HE Space (Netherlands)

This paper discusses the SuperNova power conditioning and distribution unit (PCDU) built by Bradford Space as part of their integrated avionics stack aiming to capture the growing market of microsatellite avionics. The SuperNova PCDU is a highly modular unit that is designed to handle power levels from 100 up to 1500 watts on both solar input and distributed output with a nominal 28 volts unregulated battery bus. The paper explores the innovative architectural decisions, design and testing methodology that enabled the unit to be optimized for compactness, lightness, and cost-effectiveness, positioning it as a leading product in the PCDU market for new-space applications.

<strong class="journal-contentHeaderColor">Abstract.</strong> During the tandem phase of Sentinel-3A and -3B in summer 2018 the Ocean and Land Color Imager (OLCI) mounted on Sentinel-3B satellite was reprogrammed to mimick ESA&rsquo;s 8th Earth explorer the Fluorescence explorer (FLEX). OLCI in FLEX configuration (OLCI-FLEX) had 45 spectral bands between 500 nm and 792 nm. The new data set with high resolution measurements (band width: 1.7&ndash;3.7 nm) serves as preparation of the FLEX mission. Co-registered measurements of both instruments will be used to describe the atmosphere and the surface. For such combined products, it is essential that both instruments are radiometrically consistent. We developed a transfer function to compare radiance measurements from different optical sensors and to monitor their consistency. In the presented study, the transfer function shifts information gained from high-resolution "FLEX-mode" settings to information convolved with spectral response of the normal (lower) spectral resolution of the OLCI sensor. The resulting reconstructed low resolution radiance is representative for the high resolution data and it can be compared with the measured low resolution radiance. This difference is used to quantify systematic differences between the instruments. Applying the transfer function, we could show that OLCI-A is about 2 % brighter than OLCI-FLEX for most bands. At the longer wavelengths OLCI-A is about 5 % darker. Sensitivity studies showed that the parameters affecting the quality of the comparison of OLCI-A and OLCI-FLEX with the transfer function are mainly the surface reflectance and secondarily the aerosol composition. However, the aerosol composition can be simplified as long it is treated consistently in all steps in transfer function. Generally, the transfer function enables direct comparison of instruments with different spectral responses even with different observation geometries or different levels of observation. The method is sensitive to measurement biases and errors resulting from the processing. One application could be the quality control of the FLEX mission.

Unmanned aerial vehicles have become a crucial technology in a wide variety of fields. The availability and integrity of exact positioning feedback information are of paramount importance for the safety of many UAV applications. Global navigation satellite system receivers provide reliable and accurate positioning solutions in outdoor environments. However, they suffer strong performance degradation in harsher scenarios such as forests, urban canyons, or indoor environments. This paper addresses the performance of GNSS receivers installed on a drone. They were tested in different scenarios such as under open sky or in adverse conditions of signal reception. The solutions offered by the receivers were compared to RTK reference trajectories. Moreover, the advantage of including a stereo tracking camera in the setup to obtain a more accurate reference trajectory in some scenarios was analyzed. The results give insights on the accuracy and the quality of the measurements of current GNSS technologies in aerial applications.

TNO, in cooperation with Micromega-Dynamics, SRON, Dutch Space and CSL, has designed a compact breadboard cryogenic delay line (figure 1) for use in future space interferometry missions. The work is performed under ESA contract 17.747/03 in preparation for the DARWIN mission. The breadboard (BB) delay line is representative of a flight mechanism. The delay line has a single stage voice coil actuator for Optical Path Difference (OPD) control, driving a two mirror cat’s eye. Magnetic bearings provide frictionless and wear free operation with zero-hysteresis. The design of the BB delay line has been completed. The development test program, including operation at 100 K has been completed. The verification test programme is currently being carried out and will include functional testing at 40 K.

