SWAP onboard PROBA 2, a new EUV imager for solar monitoring

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Abstract

SWAP (Sun Watcher using Active Pixel system detector and image processing) is a solar imager in the extreme ultraviolet (EUV) that has been selected to fly in 2007 on the PROBA 2 technological platform, an ESA program. SWAP will use an off-axis Ritchey Chrétien telescope equipped with an EUV enhanced active pixel sensor detector (coated APS). This type of detector has advantages that promise to be very profitable for solar EUV imaging. SWAP will provide solar coronal images at a 1-min cadence in a bandpass centered on 17.5 nm. Observations with this specific wavelength allow detecting phenomena, such as solar flares or EIT-waves, associated with the early phase of coronal mass ejections. Image processing software will be developed that automatically detects these phenomena and sends out space weather warnings. Together with its sister instrument LYRA, also onboard PROBA 2, SWAP will serve as a high performance solar monitoring tool to be used in operational space weather forecasting. The SWAP data will complement the solar observations provided by instruments like SOHO-EIT, and STEREO-SECCHI.

Section snippets

PROBA 2, a micro-satellite as solar observatory

PROBA 2 is a follow up of the successful PROBA 1 (Teston et al., 2004) program, in orbit since October 2001. The spacecraft is a micro-satellite not larger than a domestic washing machine with a weight of 100 kg. It will be launched on a Rockot launcher in February 2007 as a piggy back payload together with the ESA SMOS satellite. PROBA 2 will be launched to a heliosynchronous polar orbit along the dawn-dusk line which guarantees nearly uninterrupted solar viewing (besides eclips season of max 20

Technical innovations

As a part of a technology demonstration mission, SWAP contains several technical innovations which are necessary to stay within the very strict resource budget: SWAP mass is limited to 10 kg, with a mean power dissipation lower than 5 W. The SWAP telescope is based on a novel off-axis Ritchey-Chrétien scheme (Defise et al., 2004). The off-axis design leads to several advantages: (i) smaller and lighter primary mirror for a given pupil area (no central obscuration); (ii) smaller aluminum foil

SWAP images

The aspheric mirrors are polished from zerodur with a micro-roughness below 0.5 nm. The EUV reflectivity and spectral selection is provided by specific multilayer coatings deposited on the mirrors. The mirrors will be coated by Institut d’Optique Théorique et Appliquée (IOTA, France). The coating is a mutilayer composed of 30 alternating layers of 2 different materials (Mo/Si) optimized for the best near normal reflection in the 1.3 nm band centered on 17.5 nm. First results of efficiency

Science and space weather services

The SWAP design will allow imaging of the various solar drivers of space weather such as coronal holes, flares and last but not least coronal mass ejections. Thanks to its enlarged field of view and higher cadence, SWAP will be better suited than EIT to catch eruptions above the limb. Also on-disc signatures of coronal mass ejections, such as EIT waves and dimmings will be better observed. With the nominal EIT cadence of 12 min, an EIT wave is typically observed in 3–4 images. This is sufficient

The road ahead

Despite very limited platform resources, a solar payload will be operated on a technology demonstration micro-satellite. SWAP and LYRA have been designed to provide valuable inputs for space weather monitoring and new data for scientific research.

SWAP and LYRA will demonstrate the feasibility of key-technology that will be highly beneficial in the context of the Solar Orbiter ESA mission. New detectors, new compact optical scheme and on-board processing are essential elements for this ESA

Acknowledgements

The development of the SWAP instrument is funded by the Belgian Federal Science Policy Office (BELSPO), through the ESA/PRODEX programme. The SWAP project is supported by the German and Italian Co-Investigator’s institutions, the Max-Plank-Institut für Sonnensystemforschung and the University of Padova. During the preparation of this paper, we have learnt the sudden death of Pierre Cugnon. He was the department head of the ROB Solar Physics department, but was also a dear friend or a colleague

References (11)

  • D. Berghmans et al.

    The solar influences data analysis centre

    J. Atmos. Terr. Phys.

    (2002)
  • Defise, J., Berghmans, D., Hochedez, J.F., Lecat, J.M., Mazy, E., Rochus, P.L., Thibert, T., Nicolosi, P., Pelizzo,...
  • J.-P. Delaboudiniere et al.

    EIT: Extreme-Ultraviolet Imaging Telescope for the SOHO Mission

    Sol. Phys.

    (1995)
  • K.P. Dere et al.

    CHIANTI – an atomic database for emission lines

    Astron. Astrophys.

    (1997)
  • Dierickx, B., Meynants, G., Scheffer, D. Near 100% fill factor CMOS active pixels, in: IEEE CCD & AIS workshop...
There are more references available in the full text version of this article.

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