BROADBAND DUAL APPLICATION: THE ITALIAN PAYLOAD ON ATHENA FIDUS - IN ORBIT TESTING PREPARATION Giampiero Di Paolo, Thales Alenia Space-Italia S.p.A., via Saccomuro 24, 00131 Rome Italy Telephone:+39-06-41512177; giampiero.dipaolo@thalesaleniaspace.it Francesca Finocchiaro, Thales Alenia Space-Italia S.p.A., via Saccomuro 24, 00131 Rome Italy Telephone:+39-06-41514159; francesca.finocchiaro@thalesaleniaspace.it Gian Luca Natale, Thales Alenia Space-Italia S.p.A., via Saccomuro 24, 00131 Rome Italy Telephone:+39-06-41514316; gianluca.natale@thalesaleniaspace.it Carmela Ruta, Thales Alenia Space-Italia S.p.A., via Saccomuro 24, 00131 Rome Italy Telephone:+39-06-41514649; carmela.ruta@thalesaleniaspace.it Sabrina Wahib, Thales Alenia Space-Italia S.p.A., via Saccomuro 24, 00131 Rome Italy Telephone:+39-06-41514632; sabrina-aziza.wahib@thalesaleniaspace.it Abstract Launched on Feb 6th 2014, the ATHENA FIDUS Satellite embarks an Italian Payload that operates in the EHF/Ka/K Band for Military and Civilian Dual Use applications. The Italian Payload shares the Spacecraft with a French Payload that also operates in Ka Band, whose presence places constraints on both the Payload Architecture and Frequency Plan. The Italian Payload In Orbit Tests (IOT) were performed after the LEOP phase, from mid-february to mid-march 2014. Testing demonstrated the good health of the payload and its compliance to the System Functional Specification. The good health was demonstrated by the match between the measured data and the predictions, that is the expected results based on the on ground testing in TVAC and FFT. This paper provides a brief overview of the Payload architecture and presents the In Orbit Testing. The focus will be on the In Orbit Test preparation based on the on Satellite AIT phase and on the definition and validation of the Flight Operational Procedures with the Operations team. It also provides an overview of those steps taken prior to the RF testing itself, such as outgassing, and in addition to the RF testing, such as the 24h Monitoring to simulate flight operating conditions. Introduction The Italian Payload embarked on the ATHENA FIDUS Spacecraft, a joint French-Italian mission, caters to both Military and Institutional clients. It offers broadband communications services to Italian Military and Institutional/Civilian users over the Italian National Coverage in EHF and Ka bands. Users are allocated Transparent Star and Mesh communication channels. In addition, communication channels are defined for Transparent Star and Multi-Star communications in Intra- and between s and the Italian Fixed coverage. ATHENA FIDUS is positioned at 37.8 E, but the Italian Payload s two lateral antennas mounted on the West Panel are designed to provide fixed Italian coverage over a wide orbital arc: from 23.7 E to 49 E. The two Antennas, mounted on the Earth Antenna Module together with five Antennas belonging to the French Payload, can be steered over the entire visible globe. A global horn provides Beacon coverage over the visible globe to aid the users to lock onto the Satellite. The Italian Repeater is assembled on the South Panel with only a few passive units on the Earth Facing panel.
The Italian Payload is apportioned between the Civilian/Institutional and Military sections: the Antennas and Repeater Input Section are for each of these customer s exclusive use, while the High Power Amplification section is in a common redundancy ring. The Payload was fully tested in orbit in TPZ facilities in Fucino to demonstrate full compliance to the System Functional Specification requirements. Italian Payload Architecture The Italian Payload is composed of twelve Transparent Transponders that allow for potential ground segment evolution: six in Civilian Ka Band, four in NATO Ka Band and two in EHF/Ka Band. The Fixed Italian Coverage comprises Italy including the islands of Sardinia and Sicily. Two different lateral antennas (IFA1 and IFA2) have the same coverage: the IFA1 is a 1.4m antenna with the Tri- Band (44/) Feed for the NATO Ka band frequencies, while the IFA2 is a standard 1.7m 20/30GHz Antenna in the Civilian Ka band. Two mobile circular Spots (1000km diameter at the equator) can be positioned anywhere over the visible earth, which from today s orbital position (37.8 E) means from 26 W to 95 E. The Repeater is a classical bent pipe. The Ka Band input section is composed of Low Noise Amplifiers () and Down-CONverters (DOCON) with appropriate filtering before and after the 30 to 20 GHz conversion. The s for the Antennas are mounted on the Box at the top of the EAM module. The EHF input section has a Receiver that includes both the function and 44 to 20 GHz down-conversion. The High power section has a single 16:12 redundancy ring. TWTs are coupled to Dual EPCs in order to save mass and volume. Nominal LTWTAs output power can be 105W or 130W, redundant units have nominal Output power 130W. In case of failure of 105W LTWTA without Output section reconfiguration, the 130W redundant HPA used to recover the failure is properly backed off in order to maintain the required Output power. In case of multiple failures of 130W LTWTAs there is sometimes the need of output power section reconfiguration. In these cases a TASI proprietary software avoids recovery of 130W TWTs with 105W TWTs. This High Power Amplification redundancy ring guarantees the proper recovery of up to four TWTs/LDLAs failure and up to two EPCs located anywhere in the