1. BRITE-Constellation currently consists of two satellites, UniBRITE and BRITE-AUSTRIA (TUGSAT-1) and two satellites to be funded by the Canadian Space Agency (CSA). Each will fly a CCD camera to perform high-precision two-color photometry continuously for two years or more, primarily of stars brighter than 4 th magnitude (V), and with reduced accuracy also of fainter stars. The primary science goals are studies of massive stars in our Galactic neighbourhood, 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 is made possible by innovative technology currently developed in collaboration between Canada and Austria. A launch of UniBRITE and BRITE-AUSTRIA in late 2010 is envisioned. Each of the 7kg BRITE 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 and momentum dumping. Attitude determination is provided by a magnetometer, six sun sensors and a star tracker. This equipment will enable attitude determination to 1 arcminute or better, attitude control accuracy to better than a degree, and attitude stability down to one arcminute rms. Instrument The 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 pixels, along with a baffle to reduce stray light. The instrument has a resolution of 26.52 arcseconds per pixel and a field-of-view of 24 degrees. Figure: BRITE telescope and CCD BRITE Filters The effective wavelength range of the UniBRITE instrument will be defined by a blue filter covering 390-460nm and the BRITE-AUSTRIA instrument by a red filter constrained to 550-700nm. Figure: Field of view centered on Orion BRITE-Constellation will photometrically measure low-level oscillations and temperature variations in stars brighter than visual magnitude 4.0 (and with less accuracy also down to a visual magnitude of 7.0). There are 534 stars brighter than V = 4.0 mag in the sky and observable at the proposed precision level with BRITE-Constellation. Considering the typical time scales for their variability ranging from an hour to several weeks and aiming for a frequency resolution sufficient for astero- seismology, BRITE-Constellation expects to observe on average 20 stars simultaneously. The figure below shows the location of the 534 stars with V ≤ 4 mag 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 from the community has been released (Sep. 2008) at www.brite-constellation.at by the BRITE Executive Science Team. Figure: The HRD of the 534 brightest (V ≤ 4 mag) targets Ground stations Up to 400 data sets will be obtained from a target field per day and transmitted via ground stations located in Graz, Vienna and Toronto. Figure: BRITE ground station located in Graz Engineering Team Science Team Funding Agencies Nanosatellites for Astrophysics www.brite-constellation.at Contact: Werner Weiss (UniBRITE, U. Vienna), Otto Koudelka (BRITE-AUSTRIA, TU Graz), Anthony Moffat (Canadian BRITEs, U. Montréal), Robert Zee (Canadian Program Manager, U. Toronto)