In the past, European scientists have built solar UV imagers, spectrometers, coronagraphs and total solar irradiance radiometers; but LYRA is their first solar UV radiometer. LYRA consists of four large pass band channels. Each channel observes the irradiance of the Sun behind a thin metallic foil or behind an interference filter. The detectors are either UV silicon diodes or diamond detectors, the latter having been specifically designed for LYRA. The combination of the spectral transmission of the filters and of the detector’s responsivity makes the twelve LYRA channels sensitive to different soft X-ray and UV pass bands. Their exact choice was made in relation to scientific questions in solar physics, aeronomy, and space weather.
In a strategy to maximize the accuracy of the measurements, LYRA comprises three similar independent units, consisting of four abovementioned channels each. Together with a set of two Light Emitting Diodes (LEDs) per channel and knowing that each unit degrades as a function of observing time, this configuration permits to prolong LYRA's calibration. Indeed, by infrequent use of two units, the more degraded response of the third unit can be corrected, and the evolution of the properties of the new diamond detectors and of the silicon detectors can be compared under real space conditions. The diamond detectors represent a novel UV technology that is hoped to replace silicon-based detectors. The former exhibit less dark current and should degrade more slowly under the harmful solar light measured by LYRA, as well as the harsh space environment (ionizing particles). It is already clear that the diamond detectors are much less sensitive to the protons of the South Atlantic Anomaly than Si detectors.
After tests in the dark in November and December 2009, the three LYRA doors were unlocked and opened on 5 and 6 January 2010. The PROBA2 spacecraft was not yet pointed to the Sun, but when it was in the evening of January 6, all twelve detectors measured signals. The fragile, thin metal filters have not shattered at launch nor developed pinholes. The detectors’ responsivity has not substantially changed substantially.
Weighing 3.53 kg and measuring 315 mm x 92.5 mm x 222 mm, LYRA’s development has been led by the Principal Investigator team at the Royal Observatory of Belgium in Brussels, in close collaboration with the Swiss Co-Investigator team at the PMOD/WRC in Davos. The project management was with the Centre Spatial de Liège and the German Co-Investigator at the Max-Planck-Institut für Sonnensystemforschung provided the radiometric calibration using the BESSY synchrotron at the Physikalisch-Technische Bundesanstalt in Berlin. Collaborators from Japan, France, the USA, and Russia are also acknowledged.

Credits: ESA/ROB

Initial in-flight tests of the DSLP instrument were performed during the Proba-2 commissioning phase within the third and forth week after the launch of the satellite. First connection with the DSLP processing unit was successfully established on November 18, 2009, and data acquired in the mission operations centre (Redu, Belgium) confirmed a good health status of the whole experiment. In the following days, the DSLP team verified the functionality and data acquisition in all DSLP scientific modes. Till now, already more than 15 000 scientific data samples were acquired including current-voltage characteristics from all DSLP segments and also electric filed measurements between the two DSLP sensors. Preliminary scientific analysis of DSLP measurements shows good qualitative agreement with theoretical models and observed plasma characteristics are corresponding to predicted properties of ionospheric plasmas.

Credits: ESA/Academy of Sciences of the Czech Republic

The DSLP is one of the four scientific experiments on board the ESA microsatellite Proba-2. The DSLP instrument has been developed and manufactured in the Czech Republic by a scientific-industrial consortium within the ESA PECS/PRODEX program. The consortium is led by the Astronomical Institute (Academy of Sciences of the Czech Republic) with technological and industrial support provided by the Research and Scientific Support Department of ESTEC/ESA (Noordwijk, Holland) and the Czech Space Research Center company (Brno, Czech Republic). As a part of the Plasma Measurement Equipment, the DSLP instrument will aim at studying characteristic macroscopic properties (e.g. density, temperature or flow dynamics) of ionospheric plasmas and, with use of SWAP and LYRA observations, try to identify observed irregularities with possible solar-terrestrial connection related to sudden space weather events. A comprehensive knowledge of the ionospheric environment is important from many not solely scientific aspects. Intense solar events cause massive geomagnetic storms that represent possible risk of damage for communication and navigation satellite systems, ground electric grids and pipelines, or even radiation hazards for humans. Detailed study of ionospheric processes and their space weather relations thus becomes an considerable issue in current space research activities.

Credits: ESA/Academy of Sciences of the Czech Republic