ISSN:0737-2884    

DOI:10.1002/sat.4600130502

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1995

数据来源: WILEY

ISSN:0737-2884    

DOI:10.1002/sat.4600130503

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1995

数据来源: WILEY

摘要:

AbstractThis paper presents the design and realization of regenerative satellite on‐board bypass test equipment. Furthermore, two particular examples of an in‐orbit test transponder (IOTT) are discussed in detail. The IOTT1, developed for the first 30/20 GHz ITALSAT satellite (F1), was launched in January of 1991. IOTT1 has been a useful tool during satellite assembly, integration and pre‐launch tests. IOTT1 was successfully used to fully characterize the multibeam ITALSAT satellite in orbit.In general, the IOTT functions to bypass the demodulator, the baseband switchboard and the modulator of the multibeam package of the ITALSAT spacecraft payload, providing the ability to fully characterize the satellite's transponders using well‐established IOT test techniques.This paper describes and compares the design, fabrication and test of both ITALSAT in‐orbit test RF bypass transponders (IOTT1 and IOTT2) mounted on board the ITALSAT multibeam spacecraft, (F1) and (F2), respectively. The IOTT1 contains the first MMIC circuitry ever launched into space on a communications satellite. The improved IOTT2, fabricated for the second 30/20 GHz ITALSAT satellite (F2), is schedule for launch in early 1996.These fully space‐qualified designs incorporate COMSAT Laboratories' designed and fabricated MMICKu‐band amplifiers, lightweight waveguideKu‐band channel filters and electronic power conditioner (EPC) and combined IOTT telemetry/command

ISSN:0737-2884    

DOI:10.1002/sat.4600130504

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1995

数据来源: WILEY

摘要:

AbstractThis paper describes the in‐orbit test of the first United States direct broadcasting satellite (DBS‐1) developed by Hughes Space and Communications (HSC) for Hughes Communications Galaxy, Inc. and DIRECTV Inc. This satellite provides direct broadcast of digitally compressed television channels across the United States for service providers DIRECTV™ and United States Satellite Broadcasting (USSB).Following a brief description of the communication system of the spacecraft, the in‐orbit test set‐up and the measurements that were performed are described. Measurements which have not been described elsewhere (antenna contour verification, modulated e.i.r.p., e.i.r.p. with wide band energy dispersal function (EDF), auto saturation, etc.) are covered in some detail.Finally, the results of the in‐orbit test of DBS‐1 which was performed in January 1994

ISSN:0737-2884    

DOI:10.1002/sat.4600130505

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1995

数据来源: WILEY

摘要:

AbstractThe expected introduction of new TDMA earth‐stations in the EUTELSAT network with a lower diameter antenna, together with the need to ensure the high quality of services are the two principal reasons why regular review of the performance trend of TDMA links is becoming so vital. Such a review will allow overall optimization of the EUTELSAT TDMA system by ensuring that the transponders are operated at their specified points, and will make it possible to be prepared in advance in the event of a transponder gain drop to reconfigure the system with no loss of traffic.To implement these tests, EUTELSAT at its IOT facilities near Paris has installed a burst mode saturation analyser' (BMSA) developed by Hollis Electronics Company. The BMSA has been specially designed as a stand‐alone test system for testing TDMA channels in a burst mode without interrupting the operational traffic.This paper describes how the BMSA operates and in particular how the system self synchronizes in order to position the BMSA test burst correctly in the frame, and how the burst is allowed to vary in amplitude in order to characterize the channel under test. This paper also discusses how the BMSA is interfaced to the host IOT station and how the tight measurement accuracy in terms of absolute transmit e.i.r.p. and spacecraft IPFD have been met.The paper concludes by comparing results obtained by classical CW test methods with this new burst method. The conclusions also discuss the limitations of the system and suggest possible improveme

ISSN:0737-2884    

DOI:10.1002/sat.4600130506

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1995

数据来源: WILEY

摘要:

AbstractThis paper describes the system, consisting of hardware and software, and two of the two‐station in‐orbit test (IOT) measurements that were developed for INTELSAT as part of their IOTE (in‐orbit test equipment) project. Three systems have been designed and manufactured by SED Systems, and installed in Beijing, Clarksburg and Fucino. The system is capable of two types of synchronized sweeps: sweeps in power and sweeps in frequency; gain transfer and frequency response, respectively, are given as examples. Two‐station measurements are used on complex satellites that contain transmit and receive beams (such as spot beams) that cannot both be seen at the same earth‐station. This paper briefly describes how the measurements are done and discusses some of the more important performan

