BRITE (BRIght-star Target Explorer) Constellation / BRITE Poland / Lem / Heweliusz
The BRITE constellation, under development at UTIAS/SFL (University of Toronto, Institute for Aerospace Studies/Space Flight Laboratory), consists of a group of up to six nanosatellites with the following participants of the BRITE consortium: 1)
1) The University of Vienna and FFG/ALR (Austria's Space Agency) are financing the development of two BRITE nanosatellites and development is nearing completion in 2010.
2) The CSA (Canadian Space Agency) is also expected to fund two nanosatellites in the constellation (ordering in 2010).
3) SRC/PAS (Space Research Center/ Polish Academy of Sciences), Warsaw, Poland will be preparing two additional satellites. The first Polish satellite, BRITE-PL-1, will be a modified version of the original SFL design. The second Polish satellite, BRITE-PL-2, will include the significant changes to be implemented by SRC PAS.
The Polish technical participation in the BRITE project is supported by the Ministry of Science and High Education. The participation in the BRITE consortium gives Poland the possibility to launch its first Polish scientific satellite into space. The Polish participation in the BRITE consortium was established in October 2009 by SRC/PAS and NCAC/PAS (Nicolaus Copernicus Astronomical Center/ Polish Academy of Sciences). 2) 3)
In February 2006, FFG/ARL (Austrian Aeronautics and Space Agency) of Vienna, Austria, funded a small satellite program, called BRITE, with the following partners:
- TUG (Graz University of Technology)
- University of Vienna and the Technical University Vienna.
Close cooperation had already been established with UTIAS/SFL - providing significant expertise in building and operating of small satellites. The BRITE project is based on the successful Canadian CanX satellites.
On Feb. 25, 2013, the two first BRITE nanosatellites, referred to as TUGSat-1 or BRITE-Austria of TUG, and UniBRITE of the University of Vienna and the Technical University Vienna, were launched as secondary payloads on the PSLV-C20 vehicle of ISRO. 4)
The BRITE project gives Polish scientists a big opportunity to realize a very interesting scientific program by participating in a relatively low cost space experiment. On the other hand, the same BRITE project has been found as a very good platform for Polish engineers to learn how to build (in sense of designing, manufacturing, integrating, testing, managing and finally operating) complete small satellites. These two advantages of BRITE played an important role when the BRITE-PL agreement had been signed in December 2009 between NCAC (Nicolaus Copernicus Astronomical Center) and SRC (Space Research Center), both of the Polish Academy of Sciences and both from Warsaw.
The next step had been done when the Ministry of Science and Higher Education in Poland approved a grant for the BRITE-PL project in early 2010. In parallel, at the beginning of 2010, the Polish group has been invited to the BRITE Consortium (Austria and Canada), offering to the consortium the scientific collaboration and additional two satellites for the BRITE constellation. - In May 2010, an official agreement was signed between SRC and UTIAS/SFL covering the technical program of BRITE-PL. 5)
The BRITE technical program in Poland will be realized mostly in SRC/PAS. UTIAS/SFL is the main partner and contractor for the delivery of the BRITE satellite constellation. SFL has the full copyrights for BRITE satellite design.
The contract negotiations between Poland and UTIS/SFL cover the mentoring activities, the transfer of BRITE satellite know-how and finally the two sets of BRITE satellite subsystems to be delivered to Poland. The different pieces of Ground Segment including the part of hardware and part of software are also included. Both sets of satellite subsystems will be integrated and tested by the Polish team with mentoring and supervising support from UTIAS/SFL.
BRITE-PL-1 is planned to be a copy of one of the Austrian satellites – the one which is equipped with the blue filter. Only a few differences in manufacturing process are taken into account for this satellite. Close cooperation with colleagues from Graz, where a similar satellite is integrated, is planned. The second satellite, BRITE-PL-2, will be significantly different. Some of the subsystems of BRITE-PL-2 are to be completely redesigned, some of them are to be modified.
The integration of both satellites in Poland is very important for Polish authorities, particularly with the respect to carry out complete testing before launching them into the orbit.
Polish activities within the BRITE program:
• Work package 1 is dedicated to BRITE-PL-1 manufacturing activities. The satellite will be almost identical to the "blue" Austrian nanosatellites. The main purposes of this work package are:
- Getting familiar with the technology of the BRITE satellite, incoming activities done for BRITE-PL 1 subsystems delivered from SFL, assembly, integration, verification, and tests of the first satellite in Poland. The important part of this work package will be the refurbishment of SRC infrastructure (upgrade the clean room, set up of additional laboratories, design and manufacturing of necessary GSE).
