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SILEX: Overview on the European optical communications programme
Pergamon 0094~5765(95)00062-3
Acto Astronourica Vol. 31. pp. 417-423. 1995 Copyright 0 1995 Elsevier Science Ltd Printed in Great Britain. All right: rererved 0094-5765195 59.50+0.00
link performances. It will be the first civilian link between two satellites, to be completed later on by a link between Artemis and the Japanese OICETS spacecraft (LEO). The terminal design is also capable to provide potentially a GEO-GEO ISL link. SILEX has two goals : - The first, which is experimental, is to establish how this type of link behaves in orbit. Thus PASTEL will send fictitious data to determine the quality of the link, together with mission telemetry to permit analysis of the optical I pointing performance in particular ; - The other, which is pre-operational, is to transmit the video images from SPOT IV’s HRV (high resolution visible) cameras and thus to rationalise/optimise the use of SPOT IV’s magnetic recorders. This is why a rate of 50 Mbit/s has been adopted for the LEO-to-GE0 link (A HRV camera = 25 Mbit/s), while the GE0 could also communicate at a rate of 2 Mbit/s with a future user in low orbit (to relay remote control messages, for example). Thanks to the presence of the two optical terminals on SPOT IV and Artemis respectively, SPOT IV will be able to communicate with Toulouse for periods of up to 50 minutes per orbit with the help of the laser link and a Ka-band link between the GE0 and the ground (see figure 1).
SILEX : OVERVIEW ON THE EUROPEAN OPTICAL COMMUNICATIONS PROGRAMME B. Laurent Matra Marconi Space 3 1, rue des cosmonautes - Z.I. du Palays 3 1077 Toulouse Cedex FRANCE Abstract SILEX (Semi-Conducteur Intersatellite Link Experiment) is the first civilian optical communications programme (in the frame of ESA DRTM). It will demonstrate in 1997 high data rate transmission between a Low Earth Orbit Satellite (SPOT IV, built by MMS for CNES) and a Geostationnary spacecraft (ARTEMIS, realized by ALENIA for ESA). After the opto/mechanical/thermal qualification obtained mid of 1994, the SILEX programme is entered in an intensive phase with : - the integration/validation for the LEO flight model (PASTEL) - the preparation of integration of the GE0 qualification STM and electrical/SW models (OPALE) The article describes the overall development status including the major terminal validation steps as well as the significant technological progress obtained through the qualification at equipment/terminal level. Introduction The SILEX programme is part of the Data Relay and Technology Mission (“DRTM”) ESA programme. It is currently in C/D phase for both LEO terminal (called “PASTEL” for PAssenger on Spot for Telecommunications with Laser) and GE0 terminal (called “OPALE” for Optical Payload for Artemis Laser link Experiment). This European Optical Communications programme is under Matra Marconi Space (MMS) prime contractorship for respectively ESA (supported by CNES) and ALENIA (ARTEMIS) SILEX Mission The purpose of the SILEX mission is to demonstrate in full scale the laser intersatellite
Figure 1 : characteristics of ISL and IOL links
417
418
45th
SILEX concent : main features The SILEX optical terminals on the two satellites are very similar. They are autonomous instruments which manage their own different operating modes and configuration. They are made up of (cf. fig. 2) Fixed part electronics comprising the onboard processor (OBP), the coarse pointing drive electronics and the communications electronics interfacing with the signals coming from the LEO terminal (or going to the GE0 terminal) ; _ an aerial composed of a satellite interface structure which carries the coarse pointing mechanism (CPA) and fixing arms for the launch (LLD). The mobile part (moved about two axes by the CPA) comprises : the telescope ; the focal plane incorporating all sensitive elements such as the mechanisms, sensors, sources and optical components, requiring high stability and thus efficient thermal control ; the proximity electronic devices which control this equipment After an acquisition phase - when the partner is detected with the help of a specific beacon on the geostationary terminal - the laser beams are
