Site: Oerlikon Contraves Space
Schaffhauserstrasse 580
CH-8052 Zurich, Switzerland
http://www.contravesspace.com

Date Visited: September 18, 1997

WTEC: Ramon P. DePaula (report author)

Hosts:

• Dr. Reinhard Czichy, Vice President Space Communications
  email: czczy@ocag.ch
• Dr. Klaus Pribil, Director Optical Communications
  email: czprib@ocag.ch

BACKGROUND

Oerlikon Contraves Division

The Oerlikon Contraves Division, which forms part of the Oerlikon-Buhrle Group is comprised of the Defense and Space Sectors. Oerlikon Contraves Defense is active throughout the world in the development, production, sale and technical support of weapons systems for air defense.

Oerlikon Contraves Space

The space activities of the Oerlikon Contraves Division are brought together in the Contraves Space Sector. Contraves Space in Zurich has been involved in the development and production of spacecraft structures, payload fairings for launchers, precision mechanisms, and instruments for the scientific exploration of space for more than 30 years. The main customers of Contraves Space are the European Space Agency (ESA) and Arianespace, which operates commercial space activities.

The Oerlikon Contraves Division with its more than 2,600 employees generates sales around CHF 700 million. Its headquarters is in Zurich. The division also operates other companies in Switzerland, Germany, Italy, Canada, Singapore, Malaysia, and the United States.

More recently, Contraves Space has become one of the world leaders in the development of satellite free space optical communications systems. Currently its main customers for optical communications development are Motorola and ESA. The other leaders in free space optical communications are Ball Aerospace/COM DEV (U.S./CA), NEC (Japan) and Matra Marconi Space (France)

Market

GEO-GEO intersatellite links (ISL) (72,000 km), LEO to LEO ISL (4,500 km), MEO-MEO ISL, LEO-GEO inter-orbit links.

FREE SPACE OPTICAL COMMUNICATIONS R&D ACTIVITIES

Oerlikon Contraves Space started a program in mid 1995 to develop miniature optical terminals for free space laser communications links. This program is now considered a cornerstone of the company's future core business. It combines the long standing expertise of Oerlikon Contraves in the field of complex optoelectronic systems with know-how of leading Swiss research institutes and the resources of international industrial partners active in this field.

The Oerlikon Contraves development activities are harmonized with various projects of the Swiss national research commission. The leading edge technologies elaborated within these projects in the field of microsystem technology and microelectronics provide important prerequisites in developing advanced new generation miniature free space optical communications systems.

Based upon the first results of this program, ESA in February 1996 awarded Oerlikon Contraves Space a contract for the development of a "Terminal for Short Range Optical Intersatellite Links (SROIL)." The SROIL Terminal, one model of a larger product family, is designed for a wide range of applications in mobile satellite communication, voice, and multimedia networks having high data rate requirements. There are other terminal types of this product family targeted for use on geostationary satellites, e.g., co-located satellite clusters or for intersatellite links between widely spaced GEO spacecraft.

The mature features of the Oerlikon-Contraves Miniature Optical Terminals provide exciting solutions to the user's basic requirements:

• highest data rate system with attractive growth potential (presently up to 5.0 Gbps)
• coherent detection scheme with highest sensitivity (up to 8 photons/bit demonstrated)
  • laser diode pumped Nd-YAG laser transmitter operating at 1.064 µm
  • homodyne detection receiver with integrated coherent tracking sensor
• high bandwidth pointing, acquisition, and tracking (PAT) system providing comfortable margins
  • full hemispherical pointing capability with combined coarse/fine pointing assembly
  • PAT system bandwidth > 1kHz
  • insensitivity to spacecraft induced vibrations
  • wide-field acquisition sensor providing full coverage of most counter terminal uncertainty fields
  • closed-loop controlled point-ahead assembly
• integrated high precision ranging capability
• high modularity of optical head and electronics unit offers adaptability to a wide range of user needs and easy interchangeability of assemblies and components
• advanced miniature optical head
  • small telescope aperture (e.g., 35 mm diameter for Model B) with combined transmit/receive path
  • laser sources in self contained laser unit and fiber coupling with optical bench
  • monolithic optical bench with passively athermalized optical system
  • self-alignment capability via point ahead system
• designed for operation in highly dynamic LEO communication networks
• inter-terminal service channel link for autonomous system performance optimization
• safe design with highest reliability assures long in-orbit lifetime
• adaptive and efficient operational mode-logic with priority on:
  • in-orbit reconfiguration capability
  • autonomous terminal operations
  • highest operational safety
• attractive mass, dimension and power budgets