- In addition to the subsystems delivered by SFL, the mechanical and thermal calculations should be fully done in Poland, the mechanical structure should be manufactured fully in Poland according to SFL documentation and the optical part of the telescope should be modified or refurbished.
• Work package 2 is dedicated to BRITE-PL-2 manufacturing activities. There are two main goals of this work package:
- First - to manufacture the second satellite with almost the same functionality as BRITE-PL-1 (UV instead blue range is an exception)
- Second - to replace a few SFL subsystems by their replicas developed in SRC. Some proposed changes are:
1) Change of the spectral band range used. Observations in the range 350-400 nm are found as very promising complimentary ones to the data collected in "blue" and "red" bands.
2) Improvement of the OBC architecture in terms of reliability.
• Work package 3 is dedicated to all activities connected to Polish ground station. The Nicolaus Copernicus Center leads this work package with the technical support from SRC. The activities include the development of the ground station (HW and SW), the development of the MCC (Mission Control Center), the preparation of the data analysis software, and finally the coordination of the radio frequency for the ground station.
• Work package 4 is dedicated to all managerial, administrative and PQA (Project Quality Assurance) activities. The important part of this work package is the launch preparation of both satellites.
BRITE-PL-1 and BRITE-PL-2 nanosatellites:
All spacecraft in the constellation use the GNB (Generic Nanosatellite Bus) platform, referred to as CanX-3, developed at UTIAS/SFL (of CanX-2 heritage). The description summarizes the design of BRITE satellite.
Figure 1: Illustration of the BRITE spacecraft (image credit: UTIAS/SFL)
The GNB was originally developed in SFL for BRITE and Can-X-4/5 missions. The satellite measures 200 mm x 200 mm x 200 mm in size, has the mass of about 7 kg and includes a full suite of advanced capabilities. This includes:
• A dual battery, gallium arsenide triple-junction solar cell based power system that includes peak power tracking capabilities
• A full 3-axis attitude determination and control system that allows arbitrary inertial or orbit-frame alignment (including nadir, along-track and cross-track)
• A powerful complement of on-board computer processing systems, include a computer dedicated to payload activities
• A flexible TT&C and payload data RF communication system, allowing for variable and high speed data downlinks to the ground
• A large accommodation for payloads, including volume, mass, power, and spacecraft surface area
• Attitude determination: 10 arcseconds
• Attitude control accuracy: better than 1.0º
• Attitude control stability: 1 arcmin rms (root mean square)
• Power: 5.4 W to 10 W
• Battery capacity 5.3 Ah
• Data downlink: up to 256 kbit/s
• Payload data storage capacity: up to 256 MB.
Figure 2: SFL GNB (Generic Nanosatellite Bus), some subsystems are optional and are not used for BRITE (image credit: UTIAS/SFL
The additional scientific requirements for a BRITE satellite are: visual magnitude limit for observed stars - minimum +3.5, positional constrains - none except for Sun, Earth and Moon exclusion zones, telescope FOV (Field of View): 24º diameter, differential photometry < 0.1%, error of amplitude spectrum for the period > month - 2 x 10-5 (20 ppm), cadence (repeat of the same field) < 100 minutes, duration of the mission for any satellite - longer than 2 years.
The structural design of the GNB has evolved into the current dual tray design, with a standard volume payload bay between both trays. The structural strength of the satellite responsible for supporting the vibration loads experienced during launch is mainly ensured by the trays and the payload support structure.
Figure 3: Exploded view of Can X-3 (BRITE) satellite (image credit: UTIAS/SFL)
The 2 mm thick panels with cross braces offer additional rigidity to the structure providing a mounting surface for the solar cells, most sun sensors, the magnetometer boom, the magnetorquers and the various antennas. All other components, such as the reaction wheels, various computer boards, battery assemblies, radios and some of the sun sensors are mounted directly to either tray.
The thermal control of the spacecraft is mostly accomplished using passive methods (10-30ºC). A battery heater is included to keep the batteries sufficiently warm.
