From/de Gregg Wade
(Cassiopeia – Summer/été 2016)
BRITE-Constellation (where BRITE stands for BRIght Target Explorer) is a network of five nanosatellites operating in low Earth orbit, designed to explore the properties of the brightest stars in the night sky.
Figure 1 – The mission patch of the BRITE-Constellation mission.
The BRITE mission is supported by three countries — Canada, Austria and Poland — where Canadian funding comes mainly from the Canadian Space Agency (CSA) and the prime contractor is the University of Toronto Institute for Aerospace Studies – Spaceflight Laboratory (UTIAS-SFL). The mission was planned to have 6 BRITE nanosats, a pair from each partner country, but one of the Canadian nanosats did not detach from the third stage of its launch vehicle. Each BRITE nanosat (mass = 7 kg; dimensions 20 × 20 × 20 cm) has a 3-cm optical telescope feeding a CCD detector. The Constellation was designed to monitor photometrically through blue and red filters the brightness and temperature variations of stars generally brighter than V ~ 4 with precision, cadence and time coverage not possible from the ground. Each BRITE instrument has an enormous field-of-view: 24° square, large enough to encompass the entire constellation of Orion (but at a resolution of only about half an arcminute per pixel). That means BRITE-Constellation can collect data on several dozens of stars simultaneously.
Figure 2 – Hertzsprung-Russell diagram of the stars of brightest apparent magnitude, V<4.5. These ∼ 600 stars are the primary BRITE targets.
The sample of the apparently brightest stars in the night sky is a sample dominated by the most intrinsically luminous stars in the Galaxy: hot massive stars at all evolutionary stages, and evolved intermediate-mass stars at the very end of their nuclear-burning phases. The main goals of BRITE-Constellation are to (1) measure the frequencies of pulsations (both acoustic and gravity modes) to probe the interiors and ages of stars through asteroseismology; (2) measure the rotational modulation of stars due to star spots carried across their disks; (3) search for exoplanets through transits; and (4) obtain light curves of massive eclipsing binaries. While goal (2) is often associated with cool solar-type stars, spots in the photospheres of luminous stars could be the sources of co-rotating interaction regions in the winds, possibly arising from magnetic subsurface convection in hot, massive stars.
A detailed overview of the scientific motivation of the mission, and technical aspects of the system, are provided by Weiss et al. (2015, PASP 126, 573).
Mission Status and Data Releases
Five of the planned six BRITE nanosats are currently operating nominally in low-altitude (600-800 km) orbits. (One satellite currently remains unusable in a higher elliptical orbit due to a malfunction in the release mechanism of the Russian rocket third stage.)
Figure 3 – The two Canadian BRITE nanosatellites (named “BRITE-Montreal”, blue filter and “BRITE-Toronto”, red filter), at UTIAS-SFL prior to shipment in 2014.
Eleven fields have been observed so far, and ten data releases to BRITE Target PIs have occurred. The first was a set of science commissioning data, including about 5 months of quasi-continuous observation of 15 stars in Orion. Subsequent releases were 6-month campaigns of fields in Centaurus and Lupus (30 stars), Sagittarius (18 stars), Cygnus (37 stars), and Perseus (31 stars). Orion was observed again, as were fields in Vela and Puppis (20 stars), Scorpius (26 stars), Cygnus-II (34 stars) and Cassiopeia/Cepheus (25 stars). The distribution of the third Orion field and the second Vela and Puppis field data will begin shortly. Reduction of the recently-observed Canis Majoris and Puppis field images is ongoing and shall be completed by the end of June. Currently, the Crucis and Carina field is being observed (and will remain visible until July), as are the second Sagittarius and the Cygnus and Lyra fields (which will continue to be visible until September/October 2016).
The first BRITE science results have been accepted in refereed journals: Three science papers by Weiss et al. on the pulsating magnetic star α Cir, by Baade et al. on the short-term variability and mass loss of the Be stars μ and η Cen, and by Pigulski et al. on the triple system β Cen (a complex system containing at least one β Cep pulsator) have been published together in issue 588 of Astronomy and Astrophysics.
