Hakan Kayal

ASAP: Autonomy through on-board planning

Usually a satellite is entirely controlled from ground. Its tasks are planned in advance by a satellite operations team using specialized scheduling software. When the orbiting satellite enters the transmission range of the ground station, communication is possible, and a newly generated plan (if required) can be uploaded and executed in due time. Although this approach is well-established and has been used for decades, it has some major drawbacks. It binds resources (e.g. personal staff, communication links, etc.) and prohibits fast reactions to transient events, due to the required change of the currently active plan. In the traditional approach, the changes can only be achieved by transmitting a new plan from the ground station to the satellite. This communication imposes time delays which are not acceptable for fast reactions and responses. A way to overcome this problem is to equip the satellite with an autonomous decision-making system which is able to alter the operation plan onboard the satellite. The department of Computer Science VIII of the University of Wuerzburg is currently developing such a system named ASAP and will present it in this paper. The focus lies on the interaction between ASAP and the OnBoard-Computer of the satellite.

A nano satellite constellation for detection of objects in earth orbit

To support the European space situational awareness program a nano satellite constellation consisting of two satellites has been studied in the frame of a team design project. The very first study results shows that such a system can be a valuable contribution to the SSA program using a optical sensor system in orbit at a very low cost compared to larger satellites. The main advantage of such a system is independence from weather conditions and a large field of view, which promises a larger number of detections in shorter time compared to large aperture sized telescopes.

Design and Implementation of a Remote, Server-Client- Based Telemetry Retrieval and Monitoring System

Telemetry retrieval and monitoring is one of the basic functionalities of every satellite Electrical Ground Support Equipment, EGSE. There are hence a vast number of different tools and systems available for this purpose. Most of these systems have been, however, developed in the context of individual satellite projects or in some cases even a single payload. A limited number of multi-mission and more general purposed telemetry retrieval systems exist presently as an integrated part of major commercial EGSE systems, which are used at the professional satellite control centres. The use of these systems in a new satellite projects requires respectively certain adaptation of the system or the satellite hardware/software. Another lacking functionality of many telemetry retrieval systems is their local accessibility, where there is no or limited remote interface to the system through the internet. In this paper a low-cost, modular and flexible telemetry retrieval system with a server-client based architecture is presented. It allows the remote clients to login to the system through the internet, using conventional web-browsers and monitor the satellite telemetry data in real-time during a satellite pass. It also offers functionalities for off-line data analysing, graphical visualising and telemetry database administration through the web interface. The system has been developed at the German Aerospace Centre, DLR and the TU-Berlin and is being used for retrieving telemetry data of the DLR satellite BIRD at TUBerlin. The ESA Young Engineers Satellite, YES2 is another potential user of the system. The complete platform independency of the system and its pure object oriented and modular software architecture makes it a highly flexible and reusable telemetry retrieval and monitoring system. The objective of an easy adaptation and cross-mission reusability of the system has been the major design deriver and has lead to the development of a dedicated Application Programming Interface, API. Satellite engineers can use the introduced API to develop new modules and to extend the existing ones, in order to adapt the system to the requirements of a new satellite project.

A WEB-BASED MODULAR AND FLEXIBLE DATA ACQUISITION AND TELEMETRY MONITORING SYSTEM FOR MICRO SATELLITES

The process of software development for the ground segment of micro satellites is a very time consuming and costly procedure. Most of the micro satellite projects have come up, therefore, with their own specific, non standard software solutions, which are generally customized to the specific project requirements and hence not reusable in other projects. In this paper a generic, flexible and reusable software architecture and a corresponding application programming interface (API) are introduced, which can reduce the time and costs of the software developments significantly for new missions.