IAF Congress
used both to communicate and to track the partner using angle-error measurement detectors which indicate the direction of reception. The basic principle is to take advantage of the magnification of the telescope -8 mm to 25 cm, i.e. about 30x) in order to achieve the required performance. Two stage pointing is thus incorporated, allowing coverage of a hemisphere while attaining a precision of approximately two microradians. The main characteristics are summarized on figure 3 hereafter. r FiR. 3 : SILEX : MAR CHARACTERISTICS 1 Link Performance 0 Wavelength 0 Laser diode power 0 Useful received power 0 Data rate
0 Bit error rate 0 Pointing accuracy Terminal Design 0 Mass Cl Telescope diameter 0 DC input power
Figure 2 : SILEX Functional diagram
0.8 - 0.85 pm (near IR) 60 mW (average) 1.5nW 50 Mbits/s (LEO-GEO) up to 2 Mbits/s (GE@ LEO) < 10-6 0.3 prad (random) 0.8 prad (static) 160 Kg (including spacecrafi interface) 0.25 m 18OW
419
45th IAF Congress
Developments status The SILEX development is characterized by the necessity to adapt a common design to two different spacecrafks. This has imposed to realize different structures on top of the specific LEO transmitter/modulator function or GE0 beacon/receiver function. As a consequence, the development is based on various models : _ interface models for decoupling spacecraft and terminal developments in particular for mechanical/ thermal/ electricaV sofhvare verification - terminal qualification models (called STM) on thermal/ mechanical/ optomechanical stability/microvibrations aspects -terminal protoflight models
The present situation is summa&d on figure 4. After the successful1 campaing in 93 at S/L level with LEO interface models, the main event in 1994 was the successful qualification of the LEO design as mechanical environment (including new ARIANE launch enviromnent) microvibrations hasbeen supported, characteristics have been measured, thermal behaviour/prediction have been verified and optomechanical stability (alignmentkfws) has been demonstmted. The remainmg tests at LEO terminal level to be performed are mainly ConcenWatedon OpkalIPointing performances (ambient / vacuum) knowing that first results with the System Test Bed are encouraging.
ElectricaVSW I/F
MI deliveredto S4 IM
Structuralor/and thermal
Figure 4 : Overall SILEX development status
: under preparation
45th IAF Congress
420 EQUIF’MENT ACRONYM CPM
I
EQIJII’MENT coarse Pointing Mecanism
I
ng and Sensor Control
STATUS Mechanically qualified. Lifetest
QualikxUEQM delivered
both LEO/GE0
On Board Processor
Qualified - Modified with 128K
Fixed part to S/C I/F Structure
Successful vibration qualification at
Coarse Pointing Support Bracket
Figure 5 : status of qualification
at equipment level
45th
M’am test results and teclmoloEical Dmgess Apart the design qualifications at equipment level@enerauyalreadyperfbrmed-seefigure 5) and temIil& level, the main test results CMlcenrthepclfbrmanceSilltlUeeanaS: - Optical, where very tight pe&rmances on primary/secondary mirrors stabilii and unit alignment are mandatory - point& especially the aquisitio&acking performances linked to video chain capability, rejection and noise figures - Communicati~ as tbe required sensitivity is very high to allow 50 Mbit/s data rate with 1SnWusefblpower In these 3 domains (see figure 6), the specified performances have been achieved and verified with DM’s or EQM’s.
DOMAIN Optical
On top of these performances, it shall be highlighted that SILEX termi& gather a lot ofkeytechnologieswhicllareatthestateofthe art, from components to software including materials, coatings, electronics, processes... (see figure 9). This ambitions texAnol@cal programme has requested numerous spe45fk evaluations/qualifications which are today close to the end. The main critical areas which are still not qualified concern the piezzoactuators, position sensor hybrid (PM), the DC/DC’s and the behaviour of zerodur under radiations.
