while a star tracker provides low frequency long-term stable attitude measurements, the attitude computed from the high-frequency gyro measurements is only short-term stable. Il est construit par une équipe algéro-britannique dans le cadre de la mise en œuvre de l'accord de coopération signé entre l'Agence spatiale algérienne et l'Agence spatiale du Royaume-Uni. • StudSat (Student Satellite), a picosatellite (1 kg) built by a consortium of seven Engineering colleges from Hyderabad and Bangalore, India. The secondary, tertiary and folding mirrors are also made of SiC. - 4 Reaction Wheels (0.12 Nms) Figure 14: Identification and delimitation of burned zones acquired by AlSat-2A on September 6, 2014 in the Oued Soudane Forest (image credit: ASAL, W.Skikda), • The AlSat-2A spacecraft and its payload are operating nominally in 2013. RF communications: AlSat-2 features an onboard SSR (Solid-State Recorder) of 64 Gbit capacity. 9). According to these observed results where there are different maneuvers and transitions from day to night and back that are well represented by the angular rates (see Figure 9, right), we can say that the gyro stellar performances are acceptable with respect to the requirements, due to a better robustness of the SST tracking loss and a better on-board autonomy. • December 15, 2016: According to WMO OSCAR, the AlSat-2A and -2B satellites are operational. - Autonomous GPS position determination So, in Figures 6 and 7, we present the observed SST unavailability periods through these last two years, we can notice that the SST availability is about 98% of the time when there is a mission plan uploaded and when there is no mission plan the SST availability falls down to 66%. • BlackSky Pathfinder-1, a high-resolution (1 m) imaging microsatellite (~44 kg) of BlackSky Global. Figure 17: AlSat-2A image of the Greek capital Athens with NAOMI in Sept. 2010 (image credit: ASAL). Le 1er février 2006, EADS Astrium annonce[1] la signature d'un contrat visant à la réalisation de deux satellites (Alsat-2A et Alsat-2B) faisant partie du programme Alsat-2. The different satellite pointing modes are illustrated in Figure 11. 20). Lancé en 2002 à partir du centre spatial Plesetsk en Russie, il a été réalisé grâce à un partenariat avec le Royaume-Uni via Surrey Space Technology (SSTL). Alsat-1 est un micro-satellite de cartographie. Following this agreement, the US Government has given clearance in August 2009 for launch by ISRO of the Algerian satellites ALSat-2A and ALSat-2B, which have US components, on board an Indian space launch vehicle. In addition, there is a monitoring of this estimator, it concerns the gyro only estimation, if the SST is not available for a long time and the SST innovation by outing a threshold value on the level of the innovations. 25), Figure 15: Global view of the town of Skikda with industrial zone observed with AlSat-2A at a resolution of 2.5 m (image credit: CNTS, ASAL) 26), Figure 16: Sample image of NAOMI observed in October 2010 located near Skikda in north eastern Algeria (image credit: CNTS, ASAL). 15). Alsat-1 C'est le premier satellite artificiel algérien. - The mirror surface can to be polished down to a roughness of a few angstrom (1Å= 10-10 m). Figure 24: The FPA architecture of the Pan + MS bands (image credit: EADS Astrium SAS). =article&id=181%3Aus-clears-launch-of- En revanche, en fin de vie depuis 2010, Alsat-1, le tout premier satellite algérien, a servi trois ans de plus que sa durée de vie normale prévue pour 5 ans. The imager provides imagery of 2.5 m in Pan and 4 multispectral (MS) bands of 10 m GSD. Conversely, the star tracker allows compensating for long term gyro natural drift and gyro-scale factor errors during maneuvers. It should be noticed here that along these two years, the obtained results fulfill the requirements and all of them fall under the specifications. Figure 19: Overview of NAOMI detection chain (image credit: EADS Astrium SAS), Figure 20: Photo of the area array detector (image credit: EADS Astrium), - Korsch telescope with a TMA design in SiC Four reaction wheels mounted in pyramidal configuration aimed to increase the angular momentum and finally a propulsion subsystem with four thrusters for orbit control. Alsat-1 est arrivé en fin de vie le 15 août 2010. • Since July 21, 2010, the spacecraft operations are performed from the ALSAT-2 ground segment located in Ouargla (Algeria). The transfer phase consisted therefore in increasing the semi-major axis and correcting the inclination to reach the predefined targets while targeting the frozen eccentricity. The launch site was the Satish Dhawan Space Centre (SDSC) SHAR, Sriharikota, India. « La capture et la réception de cette première image en couleur d’Alsat 1N, par une […] B4: 0.76-0.89 µm (NIR), 1.5-2.5 m Pan at nadir The star tracker in this case will be directly blinded by the earth for some periods reaching 20 minutes of unavailability measurements. ALSAT -B's great success demonstrates that ASAL's engineers are fully competent and have acquired a great autonomy through this program.16), • May 2019: The ALSAT-2B satellite is in orbit since 26 September 2016. Le troisième satellite algérien (Alsat 3) sera lancé “entre 2013 et 2014”. B Benbouzid, J. J