A new paper describing the characteristics of the BRITE hardware and technical problem-solving on the ground and after launch led by Dr. Bert Pablo (Université de Montréal) has been submitted to PASP.
The first BRITE science conference, “Science with BRITE Constellation: Initial Results” took place during 14 – 18 September 2015 in Gdansk Sobieszewo, Poland. The next BRITE science workshop is planned from 22-26 August in Innsbruck, Austria. Registration is now available at this link.
Figure 4 – Light curves of the eclipsing binary V Pup, observed as part of the BRITE Vela/Puppis field. Shown here is a 5-day interval of the BRITE-Austria (blue) and BRITE-Toronto (red) observations.
Mission Management and Contact
Executive decisions about the mission are made by the BEST (BRITE Executive Science Team), consisting of representatives from all three partner nations. The Canadian BEST members are Jaymie Matthews (UBC), Tony Moffat (Université de Montréal), Slavek Rucinski (University of Toronto), and Gregg Wade (BEST Vice-Chair and Canadian PI, Royal Military College), with Jason Rowe (Université de Montréal) and Stefan Mochnacki (University of Toronto) serving as non-voting BEST members.
Setting priorities on BRITE targets and science goals was overseen by BEST, with input from the BRITE International Science Advisory Team (BIAST), consisting of 130 astronomers around the globe. Interested in joining BIAST, to participate in data analysis, and receive monthly mission updates? Please contact BEST through Gregg Wade (firstname.lastname@example.org).
Baade, D.; Rivinius, Th.; Pigulski, A.; Carciofi, A. C.; Martayan, Ch.; Moffat, A. F. J.; Wade, G. A.; Weiss, W. W.; Grunhut, J.; Handler, G.; Kuschnig, R.; Mehner, A.; Pablo, H.; Popowicz, A.; Rucinski, S.; Whittaker, G., 2016, “Short-term variability and mass loss in Be stars. I. BRITE satellite photometry of η and μ Centauri”, A&A, 588, 56
“The BRITE Constellation cubesat mission: Testing, commissioning and operations”, B. Pablo and 28 co-authors, under review for publication in Publications of the Astronomical Society of the Pacific
Pigulski, A.; Cugier, H.; Popowicz, A.; Kuschnig, R.; Moffat, A. F. J.; Rucinski, S. M.; Schwarzenberg-Czerny, A.; Weiss, W. W.; Handler, G.; Wade, G. A.; Koudelka, O.; Matthews, J. M.; Mochnacki, St.; Orleański, P.; Pablo, H.; Ramiaramanantsoa, T.; Whittaker, G.; Zocłońska, E.; Zwintz, K.; 2016, “Massive pulsating stars observed by BRITE-Constellation. I. The triple system beta Centauri (Agena)”, A&A, 588, 55
Weiss, W.W.; Rucinski, S.M.; Moffat, A.F.J.; Schwarzenberg-Czerny, A.; Koudelka, O.F.; Grant, C.C.; Zee, R.E.; Kuschnig, R.; Mochnacki, St.; Matthews, J.M.; Orleanski, P.; Pamyatnykh, A.; Pigulski, A.; Alves, J.; Guedel, M.; Handler, G.; Wade, G.A.; Zwintz, K., 2014, “BRITE-Constellation: Nanosatellites for Precision Photometry of Bright Stars”, PASP 126, 573.
Weiss, W.W.; Frohlich, H.-E.; Pigulski, A.; Popowicz, A.; Huber, D.; Kuschnig, R.; Moffat, A.F.J.; Matthews, J.M.;, Saio, H.; Schwarzenberg-Czerny, A.; Grant, C; Koudelka, O.; Lueftinger, T.; Rucinski, S.; Wade, G.A.; Alves, J.; Guedel, M.; Handler, G.; Mochnacki, S.; Orleanski, P.;, Pablo, B.; Pamyatnykh, A.; Ramiaramanantsoa, T; Rowe, J.; Whittaker, G.; Zawistowski, T.; Zoconska, E.; Zwintz, K., 2016, “The roAp star alpha Cir seen by BRITE-Constellation”, A&A, 588, 54