Dr. Wolfgang Griethe Profile

Dr. Wolfgang Griethe

Managing Director at G2Aerospace GmbH

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Publications (3)

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Proceedings Article | 19 May 2015 Paper

Laser links for mobile airborne nodes

Wolfgang Griethe, Markus Knapek, Joachim Horwath

Proceedings Volume 9460, 946007 (2015) https://doi.org/10.1117/12.2176236

KEYWORDS: Sensors, Satellites, Nominal ocular hazard distance, Skin, Staring arrays, Airborne laser technology, Digital signal processing, Fourier transforms, Satellite communications, Data communications

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Remotely Piloted Aircrafts (RPA’s) and especially Medium Altitude Long Endurance (MALE) and High Altitude Long Endurance (HALE) are currently operated over long distances, often across several continents. This is only made possible by maintaining Beyond Line Of Side (BLOS) radio links between ground control stations and unmanned vehicles via geostationary (GEO) satellites. The radio links are usually operated in the Ku-frequency band and used for both, vehicle command & control (C2) - it also refers to Command and Non-Payload Communication (CNPC) - as well as transmission of intelligence data - the associated communication stream also refers to Payload Link (PL). Even though this scheme of communication is common practice today, various other issues are raised thereby. The paper shows that the current existing problems can be solved by using the latest technologies combined with altered intuitive communication strategies. In this context laser communication is discussed as a promising technology for airborne applications. It is clearly seen that for tactical reasons, as for instance RPA cooperative flying, Air-to-Air communications (A2A) is more advantageous than GEO satellite communications (SatCom). Hence, together with in-flight test results the paper presents a design for a lightweight airborne laser terminal, suitable for use onboard manned or unmanned airborne nodes. The advantages of LaserCom in combination with Intelligence, Surveillance and Reconnaissance (ISR) technologies particularly for Persistent Wide Area Surveillance (PWAS) are highlighted. Technical challenges for flying LaserCom terminals aboard RPA’s are outlined. The paper leads to the conclusion that by combining both, LaserCom and ISR, a new quality for an overall system arises which is more than just the sum of two separate key technologies.

Proceedings Article | 31 May 2013 Paper

LaserCom in UAS missions: benefits and operational aspects

Wolfgang Griethe, Frank Heine, Lester Begg, Detao Du

Proceedings Volume 8713, 87130A (2013) https://doi.org/10.1117/12.2015226

KEYWORDS: Satellites, Relays, Sensors, Space operations, Free space optical communications, Laser communications, Reconnaissance, Surveillance, Telecommunications, Homodyne detection

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Free Space Optical Communications (FSOC) is progressing continuously. With the successful in-orbit verification of a Laser Communication Terminal (LCT), the coherent homodyne BPSK scheme advanced to a standard for Free-Space Optical Communication (FSOC) which now prevails more and more. The LCT is located not only on satellites in Low Earth Orbit (LEO), with spacecrafts like ALPHASAT-TDP and the European Data Relay Satellite (EDRS) the LCT will also exist in Geosynchronous Orbit (GEO) in the near future. In other words, the LCT has reached its practical application. With existence of such space assets the time has come for other utilizations beyond that of establishing optical Inter-Satellite Links (ISL). Aeronautical applications, as for instance High Altitude Long Endurance (HALE) or Medium Altitude Long Endurance (MALE) Unmanned Aerial Systems (UAS) have to be addressed. Driving factors and advantages of FSOC in HALE/MALE UAS missions are highlighted. Numerous practice-related issues are described concerning the space segment, the aeronautical segment as well as the ground segment. The advantages for UAS missions are described resulting from the utilization of FSOC exclusively for wideband transmission of sensor data whereas vehicle Command and Control can be maintained as before via RF communication. Moreover, the paper discusses FSOC as enabler for the integration of air and space-based wideband Intelligence, Surveillance and Reconnaissance (ISR) systems into existent military command and control systems.

Proceedings Article | 26 May 2011 Paper

High-speed laser communications in UAV scenarios

Wolfgang Griethe, Mark Gregory, Frank Heine, Hartmut Kämpfner

Proceedings Volume 8020, 80200B (2011) https://doi.org/10.1117/12.884274

KEYWORDS: Unmanned aerial vehicles, Satellites, Satellite communications, Laser communications, Sensors, Relays, Optical communications, Atmospheric optics, Signals intelligence, Surveillance

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Optical links, based on coherent homodyne detection and BPSK modulation with bidirectional data transmission of 5.6 Gbps over distances of about 5,000 km and BER of 10^-8, have been sufficiently verified in space. The verification results show that this technology is suitable not only for space applications but also for applications in the troposphere. After a brief description of the Laser Communication Terminal (LCT) for space applications, the paper consequently discusses the future utilization of satellite-based optical data links for Beyond Line of Sight (BLOS) operations of High Altitude Long Endurance (HALE) Unmanned Aerial Vehicles (UAV). It is shown that the use of optical frequencies is the only logical consequence of an ever-increasing demand for bandwidth. In terms of Network Centric Warfare it is highly recommended that Unmanned Aircraft Systems (UAS) of the future should incorporate that technology which allows almost unlimited bandwidth. The advantages of optical communications especially for Intelligence, Surveillance and Reconnaissance (ISR) are underlined. Moreover, the preliminary design concept of an airborne laser communication terminal is described. Since optical bi-directional links have been tested between a LCT in space and a TESAT Optical Ground Station (OGS), preliminary analysis on tracking and BER performance and the impact of atmospheric disturbances on coherent links will be presented.

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