ring. The following figure shows the Functional Payload Block Diagram, where the Military Payload is shaded in blue and the Civilian/institutional Payload is shaded in gold. EHF/Ka/K IFA1 Antenna RX EHF RX Ka Circular Pol K06 FSS Forward K05 FSS Return K01 Mesh K07 MSS Forward K08 MSS Forward 6 44/20 GHz DOCON LO2 1 7 DOCON LO2 8 K06 FSS Forward K5&9&10 Return K01 Mesh EHF/Ka/K IFA1 Antenna Antenna 1 RX Ka K09 MSS Return K02 Intra- 5 K07 MSS Forward K02 Intra- Antenna 1 9 Antenna 2 RX Ka K10 MSS Return K02 Intra- 10 2 K08 MSS Forward K02 Intra- Antenna 2 K16 FSS Forward Ka/K IFA2 Antenna RX Ka Circular Pol K16 FSS Forward K18 FSS Forward K03 Transp Mesh K04 Transp Mesh K19 Transp Mesh K15 FSS RTN 16 DOCON LO3 18 3 4 DOCON LO2 19 DOCON LO4 15 K18 FSS Forward K03 Transp Mesh K04 Transp Mesh K19 Transp Mesh K15 FSS RTN Ka/K IFA2 Antenna
ATHENA FIDUS Italian Payload In Orbit Test Campaign Preparation The validation approach for In Orbit Test testing was similar to the one used during Satellite AIT. It is based on the comparison both with respect to the expected value (predictions) and to the behaviour of similar test paths (trend analysis). Predictions for the In Orbit Test are based on the measurements made during the AIT Campaign. The validation is based on the comparison of performance vs prediction; each parameter has a maximum allowed variation with respect to the predictions based on the experience of the heritage programs; furthermore the trend analysis of test results and their delta with respect to predictions is expected to show similar behaviour for similar tests/test paths. Test results trend analysis is performed classifying the test results in a proper way that allows to isolate anomalies on a path or in a single test and to easily detect calibration offsets in the Ground Station (GS). In general it is possible that a test is defined in trend even if it is different from the predicted value. If one measurement is noticeably different from the others it is defined as out of trend and is first of all repeated. When variations between measurements or with respect to predictions are larger than expected investigations begin, even when the parameter is compliant to the specification. In order to avoid the daily Gain and Noise Figure variations due to temperature, a specific thermal control that simulated the ambient temperature on ground was foreseen throughout the In Orbit Test phase. Therefore, the In Orbit Test predictions were based mainly on the Repeater performances during the Final Functional Test (FFT) campaign in Cannes. The other elements of the predictions were the Payload Antenna Gain calculated for the Ground Station s position and the Ground Station characteristics. Of course, the predictions must take into account the fact that the Ground Station (GS) in Fucino is close to the Centre of Coverage (COC) and that the measurements in In Orbit Test are performed at Beginning of Life (BOL). In most cases specific success criteria for the In Orbit Test were derived from Payload Specification. In fact it was necessary to scale the specification limits in order to declare compliance to the Technical Specification that includes performance degradation over temperature, coverage and lifetime. The In Orbit Test Operations were based on a number of procedures whose primary objective was to operate the Payload in a safe way. All Flight Operational Procedures (FOP) and In Orbit Test Operational Procedures and subroutines were validated on the Satellite Simulator in Cannes. Procedures were foreseen for nominal operations, such as to switch ON/OFF the low power units, to manage the LDLA Gain Settings and status, to set the USO frequency word and to modify the Intra connectivity. In addition some contingency procedures were foreseen to manage reconfigurations or to switch off the Payload. The Payload Configurations for In Orbit Test were chosen in order to reduce as much as possible unit ON/OFF and switch position variations while completely testing the Payload. The objective was not to reproduce all the tests performed during Satellite AIT on ground, but simply to measure the nominal Payload performances and verify that all units were functioning properly, both main and redundant. This task should be achieved with the least possible number of tests. Three configurations were necessary to accomplish this: Configuration 1: this configuration is the payload as depicted in the block diagram, the one that will be operative for nominal use. Channel 2 Intra-theatre is on spot ISA2. Configuration 2: this configuration tests the most of the redundant input section, keeping the nominal Amplification Section. Channel 2 Intra-theatre is on spot ISA1. Configuration 3: this configuration tests the four redundant TWTs, the remaining units of the input section and the redundant beacon. The test matrix that resulted from the three configurations described above comprised 180 RF tests. Specific procedures were developed and tested on the Simulator to change from one configuration to the next and from any configuration to the Configuration 1. It was decided to perform the ATHENA FIDUS In Orbit Test venting phase with noise. The use of noise allows to vent more paths simultaneously even without a multicarrier generator and at the same time guarantees to be completely safe from any interfering signal. In fact, input section switches are in a position that enables them to interrupt the RF path between the Repeater and the Antenna.