The power subsystem uses direct energy transfer to distribute power generated by high-efficiency triple junction solar cells to the satellite components. The bus voltage is unregulated and is nominally 4.0 V. A 5.3 Ah rechargeable lithium-ion battery provides power for use during eclipses and periods of peak power usage. In the nominal case, at least six cells can be placed on a face for a maximum instantaneous power generation of about 10W. The worst-case power generation is approximately 5.4 W.
The satellite contains a main OBC (On-Board Computer) and an attitude determination and control computer. These computers use an identical design, which is built around an ARM7 processor operating at approximately 60 MHz. Each OBC contains 256 kB of FLASH memory for code storage, 1 MB of EDAC protected SRAM for storage of data and variables and 256 MB of Flash for long-term storage of telemetry and payload data.
RF communications: Each CanX-3/BRITE nanosatellite is capable of full duplex communications with the ground. The uplink uses UHF while an S-band transmitter with BPSK modulation is used in the downlink. Each satellite can also support a VHF beacon.
The uplink is provided through a SFL-developed UHF transceiver (437.365MHz, 4Kbps). An S-band transmitter (2234.4 MHz, 0.5 W, Figure 4), also developed at SFL provides the primary downlink and can work at data rates from 32 kbit/s to 256 kbit/s, max 2 MB/day (BPSK/QPSK). Each radio system is housed in a separate enclosure to minimize noise and interference. The UHF transceiver communicates with the ground via a pre-deployed quadcanted monopole antenna array, which provides near omnidirectional coverage. The S-band transmitter uses two 5.5 cm x 5.5 cm SFL-developed patch antennas, installed on opposite sides of the spacecraft. Combined, these patches provide near omni-directional coverage.
The BRITE satellite bus houses three orthogonal reaction wheels, each 5 cm x 5 cm x 4cm, 185 g, 100 mW nominal power (Figure 5) and three orthogonal vacuum-core magnetorquer coils for three-axis attitude control and momentum dumping. Attitude determination is provided by a magnetometer and six SFL developed sun sensor packages, each of which is equipped with coarse and fine sun-sensing elements. The bus will also carry a nanosatellite star tracker. This will enable attitude determination to 10 arcseconds, attitude control accuracy to better than 1º, and attitude stability to within one arc minute rms. The reaction wheel assembly was developed by Sinclair Interplanetary of Toronto in collaboration with UTIAS/SFL. The BRITE constellation is the first mission to use this actuator (3 wheels).
Figure 5: Photo of the reaction wheel shown with a penny for scale (image credit: UTIAS/SFL)
Table 1: Summary of the BRITE spacecraft bus specifications
Launch: The BRITE-PL-1 nanosatellite (also referred to as "Lem" after the late Polish science fiction writer Stanislaw Lem) was launched on Nov. 21, 2013 (07:10:11 UTC) as a secondary payload on a Dnepr-1 vehicle from the Yasny Cosmodrome in Russia. The launch provider was ISC Kosmotras of Moscow. The primary payloads on the flight were: DubaiSat-2 of EIAST, Dubai (mass of ~ 300 kg) and STSat-3 (Science and Technology Satellite-3) of KARI, Korea (mass of ~ 150 kg). 6) 7) 8) 9) 10) 11)
The secondary payloads on this flight were:
• SkySat-1 of Skybox Imaging Inc., Mountain View, CA, USA, a commercial remote sensing microsatellite of ~100 kg.
• WNISat-1 (Weathernews Inc. Satellite-1), a nanosatellite (10 kg) of Axelspace, Tokyo, Japan.
• BRITE-PL-1, a nanosatellite (7 kg) of SRC/PAS (Space Research Center/ Polish Academy of Sciences of Warsaw, Poland.
