- Email: [email protected]
Proteus: A mutlimission platform for low earth orbits
Small Satellites
PROTEUS: A Multimission Platform for Low Earth Orbits Jean-Jacques
DECHEZELLES,
G&at-d HUlTlN
PROTEUS is a standard multimission platform for Low Earth Orbits. This product line results from a very close collaboration between CNES and A/cute/ Space. It draws on the very best of this partnership experience to achieve outstanding robustness und reliability figures, and is specifically designed to offer accommodation to CY/urge range of applications, flexibility in choice of orbital parameters, various pointing modes, and compatibility with small launch vehicles. A typical satellite using PROTEUS would weigh 500 kg for an electrical power of 600 wcxtts. II Europe, the PROTEUS platform leads the Small Satellites approach, aiming at both low cost missions and high standards of performance and quality. The PROTEUS platform (fisures 1 and 2) is designed as a multimission product offering a large flight domain, a high payload capacity and interfaces for simple accommodation of each
application. This platform has already attracted a wide range of customers concerned with an easy and fast mission achievement.
A large flight domain The PROTEUS platform is compatible with all low cost launch vehicles supporting the 500 to 1000 kg satellite class. It has been designed to be compatible with various orbits (phased, sun synchronous, frozen and inertial orbits) at altitudes ranging from 500 km to 1500 km and for an orbit plane inclination typically between 20 degree to 145 degree The platform provides a wide range of payload pointing capabilities (Earth, anti-Earth,
Inertial and Sun pointing) with a typical pointing accuracy of 0.05 degree (30), meeting most of the scientific and earth observation generic mission requirements. Its in-flight lifetime is five years.
A high payload capacity In its flight domain, PROTEUS allows for a payload of around 300 kg, an electrical power of 200 watts to 300 watts according to orbit and a peak power of 800 watts maximum for 20 minutes per orbit. A typical satellite configuration based on PROTEUS is shown in figure 3.
A compact and robust architecture The multimission design and the ability to accommodate various payloads and to fit a wide range of launch vehicles resulted in two main features for the concept: a modular and very robust mechanical structure, based on flight proven technologies (Globalstar); 9 an electrical, on-board command and data handling architecture centralised on a single computer, called the Data Handling Unit (DHU). Figure 4 shows the general lay-out of a PROTEUS platform. l
Figure 1. PROTEUS platform in Sun Vacuum Test (Dot. ALCATEL SPACE).
Figure 2. Internal lay-out of PROTEUS Platform (Dot. ALCATEL SPACE). AIR
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and active regulation with heaters, monitored by the central computer. Electrical power is generated by two symmetric wing arrays attached near to the satellite centre of mass, with two single-axis stepping motor drives. Each wing is comprised of four 1.5 x 0.8 m panels covered with classical silicon cells. The power is distributed through a single non-regulated primary electrical bus (23/36 volts with an average voltage of 28 volts), using a recurrent Ni-Cd battery. Normal in-orbit platform attitude control is based on a gyro-stellar concept. Accurate attitude determination is based on two star trackers (nominal and redundant). Three accurate, 2-axis gyrometers are used for stability requirements and attitude propagation. Attitude acquisition is obtained using magnetic and solar measurements (two 3-axis magnetometers and eight coarse sun sensors). Four small reaction wheels generate torques for attitude command, and are unloaded through use of magnetic torquers. A Global Positioning System (GPS) receiver provides satellite position information for accurate orbit ephemeris determination and on-board time delivery. The Data Handling Unit (DHU) is the heart of the electrical, on-board command and data handling architecture, as shown infigure 5. The primary functions handled by the DHU are: satellite mode management consisting in automatic mode transitions and routines; on-board failure detection and recovery, consisting in monitoring satellite health and switching to safe-holdmode if necessary; in generation, maintenance, and downlinking of housekeeping telemetry data; satellite commandability, consisting of processing commands sent by ground either to hardware or software.
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l
Fgure 3. Tvpical sate/Me conliguraiion based on PROTEUS: the Jason 1 mission, 475 kg/400 watts altitude 1336 km/ inclination 66 degree/Earth pointing (Doc.ALCATEL SPACE).
