BRITE-Constellation: Nanosatellites for precision photometry of bright stars

Author(s)
W. W. Weiss, A. F. J. Moffat, A. Schwarzenberg-Czerny, O. F. Koudelka, C. C. Grant, R. E. Zee, R. Kuschnig, St. Mochnacki, S. M. Rucinski, J. M. Matthews, P. Orleański, A. A. Pamyatnykh, A. Pigulski, J. Alves, M. Guedel, G. Handler, G. A. Wade, A. L. Scholtz
Abstract

BRITE-Constellation (where BRITE stands for BRIght Target Explorer) is

an international nanosatellite mission to monitor photometrically, in

two colours, brightness and temperature variations of stars brighter

than V ~ 4, with precision and time coverage not possible from the

ground. The current mission design consists of three pairs of 7 kg

nanosats (hence ``Constellation'') from Austria, Canada and Poland

carrying optical telescopes (3 cm aperture) and CCDs. One instrument in

each pair is equipped with a blue filter; the other, a red filter. The

first two nanosats (funded by Austria) are UniBRITE, designed and built

by UTIAS-SFL (University of Toronto Institute for Aerospace

Studies-Space Flight Laboratory) and its twin, BRITE-Austria, built by

the Technical University Graz (TUG) with support of UTIAS-SFL. They were

launched on 25 February 2013 by the Indian Space Agency, under contract

to the Canadian Space Agency.

 

Each BRITE instrument has a wide field of view (~ 24 degrees), so up to

15 bright stars can be observed simultaneously in 32 × 32

sub-rasters. Photometry (with reduced precision but thorough time

sampling) of additional fainter targets will be possible through

on-board data processing. A critical technical element of the BRITE

mission is the three-axis attitude control system to stabilize a nanosat

with very low inertia. The pointing stability is better than 1.5

arcminutes rms, a significant advance by UTIAS-SFL over any previous

nanosatellite.

 

BRITE-Constellation will primarily measure p- and g-mode pulsations to

probe the interiors and ages of stars through asteroseismology. The

BRITE sample of many of the brightest stars in the night sky is

dominated by the most intrinsically luminous stars: massive stars seen

at all evolutionary stages, and evolved medium-mass stars at the very

end of their nuclear burning phases (cool giants and AGB stars). The

Hertzsprung-Russell diagram for stars brighter than mag V=4 from which

the BRITE-Constellation sample will be selected is shown in Fig. 1. This

sample falls into two principal classes of stars:

 

(1) Hot luminous H-burning stars (O to F stars). Analyses of OB star

variability have the potential to help solve two outstanding problems:

the sizes of convective (mixed) cores in massive stars and the influence

of rapid rotation on their structure and evolution.

 

(2) Cool luminous stars (AGB stars, cool giants and cool supergiants).

Measurements of the time scales involved in surface granulation and

differential rotation will constrain turbulent convection models.

 

Mass loss from these stars (especially the massive supernova

progenitors) is a major contributor to the evolution of the interstellar

medium, so in a sense, this sample dominates cosmic ``ecology'' in terms

of future generations of star formation. The massive stars are believed

to share many characteristics of the lower mass range of the first

generation of stars ever formed (although the original examples are of

course long gone).

 

BRITE observations will also be used to detect some Jupiter- and even

Neptune-sized planets around bright host stars via transits, as expected

on the basis of statistics from the Kepler exoplanet mission. Detecting

planets around such very bright stars will greatly facilitate their

subsequent characterization. BRITE will also use surface spots to

investigate stellar rotation.

 

The following Table summarizes launch and orbit parameters of

BRITE-Constellation components.

 

The full version of this paper describing in more detail

BRITE-Constellation will be published separately in a journal. The

symposium presentation is available at

iaus301.astro.uni.wroc.pl/program.php

Organisation(s)
Department of Astrophysics
External organisation(s)
University of Montreal, Polish Academy of Sciences (PAS), Technische Universität Graz, University of Toronto, Royal Military College of Canada, Technische Universität Wien
Volume
301
Pages
67-68
DOI
https://doi.org/10.1017/S1743921313014105
Publication date
02-2014
Austrian Fields of Science 2012
103003 Astronomy, 103004 Astrophysics
Keywords
Portal url
https://ucris.univie.ac.at/portal/en/publications/briteconstellation-nanosatellites-for-precision-photometry-of-bright-stars(b6a6e2d5-90f1-41b1-b66c-ac682c47e319).html