Sabine Philipp-May

Quantum-limited measurements of optical signals from a geostationary satellite

The measurement of quantum signals that traveled through long distances is of fundamental and technological interest. We present quantum-limited coherent measurements of optical signals, sent from a satellite in geostationary Earth orbit to an optical ground station. We bound the excess noise that the quantum states could have acquired after having propagated 38600 km through Earths gravitational potential as well as its turbulent atmosphere. Our results indicate that quantum communication is feasible in principle in such a scenario, highlighting the possibility of a global quantum key distribution network for secure communication.

The European Data Relay System, high speed laser based data links

The European Data Relay System (EDRS) is currently implemented as the first operational laser based data relay service, creating a virtual ground station for low earth orbit earth observation missions. It is based on the Tesat Laser Communication Terminal (LCT), which was developed under contract from DLR for continuous communication service in LEO and GEO orbits. The paper details the structure, development and verification of the LCT, and describe the developments at Tesat for single photon heterodyne detection, that can be used as receiver for deep space communication links to enable communications even under severe background noise levels like near to sun communication links.

LCT for EDRS: LEO to GEO optical communications at 1,8 Gbps between Alphasat and Sentinel 1a

The European Data Relay System (EDRS) relies on optical communication links between Low Earth Orbit (LEO) and geostationary (GEO) spacecrafts. Data transmission at 1,8 Gbps between the S/Cs will be applied for link distances up to 45000 km. EDRS is foreseen to go into operation in 2015. As a precursor to the EDRS GEO Laser Communication Terminals (LCT), a LCT is embarked on the Alphasat GEO S/C, which was launched in July 2013. Sentinel 1A is a LEO earth observation satellite as part of ESAs Copernicus program. Sentinel 1A also has a LCT on board. In November 2014, the first optical communication link between a LEO and a GEO Laser Communication Terminal at gigabit data rates has been performed successfully [1]. Data generated by the Sentinel 1A instrument were optically transferred to Alphasat. From Alphasat, the data were transmitted via Kaband to a ground station. In the ground station, the original data were recovered successfully. So the whole chain from LEO to ground was verified. Since then, many optical communication links between the Alphasat LCT and the Sentinel 1A LCT were performed. During these tests, the acquisition and tracking performance was investigated. The first communication links showed a very robust link acquisition capability and tracking errors in the sub-μrad range. The communication link budget was verified and compared to the predictions, showing excellent overall system behavior with sufficient margin to support future GEO GEO link applications.

LCT for the European data relay system: in orbit commissioning of the Alphasat and Sentinel 1A LCTs

The European Data Relay System (EDRS) relies on optical communication links between Low Earth Orbit (LEO) and geostationary (GEO) spacecrafts. Data transmission at 1.8 Gbps between the S/Cs will be applied. EDRS is foreseen to go into operation in 2015. As a precursor to the EDRS GEO Laser Communication Terminals (LCT), an LCT is embarked on the Alphasat GEO S/C. Sentinel 1A is a LEO earth observation satellite as part of ESAs Copernicus program and carries an LCT on board. Both the Alphasat and the Sentinel 1A LCT have completed their individual in orbit commissioning and a joint link commissioning phase, with first LEO to GEO optical communication links in 2014. In this presentation, the design principle of the LCT applied for EDRS will be investigated. The most recent results of the in-orbit link commissioning phase of the LCTs on board of Alphasat and Sentinel 1A will be presented.

Alphasat and sentinel 1A, the first 100 links

The paper details the approach, sequence, and results of the in-orbit campaign for E/O data relay using the Tesat Laser Communication Terminals from a LEO spacecraft - Sentinel 1A - a part of the EU Copernicus program, to the TDP1 payload of Alphasat, Europes largest telecommunication satellite. After configuring the LCT́s on both spacecrafts to a standard operating mode in the first 2 month of the campaign, the next few months have been used for testing the capabilities of the systems. Links with transmit powers as low as 100mW over 42000km and links probing the upper atmosphere are examples of this test campaign. In addition, far field laser beam profile and tracking performance measurements have been performed, using the unique capability of the LCT on board of Alphasat to deliver 25kHz sampled data for all internal sensors (tracking and acquisition).

German Roadmap on Optical Communication in Space

Germany identifies optical communication as a strategic space-technology. Past and present in-orbit achievements and future goals on the German Roadmap towards optical communication in space are discussed. Inter-satellite and Ground link results are covered.

Optical LEO-GEO Data Relays: From Demonstrator to Commercial Application

Laser Communication in Space have left the status of R&D programs and are now used in commercial satellite communication systems. The European Data Relay System (EDRS) is currently being implemented as the first commercially operational laser based LEO-GEO data relay service, creating a Space Data Highway for earth observation missions. It is based on the Tesat Laser Communication Terminal, which was developed under contract from DLR for long-term communication service in LEO and GEO orbits. This paper provides an overview of the optical data relay system and its advantages and describes the results of first links from GEO to ground obtained recently during in-orbit commissioning on EDRS precursor mission Alphasat TDP1.

Quantum-limited measurements of optical signals from a satellite in geostationary earth orbit

Quantum key distribution (QKD) has raised increased attention over the past years as one of the most attractive quantum technologies for practical implementation. QKD has already been implemented in intra-city networks all around the world. But up to now, bridging global distances with quantum communication remains an outstanding challenge. A promising candidate to provide this link is via optical satellite communication. As space-to-ground communication is already well developed for classical applications, one can make use of the already existing technology for QKD, i.e. modern Laser Communication Terminals (LCTs) may be adapted for quantum communication. An important first step to achieve this goal is a precise characterization of the system and the channel with regard to their quantum noise behaviour.

LCTS on ALPHASAT and Sentinel 1a: in orbit status of the LEO to geo data relay system

The performance of sensors for Earth Observation Missions is constantly improving. This drives the need for a reliable, high-speed data transfer capability from a Low Earth Orbit (LEO) spacecraft (S/C) to ground. In addition, for the transfer of time-critical data to ground, a low latency between data generation in orbit and data reception at the respective mission control center is of high importance. Laser communication between Satellites for high data transmission in combination with a GEO data relay system for reducing the latency time addresses these requirements.

Quantum measurements of signals from the Alphasat TDP1 laser communication terminal

Quantum optics [1] can be harnessed to implement cryptographic protocols that are verifiably immune against any conceivable attack [2]. Even quantum computers, that will break most current public keys [3, 4], cannot harm quantum encryption. Based on these intriguing quantum features, metropolitan quantum networks have been implemented around the world [5-15]. However, the long-haul link between metropolitan networks is currently missing [16]. Existing fiber infrastructure is not suitable for this purpose since classical telecom repeaters cannot relay quantum states [2]. Therefore, optical satellite-to-ground communication [17-22] lends itself to bridge intercontinental distances for quantum communication [23-40].