A preliminary activity was carried out on ground in order to be able to perform venting with noise. In fact AM/AM testing with noise was performed during SAT AIT in order to map LTWTAs telemetries and to safely control the satellite drive in orbit. In addition the venting procedure was prepared on ground and tested on the simulator. ATHENA FIDUS Italian Payload In Orbit Test Campaign Preliminary Activity The In Orbit Test campaign for the Italian Payload was performed in TPZ facilities in Fucino. Testing was performed by TPZ personnel, while TAS was responsible for the test Validation and for the Operations. The whole In Orbit Test process began with the Venting of the output section of the Payload in order to enable its safe operation. The plan was to perform first the Venting, then the Payload Full Load 24h monitoring requested by the Customers and then the Antenna Mapping. The venting was achieved by gradually stepping the LDLA gain settings according to a pre-arranged sequence. The sequence starts with OBO 9 db and ends with the LTWTAs in Saturation. A five minute time interval is observed between steps. The working point of the LTWTAs at each step was observed by means of the Helix Current and EPC Current Telemetries. At the end of the venting sequence all the LTWTAs were set in FGM at the Low Gain value and with Blanking ON. The venting configurations were also used to perform the 24h monitoring and the Antenna Mapping in order to perform these tasks without any possible interference by signals from ground and at the same time to minimise the switch commutations and the unit ON/OFF or blanking. The objective of the 24h Full Load Monitoring was to monitor the thermal behaviour of the Satellite when both French and Italian Payloads were ON with all their TWTs at their nominal working point. As mentioned before this was achieved with noise, stepping each TWT carefully to the nominal working point by monitoring the Telemetries for the Helix current and the EPC current. Due to the Input Section redundancy topology, the 24h monitoring had two channels open to the antenna. Therefore, it was necessary to monitor these channels and verify that no interfering signal changed the TWT working point. The result of the monitoring showed that the spacecraft was slightly colder than calculated for the Pre Shipment Review (PSR) on the basis of the TVAC testing, so the foreseen dissipation margins were fully confirmed. Antenna Mapping was performed only for the Transmit Function using noise. The aim of the Antenna Mapping is to verify the antenna optics with respect to that measured in Compact Antenna Test Range (CATR) by measuring the transmit pattern. The mapping is performed on two cuts: one for azimuth and one for elevation with the transponder in saturation. In particular it is necessary to confirm that the Antenna Deployment and Pointing Mechanism (ADPM) steps used to open the reflector have resulted in the correct pointing. The Satellite position was defined after the completion of its on ground test campaign. During all phases of this campaign, from Antenna Subsystem level to Satellite level, the orbital position was always assumed to be the nominal position (25 E). The Antenna RF model was validated by the Near Field Test Range (NFTR) antenna measurements. These measurements were confirmed by the Compact Antenna Test Range (CATR) test phase. Therefore it was possible to use this RF model to calculate the predicted antenna performance at 37.8 E that is the today s nominal position. Mapping for both IFA1 and IFA2 performed at 1900UT was in line with the predicted values. Also the predicted values for the Italian Steerable Antennas (ISA1&2) were based on an analysis. No antenna measurement performed on ground in either bore-sight, stowed or extreme North, East, South or West positions could be compared to the measurements performed during the In Orbit Test because in this case both antennas were pointed to the Ground Station at Fucino. In the same way as the IFA antennas, the In Orbit Test performance validation for the Steerable Antennas was performed
with respect to predictions based on the RF Antenna model validated during the on Ground testing phase. ISA1 and ISA2 mapping was in line with the predicted values. Conclusion This paper has described the preparation of the ATHENA FIDUS Italian Payload In Orbit Test and the preliminary activity. The activity was carried out according to plan and the In Orbit Test Leading Procedure.