ASSY LEVEL
SPECIFIED PERFORMANCE
Telescope(flight)
TEST RESULTS
WFE < A I20
,
OK ()1/19) Irradiations
()1/10 on acquisitionFOV)
impactto be waluatcd I
Filters flight
Rcjcctionof IO& width 8 nm bandwidth
Terminal (STM)
Dcfofus thermalenvironmentimpact< 2.5 p mechanicalenvironment<
Pointing
421
IAF Congress
Iu
FPSCE + sensors
videochain at 3 MHz
PAT chain
Aqoisition/trackingtracking
(OK 2 )I
lu OK
-rejection : O.dB at 100 Hz
OK - De-signrnprovcd to 0 dB at 130 Hz for
I Terminal STM
1flight
I
I
-noisca=0.35flrad
n = 0.20 prad
Impact of microvibrationc 0.5 prad
coupled
test
with
SPOT4 - OK Communication
RFEAXO TEFP EQM
Sensitiwty bcttcr than - 58.3 dBm with -58.7dBm backgroundandPNlS(BER=
10d)
Figure 6 : Main test results during 93/94 SILEX test campaign at equipment or terminal level
45th IAF Congress
422
Figure 7 : SILEX telescope developed by ZEISS mounted on the Optical Head Bench
Figure 8
LEO qualification model (STM) mounted on SPOTIV
45th IAF Congress
423
Figure 9 : Main technological progress in the frame of SILEX programme
TECHNOLOGY FPGA I .2 p (Actel) CCD 16x16 pixels (Thomson) Slik APD 120 mW (SDL) Laser diodes I W (SDL) 1750-MAS 281 processor ASDP 2100 Zerodur for both mirrors&wtun Beryllium CFRP with high stability Pie2.o actuators optical fibers with 99.5 Anti reflective coating transmissioo TIC (PVD) narrow filters with lnterferential bandwidth (< 10 nm) and high transmittance or reflectance (> 98%) Hybrids (Position sensors. DCiDC... Surface. Mounting Technology FLAT miniature transformer ADA language
AREA components
Materials
Coatings
Electronics/process
SW
EQUIPMENT (SUBCONTRACTOR) _ FPSCE (MMS) TSDU (SIRA) Receiver Front End (EC&G/ANT) LDTP (Matra UAO today SFIM ODS) Beacon (SBI) OBP (MMS) FPSCE (MMS) Telescope ff 1.5(ZEISS) PAA/CPA (MMS) OH9 (CASA) PAA (MMS UK) Beacon (SBVBERTIN) Optical components (MATRA UAO today SFIM) LLD (SENER) Filten (Matm UAO today SFIM ODS)
PAA (MMS UK), DCiDC (ETCA) FPSCE (MMS-Fr) FPSCE (MMS-Fr) SW MMS I MTECS
Figure 10 : Evolution of Laser Diodes power during the last 10 years mW -
1000 900
-
800
-
700
-
:ZG”E
600
T
500
-
400
-
300
- FABRYpu#3T DOUBLE HmROSTRUCNRE
200 100
/
SILEXGE0
FABRY PQUANnQUE
SILEX LEO \>/ -__c__-
-
O_’ 1983
1985
1988
Conclusions - Future Outlook Following the qualification phase of SILEX LEO terminal and the first results obtained with flight hardware, we can consider that the required performances will be achieved. The flight laser diodes for LEO and GE0 (communications and beacon) have been delivered and the obtained very good performances - more than 150 mW (useful power on LEO/GE0 60 mW) and 1.2 W diodes (useful power on GE0 : 600 mW) respectively - will secure the link The key events in the coming years will be : 1) the air vacuum optical performances demonstration for both optical head/terminal assemblies (LEO) and obviously the LEO flight terminal full integration
1989
1990
1992
1993
2) the GE0 qualification (STM) and flight terminal integration In parallel, thanks to the fast development of diode lasers as depicted on figure 10, a next generation of Optical terminal shall be engaged in order to be prepared to satisfy at the beginning of next century customer needs in data transmission with limited constraints on the spacecraft Acknowlednments Technical collaboration with ESA, CNES and ALENIA, as well as all MMS subcontractors is acknowledged in the development of SILEX GEO/LEO terminals, which is financially supported by ESA.