• AprizeSat-7 and AprizeSat-8, nanosatellites of AprizeSat. AprizeSat-7 and 8 are the ninth and tenth satellites launched as part of the AprizeSat constellation, operated by AprizeSat. The constellation, which was originally named LatinSat, was initially operated by Aprize Argentina; however ownership of the constellation was later transferred to their US parent company AprizeSat. The AprizeSat constellation is used for store-dump communications, and some satellites carry AIS (Automatic Identification System) payloads for Canadian company ExactEarth. The AprizeSat spacecraft were built by SpaceQuest Ltd. Of Fairfax, VA, USA, and each has a mass of 12 kg. 12)
• UniSat-5, a microsatellite of the University of Rome (Universita di Roma "La Sapienza", Scuola di Ingegneria Aerospaziale). The microsatellite has a mass of 28 kg and a size of 50 cm x 50 cm x 50 cm. When on orbit, UniSat-5 will deploy the following satellites with 2 PEPPODs (Planted Elementary Platform for Picosatellite Orbital Deployer) of GAUSS:
- PEPPOD 1: ICube-1, a CubeSat of PIST (Pakistan Institute of Space Technology), Islamabad, Pakistan; HumSat-D (Humanitarian Satellite Network-Demonstrator), a CubeSat of the University of Vigo, Spain; PUCPSat-1 (Pontificia Universidad Católica del Perú-Satellite), a 1U CubeSat of INRAS (Institute for Radio Astronomy), Lima, Peru; Note: PUCPSat-1 intends to subsequently release a further satellite Pocket-PUCP) when deployed on orbit. 13)
- PEPPOD 2: Dove-4, a 3U CubeSats of Cosmogia Inc., Sunnyvale, CA, USA
MRFOD (Morehead-Roma FemtoSat Orbital Deployer) of MSU (Morehead State University) is a further deployer system on UniSat-5 which will deploy the following femtosats:
- Eagle-1 (BeakerSat), a 1.5U PocketQube, and Eagle-2 ($50SAT) a 2.5U PocketQube, these are two FemtoSats of MSU (Morehead State University) and Kentucky Space; Wren, a FemoSat (2.5U PocketQube) of StaDoKo UG, Aachen, Germany; and QBSout-1S, a 2.5U PocketQube of the University of Maryland, testing a finely pointing sun sensor.
• Delfi-n3Xt, a nanosatellite (3.5 kg) of TU Delft (Delft University of Technology), The Netherlands.
• Triton-1 nanosatellite (3U CubeSat) of ISIS-BV, The Netherlands
• CINEMA-2 and CINEMA-3, nanosatellites (4 kg each) developed by KHU (Kyung Hee University), Seoul, Korea for the TRIO-CINEMA constellation.
• GOMX-1, a 2U CubeSat of GomSpace ApS of Aalborg, Denmark
• NEE-02 Krysaor, a CubeSat of EXA (Ecuadorian Civilian Space Agency)
• FUNCube-1, a CubeSat of AMSAT UK
• HiNCube (Hogskolen i Narvik CubeSat), a CubeSat of NUC (Narvik University College), Narvik, Norway.
• ZACUBE-1 (South Africa CubeSat-1), a 1U CubeSat (1.2 kg) of CPUT (Cape Peninsula University of Technology), Cape Town, South Africa.
• UWE-3, a CubeSat of the University of Würzburg, Germany. Test of an active ADCS for CubeSats.
• First-MOVE (Munich Orbital Verification Experiment), a CubeSat of TUM (Technische Universität München), Germany.
• Velox-P2, a 1U CubeSat of NTU (Nanyang Technological University), Singapore.
• OPTOS (Optical nanosatellite), a 3U CubeSat of INTA (Instituto Nacional de Tecnica Aerospacial), the Spanish Space Agency, Madrid.
• Dove-3, a 3U CubeSats of Cosmogia Inc., Sunnyvale, CA, USA
• CubeBug-2, a 2U CubeSat from Argentina (sponsored by the Argentinian Ministry of Science, Technology and Productive Innovation) which will serve as a demonstrator for a new CubeSat platform design.
• BPA-3 (Blok Perspektivnoy Avioniki-3) — or Advanced Avionics Unit-3) of Hartron-Arkos, Ukraine.
Deployment of CubeSats: Use of 9 ISIPODs of ISIS, 3 XPODs of UTIAS/SFL, 2 PEPPODs of GAUSS, and 1 MRFOD of MSU.
To facilitate rapid launches, UTIAS/SFL has adopted an approach to build customizable separation systems for any nanosatellite. These separation systems can be integrated with the satellites prior to launch site delivery and hence, make launch coordination easier. The SFL XPOD (Experimental Push Out Deployer) separation system interfaces the GNB-based spacecraft to practically any launch vehicle. Spacecraft up to 14 kg and arbitrary dimensions may be accommodated in existing XPOD designs. The XPOD interface device is an enclosed "jack-in-the-box" container for separating nanosatellites from virtually any launch vehicle - and an SFL patent.
Figure 6: Illustration of the nanosatellite (GNB) separation system (XPOD Duo), image credit: UTIAS/SFL
Orbit: Sun-synchronous elliptical orbit of 600 km x 900 km, inclination = 97.8º, LTDN (Local Time on Descending Node) = 9:30 hours.
