Smart CMOS image sensor for lightning detection and imaging

We present a CMOS image sensor dedicated to lightning detection and imaging. The detector has been designed to evaluate the potentiality of an on-chip lightning detection solution based on a smart sensor. This evaluation is performed in the frame of the predevelopment phase of the lightning detector that will be implemented in the Meteosat Third Generation Imager satellite for the European Space Agency. The lightning detection process is performed by a smart detector combining an in-pixel frame-to-frame difference comparison with an adjustable threshold and on-chip digital processing allowing an efficient localization of a faint lightning pulse on the entire large format array at a frequency of 1 kHz. A CMOS prototype sensor with a 256×256 pixel array and a 60 μm pixel pitch has been fabricated using a 0.35 μm 2P 5M technology and tested to validate the selected detection approach

Conceptual Study on Laser Networks for Near‐Term Collision Avoidance for Space Debris in the Low Earth Orbit

Due to the increasing amount of space debris, several laser‐based concepts for orbit modification have been proposed in the recent years. Since the sparse availability of pulsed lasers with high energy (> 10 kJ) seems to render laser‐ablative debris nudging for collision avoidance into a solution only for the long run, alternative options which can be realized earlier are mandatory to counter the rapidly increasing number of space debris in low Earth orbit. In this regard, high‐power CW lasers (> 10 kW) have been proposed in the past for debris nudging by photon pressure. With momentum coupling being 3 – 4 orders of magnitude lower than in the case of laser ablation, this might appear as a poor alternative at first glance, but the opposite is the case when a greater number of laser stations are combined forming an international network for laser tracking and momentum transfer (LTMT). From this viewpoint, we report on our findings on photon momentum transfer to space debris from our work performed under the conceptual study LARAMOTIONS (SSA P3‐SST‐XV) funded by the European Space Agency (ESA) in the framework of ESA’s Space Situational Awareness Program. Commercial availability of high power CW lasers allows for the setup of a network of relatively cost‐efficient laser stations in the next decade. Such an LTMT network would serve for both momentum transfer to space debris as well as for high precision laser tracking as a prerequisite for conjunction alert assessment and high‐power laser beam pointing. Depending on the network size, geographical distribution of stations, orbit parameters and remaining time to conjunction, multi‐pass irradiation enhances the efficiency of photon momentum coupling by 1 – 2 orders of magnitude and has the potential to eventually yield a promisingly significant reduction of the collision rate in low Earth orbit

Lunar Optical Communications Link (LOCL): Measurements of Received Power Fluctuations and Wavefront Quality

During the laser communication link experiments between NASA’s LADEE and ESA’s optical ground station on Tenerife island, DLR-IKN carried out received-power measurements using a highly sensitive power detector, and wavefront quality analysis using the focal speckle pattern method. This paper reports on the evaluation of power fluctuation statistics and wave-front quality under varying elevations, times of day, and lunar background light

Laser Guide Stars for Optical Free-Space Communications

The German Aerospace Center (DLR) and the European Southern Observatory (ESO) performed a measurement campaign together in April and July 2016 at Teide-Observatory (Tenerife), with the support of the European Space Agency (ESA), to investigate the use of laser guide stars (LGS) in ground to space optical communications. Atmospheric turbulence causes strong signal fluctuations in the uplink, due to scintillation and beam wander. In space communications, the use of the downlink channel as reference for pointing and for pre-distortion adaptive optics is limited by the size of the isokinetic and isoplanatic angle in relation to the required point-ahead angle. Pointing and phase errors due to the decorrelation between downward and upward beam due to the point-ahead angle may have a severe impact on the required transmit power and the stability of the communications link. LGSs provide a self-tailored reference to any optical ground-to-space link, independently of turbulence conditions and required point-ahead angle. In photon-starved links, typically in deep-space scenarios, LGSs allow dedicating all downlink received signal to communications purposes, increasing the available link margin. The scope of the joint DLR-ESO measurement campaign was, first, to measure the absolute value of the beam wander (uplink-tilt) using a LGS, taking a natural star as a reference, and, second, to characterize the decrease of correlation between uplink-tilt and downlink-tilt with respect to the angular separation between both sources. This paper describes the experiments performed during the measurement campaigns, providing an overview of the measured data and the first outcomes of the data post-processing

