www.brite-constellation.atBRITE-Constellation consists of six nano-satellites: UniBRITE and BRITE-AUSTRIA (TUGSAT-1) are funded by Austria, two more by Poland and the remaining two satellites by the Canadian Space Agency. Each will fly a CCD camera to perform high-precision, two-color photometry primarily of bright stars, and continuously for two years or more. BRITE-Constellation expects to observe on average 20 stars simultaneously.

The primary science goals are studies of massive stars in our Galactic neighborhood, representing objects which dominate the ecology of our Universe, and also highly evolved giant stars of lower mass to probe the future develop-ment of our Sun. The operation policy will be to observe a few fields over a long time span and possibly some short runs in between, which will assure optimum use of near polar low-earth orbits.

BRITE-Constellation reflects technology currently developed in collaboration between Canada and Austria. A launch of the first pair, UniBRITE and BRITE-AUSTRIA, is planned in mid 2011 by a PSLV from India.

SatellitesEach of the 7kg BRITE nano-satellites is equipped with a small dioptric telescope. A “constellation” of satellites provides improved time coverage and two-color information: one satellite carries a blue and the other a red filter.

The 20cm cube structure houses three orthogonal reaction wheels and three magnetorquer coils for three-axis attitude control. Attitude determination is provided by a magnetometer, six sun sensors and a star tracker. This equipment will enable pointing accuracy to better than one degree, attitude deter-mination to one arcminute or better, and attitude stability down to one arcminute rms.

BRITE FiltersThe effective wavelength range of the UniBRITE instrument will be defined by a red filter covering 550-700nm, and the BRITE-AUSTRIA instrument by a blue filter covering 390-460nm.

Figure: BRITE BLUE and RED Filter transmission

Targets are the 534 stars brighter than V = 4.0 mag and with reduced accuracy also fainter stars. Typical time scales for their variability range from an hour to several weeks which calls for long and uninterrupted data sets providing a frequency resolution sufficient for astero-seismology.

Figure: position of brightest stars (<= 4mag)

The figure below shows the location of the bright targets in the Hertzsprung-Russell Diagram color-coded with the object types taken from the VISAT database.

The first Announcement of Opportunity for submission of observing proposals has been released in 2008 to the community and more than 40 proposals were submitted to the BRITE Executive Science Team (BEST).

Figure: HRD of the brightest stars (<= 4mag)

InstrumentThe science payload of the satellite consists of a five-lens telescope with an aperture of 30mm and an interline CCD detector (KAI 11002-M) from Kodak with 11M (4008x2672) pixels, along with a baffle to reduce stray light. The instrument has a resolution of 26.5 arcseconds per pixel and a field-of-view of 24 degrees.

Figure: BRITE telescope and CCD

Ground stationsUp to 400 data sets will be obtained from a target field per day and transmitted via ground stations located in Graz, Vienna, Toronto and Warsaw.

Figure: BRITE ground station at the TUG Graz

Poster Design: Rainer Kuschnig, Alex Kaiser, Werner W. Weiss, Institute for Astronomy University Vienna, Austria Contact: rainer.kuschnig@univie.ac.at

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