Development of a New, High-Power Solar Array for Telecommunication Satellites

Airbus is currently developing the Next Generation Solar Array (NGSA) for telecommunication satellites. It is based on a hybrid array concept which combines a conventional rigid panel array with lightweight, semi-rigid lateral panels. The main figures of merit power/mass and power/volume can be doubled through this concept. Mechanically, the semi-rigid panels are the key new element. Through acoustic testing as well as sine vibration testing in air and in vacuum it was verified that these panels are suitable as cell support in stowed configuration. With the help of finite element modelling it is demonstrated that the semi-rigid panels are compatible with a free deployment. Electrically, the new array is to be equipped with a new generation of 4 junction solar cells with efficiencies above 30%. The increased radiation dose due to electric orbit raising has to be taken into account to arrive at the optimum shielding while still minimizing the array mass. By adjusting the ratio of rigid to semi-rigid panels and through the choice of solar cell type and mass, the NGSA can be tailored in a wide range to needs of a given platform. This is illustrated for the solar array to be flown on the new Airbus platform Eurostar Neo

All-trans retinoic acid enhances, and a pan-RAR antagonist counteracts, the stem cell promoting activity of EVI1 in acute myeloid leukemia

Ecotropic virus integration site 1 (EVI1), whose overexpression characterizes a particularly aggressive subtype of acute myeloid leukemia (AML), enhanced anti-leukemic activities of all-trans retinoic acid (atRA) in cell lines and patient samples. However, the drivers of leukemia formation, therapy resistance, and relapse are leukemic stem cells (LSCs), whose properties were hardly reflected in these experimental setups. The present study was designed to address the effects of, and interactions between, EVI1 and retinoids in AML LSCs. We report that Evi1 reduced the maturation of leukemic cells and promoted the abundance, quiescence, and activity of LSCs in an MLL-AF9-driven mouse model of AML. atRA further augmented these effects in an Evi1 dependent manner. EVI1 also strongly enhanced atRA regulated gene transcription in LSC enriched cells. One of their jointly regulated targets, Notch4, was an important mediator of their effects on leukemic stemness. In vitro exposure of leukemic cells to a pan-RAR antagonist caused effects opposite to those of atRA. In vivo antagonist treatment delayed leukemogenesis and reduced LSC abundance, quiescence, and activity in Evi1high AML. Key results were confirmed in human myeloid cell lines retaining some stem cell characteristics as well as in primary human AML samples. In summary, our study is the first to report the importance of EVI1 for key properties of AML LSCs. Furthermore, it shows that atRA enhances, and a pan-RAR antagonist counteracts, the effects of EVI1 on AML stemness, thus raising the possibility of using RAR antagonists in the therapy of EVI1high AML

Microspacecraft Platform with Bipropellant Propulsion System and 3-Axis Stabilization for Missions in Earth Orbit and Beyond LEO

This paper presents a low-cost microspacecraft platform concept for missions which require high D-v capabilities of up to about 1,500 m/s, using auxiliary launch opportunities, e.g., from the Ariane 5 ASAP. The proposed concept is extremely flexible and can be adapted to specific mission requirements, thus permitting low-cost missions to Earth orbit, as well as to the Moon, Mars, and selected asteroids. A particular focus of this paper is on the modularity of the proposed concept, including the bipropellant propulsion system needed to provide the required D-v, the lightweight structural concept, and the 3-axis attitude determination and control system (ADCS), as well as the available P/L masses and the most important spacecraft characteristics and constraints. The proposed microspacecraft platform is derived from the LunarSat concept, which has been developed by a team led by the Technische Universität München, Germany, and Surrey Satellite Technology Ltd., UK. Consequently, the LunarSat spacecraft and mission are presented as an example of the proposed concept