The Modular Multispectral Imaging Array (MMIA) is a suite of optical sensors mounted on an external platform of the European Space Agency's Columbus Module on the International Space Station. The MMIA, together with the Modular X-and Gamma-ray Sensor (MXGS), are the two main instruments forming the Atmosphere-Space Interactions Monitor (ASIM). The primary scientific objectives of the ASIM mission are to study thunderstorm electrical activity such as lightning, Transient Luminous Emissions (TLEs) and Terrestrial Gamma-ray Flashes (TGFs) by observing the associated emissions in the UV, near-infrared, x-and gamma-ray spectral bands. The MMIA includes two cameras imaging in 337 nm and 777.4 nm, at up to 12 frames per second, and three high-speed photometers at 180-230 nm, 337 nm and 777.4 nm, sampling at rates up to 100 kHz. The paper describes the MMIA and the aspects that make it an essential tool for the study of thunderstorms. The mission architecture is described in Neubert et al.

The Soil Moisture and Ocean Salinity Mission (SMOS) delivers global surface soil moisture fields at high temporal resolution which is of high relevance for water management and climate predictions. For data validation, an airborne campaign with the L-band radiometer EMIRAD-2 and concurrent ground sampling was carried out within one SMOS pixel in the Skjern River Catchment, Denmark. By means of this dataset the objective of this study is a step-wise comparison of brightness temperatures from point via air-to spaceborne (SMOS) scale. From soil moisture samples brightness temperatures were estimated through the L-band Microwave Emission of the Biosphere (L-MEB) model with land-cover specific model settings. A simple uncertainty assessment by means of a set of model runs with parameters varied within a most likely interval resulted in a considerable range of brightness temperatures. Under certain constellations the ground data was in good agreement with EMIRAD. Likewise was the latter in accordance with SMOS data. The comparison of more sophisticated upscaling by means of air-and spaceborne weighting functions and a simple mean showed no significant change. Small temporal variability in soil moisture conditions and RFI-prone SMOS data throughout the campaign limited the extent of the validation work. Further attempts over longer time frames are planned by means of soil moisture network data as well as studies on the impacts of organic layers under natural vegetation and higher open water fractions at surrounding grid nodes.

The Modular X-and Gamma-ray Sensor (MXGS) is an imaging and spectral X-and Gamma-ray instrument mounted on the starboard side of the Columbus module on the International Space Station. Together with the Modular Multi-Spectral Imaging Assembly (MMIA) (Chanrion et al. this issue) MXGS constitutes the instruments of the Atmosphere-Space Interactions Monitor (ASIM) (Neubert et al. this issue). The main objectives of MXGS are to image and measure the spectrum of X-and γ -rays from lightning discharges, known as Terrestrial Gamma-ray Flashes (TGFs), and for MMIA to image and perform high speed photometry of Transient Luminous Events (TLEs) and lightning discharges. With these two instruments specifically designed to explore the relation between electrical discharges, TLEs and TGFs, ASIM is the first mission of its kind. With an imaging system and a large detector area MXGS will, for the first time, allow estimation of the location of the source region and characterization of the energy spectrum of individual events. The sensors have fast readout electronics to minimize pileup effects, giving high time resolution of photon detection for comparison with measurements on µs-time scales of lightning processes measured by the MMIA and other sensors in space or on the ground. The detectors cover the large energy range of the relevant photon energies. In this paper we The ASIM mission on the International Space Station B N. Østgaard Page 2 of 28 N. Østgaard et al.describe the scientific objectives, design, performance, imaging capabilities and operational modes of the MXGS instrument.

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Abstract-In support of the European Space Agency SoilMoisture and Ocean Salinity (SMOS) mission, a number of soil moisture and sea salinity campaigns, including airborne L-band radiometer measurements, have been carried out. The radiometer used in this context is fully polarimetric and has built-in radio-frequency-interference (RFI)-detection capabilities. Thus, the instrument, in addition to supplying L-band data to the geophysicists, also gave valuable information about the RFI environment. Campaigns were carried out in Australia and in a variety of European locations, resulting in the largest and most comprehensive data set available for assessing RFI at L-band. This paper introduces the radiometer system and how it detects RFI using the kurtosis method, reports on the percentage of data that are typically flagged as being corrupted by RFI, and gives a hint about geographical distribution. Also, examples of polarimetric signatures are given, and the possibility of detecting RFI using such data is discussed.

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