Launch: The BRITE-PL-2 nanosatellite, also referred to as Heweliusz, was launched as a secondary payload on August 19, 2014 (03:15:05 UTC) on a Chinese Long March-4B vehicle (CZ-4B) from TSLC (Taiyuan Satellite Launch Center), China. The primary payload on this flight was Gaofen-2, a high-resolution imaging satellite, configured with one 1 m Pan/4 m MS camera. 14) 15)
Orbit: Sun-synchronous near-circular orbit, altitude of 625 km, inclination = 98º.
The launch of BRITE-PL-2 completes the BRITE constellation consisting of 6 nanosatellites built by UTIAS/SFL:
1) UniBRITE (CanX-3A) of the University of Vienna, and BRITE-Austria (TUGSat-1, Canx-3B) of the Technical University of Graz, Austria, launched on Feb. 25, 2013 on the PSLV-C20 vehicle of ISRO/Antrix from Sriharikota/India.
2) BRITE-PL-1 (Lem, CanX-3C) of SRC/PAS (Space Research Center/ Polish Academy of Sciences), Warsaw, Poland, launched on Nov. 21, 2013 on a Dnepr-1 vehicle from the Yasny Cosmodrome in Russia.
3) The two Canadian nanosatellites of UTIAS/SFL, BRITE-CA-1 and -2 (CanX-3E, and CanX-3F), were launched on June 19, 2014 on a Dnepr-1 cluster launch. The launch site was the Yasny Cosmodrome in the Dombarovsky region of Russia.
4) BRITE-PL-2 ( Heweliusz, CanX-3D) of SRC/PAS, Warsaw, Poland was launched on Aug. 19, 2014 on a CZ-4B vehicle from TSLC (Taiyuan Satellite Launch Center), China.
Figure 7: Photo of the BRITE-PL-2 / Heweliusz nanosatellite mounted onto the flight vehicle (image credit: China Great Wall Industry Corporation)
Mission status of the BRITE constellation:
• December 16, 2016: To date, 350 stars have been observed for a duration of up to half a year each. The main aim of the mission is to study variability in the light output of bright stars of high mass. This variability is caused by physical processes in the star, which can therefore be studied and constrained. In this way, knowledge about the interior structure of the stars, but also their rate of rotation, the presence and effects of binary companions, circumstellar material etc. can be obtained. 16) 17) 18)
- A very recent new result from BRITE is the discovery of massive heartbeat stars, a class of close binaries in eccentric orbits that show brightening events near periastron. So far, the Kepler mission has discovered about two dozens of such objects, all having masses less than twice that of our Sun. BRITE has revealed three massive representatives, among them Iota Orionis that consists of stars 23 and 13 times the Sun's mass, respectively.
• Feb. 5, 2016: The BRITE Constellation of five nanosatellites is operational in 2016. — The constellation is revealing new information about a well-studied star, Alpha Circini. A data analysis of the BRITE Constellation Team shows a behavior in this star that has not been observed before according to Werner Weiss from the University of Vienna, Austrian Principal Investigator for BRITE and lead author of the paper. The "BRITE Constellation shows complex behavior in Alpha Cir due to both rotation and pulsation. Moreover, that behavior is different when observed in different colors. This result clearly demonstrates the power of BRITE-Constellation and the unique science that is possible using these tiny two-color precision instruments in space." 19) 20)
- The BRITE-Constellation is a coordinated mission of five nanosatellites in LEO, each hosting an optical telescope of 3 cm aperture feeding an uncooled CCD, and observing selected targets in a 24º FOV. Each nanosatellite is equipped with a single filter; three have a red filter (~ 620 nm) and two have a blue filter (central wavelength (~ 420 nm). The satellites have overlapping coverage of the target fields to provide two-color, time-resolved photometry.
- The five nanosatellites, each of ~7 kg, are designated as: BRITE-Austria and UniBRITE (Austria), BRITE-Lem and BRITE-Heweliusz (Poland) and BRITE-Toronto (Canada). A sixth nanosat, BRITE-Montreal, did not detach from its launch vehicle.
Figure 8: Location of α Circini in the southern constellation Circinus (image credit: BRITE collaboration)
- The BRITE data are so valuable to astronomers due to their multi-colored observation. For stars, color and temperature go hand-in-hand. Having the ability to examine stars in different colors with data taken every few minutes for up to six months is providing new insights into their inner workings.