The main technical features are described as follows: The platform structure has a one-meter side cubic shape. All of the equipment units are accommodated on four lateral panels; the hydrazine mono-propellant system with a 40&e tank and four 1 N thrusters are mounted on the base plate at the aft section. The interface with the launch vehicle is achieved with an adapter (specific l
to each launch vehicle) bolted to the bottom of the structure. The platform primary structure features a truss framework, permitting independent panel removal and easy integration. The thermal control subsystem is dimensioned to withstand the maximum thermal loads defined by the PROTEUS candidate missions. The concept relies on passive radiators l
l
l
l
l
l
Figure 4. PROTEUS platform overview (Dot. ALCATEL SPACE).
A bare 727 kbit/s S band QPSK downlink (without encoding - Reed Solomon and Viterbi - and frame packeting) is available for telemetry. A ground control capacity is provided by a 4 kbit/s S-band up-link. The CCSDS packet standard protocol is used for TM encoding and TC decoding.
Payload interface data PROTEUS offers generic interfaces to the payload for an easy accommodation of any application: electrical interfaces with power supply through a non-regulated bus (23/ 36 volts), 16 power lines and 16 pyrotechnic lines; thermal control managed by the platform DHU and heater power lines in all satellite modes; standard mechanical interfaces through four points at the corners of the upper panel of the platform: payload management data via: - MIL- STD-1553 B bus (redundant); - high speed line; - command and acquisition lines; - datation lines delivering one pulse per second. Any potential User or Mission Planner wishing to assess the compatibility of specific payload and mission requirements with the PROTEUS platform l
figure 5. PROTEUS platform functional block diagram (Dot. ALCATEL SPACE).
l
The processor generates a clock reference, manages satellite data storage, and ensures telemetry frame decoding. The DHU also manages the payload throughout the commands and electrical interfaces. The DHU has an internal mass memory organised into two main sectors: - A housekeeping area to register payload and platform housekeeping data during out-of-visibility periods; - A data payload memory of 2 Gbits, split into two programmable areas, to independently store and transmit payload data to ground during visibility periods.
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Figure 7. Picasso-Cena (Dot. CNEWNASA). AIR
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Figure 8. Corot: a high accuracy photometry experiment for astronomy and exoplanet
detection (Dot. CNES).
can find more detailed information in the “PROTEUS User’s Guide”.
PROTEUS services Together with the PROTEUS platform product, Alcatel Space proposes a set of services to customers. Those are, separately or in combination: to provide a generic PROTEUS platform qualified and accepted; 9 the tuning to the mission parameters, called “missionisation”, mainly for the on board software; the payload instruments module based on a standard design consistent with PROTEUS platform and easily adaptable; the satellite assembly, integration and tests activities; the satellite transportation and launch campaign activities; . the in-flight acceptance; l
l
l
l
l
to provide a generic ground control segment including a ground station and a control centre.
PROTEUS product line The first satellite based on PROTEUS will fulfil the altimetry and oceanography mission JASON 1, led by CNES and NASA. At an orbit of 1336 km and an inclination of 66 degree, the platform ensures a stable geocentric pointing and an accurate maintenance of orbit parameters to the radar altimetry payload. This permits the achievement of the scientific objective: ocean level knowledge better than 2 cm in any place. Today, Jason satellite stands in integration phase at Alcatel Space, as shown in figure 6. The launch is foreseen in year 2000 with Delta 2 launch vehicle. In addition to JASON 2, which will ensure continuity of oceanographic data,
Figure 9. Megha Tropiques (Dot. CNES/ISRO).
many other applications are under study. PICASSO-CENA (Pathfinder Instruments for Cloud and Aerosol Spaceborne Observation - Climatologie des Etendues des Nuages et des Aerosols) will provide crucial measurements for the development and improvement of climatic forecasting (figure 7). The Proteus platform will embark a payload of four co-aligned near-nadir viewing instruments, the most important of which is a dual wavelength polarisation sensitive Lidar. The satellite will fly in formation with two other American satellites on a sun synchronous orbit at an altitude of 70.5 km. The mission is a CNES-NASA Langley co-operation. The launch is foreseen in year 2003 with a Delta 2 launch vehicle. COROT (Convection ROTation) will be a very high accuracy stellar photometry experiment for Astronomy research (figure 8). The scientific objectives will consist of the study of the internal structure of stars and the detection of exoplanets (out of solar system) of telluric type (like the Earth). Its orbit will be polar, inertial, with an altitude around 900 km. PROTEUS will carry a telescope with a pointing stability better than 1 arc second. This mission is led by CNES and French laboratories. MEGHA-TROPIQUES (figure 9) mission will study convective systems, water cycle and energy budget in the tropical atmosphere above seas and continents. A PROTEUS based satellite will fly on an orbit with an inclination of 22 degree and an altitude around 800 km. The mission is a CNES-ISRO (Indian Space Research Organization) cooperation. The launch is tentatively planned for 2004 with a PSLV launch vehicle. Although these planned missions show the flexibility of the multimission concept, PROTEUS uses are not limited to scientific missions. PROTEUS is well suited to optical missions for the Earth observing programmes like
Small Satellites the follow-on of the French programme SPOT and may well be adapted to radar missions. Optical and radar payloads are an interesting prospect for PROTEUS based combined observation systems from Space. Finally PROTEUS is adapted or adaptable to telecommunication and navigation missions. The Skybridge constellation satellites will use an avionics based on PROTEUS heritage. Galileo, a navigation European programme, may be based on satellites deriving from the PROTEUS platform.