Arnoux, E. Chinal, C Massol, P. Rouchit(1), S. de Zotti, "NAOMI instrument: a product line of compact & versatile cameras designed for high resolution missions in Earth observation," Proceedings of the 7th ICSO (International Conference on Space Optics) 2008, Toulouse, France, Oct. 14-17, 2008, 30) Information provided by Hervé Lambert of EADS Astrium SAS, Toulouse, France. AlSat-1 was launched on Nov. 28, 2002, the spacecraft is operating nominally as of 2009 providing multispectral imagery of 32 m resolution in a swath of 600 km. The gyro stellar main performances as the estimated quaternion, the angular rate, the SST innovation and the estimated gyro drift are illustrated in Figures 9 and 10, respectively. The AlSat-2 program includes the construction of two ground control segments as well as one station for high-speed downlinks of imagery permitting spacecraft operations from Algerian territory, a country of 2.38 million km2 in size. Le système d'imagerie couvre le vert, le rouge et le proche infrarouge, pour une résolution de 32 mètres. NAOMI (New AstroSat Optical Modular Instrument): NAOMI is a high-resolution imager designed and developed at EADS Astrium SAS: The instrument design is mainly driven by mission parameters and detector characteristics. The estimator has proved its performance and robustness along all this period and continue providing correct measurements. Le lancement du troisième satellite algérien ALSAT 3, pourrait intervenir au mois de janvier 2014, depuis le site de lancement de Hammaguir, au Sud-ouest de l'Algérie. - ALSAT-2B delivers a high-resolution products consisting of a 2.5m resolution for the panchromatic band, and a 10 m resolution for the four multispectral bands, with a 17.5 km swath for both modes. Alsat-1. 1) 2) 3) 4), The cooperation agreement makes provision for Algerian engineers to work side-by-side with the EADS Astrium development team, with intensive training given in space technology. 6-10 m MS at nadir, Silicon area array with 7000 pixels Pan, 1750 pixels in each MS band, The Pan band offers TDI services for SNR improvement of the signal, ±30º (spacecraft tilting capability about nadir for event monitoring). So, if one of these monitoring parameters is out of range a transition to survival mode is commanded. The motivation to fuse star tracker and gyro is to generate a long-term stable attitude estimate at gyro measurement frequency of attenuated noise compared to the star tracker measurement and, hence, to optimally bridge periods where no star tracker measurement is available. Prochain lancement du satellite algérien ’’Alsat 2’’. - Regarding the gyro stellar estimator performance we tried to select the main observed performance. The very good detector characteristics (high MTF and high quantum efficiency) significantly contribute to the instrument optical performance. The heliocentric pointing is within the daylight and the geocentric pointing appears during eclipse phase or when the satellite is in imaging or downloading modes. - 1 Li-ion battery 15 Ah BOL; PCDU (Power & Control Distribution Unit), - On-board computer (T805, 1 Gbit DRAM/EDAC, 8 Mbit Flash EEPROM) The focal plane accommodates detectors, filters and front-end electronics. ***** ***** Extrait du numéro 2593, du quotidien d'oran. Right: Estimated angular rate (12 hours observation), image credit: ASAL. The camera has a mass of 13 kg. As actuators, there is three magnetorquers used for detumbling at the beginning, after that they will be used for wheel unloading. The MEV provides the F2EM with the primary power supplies and clocks necessary to front-end operation. The optical filtering is ensured by highly integrated filters, including masks to minimize spectral cross-talk. In Feb. 2006, CNTS signed an agreement with EADS Astrium SAS to design and built two satellites. star tracker dazzling, payload sun exposure), also for the solar array power generation, since the satellite solar arrays point the sun in the day phase, with ~ 0.025 º/s rotation about its –X-axis, and for thermal balancing too. However, the reaction wheels, like all the equipments in space, are facing the external harsh environment to which the FDIR (Fault Detection Isolation and Recovery) strategy has been implemented to overcome these constraints especially for the SEUs (Single Upset Events). L'agence spatiale algérienne a conduit les opérations de tests et corrections d'orbite en autonomie depuis que le satellite a émis ses premiers signaux[8]. Ils ont les caractéristiques suivantes[1] : Les deux satellites forment une constellation, ce qui permet d'augmenter la fréquence de prise de vues . - Since 2003, there is a collaboration between ASAL and INVP (Institut National de la Protection des Vegetaux). The NIEU represents the core of the electrical architecture. Now for the imaging mode and with the agility as a key feature, ALSAT-2B carries out the maneuvers to reach 30 deg either being along track or cross track. Le satellite algérien ’’Alsat 2’’ sera prochainement lancé et mis sur orbite, a annoncé avant-hier soir à Saida au terme de la première journée de sa visite de travail dans la wilaya le ministre de la Poste et des Technolo
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