Seventeen European space agencies or companies were visited. Table 2.24 depicts a wide di versity of OBP capabilities noted by the NASA/NSF panel. The reader is reminded that the panel may have not observed many skills of the visited organization; therefore, the above chart may be incomplete. Notwithstanding, the capabilities listed in the c hart represent a significant capability for OBP when the entire European community is considered as a whole. Further, the individual capabilities of Alcatel, Alenia Spazio, ANT, DLR, ESTEC, Matra-Marconi Space, and Telespazio show the potential for their independent capability to pursue the OBS/OBP business.
Key OBP capabilities were noted at several European satellite agencies and companies. Companies are listed alphabetically.
Alcatel. DRS: Alcatel is performing significant work on inter-orb it links for ARTEMIS. (Alenia Spazio is responsible for OBP for ephemeris calculations for pointing, look- ahead calculations, etc. for the DRS.)
Alcatel has a product improvement program emphasizing MMIC and ASIC packaging and modularity, OBS and, l ater, OBP. They are now space-qualifying MMICs with Triquent and Plessy. They are applying their MMIC capabilities with work on a Ku-band multibeam antenna with MMIC SSPAs producing 1 W, using MESFET technology.
Alcatel has capability for automatic manufacturing of BFNs with low impedance in aluminum. They use an auto machining process for fixed BFNs. Alcatel is workingon dynamically programmable MMIC BFNs with phase and amplitude control. They believe that present MMICs are not fast enough (13 M Hz clock speeds) for beam hopping, but are fast enough for beam switching.
On-Board-Processing Technology Matrix - Europe
By identifying certain main technical needs, Alcat el has indicated their intent to further pursue technologies important to their OBP program. They have identified active antennas, MMICs, signal and data processing including parallel processing, data acquisition, and mass memory.
Alenia Spazio S.p.A. Alenia is responsible for OBP for ephemeris calculations for pointing, look-ahead calculations, etc. for the DRS.
SILEX uses S-band for crosslink telemetry. The transmit frequency is approximately 2.9 GHz. This system is deemed espec ially important for communications with satellites that are periodically out of view.
ANT (Backnang). Until recently, ANT had a significant project called modular on- board switching system (MOBS). The system was complete through the des ign phase and included: on-board switching, signalling and network synchronization; a new concept of "distributed memory switching;" uplink via time division multiple access (TDMA) and multiple beam antennas; downlink with one TDM carrier per b eam; and a throughput of several Gbits/sec. The MOBS architects were also considering on-board packet switching.
The MOBS concept included 16 uplink beams with a total of 64 uplink carriers and approximately 17 Mbits/sec per carrier, thus providing approximately 1 Gbits/sec uplink capacity. The downlink was designed for 16 carriers (one per beam) at approximately 65 Mbits/sec per carrier.
The MOBS project was shelved prior to completion. Elements completed in addition to the design include d a payload receiver/transmitter section, a baseband section (switch), and a laboratory model of the receiver/transmitter chain and switch.
ANT is building a T-stage, on-board circuit switch for ESTEC. ANT completed the design and the fabrication u sing a CMOS ASIC. The switch controller is being build by Laben in Italy. They are considering a optional S-stage to be built by Alenia. (Alenia also has a parallel contract from ESTEC to build an on-board T-stage switch.) ANT is having its T-stage AS ICs designed by Cadiz in Germany. Cadiz is affiliated with a university in Aachen.
ANT has developed a full set of networking protocols for on-board implementation. These protocols were intended for in-channel implementation. The work was done at the University of Stuttgart.
With regard to hardening of on-board integrated circuits, ANT recommends use of CMOS chips which are hard and also offer high efficiency (power). ANT is aware of only one European company making radiation tolerant chip s with complexities of 30 K gates, and that is the joint French firm of Matra/Harris.
ANT completed a study and developed a network simulator for a packet switched network with OBS (packet routing) for ESA. The system was designed for VSAT applica tions with VSAT data rates up to 2 Mbits/sec and a system throughput of 660 Mbits/sec. (it should be noted that when ANT does a study they frequently develop prototype hardware and electronics to support/verify their findings.)
German Aerospace Research Establishment (DLR). DLR claims significant research or expertise in many areas related to this study:
DLR conducts two types of research: internal projects and projects with external cooperation with a wide variety of German and foreign partners.
Internal research projects being conducted in 1991/1992 included the following:
1991/1992 projects involving external cooperation included the following:
Laser Transmission Coding & Modulation. DLR has a newly installed Free Space Optical Test Facility. The system has just been established with little research results to date. This research could find app licability to ISLs from either GEO-GEO or GEO-LEO. Laser transmitter and receiver were installed on roof top with a reflecting mirror about 5 m distant. As soon as the system is calibrated the reflecting mirrors will be relocated to a distance of severa l hundred of meters. Stated objectives of the research were to investigate advanced modulation techniques for laser communications with focus on countering atmospheric effects. Investigations are planned for heterodyne, homodyne PSK and DPSK modulations schemes with data rates up to 560 Mbits/sec. No papers were available because the program was in its infancy.