- Using these precision instruments, the BRITE-Constellation's mission is to perform a survey of the most luminous stars in the Earth's sky via a branch of astronomy called asteroseismology – literally, the study of "starquakes". Typically, massive and short-lived, these stars dominate the ecology of the Universe and are responsible for seeding the interstellar medium with the "heavy" elements critical for the formation of planetary systems and organic life. In short, BRITE studies classes of stars that, billions of years ago, made life on Earth possible.
- With an apparent magnitude of 3.19, Alpha Cir is the brightest star in the southern constellation Circinus and belongs to the class of stars known as rapidly oscillating Ap stars. The star in question was observed by four of the BRITE satellites from March to August 2014 and will be observed again in 2016. It is hoped, that these new observations will provide both a better understanding of its complex behavior and a chance to confirm a new oddity about this already peculiar star; that its speed of rotation is decelerating.
• On Nov. 21, 2014, BRITE-PL-1 (Lem) was 1 year on orbit. "Lem" operates as planned and performs a regular research and observations according to the BRITE mission plan. 21)
• Sept. 2014: All subsystems of the satellite "Heweliusz" have been successfully checked within the first week after its launch. Now the operating modes are under testing phase.
• On Aug. 19, 2014, the communication team from CAMK (Nicolaus Copernicus Astronomical Center) received the first signal from the BRITE-PL-2 (Heweliusz) satellite and established a communication link. 22)
• In July 2014, the BRITE-PL-1 (Lem) completed commissioning and, along with BRITE-Toronto (of UTIAS/SFL), is currently observing the Cygnus field. 23)
• On 29 January 2014 BRITE-PL-1 (Lem) orbited the Earth for the thousandth time! Until then, all subsystems of the satellite have been checked and since the beginning of February 2014, tests of operating modes have started. 24)
• Nov. 28, 2013: Application software was uploaded to the ADCC (Attitude Determination and Control Computer) which controls the satellite spatial orientation. Functional tests of the ADCC have been completed. That concludes the first part of the commissioning phase. The correct operation of the two on-board computers (HKC and ADCC) was fully tested (Ref. 25).
• Nov. 25, 2013: LFFTs (Long Form Functional Tests) of the HKC (House Keeping Computer) were completed. HKC is one of three computers installed aboard the Lem. The test completion means the end of HKC commissioning and it is the first step to reach the full functionality of the satellite. The second computer controlling the attitude control of the satellite (ADCC computer) has been turned on and is undergoing functionality tests.
• Nov. 21, 2013: In the first twelve hours after inserting "Lem" into orbit, communications with the satellite was established several times. The first contact occurred over Europe during the first satellite pass. 25)
The objective is to examine the apparently brightest stars in the sky for variability using the technique of precise differential photometry in time scales of hours and more. The constellation of four nanosatellites is divided into two pairs, with each member of a pair having a different optical filter. The requirements call for observation of a region of interest by each nanosatellite in the constellation for up to 100 days or longer. 26)
The science payload of each nanosatellite consists of a five-lens telescope with an aperture of 30 mm and the interline transfer progressive scan CCD detector KAI 11002-M from Kodak with 11 M pixels, along with a baffle to reduce stray light. The optical elements are housed inside the optical cell and are held in place by spacers. The photometer has a resolution of 26.52 arcsec/pixel and a field-of-view of 24º. The mechanical design for the blue and for the red instrument is nearly identical; only the dimensions of the lenses are different .
Figure 9: Illustration of the BRITE telescope and baffle (image credit: UTIAS/SFL)
Figure 10: The optics design of the photometer (image credit: UTIAS/SFL, Ceravolo)
The effective wavelength range of the instrument is limited in the red by the sensitivity of the detector and in the blue by the transmission properties of the glass used for the lenses. The filters were designed such that for a star of 10,000 K (average temperature for all BRITE target stars) both filters would generate the same amount of signal on the detector.
The shape of the PSF (Point Spread Function) should fulfill the following requirements: 6 ±1 pixel FWHM (Full Width Half Maximum), Gaussian as possible, 99% encircled energy in 12 pixel diameter and the spikes in the PSF shall be minimized. The optics is equipped in red (550-700 nm) or blue (390-460nm) bandpass filters (Figure 11).
