ABSTRACT. Melt rates of glacier surfaces are strongly influenced by the existence of a debris cover. Dependent on thickness and other physical parameters the debris layer can enhance or reduce ablation as compared to bare ice conditions. Supraglacial moraines appear very frequently on Central Asian glaciers, highly affecting water yield from these high mountain regions. In summer 2005, a network of 22 ablation stakes was drilled into locations with varying debris thicknesses on Southern Inylchek glacier in the central Tian Shan. Mean ablation rates varied from 2.8 to 6.7 cm/d, strongly correlated with moraine thickness. Parallel observation of air temperature allowed the application of a simple degree-day approach and the calculation of ablation rates. Efforts to improve calculations of melt rates by incorporating relative air humidity to account for latent heat fluxes failed. This proves that air temperature is already a very good melt indicator. Ice albedo measurements show that reflectivity might be controlled by the occurrence of evaporation or condensation, but this topic needs further investigation.

The Inylchek glacier system in Central Tian Shan, Kyrgyzstan, comprises a large glacierdammed lake which usually drains once a year through a subglacial drainage system. Detailed GPS measurements on the ice dam and the analysis of Aster scenes from several subsequent years provide insight into the post-drainage dam response and the changed ice dynamic conditions. We demonstrate that during high water levels in the lake a large part of the ice dam is afloat, lifting the ice surface up to almost 20 m in the central dam region. During this phase of extensive flotation strong calving is facilitated, which is supported by the high density of ice debris in the lake. In general, surface ice velocities are about 1.5-2 times higher during summer than winter. Closer to the lake, however, ice velocities increase considerably after the drainage event, showing values more than three times the annual mean. The increased mass flux during the phase of high lake level needs to be compensated by replenishment of the lost ice from the dam. Therefore the ice velocities show compressive flow during the remaining part of the year. These results show that Southern Inylchek glacier is strongly influenced by the existence of the lake.

[1] This paper evaluates the usage of reflected GPS signals for Earth observations to study changes of sea level and sea-ice in remote sensing. In a coastal setup, ∼670 m above Disko Bay (Greenland), signals with different carriers L1 and L2 were recorded. A method is presented that analyses the interferometric phase between the reflected and the direct signals and derives the height of the reflecting surface. The analysis includes a ray tracing and an estimation of signal coherence. It is shown that coherent reflections are related to sea-ice coverage. Absolute heights are derived with a time interval of ∼30 min. The altimetric results show semidiurnal tides that are validated using the AODTM-5 tide model. The residual height has a mean of 9.7 cm for L1 and 22.9 cm for L2. The dispersion is not significant but a significant tropospheric bias is detected with an error of up to 20 cm.

Abstract. Within the German-Indonesian

Systems Engineering has successfully supported the space industry since its inception with methodologies and techniques to handle complex projects. However, the conventional design approach, ‘Document‐Based Systems Engineering’ (DBSE), is more and more reaching its limits. This research evaluates the benefits and the cost associated with the paradigm of ‘Model Based Systems Engineering’ (MBSE) instead of DBSE by applying the Systems Modelling Language (SysML) in the frame of the Atomic Clock Ensemble in Space (ACES) project. ACES is indeed deemed to be a suitable project for this study as it includes both a very complex ground segment as well as a challenging space segment on board the International Space Station. Following an introduction to SysML and the ACES mission, we first develop the metrics on which the cost‐benefit analysis is based on. Then, we explain the methodology and models used to perform the analysis which targets to characterise DBSE versus MBSE based on the ACES ground segment development. Then, we use the Analytical Hierarchical Process to determine weighted criteria where attention is also given to the transitional process between DBSE and MBSE. After a critical reflection upon the analysis methodology and its results, we focus on lessons‐learned from the use of SysML for the implementation of MBSE in space projects. We have identified five key areas of lessons‐learned for using MBSE with SysML itself as well as main deficiencies for Enterprise Architect, the tool used to implement SysML. We conclude with seven suggested improvements which are considered valuable to help improving the performance and acceptance of MBSE for the development of (space) projects in the future.