Acto Astronourica Vol. 31. pp. 417-423. 1995 Copyright 0 1995 Elsevier Science Ltd Printed in Great Britain. All right: rererved 0094-5765195 59.50+0.00
link performances. It will be the first civilian link between two satellites, to be completed later on by a link between Artemis and the Japanese OICETS spacecraft (LEO). The terminal design is also capable to provide potentially a GEO-GEO ISL link. SILEX has two goals : - The first, which is experimental, is to establish how this type of link behaves in orbit. Thus PASTEL will send fictitious data to determine the quality of the link, together with mission telemetry to permit analysis of the optical I pointing performance in particular ; - The other, which is pre-operational, is to transmit the video images from SPOT IV’s HRV (high resolution visible) cameras and thus to rationalise/optimise the use of SPOT IV’s magnetic recorders. This is why a rate of 50 Mbit/s has been adopted for the LEO-to-GE0 link (A HRV camera = 25 Mbit/s), while the GE0 could also communicate at a rate of 2 Mbit/s with a future user in low orbit (to relay remote control messages, for example). Thanks to the presence of the two optical terminals on SPOT IV and Artemis respectively, SPOT IV will be able to communicate with Toulouse for periods of up to 50 minutes per orbit with the help of the laser link and a Ka-band link between the GE0 and the ground (see figure 1).
SILEX : OVERVIEW ON THE EUROPEAN OPTICAL COMMUNICATIONS PROGRAMME B. Laurent Matra Marconi Space 3 1, rue des cosmonautes - Z.I. du Palays 3 1077 Toulouse Cedex FRANCE Abstract SILEX (Semi-Conducteur Intersatellite Link Experiment) is the first civilian optical communications programme (in the frame of ESA DRTM). It will demonstrate in 1997 high data rate transmission between a Low Earth Orbit Satellite (SPOT IV, built by MMS for CNES) and a Geostationnary spacecraft (ARTEMIS, realized by ALENIA for ESA). After the opto/mechanical/thermal qualification obtained mid of 1994, the SILEX programme is entered in an intensive phase with : - the integration/validation for the LEO flight model (PASTEL) - the preparation of integration of the GE0 qualification STM and electrical/SW models (OPALE) The article describes the overall development status including the major terminal validation steps as well as the significant technological progress obtained through the qualification at equipment/terminal level. Introduction The SILEX programme is part of the Data Relay and Technology Mission (“DRTM”) ESA programme. It is currently in C/D phase for both LEO terminal (called “PASTEL” for PAssenger on Spot for Telecommunications with Laser) and GE0 terminal (called “OPALE” for Optical Payload for Artemis Laser link Experiment). This European Optical Communications programme is under Matra Marconi Space (MMS) prime contractorship for respectively ESA (supported by CNES) and ALENIA (ARTEMIS) SILEX Mission The purpose of the SILEX mission is to demonstrate in full scale the laser intersatellite
Figure 1 : characteristics of ISL and IOL links
417
418
45th
SILEX concent : main features The SILEX optical terminals on the two satellites are very similar. They are autonomous instruments which manage their own different operating modes and configuration. They are made up of (cf. fig. 2) Fixed part electronics comprising the onboard processor (OBP), the coarse pointing drive electronics and the communications electronics interfacing with the signals coming from the LEO terminal (or going to the GE0 terminal) ; _ an aerial composed of a satellite interface structure which carries the coarse pointing mechanism (CPA) and fixing arms for the launch (LLD). The mobile part (moved about two axes by the CPA) comprises : the telescope ; the focal plane incorporating all sensitive elements such as the mechanisms, sensors, sources and optical components, requiring high stability and thus efficient thermal control ; the proximity electronic devices which control this equipment After an acquisition phase - when the partner is detected with the help of a specific beacon on the geostationary terminal - the laser beams are