TROPOMI, the Tropospheric Monitoring Instrument, is a passive UV-VIS-NIR-SWIR trace gas spectrograph in the line of SCIAMACHY (2002) and OMI (2004), instruments with the Netherlands in a leading role. Both instruments are very successful and remained operational long after their nominal life time. TROPOMI is the next step, scheduled for launch in 2015. It combines the broad wavelength range from SCIAMACHY from UV to SWIR and the broad viewing angle push-broom concept from OMI, which makes daily global coverage in combination with good spatial resolution possible. Using spectral bands from 270-500nm (UV-VIS) 675-775nm (NIR) and 2305-2385nm (SWIR) at moderate resolution (0.25 to 0.6nm) TROPOMI will measure O3, NO2, SO2, BrO, HCHO and H2O tropospheric columns from the UV-VIS-NIR wavelength range and CO and CH4 tropospheric columns from the SWIR wavelength range. Cloud information will be derived primarily from the O2A band in the NIR. This will help, together with the aerosol information, in constraining the light path of backscattered solar radiation. Methane (CH4), CO2 and Carbon monoxide (CO) are the key gases of the global carbon cycle. Of these, Methane is by far the least understood in terms of its sources and is most difficult to predict its future trend. Global space observations are needed to inform atmospheric models. The SWIR channel of TROPOMI is designed to achieve the spectral, spatial and SNR resolution required for this task. TROPOMI will yield an improved accuracy of the tropospheric products compared to the instruments currently in orbit. TROPOMI will take a major step forward in spatial resolution and sensitivity. The nominal observations are at 7 x 7 km2 at nadir and the signal-to-noises are sufficient for trace gas retrieval even at very low albedos (down to 2%). This spatial resolution allows observation of air quality at sub-city level and the high signal-to-noises means that the instrument can perform useful measurements in the darkest conditions. TROPOMI is currently in its detailed design phase. This paper gives an overview of the challenges and current performances. From unit level engineering models first results are becoming available. Early results are promising and this paper discusses some of these early H/W results. TROPOMI is the single payload on the Sentinel-5 precursor mission which is a joint initiative of the European Community (EC) and of the European Space Agency (ESA). The 2015 launch intends to bridge the data stream from OMI / SCIAMACHY and the upcoming Sentinel 5 mission. The instrument is funded jointly by the Netherlands Space Office and by ESA. Dutch Space is the instrument prime contractor. SSTL in the UK is developing the SWIR module with a significant contribution from SRON. Dutch Space and TNO are working as an integrated team for the UVN module. KNMI and SRON are responsible for ensuring the scientific capabilities of the instrument.

The EUSO (Extreme Universe Space Observatory) project is developing a new\nmission concept for the scientific research of Ultra High Energy Cosmic Rays\n(UHECRs) from space. The EUSO wide-field telescope will look down from space\nonto the Earth night sky to detect UV photons emitted from air showers\ngenerated by UHECRs in our atmosphere. In this article we concentrate on the\nmitigation strategies agreed so far, and in particular on the implementation of\na careful early selection and testing of subsystem materials (including\noptics), design and interfaces of the subsystem and an optimization of the\ninstrument operational concept.\n

Testing of hardware and training of astronauts in space analog environments have been performed since the beginning of the space age. In the frame of planetary exploration, the so called Analog Planetary Research (APR) can be defined as the study of flight hardware, operational constraints, procedures and planning strategies on Earth in an environment that resembles (partly or fully) the conditions of the targeted planetary body. The findings and lessons learned from APR missions can be analyzed regarding mission concept, risks and constraints and the overall mission efficiency prior to launching a real space mission.

This document describes the uplink commanding system for the ESA Gaia mission. The need for commanding, the main actors, data flow and systems involved are described. The system architecture is explained in detail, including the different levels of configuration control, software systems and data models. A particular subsystem, the automatic interpreter of human-readable onboard activity templates, is also carefully described. Many lessons have been learned during the commissioning and are also reported, because they could be useful for future space survey missions.

On 2007 December 16–17, spectra were acquired of the disk of Uranus by the Spitzer Infrared Spectrometer (IRS), ten days after the planet’s equinox, when its equator was close to the sub-Earth point. This spectrum provides the highest-resolution broad-band spectrum ever obtained for Uranus from space, allowing a determination of the disk-averaged temperature and molecule composition to a greater degree of accuracy than ever before. The temperature profiles derived from the Voyager radio occultation experiment by Lindal et al. (Lindal, G.F., Lyons, J.R., Sweetnam, D.N., Eshleman, V.R., Hinson, D.P. [1987]. J. Geophys. Res. 92, 14987–15001) and revisions suggested by Sromovsky et al. (Sromovsky, L.A., Fry, P.A., Kim, J.H. [2011]. Icarus 215, 292–312) that match these data best are those that assume a high abundance of methane in the deep atmosphere. However, none of these model profiles provides a satisfactory fit over the full spectral range sampled. This result could be the result of spatial differences between global and low-latitudinal regions, changes in time, missing continuum opacity sources such as stratospheric hazes or unknown tropospheric constituents, or undiagnosed systematic problems with either the Voyager radio-occultation or the Spitzer IRS data sets. The spectrum is compatible with the stratospheric temperatures derived from the Voyager ultraviolet occultations measurements by Herbert et al. (Herbert, F. et al. [1987]. J. Geophys. Res. 92, 15093–15109), but it is incompatible with the hot stratospheric temperatures derived from the same data by Stevens et al. (Stevens, M.H., Strobel, D.F., Herbert, F.H. [1993]. Icarus 101, 45–63). Thermospheric temperatures determined from the analysis of the observed H2 quadrupole emission features are colder than those derived by Herbert et al. at pressures less than ∼1μbar. Extrapolation of the nominal model spectrum to far-infrared through millimeter wavelengths shows that the spectrum arising solely from H2 collision-induced absorption is too warm to reproduce observations between wavelengths of 0.8 and 3.3mm. Adding an additional absorber such as H2S provides a reasonable match to the spectrum, although a unique identification of the responsible absorber is not yet possible with available data. An immediate practical use for the spectrum resulting from this model is to establish a high-precision continuum flux model for use as an absolute radiometric standard for future astronomical observations.