Accurate prediction of the arrival of solar wind phenomena, in particular coronal mass ejections (CMEs), is becoming more important given our ever-increasing reliance on technology. SCOPE is a coronagraph specifically optimised for operational space weather prediction, designed to provide early evidence of Earth-bound CMEs. In this paper, we present results from phase A/B1 of the instrument’s development, which included conceptual design and a program of breadboard testing.
We describe the conceptual design of the instrument. In particular, we explain the design and analysis of the straylight rejection baffles and occulter needed to block the image of the solar disc, in order to render the much fainter corona visible. We discuss the development of in-house analysis code to predict the straylight diffraction effects that limit the instrument’s performance, and present results, which we compare against commercially available analysis tools and the results from breadboard testing. In particular, we discuss some of the challenges of predicting straylight effects in this type of instrument and the methods we have developed for overcoming them.
We present the test results from an optical breadboard, designed to verify the end-to-end straylight rejection of the instrument. The design and development of both the breadboard and the test facility is presented. We discuss some of the challenges of measuring very low levels of straylight and how these drive the breadboard and test facility design. We discuss the test and analysis procedures developed to ensure a representative, complete characterisation of the instrument’s straylight response.
The PROBA2 mission has been launched on 2nd November2009 with a Rockot launcher to a Sunsynchronous orbit at an altitude of 725 km. Its nominal operation duration is two years with possible extension of 2 years. PROBA2 is a small satellite developed under an ESA General Support Technology Program (GSTP) contract to perform an in-flight demonstration of new space technologies and support a scientific mission for a set of selected instruments. The mission is tracked by the ESA Redu Mission Operation Center.
The “sonic region” of the Sun corona remains extremely difficult to observe with spatial resolution and sensitivity sufficient to understand the fine scale phenomena that govern the quiescent solar corona, as well as phenomena that lead to coronal mass ejections (CMEs), which influence space weather. Improvement on this front requires eclipse-like conditions over long observation times. The space-borne coronagraphs flown so far provided a continuous coverage of the external parts of the corona but their over-occulting system did not permit to analyse the part of the white-light corona where the main coronal mass is concentrated. The proposed PROBA-3 Coronagraph System, also known as ASPIICS (Association of Spacecraft for Polarimetric and Imaging Investigation of the Corona of the Sun), with its novel design, will be the first space coronagraph to cover the range of radial distances between ~1.08 and 3 solar radii where the magnetic field plays a crucial role in the coronal dynamics, thus providing continuous observational conditions very close to those during a total solar eclipse. PROBA-3 is first a mission devoted to the in-orbit demonstration of precise formation flying techniques and technologies for future European missions, which will fly ASPIICS as primary payload. The instrument is distributed over two satellites flying in formation (approx. 150m apart) to form a giant coronagraph capable of producing a nearly perfect eclipse allowing observing the sun corona closer to the rim than ever before. The coronagraph instrument is developed by a large European consortium including about 20 partners from 7 countries under the auspices of the European Space Agency. This paper is reviewing the recent improvements and design updates of the ASPIICS instrument as it is stepping into the detailed design phase.
PROBA-3 is a mission devoted to the in-orbit demonstration of precise formation flying techniques and technologies for future ESA missions. PROBA-3 will fly ASPIICS (Association de Satellites pour l’Imagerie et l’Interferométrie de la Couronne Solaire) as primary payload, which makes use of the formation flying technique to form a giant coronagraph capable of producing a nearly perfect eclipse allowing to observe the sun corona closer to the rim than ever before. The coronagraph is distributed over two satellites flying in formation (approx. 150m apart). The so called Coronagraph Satellite carries the camera and the so called Occulter Satellite carries the sun occulter disc. This paper is reviewing the design and evolution of the ASPIICS instrument as at the beginning of Phase C/D.
The SWAP telescope (Sun Watcher using Active Pixel System detector and Image Processing) is an instrument launched
on 2nd November 2009 on-board the ESA PROBA2 technological mission.
SWAP is a space weather sentinel from a low Earth orbit, providing images at 174 nm of the solar corona. The
instrument concept has been adapted to the PROBA2 mini-satellite requirements (compactness, low power electronics
and a-thermal opto-mechanical system). It also takes advantage of the platform pointing agility, on-board processor,
Packetwire interface and autonomous operations.
The key component of SWAP is a radiation resistant CMOS-APS detector combined with onboard compression and data
prioritization. SWAP has been developed and qualified at the Centre Spatial de Liège (CSL) and calibrated at the PTBBessy
facility. After launch, SWAP has provided its first images on 14th November 2009 and started its nominal,
scientific phase in February 2010, after 3 months of platform and payload commissioning.
This paper summarizes the latest SWAP developments and qualifications, and presents the first light results.
The SWAP telescope (Sun Watcher using Active Pixel System detector and Image Processing) is being developed to be
part of the PROBA2 payload, an ESA technological mission to be launched in early 2008. SWAP is directly derived
from the concept of the EIT telescope that we developed in the '90s for the SOHO mission. Several major innovations
have been introduced in the design of the instrument in order to be compliant with the requirements of the PROBA2
mini-satellite: compactness with a new of-axis optical design, radiation resistance with a new CMOS-APS detector, a
very low power electronics, an athermal opto-mechanical system, optimized onboard compression schemes combined
with prioritization of collected data, autonomy with automatic triggering of observation and off-pointing procedures in
case of Solar event occurrence, ... All these new features result from the low resource requirements (power, mass,
telemetry) of the mini-satellite, but also take advantage of the specificities of a modern technological platform, such as
quick pointing agility, new powerful on-board processor, Packetwire interface and autonomous operations.