IAF Congress
used both to communicate and to track the partner using angle-error measurement detectors which indicate the direction of reception. The basic principle is to take advantage of the magnification of the telescope -8 mm to 25 cm, i.e. about 30x) in order to achieve the required performance. Two stage pointing is thus incorporated, allowing coverage of a hemisphere while attaining a precision of approximately two microradians. The main characteristics are summarized on figure 3 hereafter. r FiR. 3 : SILEX : MAR CHARACTERISTICS 1 Link Performance 0 Wavelength 0 Laser diode power 0 Useful received power 0 Data rate
0 Bit error rate 0 Pointing accuracy Terminal Design 0 Mass Cl Telescope diameter 0 DC input power
Figure 2 : SILEX Functional diagram
0.8 - 0.85 pm (near IR) 60 mW (average) 1.5nW 50 Mbits/s (LEO-GEO) up to 2 Mbits/s (GE@ LEO) < 10-6 0.3 prad (random) 0.8 prad (static) 160 Kg (including spacecrafi interface) 0.25 m 18OW
419
45th IAF Congress
Developments status The SILEX development is characterized by the necessity to adapt a common design to two different spacecrafks. This has imposed to realize different structures on top of the specific LEO transmitter/modulator function or GE0 beacon/receiver function. As a consequence, the development is based on various models : _ interface models for decoupling spacecraft and terminal developments in particular for mechanical/ thermal/ electricaV sofhvare verification - terminal qualification models (called STM) on thermal/ mechanical/ optomechanical stability/microvibrations aspects -terminal protoflight models
The present situation is summa&d on figure 4. After the successful1 campaing in 93 at S/L level with LEO interface models, the main event in 1994 was the successful qualification of the LEO design as mechanical environment (including new ARIANE launch enviromnent) microvibrations hasbeen supported, characteristics have been measured, thermal behaviour/prediction have been verified and optomechanical stability (alignmentkfws) has been demonstmted. The remainmg tests at LEO terminal level to be performed are mainly ConcenWatedon OpkalIPointing performances (ambient / vacuum) knowing that first results with the System Test Bed are encouraging.
ElectricaVSW I/F
MI deliveredto S4 IM
Structuralor/and thermal
Figure 4 : Overall SILEX development status
: under preparation
45th IAF Congress
420 EQUIF’MENT ACRONYM CPM
I
EQIJII’MENT coarse Pointing Mecanism
I
ng and Sensor Control
STATUS Mechanically qualified. Lifetest
QualikxUEQM delivered
both LEO/GE0
On Board Processor
Qualified - Modified with 128K
Fixed part to S/C I/F Structure
Successful vibration qualification at
Coarse Pointing Support Bracket
Figure 5 : status of qualification
at equipment level
45th
M’am test results and teclmoloEical Dmgess Apart the design qualifications at equipment level@enerauyalreadyperfbrmed-seefigure 5) and temIil& level, the main test results CMlcenrthepclfbrmanceSilltlUeeanaS: - Optical, where very tight pe&rmances on primary/secondary mirrors stabilii and unit alignment are mandatory - point& especially the aquisitio&acking performances linked to video chain capability, rejection and noise figures - Communicati~ as tbe required sensitivity is very high to allow 50 Mbit/s data rate with 1SnWusefblpower In these 3 domains (see figure 6), the specified performances have been achieved and verified with DM’s or EQM’s.
DOMAIN Optical
On top of these performances, it shall be highlighted that SILEX termi& gather a lot ofkeytechnologieswhicllareatthestateofthe art, from components to software including materials, coatings, electronics, processes... (see figure 9). This ambitions texAnol@cal programme has requested numerous spe45fk evaluations/qualifications which are today close to the end. The main critical areas which are still not qualified concern the piezzoactuators, position sensor hybrid (PM), the DC/DC’s and the behaviour of zerodur under radiations.
