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Cost-effective Earth observation missions—fundamental limits and future potentials
Acta Astronautica 56 (2005) 297 – 299 www.elsevier.com/locate/actaastro
Cost-effective Earth observation missions—fundamental limits and future potentials Hans-Peter Roeser IRS, Institute of Space Systems, University of Stuttgart, Pfaffenwaldring 31, D-70569 Stuttgart, Germany
Abstract Recent technology advances, e.g. in microelectronics, nanotechnology, the fabrication of new materials, the development of new types of miniaturized instruments and communication systems at higher frequencies have opened up many new applications for Earth observation especially from micro-satellites. This paper is an attempt to summarize limitations and restrictions as well as potentials and future perspectives of micro-satellites of about 100 kg and less. © 2004 Elsevier Ltd. All rights reserved.
1. Introduction On October 4, 1957 the very first satellite SPUTNIK, having a ball-shaped size of 58 cm and a mass of 83.5 kg, was launched into Earth’s orbit. Since that time many micro-satellites in the class of 100 kg or less have followed successively including the first commercial telecommunication satellite TELSTAR on July 10, 1962 weighing only 77 kg. But then Lunar programs, interplanetary missions and rapidly increasing launch capabilities made it possible to put several thousand large and heavy satellites into different Earth orbits. As an example, very recently ENVISAT with a mass of 8200 kg was launched for a multipurpose Earth observation program. But for about 15 years there has been, parallel to these big missions, an increasing interest in small and E-mail address: [email protected] (H.-P. Roeser). 0094-5765/$ - see front matter © 2004 Elsevier Ltd. All rights reserved. doi:10.1016/j.actaastro.2004.09.022
micro-satellites mostly driven by very strong budget constraints, rapid-response requirements and also the intention of becoming a member of the club of space technology nations. 2. New technologies Advances in microelectronics and nanotechnology have dramatically increased computer performance and reduced the chip size by orders of magnitude at the same time. A world-wide communications network with mobile phones, UMTS and internet has introduced a marvel of engineering which can easily be adapted to micro-satellites. In addition, the Global Positioning System (GPS) and the availability of tiny GPS receiver components combined with low cost and light-weight star sensors enables even microsatellites with less than 50 kg total mass to achieve a very good pointing accuracy.
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H.-P. Roeser / Acta Astronautica 56 (2005) 297 – 299
Advances in material science and the development of new manufacturing processes have led to the fabrication of new materials for the development of new types of miniaturized instruments. Silicon carbide (SiC), high-temperature superconductors (HTS) and aluminium-nitride (AlN) are only a few of the very important examples. The latter is on one hand a perfect electrical isolator but on the other hand it has the property of very good heat conductivity. Last but not least very effective neuronal network processors show very good progress in machine intelligence and autonomy for aerospace systems which will turn micro-satellites into clever observing systems. Many new components and subsystems have the distinctive feature of low-power consumption, extremely small size in geometry and weight and excellent performance. They are advances for all types of satellites but in particular they will put microsatellites in the position of doing an excellent job, but for dedicated tasks only.
3. Micro-satellite BIRD Very recently the DLR Institute for Space Sensor Technology and Planetary Exploration launched the satellite BIRD with an Indian rocket in October 2001. This micro-satellite with a mass of 94 kg and dimensions of about 65 cm cube was developed under low cost aspects and is a very good example of a costeffective Earth observation mission. The mission profile and the observation results will be presented in other sessions of this symposium. But it is worth noting that the new technologies demonstrated with BIRD have considerably improved the potential of small and micro-satellites for the future. The new small satellite bus technologies demonstrated on the BIRD spacecraft are • a failure tolerant board computer system with its own operating system, • a high-precision reaction wheel for micro-satellites, • a star camera for micro-satellites (1.2 kg), • an on-board navigation system, • a very low-cost ground station and others. According to the objectives of the BIRD mission, the satellite control system requires a powerful and flexible computation and communication infrastruc-
Fig. 1. BIRD on-board computer.