Jean-JacquesDECHEZELLESis Director for Science, Environment and Meteorology at ALCATEL Space Industries.
Jean-JacquesDechezelles AKATEL Space Industries 700, boulevard du Midi 06 156 Cannes-La-Bocca cedex, France Tel.: +33 4 92 92 3 109. Fax: + 33 4 92 92 34 60 jean-jacques,dechezel/[email protected]. fr
G&arc! HUTTlNis Programme Manager for PROTEUS family and JASON I satellite at ALCATEL Space Industries. G&ad Huffin ALCATEL Space Industries 100,boulevard du Midi 06 156 Cannes-la-Bocca cedex, France Tel. : +33 4 92 92 30 89. Fax : + 33 4 92 92 33 30 gerard,hu#in~space,a/cate/.fr
Conclusion The PROTEUS platform and system environment is setting a new benchmark for the development of a Small Satellites Family. Partnership of CNES agency and Alcatel Space has revealed itself very suitable to merge experience and to achieve reliable solutions as well as lower costs and shorter
delivery times. The challenge of a multimission application is met thanks to a generic platform development in association with software and system tools to easily adapt to the context of different missions. Thus PROTEUS
AIR
& SPACE
constitutes a real beneficial European asset to implement more space missions within a given time frame and fixed budget. Moreover it satisfies the concept of more value for money that all customers are looking for. H
EUROPE
l
VOL.
2
l
No
I - 2000
PROTEUS: A Multimission Platform for Low Earth Orbits Jean-Jacques
DECHEZELLES,
G&at-d HUlTlN
PROTEUS is a standard multimission platform for Low Earth Orbits. This product line results from a very close collaboration between CNES and A/cute/ Space. It draws on the very best of this partnership experience to achieve outstanding robustness und reliability figures, and is specifically designed to offer accommodation to CY/urge range of applications, flexibility in choice of orbital parameters, various pointing modes, and compatibility with small launch vehicles. A typical satellite using PROTEUS would weigh 500 kg for an electrical power of 600 wcxtts. II Europe, the PROTEUS platform leads the Small Satellites approach, aiming at both low cost missions and high standards of performance and quality. The PROTEUS platform (fisures 1 and 2) is designed as a multimission product offering a large flight domain, a high payload capacity and interfaces for simple accommodation of each
application. This platform has already attracted a wide range of customers concerned with an easy and fast mission achievement.
A large flight domain The PROTEUS platform is compatible with all low cost launch vehicles supporting the 500 to 1000 kg satellite class. It has been designed to be compatible with various orbits (phased, sun synchronous, frozen and inertial orbits) at altitudes ranging from 500 km to 1500 km and for an orbit plane inclination typically between 20 degree to 145 degree The platform provides a wide range of payload pointing capabilities (Earth, anti-Earth,
Inertial and Sun pointing) with a typical pointing accuracy of 0.05 degree (30), meeting most of the scientific and earth observation generic mission requirements. Its in-flight lifetime is five years.
A high payload capacity In its flight domain, PROTEUS allows for a payload of around 300 kg, an electrical power of 200 watts to 300 watts according to orbit and a peak power of 800 watts maximum for 20 minutes per orbit. A typical satellite configuration based on PROTEUS is shown in figure 3.
A compact and robust architecture The multimission design and the ability to accommodate various payloads and to fit a wide range of launch vehicles resulted in two main features for the concept: a modular and very robust mechanical structure, based on flight proven technologies (Globalstar); 9 an electrical, on-board command and data handling architecture centralised on a single computer, called the Data Handling Unit (DHU). Figure 4 shows the general lay-out of a PROTEUS platform. l
Figure 1. PROTEUS platform in Sun Vacuum Test (Dot. ALCATEL SPACE).
