Imaging spectroscopy, also known as hyperspectral remote sensing, is based on the characterization of Earth surface materials and processes through spectrally-resolved measurements of the light interacting with matter. The potential of imaging spectroscopy for Earth remote sensing has been demonstrated since the 1980s. However, most of the developments and applications in imaging spectroscopy have largely relied on airborne spectrometers, as the amount and quality of space-based imaging spectroscopy data remain relatively low to date. The upcoming Environmental Mapping and Analysis Program (EnMAP) German imaging spectroscopy mission is intended to fill this gap. An overview of the main characteristics and current status of the mission is provided in this contribution. The core payload of EnMAP consists of a dual-spectrometer instrument measuring in the optical spectral range between 420 and 2450 nm with a spectral sampling distance varying between 5 and 12 nm and a reference signal-to-noise ratio of 400:1 in the visible and near-infrared and 180:1 in the shortwave-infrared parts of the spectrum. EnMAP images will cover a 30 km-wide area in the across-track direction with a ground sampling distance of 30 m. An across-track tilted observation capability will enable a target revisit time of up to four days at the Equator and better at high latitudes. EnMAP will contribute to the development and exploitation of spaceborne imaging spectroscopy applications by making high-quality data freely available to scientific users worldwide.

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The Solar Polar Imager (SPI) mission is one of several Sun-Earth Connection solar sail roadmap missions currently envisioned by NASA. A current SPI reference mission design is based on a 160 m × 160 m, 150 kg square solar sail assembly with a 250 kg spacecraft bus and a scientific payload of 50 kg (450 kg total mass), having a characteristic acceleration of 0.35 mm/s 2. Using a conservative solar sail film temperature limit of 100 • C to constrain the solar distance ("cold" mission scenario), our transfer trajectory to the SPI target orbit (circular orbit at 0.48 AU solar distance with 75 deg inclination) approaches the sun closer (to about 0.4 AU solar distance) than a current reference trajectory and therefore, exploiting the larger solar radiation pressure, takes-even with a lower hyperbolic excess energy for interplanetary insertion-only 6.4 instead of 6.7 years. For a higher sail temperature limit of 240 • C ("hot" mission scenario), the optimal transfer trajectory approaches the sun much closer (to about 0.22 AU solar distance), resulting in an even shorter transfer duration of only 4.7 years. Based on this "hot" mission scenario, we perform several mission tradeoffs to gain a deeper insight into the trade space of the SPI mission: different sail temperature limits, different characteristic accelerations, different interplanetary insertion energies, and different sail degradation behaviors are investigated.

In the years 2010-2014 the satellites TSX and TDX collected all the Synthetic Aperture Radar (SAR) data necessary to fulfill the primary TanDEM-X mission objective: the generation of a global digital elevation model with unprecedented accuracy. In September 2014, when the necessary data set was almost complete, a transition to the so-called science phase took place. Its focus was the implementation of the TanDEM-X secondary mission objectives. TSX and TDX fly in close formation in low Earth orbit in order to form a SAR interferometer in space with adjustable interferometric baselines. Due to the diversity of scientific applications, the science phase was marked by several baseline and hence formation changes and, in addition, by unusual formation geometries. Modifications to the proven operational handling of SAR payloads and the data downlink became necessary as well as the adaptation of existing safety concepts. Furthermore, the transition from one baseline setting to the other had to be managed operationally safe and in such a way that downtimes were minimal. Nomenclature SAR= Synthetic Aperture Radar TanDEM-X Mission =

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