Oerlikon Contraves Space offers a family of miniature optical terminals; the four basic models of this family cover most of the standard user requirements. Owing to systematic modularity all of these models can be customer tailored to cover a wide range of strategic applications.

The miniature optical terminal designed by Oerlikon Contraves Space is developed within the framework of a contract with ESA. Table B.1 summarizes the basic requirements for the SROIL terminal as defined by ESA. It is the aim of this ESA development contract to investigate the potential of advanced optical communications systems for high data rate transmission and to demonstrate the following: system miniaturization, growth potential to cover a wide range of mission scenarios, modularity and configuration flexibility, precise ranging capability, and long in orbit lifetime with high reliability.

In order to meet the ESA requirements, the SROIL terminal was designed using a coherent detection scheme and diode pumped Nd-YAG lasers. It has a receive telescope aperture of 35 mm diameter and a concentric transmit telescope with about 16 mm diameter. The pointing system of the SROIL terminal is based upon a coelostat type pointing assembly in front of the telescope and allows for almost full hemispherical pointing.

Based on the SROIL design (see Table B.1), Contraves is building a family of 5 terminals for many different link ranges from as low as 200 km to as far as 72,000 km (GEO to LEO). The data rates vary from 7 Gbps to 1 Gbps for the longer links.

CONCLUSIONS

Contraves is today one of the leaders in the area of free space optical communications. ESA support was critical for it to develop its capabilities. The company has made a major commitment to this technology and is successfully transferring the R&D results to operational systems. The announcement of a partnership between Motorola and Bosch with Contraves as subcontractor for optical ISLs attests to Contraves' commitment and leadership position in the area of free space optical communications.

Table B. 1
SROIL Terminal Characteristics

Detection Concept	Coherent
Modulation Format	Binary Phase Shift Keying (BPSK) with Sync Bits
Link Type	Full Duplex
Link Range	1,200 km
Transmit Laser	Semiconductor Laser Pumped Nd-YAG (1064 nm)
Telescope Aperture Diameter	35 mm
User Communication Channel	Bit Rate: 1.5 Gbps Bit Error Rate: 10-6 Comms Link Margin: +6.2 dB
Inter-terminal Service Channel	Bit Rate: 172 kbps Bit Error Rate: 10-13 Service Link Margin: +6.2 dB
Pointing Range	Full Hemispherical (azimuth ± 220°, elevation - 90°, + 95°)
Pointing System Angular Rate	50o/sec
Pointing System Acceleration	50°/sec2
Acquisition Time	15 sec, with one repetition in case of non-detection
Acquisition Field-of View	2.3° diagonal
Acquisition Margin	+5.8 dB
Tracking Bandwith	1,000 Hz @ 1.5 dB
Tracking Margin	8.9 dB
Beacon Laser	Semiconductor Laser Array, 815 nm
Power Consumption	40 W (average)
Dimensions	Optical Head: 415mm x 230 mm x 190 mm (HWD) Electronic Box: 210 mm x 280 mm x 250 mm (HWD)
Mass	Optical Head: ca. 8 kg Electronic Box: ca 7 kg
In-Orbit Lifetime	10 years in LEO
Reliability	0.8 (TBC)