Figure 2. Internal lay-out of PROTEUS Platform (Dot. ALCATEL SPACE). AIR
& SPACE
EUROPE
l
VOL.
2
l
No
I - 2000
and active regulation with heaters, monitored by the central computer. Electrical power is generated by two symmetric wing arrays attached near to the satellite centre of mass, with two single-axis stepping motor drives. Each wing is comprised of four 1.5 x 0.8 m panels covered with classical silicon cells. The power is distributed through a single non-regulated primary electrical bus (23/36 volts with an average voltage of 28 volts), using a recurrent Ni-Cd battery. Normal in-orbit platform attitude control is based on a gyro-stellar concept. Accurate attitude determination is based on two star trackers (nominal and redundant). Three accurate, 2-axis gyrometers are used for stability requirements and attitude propagation. Attitude acquisition is obtained using magnetic and solar measurements (two 3-axis magnetometers and eight coarse sun sensors). Four small reaction wheels generate torques for attitude command, and are unloaded through use of magnetic torquers. A Global Positioning System (GPS) receiver provides satellite position information for accurate orbit ephemeris determination and on-board time delivery. The Data Handling Unit (DHU) is the heart of the electrical, on-board command and data handling architecture, as shown infigure 5. The primary functions handled by the DHU are: satellite mode management consisting in automatic mode transitions and routines; on-board failure detection and recovery, consisting in monitoring satellite health and switching to safe-holdmode if necessary; in generation, maintenance, and downlinking of housekeeping telemetry data; satellite commandability, consisting of processing commands sent by ground either to hardware or software.
l
l
Fgure 3. Tvpical sate/Me conliguraiion based on PROTEUS: the Jason 1 mission, 475 kg/400 watts altitude 1336 km/ inclination 66 degree/Earth pointing (Doc.ALCATEL SPACE).
The main technical features are described as follows: The platform structure has a one-meter side cubic shape. All of the equipment units are accommodated on four lateral panels; the hydrazine mono-propellant system with a 40&e tank and four 1 N thrusters are mounted on the base plate at the aft section. The interface with the launch vehicle is achieved with an adapter (specific l
to each launch vehicle) bolted to the bottom of the structure. The platform primary structure features a truss framework, permitting independent panel removal and easy integration. The thermal control subsystem is dimensioned to withstand the maximum thermal loads defined by the PROTEUS candidate missions. The concept relies on passive radiators l
l
l
l
l
l
Figure 4. PROTEUS platform overview (Dot. ALCATEL SPACE).
A bare 727 kbit/s S band QPSK downlink (without encoding - Reed Solomon and Viterbi - and frame packeting) is available for telemetry. A ground control capacity is provided by a 4 kbit/s S-band up-link. The CCSDS packet standard protocol is used for TM encoding and TC decoding.
Payload interface data PROTEUS offers generic interfaces to the payload for an easy accommodation of any application: electrical interfaces with power supply through a non-regulated bus (23/ 36 volts), 16 power lines and 16 pyrotechnic lines; thermal control managed by the platform DHU and heater power lines in all satellite modes; standard mechanical interfaces through four points at the corners of the upper panel of the platform: payload management data via: - MIL- STD-1553 B bus (redundant); - high speed line; - command and acquisition lines; - datation lines delivering one pulse per second. Any potential User or Mission Planner wishing to assess the compatibility of specific payload and mission requirements with the PROTEUS platform l
figure 5. PROTEUS platform functional block diagram (Dot. ALCATEL SPACE).
l
The processor generates a clock reference, manages satellite data storage, and ensures telemetry frame decoding. The DHU also manages the payload throughout the commands and electrical interfaces. The DHU has an internal mass memory organised into two main sectors: - A housekeeping area to register payload and platform housekeeping data during out-of-visibility periods; - A data payload memory of 2 Gbits, split into two programmable areas, to independently store and transmit payload data to ground during visibility periods.
l
l
Figure 7. Picasso-Cena (Dot. CNEWNASA). AIR
& SPACE
EUROPE
l
VOL.
2
l
No
I - 2000
Figure 8. Corot: a high accuracy photometry experiment for astronomy and exoplanet
detection (Dot. CNES).
can find more detailed information in the “PROTEUS User’s Guide”.