ture. The satellite control system allows for a far reaching autonomous operation of the satellite and at the same time it ensures the survivability of the satellite with highest priority. The on-board computing system was realized as a distributed fault-tolerant multicomputer system which executes all control, telemetry, and monitor tasks as well as the application dependent tasks. To achieve high dependability, safety, and lifetime, the board computer consists of four identical computers (nodes). The architecture of the redundant control computer is totally symmetric. That means each of the nodes is able to execute all control tasks. Two of the computers are permanent in operation (one is the hot redundancy) and the other two are the cold redundancy. The new hardware technology was developed by the Fraunhofer Institute FIRST in Berlin and shows the following remarkable performance: a power PC core, 66 MIPS, 8 MB SDRAM, 2 MB flash, real time operation system and a latch-up protection system (Fig. 1). One part or the BIRD payload data handling system is the experimental neural network classificator. For a group of remote-sensing tasks, like disaster warning and hazard detection or dedicated monitoring of limited remote-sensing parameters (environmental pollution parameters, condition parameters, etc.) a quick classification and a short response time is mandatory. For these kinds of tasks the problems can be solved (within a limited cost frame) only by implementing a high level data processing chain on-board the satellite. Powerful processing technologies and algorithms allow for these kinds of tasks to implement the processes of data pre-processing, calibration, correction of distortions, feature extraction and classification of data on-board the satellite. With the on-board neural
H.-P. Roeser / Acta Astronautica 56 (2005) 297 – 299
Fig. 2. Comparison of micro-satellites, small satellites and a big mission.
network classificator experiment an autonomous classification up to a high level data product was done successfully on-board the BIRD satellite. For this classification special hardware based on the neural network processor NI1000 was used. This neuronal network is able to “learn” on-board by an upload of training vectors for desired classes. Up to now fire, water and clouds were classified on-board. The verification of the classification process was done by comparison with the results of the systematic and thematic on-ground data processing of the same raw data. 4. Opening for micro-satellites One has to realize that the size of, e.g. a 50 kg satellite is microscopically small compared to a big mission with about 8200 kg like ENVISAT (Fig. 2). Nevertheless, there is an opening for small and micro-satellites based on the facts listed below: Micro-satellites have a short development time of 1–3 years with reasonable costs of 10–100 k ¥/kg leading to total satellite cost of 1–10 million ¥. This enables the test of new technologies within a short time
299
frame without endangering “others” or an entire big mission. It also allows rapid response in case of unforeseen problems on Earth or loss of a single instrument on a big mission or unplanned repetition of special tasks. There is also the possibility of launching many small satellites instead of one big mission which would have the advantage of a high revisit time rate and a distribution of risk if all tasks could be performed. Size, development time line and volume of cost of micro-satellites are very appropriate for universities and offer great opportunities for students to learn about satellite subsystems but also provide a view of the satellite in its entirety. In addition, micro-satellites are very attractive from the programmatic point of view and have a very high potential for identification. For the future there will be a need especially for small satellites combined with electrical propulsion systems in the areas of formation flying studies, testing the optical interferometer principle and for inspecting other satellites. The technology available today offers microsatellites great opportunities but more important they will serve as complements for big multipurpose satellites. 5. Stuttgart small satellite programme The University of Stuttgart has established a new programme at the Institute of Space Systems with the goal of combining small satellites with electrical propulsion systems. The first satellite will be the “Flying Laptop” scheduled to be launched in 2006/2007. This micro-satellite with a size of 60 cm × 60 cm × 60 cm and a maximum electrical power of 200 Watt will be equipped with S- and Kaband systems (2.0/20 GHz down-link and 2.2/30 GHz up-link). Also on board will be a freely programmable computer system consisting of ?100 MB flash memory, 32–64 MB RAM, field programmable gate array (FPGA) with 300–600k gate equivalents using a direct hardware implementation of the control algorithms and a 100–200 MHz system clock enabling flexible configurations depending on the mission profile. A “rent-a-sat” operation modus will enable different customers to use the satellite as a whole for a certain time.