DLR satellite communications programs focus on the basic (enabling) research areas, with only limited work on areas with direct and immed iate application to the commercial telecommunications industry. Their work is of high quality. Some work under direct contract to ESA or private firms may have more immediate application. DLR has demonstrated significant capabilities in the enabling re search areas similar to, but smaller than, MITRE Bedford.
ESTEC. SILEX entails an optical full-duplex spacecraft-to-spacecraft link. This work is concentrating on GEO to LEO but is also capable of doing GEO-GEO. Typically SILEX provides 50 Mbits/sec throughput but this is not the limit. It is intended for use with SPOT IV. Matra is prime contractor for the LEO SILEX terminal. SILEX is to be finished by 1995. The SPOT IV terminal will be ready in 1995 for possible launch on an Ariane V. An optical ground station in the Canary Islands (Spain) with a 1 m aperture will be used for measurements (not communications). The LEO optical terminal will weigh 120 kg. LEO and GEO terminals are quite similar. Teldex in Heidelberg makes the final pointing mirror mechanism. There are differences in design to support installation on different platforms.
The SILEX on-board terminals use a Marconi 1750 OBP for calculations such as ephemeris. The unit is a standard European design and uses a F airchild microprocessor. The system provides for "look-ahead" pointing.
OBP has been used to describe OBS. OBS more accurately describes the state-of- the-art at ESTEC. This project falls under the ESTEC ASTP. ESTEC uses ANT Backnang for much of its OBS work. OBS is used to implement private networks over wide areas. They are targeting Integrated Services Digital Network (ISDN)-like networks with data rates ranging from 64 kbits/sec to 2 Mbits/sec. This implementation is designed to accommodate VSAT-to-VSAT connectivity without the traditional hub. The system is intended to be used with satellite multibeam antenna and at 10 W and work into a 1 m antenna. The primary mode is circuit-switched with the circuit setup being made thro ugh a ground-based master control center.
The on-board switch will be a T or TST design. The switch will mass about 5 to 10 kg. The T-switch ASICs are being implemented by ANT (and others, including Alenia Lebin of Italy). The system will use tre llis coding and TDMA on the downlink. The ASIC demods are being implemented by Alcatel Espace (France) and by another company in England. The system design calls for eight simultaneous beams (from a larger selection). As of June 1992, they were freezin g the ASIC design for the T switch with testing to be completed bye the end of 1992. The 8 x 2 Mbits/sec ASIC demodulators were to be completed by the summer of 1993. The switch is designed for a maximum throughput of 260 Mbits/sec. Hardware developmen t is to be completed by the end of 1993. The system will be ready to fly by end-of-year 1996 with a flight demonstration package. The unit would be put into service shortly thereafter. A ground test bed is to be tested by mid 1993. The system will hav e hwil with system emulators. Hardware will include the T/TST switches.
Telespazio. OBP/OBS. Telespazio is involved in the "Switchboard In the Sky" program. This involves OBS aboard the proposed ITALSAT F3. The system would implement signal regeneration and OBS for up to 4000 channels. It will use a scheme developed at Stanford University. The OBS for ITALSAT F3 would be a Time Stage or T-Stage switch (being built by Alenia Spazio). Uplink access will be clock synchroniz ed and the front end of the OBS will be frame synchronized.
There are two systems proposed, one for ITALSAT F3 and a second more advanced concept for future satellites to-be-determined.
Both systems will be based on a ground-based master control station for access control. (the system is somew hat similar to that being developed by comsat labs for the nasa acts program.) Both systems will allow access by ISDN, probably through a gateway. Other protocols may also be allowed.
An opinion was expressed that Telespazio doesn't really see a n eed for "full OBP/OBS." however, they do understand the increased efficiencies that would be achieved. The increased efficiencies probably do not justify the increased mass, power consumption, costs, and probability of unit failure under opera tion. (operational failure is assumed to be more probable due to increased on-board complexity and parts count.) Also, there are no known sources for manufacturing OBP/OBS.
Telespazio is conducting several OBP related experiments, for example loca l area network (LAN) interconnects via satellite. Telespazio has selected Ethernet and Token Ring standard LANs for their experiments. The experiment will interconnect multiple LANs via satellite. Another experiment is precise time and range derivation using code division multiple access (CDMA) transmission over satellites with a goal of timing accuracy/precision of 50 nanoseconds.