PROTEUS services Together with the PROTEUS platform product, Alcatel Space proposes a set of services to customers. Those are, separately or in combination: to provide a generic PROTEUS platform qualified and accepted; 9 the tuning to the mission parameters, called “missionisation”, mainly for the on board software; the payload instruments module based on a standard design consistent with PROTEUS platform and easily adaptable; the satellite assembly, integration and tests activities; the satellite transportation and launch campaign activities; . the in-flight acceptance; l
l
l
l
l
to provide a generic ground control segment including a ground station and a control centre.
PROTEUS product line The first satellite based on PROTEUS will fulfil the altimetry and oceanography mission JASON 1, led by CNES and NASA. At an orbit of 1336 km and an inclination of 66 degree, the platform ensures a stable geocentric pointing and an accurate maintenance of orbit parameters to the radar altimetry payload. This permits the achievement of the scientific objective: ocean level knowledge better than 2 cm in any place. Today, Jason satellite stands in integration phase at Alcatel Space, as shown in figure 6. The launch is foreseen in year 2000 with Delta 2 launch vehicle. In addition to JASON 2, which will ensure continuity of oceanographic data,
Figure 9. Megha Tropiques (Dot. CNES/ISRO).
many other applications are under study. PICASSO-CENA (Pathfinder Instruments for Cloud and Aerosol Spaceborne Observation - Climatologie des Etendues des Nuages et des Aerosols) will provide crucial measurements for the development and improvement of climatic forecasting (figure 7). The Proteus platform will embark a payload of four co-aligned near-nadir viewing instruments, the most important of which is a dual wavelength polarisation sensitive Lidar. The satellite will fly in formation with two other American satellites on a sun synchronous orbit at an altitude of 70.5 km. The mission is a CNES-NASA Langley co-operation. The launch is foreseen in year 2003 with a Delta 2 launch vehicle. COROT (Convection ROTation) will be a very high accuracy stellar photometry experiment for Astronomy research (figure 8). The scientific objectives will consist of the study of the internal structure of stars and the detection of exoplanets (out of solar system) of telluric type (like the Earth). Its orbit will be polar, inertial, with an altitude around 900 km. PROTEUS will carry a telescope with a pointing stability better than 1 arc second. This mission is led by CNES and French laboratories. MEGHA-TROPIQUES (figure 9) mission will study convective systems, water cycle and energy budget in the tropical atmosphere above seas and continents. A PROTEUS based satellite will fly on an orbit with an inclination of 22 degree and an altitude around 800 km. The mission is a CNES-ISRO (Indian Space Research Organization) cooperation. The launch is tentatively planned for 2004 with a PSLV launch vehicle. Although these planned missions show the flexibility of the multimission concept, PROTEUS uses are not limited to scientific missions. PROTEUS is well suited to optical missions for the Earth observing programmes like
Small Satellites the follow-on of the French programme SPOT and may well be adapted to radar missions. Optical and radar payloads are an interesting prospect for PROTEUS based combined observation systems from Space. Finally PROTEUS is adapted or adaptable to telecommunication and navigation missions. The Skybridge constellation satellites will use an avionics based on PROTEUS heritage. Galileo, a navigation European programme, may be based on satellites deriving from the PROTEUS platform.
Jean-JacquesDECHEZELLESis Director for Science, Environment and Meteorology at ALCATEL Space Industries.
Jean-JacquesDechezelles AKATEL Space Industries 700, boulevard du Midi 06 156 Cannes-La-Bocca cedex, France Tel.: +33 4 92 92 3 109. Fax: + 33 4 92 92 34 60 jean-jacques,dechezel/[email protected]. fr
G&arc! HUTTlNis Programme Manager for PROTEUS family and JASON I satellite at ALCATEL Space Industries. G&ad Huffin ALCATEL Space Industries 100,boulevard du Midi 06 156 Cannes-la-Bocca cedex, France Tel. : +33 4 92 92 30 89. Fax : + 33 4 92 92 33 30 gerard,hu#in~space,a/cate/.fr
Conclusion The PROTEUS platform and system environment is setting a new benchmark for the development of a Small Satellites Family. Partnership of CNES agency and Alcatel Space has revealed itself very suitable to merge experience and to achieve reliable solutions as well as lower costs and shorter
delivery times. The challenge of a multimission application is met thanks to a generic platform development in association with software and system tools to easily adapt to the context of different missions. Thus PROTEUS
AIR
& SPACE
constitutes a real beneficial European asset to implement more space missions within a given time frame and fixed budget. Moreover it satisfies the concept of more value for money that all customers are looking for. H
EUROPE
l
VOL.
2
l
No
I - 2000