MATS (Mesospheric Airglow/Aerosol Tomography and Spectroscopy) is a Swedish satellite mission designed to investigate atmospheric gravity waves. In order to observe wave patterns, MATS observes structures in the O2 atmospheric band airglow (light emitted by oxygen molecules in the mesosphere and lower thermosphere), as well as structures in noctilucent clouds (NLCs) which form around the mesopause. The main instrument is a telescope that continuously captures high-resolution images of the atmospheric limb. Using tomographic analysis of the acquired images, the MATS mission can reconstruct waves in three dimensions and provide a comprehensive global map of the properties of gravity waves. The data provided by the MATS satellite will thus be three-dimensional fields of airglow and NLC properties in 200 km-wide (across track) strips along the orbit at altitudes of 70 to 110 km. By adding spectroscopic analysis, by separating light into six distinct wavelength channels, it also becomes possible to derive temperature and microphysical NLC properties. Based on those data fields, further analysis will yield gravity wave parameters, such as the wavelengths, amplitudes, phase, and direction of the waves, on a global scale. The MATS satellite, funded by the Swedish National Space Agency, was launched in November 2022 into a 580 km sun-synchronous orbit with a 17.25 local time of the ascending node (LTAN). This paper accompanies the public release of the Level 1b (v. 1.0) dataset from the MATS limb imager. The purpose of the paper is to provide background information in order to assist users to correctly and efficiently handle the data. As such, it details the image processing and how instrumental artefacts are handled. It also describes the calibration efforts that have been carried out on the basis of laboratory and in-flight observations, and it discusses uncertainties that affect the dataset.

Global three-dimensional data are a key to understanding gravity waves in the mesosphere and lower thermosphere. MATS (Mesospheric Airglow/Aerosol Tomography and Spectroscopy) is a new Swedish satellite mission that addresses this need. It applies space-borne limb imaging in combination with tomographic and spectroscopic analysis to obtain gravity wave data on relevant spatial scales. Primary measurement targets are O-2 atmospheric band dayglow and nightglow in the near infrared, and sunlight scattered from noctilucent clouds in the ultraviolet. While tomography provides horizontally and vertically resolved data, spectroscopy allows analysis in terms of mesospheric temperature, composition, and cloud properties. Based on these dynamical tracers, MATS will produce a climatology on wave spectra during a 2-year mission. Major scientific objectives include a characterization of gravity waves and their interaction with larger-scale waves and mean flow in the mesosphere and lower thermosphere, as well as their relationship to dynamical conditions in the lower and upper atmosphere. MATS is currently being prepared to be ready for a launch in 2020. This paper provides an overview of scientific goals, measurement concepts, instruments, and analysis ideas.

The MATS satellite aims at observing airglow and noctilucent clouds in the mesosphere. The main instrument consists of a six channels limb imager in the near-ultraviolet and near-infrared. A high signal-to-noise ratio is required for detecting these mesospheric phenomena: 100 and 500 for ultraviolet and infrared, respectively. This is achieved by an optical design minimizing stray-light, but also with a dedicated design of the read-out analogue chain for the CCD on each channel. The requirements and expected light level on the imaging channels are briefly discussed before focusing on the CCD read-out analogue chain, for which the design and performances are presented.

We present measurements of the electron density, the effective electron temperature, the plasma potential, and the electron energy probability function (EEPF) in the plume of a 1.5 kW-class SPT-100 Hall thruster, derived from cylindrical Langmuir probe measurements. The measurements were taken on the plume axis at distances between 550 and 1550 mm from the thruster exit plane, and at different angles from the plume axis at 550 mm for three operating points of the thruster, characterized by different discharge voltages and mass flow rates. The bulk of the electron population can be approximated as a Maxwellian distribution, but the measured distributions were seen to decline faster at higher energy. The measured EEPFs were best modelled with a general EEPF with an exponent a between 1.2 and 1.5, and their axial and angular characteristics were studied for the different operating points of the thruster. As a result, the exponent a from the fitted distribution was seen to be almost constant as a function of the axial distance along the plume, as well as across the angles. However, the exponent a was seen to be affected by the mass flow rate, suggesting a possible relationship with the collision rate, especially close to the thruster exit. The ratio of the specific heats, the. factor, between the measured plasma parameters was found to be lower than the adiabatic value of 5/3 for each of the thruster settings, indicating the existence of non-trivial kinetic heat fluxes in the near collisionless plume. These results are intended to be used as input and/or testing properties for plume expansion models in further work.

Since 2012, European Space Agency (ESA), SITAEL and ten European universities have been developing the European Student Earth Orbiter (ESEO). The satellite bus is being designed, built and tested by SITAEL, whereas the payload modules are being developed by various universities throughout Europe. ESEO is a microsatellite to measure the radiation environment in Low Earth Orbit (LEO), test new technologies in space as well as take photos of Earth and other celestial bodies. The aim of the ESEO optical payload is to produce color images in the visible spectrum, mainly for public outreach purposes. Although, in addition to public outreach, the payload can also be used to monitor plankton blooms or changes in the polar ice caps. This paper presents the design, development and pre-launch testing of a lightweight and power-efficient dual-camera system for ESEO. The two-camera solution enables imaging of the same target with a different field of view. The wide angle camera provides context for telescopic images, making it easier to pinpoint the area that was photographed. The primary camera of the payload is a wide-angle camera based on the ESTCube-1 design with a 4.4 mm telecentric lens, VGA CMOS color sensor and a 700 nm IR cut-off filter. With a field of view of 46° × 35°, the ground resolution of the primary camera is around 1 km per pixel. The secondary camera is telescopic, has a Zeiss C Sonnar T∗ 1.5/50 lens, a 2592×1944 pixel CMOS color sensor and a Schott BG40 filter. With a field of view of 6.63° × 5°, the ground resolution of the secondary camera is about 20 m per pixel. The payload features configurable internal image processing, progressive image compression and non-volatile storage. The resulting payload weighs about 800 g, on average consumes less than 560 mW of power, with peaks up to 1.5 W. The payload is currently being tested and will be launched on ESEO at the end of 2016.

ISAAC - Infrared Spectroscopy to Analyse the middle Atmosphere Composition was a student experiment launched from SSC's Esrange Space Centre, Sweden, on 29th May 2014, on board the sounding rocket REXUS 15 in the frame of the REXUS/BEXUS programme. The main focus of the experiment was to implement an ejection system for two large Free Falling Units (FFUs) (240 mm x 80 mm) to be ejected from a spinning rocket into a predefined direction. The system design relied on a spring-based ejection system. Sun and angular rate sensors were used to control and time the ejection. The flight data includes telemetry from the Rocket Mounted Unit (RMU), received and saved during flight, as well as video footage from the GoPro camera mounted inside the RMU and recovered after the flight. The FFUs' direction, speed and spin frequency as well as the rocket spin frequency were determined by analyzing the video footage. The FFU-Rocket-Sun angles were 64.3 degrees and 104.3 degrees, within the required margins of 90 degrees +/- 45 degrees. The FFU speeds were 3.98 m/s and 3.74 m/s, lower than the expected 5 +/- 1 m/s. The FFUs' spin frequencies were 1.38 Hz and 1.60 Hz, approximately half the rocket's spin frequency. The rocket spin rate slightly changed from 3.163 Hz before the ejection to 3.117 Hz after the ejection of the two FFUs. The angular rate, sun sensor data and temperature on the inside of the rocket module skin were also recorded. The experiment design and results of the data analysis are presented in this paper.