ASSY LEVEL
SPECIFIED PERFORMANCE
Telescope(flight)
TEST RESULTS
WFE < A I20
,
OK ()1/19) Irradiations
()1/10 on acquisitionFOV)
impactto be waluatcd I
Filters flight
Rcjcctionof IO& width 8 nm bandwidth
Terminal (STM)
Dcfofus thermalenvironmentimpact< 2.5 p mechanicalenvironment<
Pointing
421
IAF Congress
Iu
FPSCE + sensors
videochain at 3 MHz
PAT chain
Aqoisition/trackingtracking
(OK 2 )I
lu OK
-rejection : O.dB at 100 Hz
OK - De-signrnprovcd to 0 dB at 130 Hz for
I Terminal STM
1flight
I
I
-noisca=0.35flrad
n = 0.20 prad
Impact of microvibrationc 0.5 prad
coupled
test
with
SPOT4 - OK Communication
RFEAXO TEFP EQM
Sensitiwty bcttcr than - 58.3 dBm with -58.7dBm backgroundandPNlS(BER=
10d)
Figure 6 : Main test results during 93/94 SILEX test campaign at equipment or terminal level
45th IAF Congress
422
Figure 7 : SILEX telescope developed by ZEISS mounted on the Optical Head Bench
Figure 8
LEO qualification model (STM) mounted on SPOTIV
45th IAF Congress
423
Figure 9 : Main technological progress in the frame of SILEX programme
TECHNOLOGY FPGA I .2 p (Actel) CCD 16x16 pixels (Thomson) Slik APD 120 mW (SDL) Laser diodes I W (SDL) 1750-MAS 281 processor ASDP 2100 Zerodur for both mirrors&wtun Beryllium CFRP with high stability Pie2.o actuators optical fibers with 99.5 Anti reflective coating transmissioo TIC (PVD) narrow filters with lnterferential bandwidth (< 10 nm) and high transmittance or reflectance (> 98%) Hybrids (Position sensors. DCiDC... Surface. Mounting Technology FLAT miniature transformer ADA language
AREA components
Materials
Coatings
Electronics/process
SW
EQUIPMENT (SUBCONTRACTOR) _ FPSCE (MMS) TSDU (SIRA) Receiver Front End (EC&G/ANT) LDTP (Matra UAO today SFIM ODS) Beacon (SBI) OBP (MMS) FPSCE (MMS) Telescope ff 1.5(ZEISS) PAA/CPA (MMS) OH9 (CASA) PAA (MMS UK) Beacon (SBVBERTIN) Optical components (MATRA UAO today SFIM) LLD (SENER) Filten (Matm UAO today SFIM ODS)
PAA (MMS UK), DCiDC (ETCA) FPSCE (MMS-Fr) FPSCE (MMS-Fr) SW MMS I MTECS
Figure 10 : Evolution of Laser Diodes power during the last 10 years mW -
1000 900
-
800
-
700
-
:ZG”E
600
T
500
-
400
-
300
- FABRYpu#3T DOUBLE HmROSTRUCNRE
200 100
/
SILEXGE0
FABRY PQUANnQUE
SILEX LEO \>/ -__c__-
-
O_’ 1983
1985
1988
Conclusions - Future Outlook Following the qualification phase of SILEX LEO terminal and the first results obtained with flight hardware, we can consider that the required performances will be achieved. The flight laser diodes for LEO and GE0 (communications and beacon) have been delivered and the obtained very good performances - more than 150 mW (useful power on LEO/GE0 60 mW) and 1.2 W diodes (useful power on GE0 : 600 mW) respectively - will secure the link The key events in the coming years will be : 1) the air vacuum optical performances demonstration for both optical head/terminal assemblies (LEO) and obviously the LEO flight terminal full integration
1989
1990
1992
1993
2) the GE0 qualification (STM) and flight terminal integration In parallel, thanks to the fast development of diode lasers as depicted on figure 10, a next generation of Optical terminal shall be engaged in order to be prepared to satisfy at the beginning of next century customer needs in data transmission with limited constraints on the spacecraft Acknowlednments Technical collaboration with ESA, CNES and ALENIA, as well as all MMS subcontractors is acknowledged in the development of SILEX GEO/LEO terminals, which is financially supported by ESA.