose of on-ground risk assessment.

Several space agencies and international entities have adopted space debris mitigation standards, guidelines, or codes of conduct. An important issue, which is addressed in most of these, is the post-mission removal of space systems, particularly from the densely populated low Earth orbit (LEO) region. This is an important measure to conserve the stability of the LEO environment in the long-term. It can be accomplished by direct de-orbiting, delayed de-orbiting to a reduced lifetime orbit, or re-orbiting to super-LEO altitudes. In the case of de-orbiting, a spacecraft or upper stage should enter into the Earth atmosphere within 25 years or less for delayed de-orbiting, and within less that one revolution for direct de-orbiting. In either case, most mitigation standards limit the acceptable risk to the ground population from surviving fragments. There are two major aspects to re-entry risk assessment: the identification of surviving spacecraft parts, and the analysis of resulting casualty probabilities for the ground population. The mathematical theory used for the analysis of both aspects will be explained, and exemplary results for a typical re-entry spacecraft will be provided. The outlined re-entry risk analysis software forms part of ESA's DRAMA tool (Debris Risk Assessment and Mitigation Analysis) in support of European space debris mitigation guidelines.