PICO SATELLITE CONCEPT OF TU BERLIN

One of the latest manifestation of miniaturization in space applications is the development of standardized pico satellites. The so called CUBESAT’s for example, which are standardized picosatellites have a size of only 10x10x10 cm3 and a maximum mass of 1 kg. They are based on concepts of California Polytechnic State University and Space Stanford University. Pico and nano satellites will be developed at the Institute of Aeronautics and Astronautics of the Technical University of Berlin as one of the major working topics within the department of astronautics. The basic vision behind the objective is to use pico satellites for demanding scientific and technological applications at a very low cost. The development of pico satellites is currently in an very early phase. It is however conceivable that reliable and powerful platforms will emerge from today’s efforts, which will enable a large number of applications for pico and nano satellites. The range of potential applications will include areas such as earth observation, space science, astronomy and on-orbit verification of new technologies. Another additional advantage of developing pico satellites at the TUBerlin is the opportunity to give hands on experience to students on complete satellite missions, including design, test, production and operations. Enabling technologies for demanding applications will surely make use of MEMS based components. Especially in the fields of attitude control, communication and propulsion there is a need for new developments in order to enable demanding applications with pico satellites. TU-Berlin is working on various concepts for the development of such components at various levels and under the involvement of external cooperation partners, companies and students. This paper will give an overview of current and future activities of the TU-Berlin related to the development of pico and nano satellite mission concepts. 1. CURRENT SITUATION More then 40 developers worldwide are working currently on CUBESATS with different objectives. Based on concepts of California Polytechnic State University and Space Stanford University, the CUBESAT specifications define the overall dimension, mass and other interfaces, in order to fit the satellite into a deployment mechanism called PPOD. Besides this specification, developers are free in the design of the satellite functions. All activities onboard a CUBESAT are strongly limited by the available space and electrical power. These two aspects are dominating and limiting all functions. While one of the most common aspects is, that students are involved it the development and operation of the CUBESAT’s, many of them are rather at a very early development stage. For example, most of the CUBESAT’s have either no attitude control or very limited attitude control capabilities, which is a precondition for rather demanding applications. The most important reason is the lack of adequate attitude control sensor and actuator elements. But not only attitude control is an important issue for future pico satellites with demanding applications. Communications at higher bit rates is also an important issue, especially for downlink. In most cases, current projects make use of low bit rate communications between 1,2 kBit/s and 9,6 kBit/s. As soon as the need for the transmission of images or other scientific data with higher volume is given, downlink capability on at least S-Band with adequate formatting and coding is required. Onboard processing of data is the next point, where many considerations are necessary within an CUBESAT environment. Demanding CUBESAT applications require high processing capability at very low available electrical power. Today, microprocessors get always faster and consuming lower power but their suitability in the space environment must be proved. Also different redundancy and power saving mechanisms for pico satellites must still be tested is space. As stated in the objectives, pico satellites are ideally suited to make such tests in orbit.

An autonomous information generation and distribution system for the next generation of small satellites: examples of the BIRD mission experiments

The general trend in remote sensing is on one hand to increase the number of spectral bands and the geometric resolution of the imaging sensors which leads to higher data rates and data volumes. On the other hand the user is often only interested in special information of the received sensor data and not in the whole data mass. Concerning these two tendencies a main part of the signal pre-processing can already be done for special users and tasks on-board a satellite. For the BIRD (Bispectral InfraRed Detection) mission a new approach of an on-board data processing is made. The main goal of the BIRD mission is the fire recognition and the detection of hot spots. This paper describes the technical solution and the first results, of an on-board image data processing system based on the sensor system on two new IR-Sensors and the stereo line scanner WAOSS (Wide-Angle-Optoelectronic-Scanner). The aim of this data processing system is to reduce the data stream from the satellite due to generations of thematic maps. This reduction will be made by a multispectral classification. For this classification a special hardware based on the neural network processor NI1000 was designed. This hardware is integrated in the payload data handling system of the satellite.

Onboard autonomy and fault protection concept of the BIRD satellite

BIRD (Bi-Spectral Infra-Red Detection) has been demonstrating new technologies since its launch on 22. October, 2001 with the PSLV-C3 from Shar/India successfully into a sun-synchronous low Earth orbit at 560 km. Besides the successful in-orbit test of the detection and evaluation of vegetation fires with micro satellites, BIRD has also been demonstrating a number of advanced spacecraft bus technologies, especially in the field of satellite autonomy and fault detection and protection. A number of ingenious features make it possible to operate the 92 kg satellite in a comfortable and safely way. Special features include the autonomous management of onboard computer failures, surveillance and response to critical parameters limit exceeding, system attitude anomalies. A robust redundancy philosophy and optimised ground-spacecraft interaction concept has contributed to the success of the BIRD mission, which was designed to operate for one year and has completed now its second year of operation. The paper describes the related new technologies and the results from the experience with BIRD.