Cost-effective Earth observation missions—fundamental limits and future potentials Hans-Peter Roeser IRS, Institute of Space Systems, University of Stuttgart, Pfaffenwaldring 31, D-70569 Stuttgart, Germany
Abstract Recent technology advances, e.g. in microelectronics, nanotechnology, the fabrication of new materials, the development of new types of miniaturized instruments and communication systems at higher frequencies have opened up many new applications for Earth observation especially from micro-satellites. This paper is an attempt to summarize limitations and restrictions as well as potentials and future perspectives of micro-satellites of about 100 kg and less. © 2004 Elsevier Ltd. All rights reserved.
1. Introduction On October 4, 1957 the very first satellite SPUTNIK, having a ball-shaped size of 58 cm and a mass of 83.5 kg, was launched into Earth’s orbit. Since that time many micro-satellites in the class of 100 kg or less have followed successively including the first commercial telecommunication satellite TELSTAR on July 10, 1962 weighing only 77 kg. But then Lunar programs, interplanetary missions and rapidly increasing launch capabilities made it possible to put several thousand large and heavy satellites into different Earth orbits. As an example, very recently ENVISAT with a mass of 8200 kg was launched for a multipurpose Earth observation program. But for about 15 years there has been, parallel to these big missions, an increasing interest in small and E-mail address: [email protected] (H.-P. Roeser). 0094-5765/$ - see front matter © 2004 Elsevier Ltd. All rights reserved. doi:10.1016/j.actaastro.2004.09.022
micro-satellites mostly driven by very strong budget constraints, rapid-response requirements and also the intention of becoming a member of the club of space technology nations. 2. New technologies Advances in microelectronics and nanotechnology have dramatically increased computer performance and reduced the chip size by orders of magnitude at the same time. A world-wide communications network with mobile phones, UMTS and internet has introduced a marvel of engineering which can easily be adapted to micro-satellites. In addition, the Global Positioning System (GPS) and the availability of tiny GPS receiver components combined with low cost and light-weight star sensors enables even microsatellites with less than 50 kg total mass to achieve a very good pointing accuracy.
298
H.-P. Roeser / Acta Astronautica 56 (2005) 297 – 299
Advances in material science and the development of new manufacturing processes have led to the fabrication of new materials for the development of new types of miniaturized instruments. Silicon carbide (SiC), high-temperature superconductors (HTS) and aluminium-nitride (AlN) are only a few of the very important examples. The latter is on one hand a perfect electrical isolator but on the other hand it has the property of very good heat conductivity. Last but not least very effective neuronal network processors show very good progress in machine intelligence and autonomy for aerospace systems which will turn micro-satellites into clever observing systems. Many new components and subsystems have the distinctive feature of low-power consumption, extremely small size in geometry and weight and excellent performance. They are advances for all types of satellites but in particular they will put microsatellites in the position of doing an excellent job, but for dedicated tasks only.
3. Micro-satellite BIRD Very recently the DLR Institute for Space Sensor Technology and Planetary Exploration launched the satellite BIRD with an Indian rocket in October 2001. This micro-satellite with a mass of 94 kg and dimensions of about 65 cm cube was developed under low cost aspects and is a very good example of a costeffective Earth observation mission. The mission profile and the observation results will be presented in other sessions of this symposium. But it is worth noting that the new technologies demonstrated with BIRD have considerably improved the potential of small and micro-satellites for the future. The new small satellite bus technologies demonstrated on the BIRD spacecraft are • a failure tolerant board computer system with its own operating system, • a high-precision reaction wheel for micro-satellites, • a star camera for micro-satellites (1.2 kg), • an on-board navigation system, • a very low-cost ground station and others. According to the objectives of the BIRD mission, the satellite control system requires a powerful and flexible computation and communication infrastruc-
Fig. 1. BIRD on-board computer.