Table 2: Characteristics of the Kodak KAI 11002-M CMOS detector
The photometer instrument has a mass of ≤ 0.9 kg and a power consumption of ≤ 3.5 W. The instrument uses a custom set of electronics to operate the imager. The electronics include four A/D converters (14 bit) to convert the analog pixel values, and 32 MB of memory to temporarily hold a full frame image. The imager and memory timing and signals are being controlled using a CPLD (Complex Programmable Logic Device).
Figure 12: Schematic layout of the CMOS detector array (image credit: University of Vienna)
Figure 13: The BRITE photometer and star tracker (image credit: TU Graz)
1) Piotr Orleanski, Rafał Graczyk, Mirosław Rataj, Aleksander Schwarzenberg-Czerny, Tomasz Zawistowski, Robert E. Zee, "BRITE-PL – the first Polish scientific satellite," Proceeding of the 4th Microwave & Radar Week, MRW-2010, Vilnius, Lithuania, June 14-18, 2010
3) "The first Polish scientific satellite BRITE-PL will help in understanding the inner structure of brightest stars in our galaxy," SRC, May 24, 2010, URL: http://www.alphagalileo.org/ViewItem.aspx?ItemId=76625&CultureCode=en
5) Information provided by Tomasz Zawistowski of SRC, BRITE-PL Project Manager, Warsaw, Poland
7) "Poland's first research satellite sent into orbit," Polska, Nov. 21, 2013, URL: http://en.poland.gov.pl/Poland%E2%80%99s,first,research,satellite,sent,into,orbit,Events,7072x4054.html
9) Patrick Blau, "Dnepr Rocket successfully launches Cluster of 32 Satellites," Spaceflight 101, Nov. 21, 2013, URL: http://www.spaceflight101.com/denpr-2013-cluster-launch-updates.html
11) "2013 in spaceflight," Wikipedia, Nov. 21, 2013, URL: http://en.wikipedia.org/wiki/2013_in_spaceflight#November
12) "Russian Dnepr conducts record breaking 32 satellite haul," NASA Spaceflight.com, Nov. 21, 2013, URL: http://www.nasaspaceflight.com/2013/11/russian-dnepr-record-breaking-32-satellite-haul/
14) Rui C. Barbosa, "Chinese Long March 4B launches Gaofen-2 and BRITE-PL-2," NASA Spaceflight.com, August 19, 2014, URL: http://www.nasaspaceflight.com/2014/08/chinese-long-march-4b-gaofen-2-brite-pl-2/
15) "Polish and Chinese Satellites Successfully Launched into Space," Astro Watch, August 19, 2014, URL: http://www.astrowatch.net/2014/08/polish-and-chinese-satellites.html
16) "BRITE-Constellation: First Scientific Results," Nicolaus Copernicus Astronomical Center, Dec. 16, 2016, URL: https://www.camk.edu.pl/en/archiwum/2016/12/16/brite-constellation-first-scientific-results/
17) G. Handler, A. Pigulski, W. W. Weiss, A. F. J. Moffat, R. Kuschnig, G. A. Wade, P. Orlea nski, S. M. Ruci nski, O. Koudelka, R. Smolec, K. Zwintz, J. M. Matthews, A. Popowicz, D. Baade, C. Neiner, A. A.Pamyatnykh, J. Rowe, A. Schwarzenberg-Czerny, "The BRITE-Constellation Nanosatellite Space Mission And Its First Scientific Results," Nov. 2016, URL: https://arxiv.org/pdf/1611.02161.pdf
18) A. Pigulski, H. Cugier, A. Popowicz, R. Kuschnig, A. F. J.Moffat, S. M. Rucinski, A. Schwarzenberg-Czerny, W. W. Weiss, G. Handler, G. A. Wade, O. Koudelka, J.M. Matthews, St. Mochnacki, P. Orleanski, H. Pablo, T. Ramiaramanantsoa, G. Whittaker, E. Zocłonska, K. Zwintz, "Massive pulsating stars observed by BRITE-Constellation," Astronomy & Astrophysics, Vol. 588, April 2016, DOI: 10.1051/0004-6361/201527872, URL: http://www.aanda.org/articles/aa/pdf/2016/04/aa27872-15.pdf
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The information compiled and edited in this article was provided by Herbert J. Kramer from his documentation of: "Observation of the Earth and Its Environment: Survey of Missions and Sensors" (Springer Verlag) as well as many other sources after the publication of the 4th edition in 2002. - Comments and corrections to this article are always welcome for further updates (email@example.com).
The BRITE Constellation: