1、.- Rep. 919-2 545 REPORT 91 9-2* PERFOBHAWCE OF A luyu-ALTITUDE, POIAB-ORBITING SATELLITE EPIRB SYSTEII (Question 90/8) (1982- 1986 -1 990 1 1. Introduction 1.1 Background The COSPAS/SARSAT * programme is an international cooperative effort between the United States of America, Canada, France (SARSA
2、T) and the USSR (COSPAS). Norway, the United Kingdom, Finland, Bulgaria and Denmark are also participating in this programme, and discussions are under way for the participation of Brazil and additional countries. The programme has the following objectives: - first, to support the existing search an
3、d rescue activities by providing position determination for aircraft emergency locator transmitters (ELTs) and maritime emerency position-indicating radio beacons (EPIRBs) transmitting at 121.5 MHz; second, to demonstrate the advantages of a new system operating at 406 MHz, which provides better per
4、formance and which better satisfies users requirements of global coverage and identification; third, to promote the development of an international operational system as soon as possible. 4 - - A summary description of the system is given in Report 761, and details are provided in USSR, er al., 1984
5、aJ; therefore, they are not repeated in this Report. The Cospas-1 (Cl), -2 (C2) and -3 (C3) satellites were launched on 30 June 1982, 25 March 1983, and 21 June 1984, respectively. Sarsat 1 (Sl), the first satellite carrying the SARSAT payload, was launched on 28 March 1983. It lost attitude stabili
6、ty and was placed out of operation in June 1984, but it was successfully reactivated in May 1985. Sarsat-2 (S2) was launched in December 1984. Sarsat-3 (S3) is planned to be launched in 1986. The initial launches started an engineering measurement effort and a demonstration and evaluation (D and E)
7、effort. The purpose of the engineering measurements was to determine that the design was functioning as expected. The purpose of the D and E programme was to demonstrate the 406 MHz system performance and the systems capability for providing effective assistance to search and rescue (SAR) operations
8、. The engineering measurements consisted of well controlled 121.5 MHz and 406 MHz engineering tests and they continue to be performed with each new satellite launched. The D and E programme demonstrated 121.5 MHz and 406 MHz system performance in a more realistic user environment. The D and E progra
9、mme was concluded in July 1984. However, additional measurement data is being continually acquired. Thereafter, the D and E data will be referred to as the ”environmental” data to differentiate it from the engineering data. Preliminary results of the programme have become available in several report
10、s (see References). It must be noted that the 406 MHz COSPASISARSAT sub-system has just entered its operational phase and is continually improving its system performance. On the other hand, the 121.5 MHz sub-system has already demonstrated its operational performance in a number of successfully reso
11、lved real distress situations. * The Director, CCIR, is requested to bring this Report to the attention of the International Civil Aviation Organization (ICAO), the International Maritime Organization (IMO) and the International Maritime Satellite Organization (INMARSAT). COSPAS: Kosmicheskaya Sisty
12、ema Poiska Avariynykh Sudov (Space System for Search of Distressed Vessels); SARSAT: Search And Rescue Satellite-Aided Tracking system. * _I Rep. 919-2 1.2 Objecrive of the Report The objective of this Report is to present a consolidation of preliminary results taken from various engineering measure
13、ment and D and E reports and papers describing the 406 MHz system performance and environmental tests performed by all the COSPAS/SARSAT participants. General test results of the 121.5 MHz system are also presented to give the user an idea of COSPAS/ SARSAT operational capabilities and a basis from
14、which to compare the effectiveness of the 406 MHz system. 1.3 Scope of the Report In researching the various reports of test results provided by the participating countries, it was found that there were variations in the methods and formats in performing the tests and in recording the results. Accor
15、dingly, it was determined necessary to use only those results that were based pn performance parameters with similar definitions and where the sample sizes of the collected data were known. The countries whose data is used in this Report are: - - the COSPAS/SARSAT partners: the United States of Amer
16、ica, Canada, France and the USSR; and the COSPASISARSAT investigators: Bulgaria. Norway, and the United Kingdom. The reports used are listed in the References. The time period for the reported test results spans from 1 February 1983 to 31 August 1985. Additional tests are planned for both the floati
17、ng EPIRBs and the end-to-end performance assessment. The floating EPIRB tests will further investigate location probability for various conditions, including high sea states: the end-to-end tests will continue to investigate system performance using a four-satellite constellation with reduced suscep
18、tibility to interference. The results of some of these tests are reporte in Annexes II and III and the comparison of this data with similar parameters measured during tne D and E phase is presented i Annex IV. 2. Mtrniml pedormrm of tk 406 MHz system This section focuses on the measured performance
19、of the COSPAWSARSAT system using the 406 MHz experimental beacons. 2.1 introduction The purpose of the engineering measurements and the environmental tests was to determine the ability of the COSPAS/SARSAT system to detect, identify, and locate 406 MHr experimental beacons operating in maritime and
20、inland environments. This was accomplished mainly by the evaluation of the following parameters for single-pass dab: beacon-detection probability, beacon-location error, ambiguity resolution, beacon-location probability, capacity,. homing range at 121.5 MHz and at 406 MHz, notification time. During
21、the perod reported, the COSPAS/SARSAT system underwent: the continudon of ground system development: addition of the C3 and S2 satellites to the space segment: implementation of new operating procedures: and improvements of on-board satellite equipment. Rep. 919-2 517 For these reasons, the test res
22、ults reflect a changing system. They afford a basis for preliminary evaluation The tests fell into two categories: engineering tests and environmental tests. Engineering tests are defined as closely controlled technical tests established to evaluate the degree to which the system .design goals have
23、been met. Environmental tests are reasonably controlled field tests designed to evaluate the impact of environmental factors (such as sea state, terrain, and weather) in a more operational mode. Engineering tests were run under very good conditions in which the environment was stable and known. The
24、true location of each beacon was accurately known to within approximately 0.50 km, output power was controlled, and beacon elevation angles to the spacecraft were accurately computed. Environmental tests, on the other hand, were performed under a wide range of conditions that were not precisely reco
25、rded nor controlled. For example, beacon true locations were estimated and frequently feil outside 0.5 km error, output power measurements were not usually taken, and elevation angles were not usually recorded; however, with a sufficient sample size, this data can be expected to characterize the ope
26、rational system. of the parameters listed above with continuing improvements expected. iJ - 2.2 Description of the tests The tests were carried out under conditions and at locations selected by the participating nations. Generally, beacons were activated in sufficient time for them to warm up prior
27、to data being taken to ensure that beacons were operating within specifications. Elevation angles from the beacons to the satellites were selected to allow message locations to be computed. To-give a representation of what could occur during a beacon activation under real circumstances, a range of e
28、nvironmental conditions were selected. Such inland environments included. flat and mountainous terrain, wet and dry weather, high to low altitudes above mean sea level, varying ambient temperatures, etc. Maritime tests were generally performed at low sea states with the EPIRBs on the decks of ships
29、and/or floating. The beacons employed were newly developed 406 MHz ELTs and EPIRBs designed to meet the international specification for experimental beacons called for in the COSPAS/SARSAT 406 MHz ELTIEPIRB specification Canada, et al., 19821. In order to cross-reference the various test results pro
30、vided in this Report, to the originating country, the , Tollowing list should be used: Series A B C D E F G . Country Bulgaria Canada France Norway USSR United States of America United Kingdom 2.2.1 Beacon-detection probability Beacon-detection probability is defined as the probability of detection
31、by a local user terminal (LUT) (see Note) of at least one beacon message with a correct code protected section for the first tracked satellite. Note. - A local user terminal is the COSPAWSARSAT receiving earth station. 2.2.1.1 Test description 2.2.1.1.1 On-land tests The C-series engineering test re
32、sults were obtained in June 1985 by the Toulouse LUT during the Sarsat-1 and Sarsat-2 comparative performance tests. A local orbitography beacon and a reference beacon, placed on the roof of a building, were used during thee tests. Rep. 919-2 The E-series environmental test results were obtained dur
33、ing January-February 1985 tests CSSC, 1985aJ. One test beacon (an industrial prototype) was placed on the roof of the Moscow LUT. The beacon was powered by internal batteries. During the 30-day test period the temperature varied between 0C and -24C. The F-series engineering test results were obtaine
34、d in August 1985 during simultaneous testing of two on-land and one on-deck field test beacons and a number of floating EPIRBs. The on-land test beacons were placed on top of two buildings, one of which was located at the Atlantic Marine Center near Norfolk, Virginia, and the other at NASA/Goddard S
35、pace Flight Center in Greenbelt, Maryland. Both of these beacons, as well as the on-deck beacon and the floating EPIRBs, transmitted at full power. 2.2.1.1.2 On-deck tests I The F-series engineering test results were obtained in August 1985 as mentioned in the preceding sub-section. A field-test bea
36、con was used with the antenna placed on the bridge of a ship, which was stationed off the coast of Norfolk, Virginia. 2.2.1.1.3 Floating tests The C-series environmental test results were obtained in April and June 1985 during the tests of three tethered and two free-floating EPIRBs, respectively CS
37、SC, 1985bl. These tests were conducted in the south-westem Atlantic Ocean coastal region of France (near Bordeaux) during low sea-state conditions. In these tests, only those satellite passes were tracked whose elevation angles exceeded 5“ ; also, only the local (regional) mode was used. The F-serie
38、s engineering tests for floating EPIRBs were conducted in August 1985 off the coast of Norfolk, Virginia, where wave heights of up to 5 feet (1.5 m) were encountered. The data reported for the 6 EPIRBs were collected simultaneously with the on-land and on-deck engineering tests. 2.2.1.2 Test results
39、 The measured beacon-detection probability is shown in Table 1. The engineering test results indicate an overall value of this parameter to be 0.999, with somewhat lower results for environmental tests, 0.98: the measured cumulative beacon-detection probability thus being .0.99. hese results were ac
40、hieved with the use of the short message type with a protective BCH code. If the long message had been used, lower results would have been achieved due to the absence of correcting code for the last 32 bits of information. 2.2.1.2.1 On-land tests In the C-series engineering tests, the beacon-detecti
41、on probability for 66 passes of Sarsat-1 and 67 passes of Sarsat-2 was measured to be 1.0. Likewise, in the F-series engineering tests, it was also measured to be 1.0 for 246 possible detections. In the E-series environmental tests, the beacon-detection probability for 262 passes of Cospas-2 and 253
42、 passes of Cospas-3 was measured to be 0.98. 2.2.1.2.2 On-deck rests The on-deck F-series engineering tests yielded a 0.99 beacon-detection probability for i30 possible detections and show essentially the same results as the on-land beacon and the floating EPIRB F-series engineering data. 2.2.1.2.3
43、Floating tests 260 possible detections. Cospas-2 and -3, and Sarsat-1 and -2 satellites was measured to be 0.98. In the F-series engineering tests, the beacon-detection probability was measured to be 1 .O for In the E-series environmental tests, the beacon-detection probability for numerous passes o
44、f Rep. 919-2 - 1 .o 515 0.98 - 1 .o 515 0.99 - 0.99 377 0.98 - 1 .o 377 0.99 892 0.99 549 266 515 246 1027 130 377 260 637 1794 TABLE I - Beacon-derecrion probability Engineering tests Environmental tests Cumulative I I II I I I Beacon Series Probability No;lefle Probability C 1 .o 266 - F 1 .o 246
45、- On-land E - - 0.98 Sub-total I .o 512 0.98 On deck F 0.99 130 - Sub-total 1 .o 260 0.98 Total 0.999 902 0.98 No. of possible detections Probability I I No. of possible detections _ c 2.2.2 Location error Location error is defined as the difference between the location calculated by the system usin
46、g measured Doppler frequencies and the actual location of the radio beacon as reported by the field personnel. One should be aware tkt measurement of location error during engineering tests is expected to be more precise than that during environmental tests because the actual beacon locations could
47、be more accurately determined. The ELT actual locations often are more accurately determined than the actual locations of the EPIRBs. Hence, confidence in the actual beacon positions obtained during environmental on-land ELT tests is generally higher than EPIRB tests run at sea. 2.2.2.1 Test descrip
48、tion 2.2.2.1.1 On-land tests The B-series results were obtained from a single test in which two experimental beacons were placed on the roof of a building and powered by an external source Canada, 1985al. The C-series engineering tests provided a large number of measurements and were taken in an are
49、a where there is considerable interference at 406 MHz USSR et nl., 1984b; Castetbert, 1984a: France, 1984a). The C-series environmental tests were conducted at airprts located throughout the world CSSC, 1985cj. The D-series engineering test results were obtained from a single beacon transmitting via the S1 satellite Hovmork, i984al. The D-series environmental tests included placing 406 MHr beacons at 16 different sites on land and in the water, including former aircraft and ship accident sites Hovmork, 1984bl. 550 Rep. 919-2 The E-series engineering test results