ture. The satellite control system allows for a far reaching autonomous operation of the satellite and at the same time it ensures the survivability of the satellite with highest priority. The on-board computing system was realized as a distributed fault-tolerant multicomputer system which executes all control, telemetry, and monitor tasks as well as the application dependent tasks. To achieve high dependability, safety, and lifetime, the board computer consists of four identical computers (nodes). The architecture of the redundant control computer is totally symmetric. That means each of the nodes is able to execute all control tasks. Two of the computers are permanent in operation (one is the hot redundancy) and the other two are the cold redundancy. The new hardware technology was developed by the Fraunhofer Institute FIRST in Berlin and shows the following remarkable performance: a power PC core, 66 MIPS, 8 MB SDRAM, 2 MB flash, real time operation system and a latch-up protection system (Fig. 1). One part or the BIRD payload data handling system is the experimental neural network classificator. For a group of remote-sensing tasks, like disaster warning and hazard detection or dedicated monitoring of limited remote-sensing parameters (environmental pollution parameters, condition parameters, etc.) a quick classification and a short response time is mandatory. For these kinds of tasks the problems can be solved (within a limited cost frame) only by implementing a high level data processing chain on-board the satellite. Powerful processing technologies and algorithms allow for these kinds of tasks to implement the processes of data pre-processing, calibration, correction of distortions, feature extraction and classification of data on-board the satellite. With the on-board neural
H.-P. Roeser / Acta Astronautica 56 (2005) 297 – 299
Fig. 2. Comparison of micro-satellites, small satellites and a big mission.
network classificator experiment an autonomous classification up to a high level data product was done successfully on-board the BIRD satellite. For this classification special hardware based on the neural network processor NI1000 was used. This neuronal network is able to “learn” on-board by an upload of training vectors for desired classes. Up to now fire, water and clouds were classified on-board. The verification of the classification process was done by comparison with the results of the systematic and thematic on-ground data processing of the same raw data. 4. Opening for micro-satellites One has to realize that the size of, e.g. a 50 kg satellite is microscopically small compared to a big mission with about 8200 kg like ENVISAT (Fig. 2). Nevertheless, there is an opening for small and micro-satellites based on the facts listed below: Micro-satellites have a short development time of 1–3 years with reasonable costs of 10–100 k ¥/kg leading to total satellite cost of 1–10 million ¥. This enables the test of new technologies within a short time
299
frame without endangering “others” or an entire big mission. It also allows rapid response in case of unforeseen problems on Earth or loss of a single instrument on a big mission or unplanned repetition of special tasks. There is also the possibility of launching many small satellites instead of one big mission which would have the advantage of a high revisit time rate and a distribution of risk if all tasks could be performed. Size, development time line and volume of cost of micro-satellites are very appropriate for universities and offer great opportunities for students to learn about satellite subsystems but also provide a view of the satellite in its entirety. In addition, micro-satellites are very attractive from the programmatic point of view and have a very high potential for identification. For the future there will be a need especially for small satellites combined with electrical propulsion systems in the areas of formation flying studies, testing the optical interferometer principle and for inspecting other satellites. The technology available today offers microsatellites great opportunities but more important they will serve as complements for big multipurpose satellites. 5. Stuttgart small satellite programme The University of Stuttgart has established a new programme at the Institute of Space Systems with the goal of combining small satellites with electrical propulsion systems. The first satellite will be the “Flying Laptop” scheduled to be launched in 2006/2007. This micro-satellite with a size of 60 cm × 60 cm × 60 cm and a maximum electrical power of 200 Watt will be equipped with S- and Kaband systems (2.0/20 GHz down-link and 2.2/30 GHz up-link). Also on board will be a freely programmable computer system consisting of ?100 MB flash memory, 32–64 MB RAM, field programmable gate array (FPGA) with 300–600k gate equivalents using a direct hardware implementation of the control algorithms and a 100–200 MHz system clock enabling flexible configurations depending on the mission profile. A “rent-a-sat” operation modus will enable different customers to use the satellite as a whole for a certain time.