ISSN:0737-2884    

DOI:10.1002/sat.4600130507

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1995

数据来源: WILEY

摘要:

AbstractThe in‐orbit tests of the satellite coverage dependent parameters require the rotation of the satellite around its pitch and roll axes in order to ‘bring’ the various coverage locations onto one fixed IOT station. Alternatively, several transportable test stations can be located at different sites in the coverage area in order to measure the satellite performances on site. Although the second technique does not provide enough measurement points to reconstruct the complete coverage of shaped beam antennas, it presents several advantages for which it is still used by EUTELSAT for the IOTs of its satellites in conjunction with measurements based on the satellite attitude movements.In particular, the transportable test stations are used to test the stability of satellite EIRP and IPFD at the edges of the coverage areas, where the performances are more sensitive to the pointing errors induced by thermal deformation or satellite attitude changes.This paper presents the common experience gained by EUTELSAT and ESA in testing the coverage dependent parameters of the first and second generation of EUTELSAT satellites. In particular, the paper deals with the use of the transportable test stations during the EUTELSAT II F1 to F3 acceptance tests and with the test campaigns performed at several sites in the eastern European countries.In the first case, the transportable test stations were used in conjunction with satellite rotations around the pitch axis in order to measure the coverage dependent parameters along several cuts parallel to the equatorial plane at different roll angles. In the second case, the transportable test stations were used to periodically repeat the EIRP measurements of many satellite channels over several hours in order to test the EIRP stability of the EUTELSAT II satellites.For both cases, the paper presents a synthesis of the most significant IOT results together with a comparison between these results and the values of the coverage dependent parameters predicted on the basis of the on‐groun

ISSN:0737-2884    

DOI:10.1002/sat.4600130508

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1995

数据来源: WILEY

摘要:

AbstractTheG/Tpredictions of communications satellites in the past usually stipulated that an antenna noise temperature of 290 K be used in the calculations. This, when compared to in‐orbit derived data, has resulted in large discrepancies (up to 3 dB). These discrepancies result directly from the use of a pessimistic value of the antenna noise temperature. The actual antenna noise temperature is lower because a portion of the spacecraft receive antenna pattern falls in deep space and because the brightness temperatures of large parts of the Earth are lower than 290 K. This discrepancy has become more apparent as technology of low noise amplifiers advances, thus making the antenna temperature the predominant factor when budgeting the system noise temperature of the spacecraft.This paper focuses on a model to determine the antenna noise temperature and especially how this model was directly verified in orbit during the acceptance campaign of EUTELSAT II‐F6 (Hot Bird 1). The methodology used for the determination of the integrated antenna temperature is also fully discussed. Full results are also presen

ISSN:0737-2884    

DOI:10.1002/sat.4600130509

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1995

数据来源: WILEY

摘要:

AbstractAfter a successful launch of a new communications satellite, it is essential to test the communications subsystem while the spacecraft is in orbit so as to compare with prelaunch data in order to ensure that no impairment has resulted from the stress of the launch and to verify that the spacecraft payload is compliant with the specifications sought.The thrust of in‐orbit test technology has stemmed from the fact that the spacecraft has to be operational very quickly while not sacrificing the number of tests that have to be performed and increasing their measurement accuracies.Thus, in order to respond favourably to the cited criteria, microwave measurement techniques with more powerful computers and software technology have been used to automate the measurements.The paper is geared to the history, design, implementation and operation of EUTELSAT's in‐orbit test (IOT) facilities, and mostly reflects technological advances in communications satellite payload testing. The paper will first detail the hardware/software novel concepts of the measurement environment. Then new measurements are summarized. New spacecraft antenna mapping procedures are detailed both in measurement and spacecraft attitude aspe

ISSN:0737-2884    

DOI:10.1002/sat.4600130510

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1995

数据来源: WILEY

摘要:

AbstractThe facilities and in orbit test methods developed by the European Space Agency over the last two decades, in the frame of the various communications satellite programmes, are reviewed. The lessons learned and the hardware and software precautions implemented to enhance accuracy and operational flexibility are described. New facilities and methods currently under development are also addressed.

ISSN:0737-2884    

DOI:10.1002/sat.4600130511

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1995

数据来源: WILEY