These new enhancements will greatly improve the operations of SWAP as a space weather sentinel from a low Earth
orbit while the downlink capabilities are limited. This paper summarizes the conceptual design, the development and the
qualification of the instrument, the autonomous operations and the expected performances for science exploitation.
PROBA2 is an ESA technology demonstration mission to be launched in early 2007. The two primary scientific instruments on board of PROBA2 are SWAP (Sun Watcher using Active Pixel System detector and Image Processing) and the LYRA VUV radiometer. SWAP provides a full disk solar imaging capability with a bandpass filter centred at 17.5 nm (FeIX-XI) and a fast cadence of ≈1 min. The telescope is based on an off-axis Ritchey Chretien design while an extreme ultraviolet (EUV) enhanced APS CMOS will be used as a detector. As the prime goal of the SWAP is solar monitoring and advance warning of Coronal Mass Ejections (CME), on-board intellige nce will be implemented. Image recognition software using experimental algorithms will be used to detect CMEs during the first phase of eruption so the event can be tracked by the spacecraft without huma n intervention. LYRA will monitor solar irradiance in four different VUV passbands with a cadence of up to 100 Hz. The four channels were chosen for their relevance to solar physics, aeronomy and space weather: 115-125 nm (Lyman-α), 200-220 nm Herzberg continuum, the 17-70 nm Aluminium filter channel (that includes the HeII line at 30.4 nm) and the 1-20 nm Zirconium filter channel. On-board calibration sources will monitor the stability of the detectors and the filters throughout the duration of the mission.
The first Meteosat Second Generation (MSG) satellite was launched in August 2002. This EUMETSAT satellite carries 2 new instruments on the geostationary orbit: the Spinning Enhanced Visible and InfraRed Imager, SEVIRI, and the Geostationary Earth Radiation Budget, GERB. The unique feature of GERB in comparison with previous measurement missions of the Earth's radiation budget (e.g. ERBE, ScaRab and CERES experiments) is the high temporal sampling afforded by the geostationary orbit, albeit for a limited region of the globe. The GERB instrument provides accurate broadband measurements of the radiant energy originating in the reflection of the incoming solar energy by the Earth-atmosphere system and in the thermal emission within this system. The synergetic use of the SEVIRI data is needed to convert these directional measurements (radiances) into radiative fluxes at the top-of-atmosphere. Additionally, the SEVIRI data allows the enhancement of the spatial resolution of the GERB measurement. This paper describes the near real-time GERB processing system that has been set up at the Royal Meteorological Institute of Belgium (RMIB). This includes the unfiltering of the instrument data, the radiance-to-flux conversions and the enhancement of the instrument spatial resolution. An early validation of the instrument data by comparison with CERES data is presented. Finally, the different data formats, the way to access them and their expected accuracy are presented.
The Geostationary Earth Radiation Budget (GERB) instrument has been launched this summer together with the Spinning Enhanced Visible and InfraRed Imager (SEVIRI) on board of the Meteosat Second Generation (MSG) satellite. This broadband radiometer will aim to deliver near real-time estimates of the top of the atmosphere (TOA) radiative fluxes at the high temporal resolution due to the geostationary orbit. In order to infer these fluxes, a radiance-to-flux conversion based on Clouds and the Earth's Radiant Energy System (CERES) angular dependency models (ADMs) need to be performed on measured radiances. Due to the stratification of these ADMs according to some CERES scene identification (SI) features such as cloud optical depth and cloud fraction, the GERB ground segment must include some SI on SEVIRI data which mimic as close as possible the one from CERES in order to select the proper ADM. In this paper, we briefly present the method we used to retrieve cloud optical depth and cloud fraction on footprints made of several imager pixels. We then compare the retrieval of both features on the same targets using nearly time-simultaneous Meteosat-7 imager and CERES Single Satellite Footprint (SSF) data. The targets are defined as CERES radiometer footprints. We investigate the possible discrepancies between the two datasets according to surface type and, if they exist, suggest some strategies to homogenize GERB retrievals based on CERES ones.
In this paper the system employed at the Royal Meteorological Institute of Belgium (RMIB) within the Climate Monitoring Satellite Application Facility (CM-SAF) for the production of Top Of the Atmosphere (TOA) radiation budget components is described. One of the goals of the CM-SAF is to provide consistent TOA and surface radiation budget components and cloud properties at high spatial resolution and on an approximate equal area grid for a region that covers at least Europe and part of the North Atlantic Ocean. The TOA radiation products will be based on data from polar orbiting satellites for northern latitudes, and on data from MSG (METEOSAT Second Generation) for mid latitudes. The instruments used for the reflected solar and emitted thermal flux estimates will be GERB (Geostationary Earth Radiation Budget) and SEVIRI as the geostationary instruments and CERES (Clouds and the Earth's Radiant Energy System) for the non geostationary instruments. Daily means, monthly means and monthly mean diurnal cycles are to be provided. Until MSG fluxes will become available, fluxes from METEOSAT and CERES are used for development. At the TOA the three radiative flux components of incoming solar radiation, reflected solar radiation and emitted thermal radiation will be given. The daily mean GERB and CERES fluxes will be merged to produce a homogenized TOA flux product. The method used for the merging of the TOA fluxes and together with results using currently available input data are shown. The merging consists in the collocation of the two instruments, detection and the removal of the systematic dependencies of the flux estimates on scene type and viewing angles and regridding on a common grid.