Implications of Sky Radiance On Deep-Space Optical Communication Links

As the number of deep-space missions that are turning to optical communications to support science operations increases, system designers are taking a more in depth look at the link budgets that govern such links. Noise sources, such as the radiance arising from scattering in the Earth’s atmosphere and light reflected from planetary bodies in close visual proximity to spacecraft, become particularly critical given the photon-starved channels normally associated with deep-space links. In the case of the Earth’s atmosphere, sky radiance becomes a significant factor when considering daytime operations especially when operators need to support spacecraft contacts close to the Sun. This paper encapsulates the implications of sky radiance on deep-space optical communication scenarios and provides an overview of the current efforts underway in Europe to further quantify its impact on future mission operations

Results from a Lunar Laser Communication Experiment between NASA's LADEE Satellite and ESA's Optical Ground Station

ESA’s optical ground station (OGS) participated in the Lunar Laser Communication Demonstration (LLCD) with the Laser Communication Space Terminal (LLST) onboard NASA’s Lunar Atmosphere and Dust Environmental Explorer (LADEE) satellite. The experiment demonstrated the capabilities of optical communication and of inter-agency cross-support for optical communication links. The OGS experimental campaign, which started on October 26 and lasted until November 20, consisted of four days of bidirectional link sessions followed by three days of no operation. Each individual link session lasted approximately 20 minutes and was repeated after two hours. Despite non optimal weather conditions multiple link sessions were performed. The paper describes the design of the transmit laser and data generation system as well as the receiver system. A special chapter is dedicated to lessons learned from transmitter/receiver alignment problems, which prevented the demonstration of data uplink and ranging from the OGS. Several possibilities to solve the alignment problem are discussed and the finally implemented solution is described

CMOS Image Sensor with on-chip Intelligence for Lightning Detection and Imaging

We present A CMOS image sensor dedicated to lightning detection and imaging. The detector has been designed for the pre-development phase of the lightning detector that will be implemented in Meteosat Third Generation Imager (MTG-I) satellite for European Space Agency (ESA). The lightning detection process (Patent applied) is performed by a smart detector combining on in-pixel frame to frame difference comparison with an adjustable threshold and onchip digital processing allowing an efficient localization of faint lightning pulse on the entire large format array at 1 kHz. A CMOS prototype sensor with a 256x256 pixel array and 60μm pixel pitch has been fabricated using a 0.35μm 2P 5M technology and tested to validate the selected detection approach. OCIS codes: (040.6070 ) Solid state detectors; (250.3140) Integrated optoelectronic circuits; (280.4788) Optical sensing and sensors; (110.2970) Image detection systems

Ground-based laser momentum transfer concept for debris collision avoidance

Satellite laser ranging (SLR) is a well-established technology within the scientific community used since the early 1960s to precisely measure distances. The technology evolved in support of the geodetic research striving for high accuracy measurements which nowadays are achieved by means of high repetition, low energy pulse lasers used in combination with satellites equipped with retroreflectors. The achieved accuracy allowed not only for quality improvement of orbit determination products but also remote estimation of the attitude of the observed target. The SLR technique constitutes a highly accurate, relatively cheap alternative to radars for the tracking of orbiting targets. In the last decade, the successful tracking of resident space objects, not equipped with retroreflectors, made SLR a fundamental and appealing technique also in the space debris domain. In this study, we will introduce a step forward - thanks to the availability of commercial high power (> 10 kW) continuous wave (CW) lasers - which consists in the setup of a network of ground stations able to efficiently contribute to space debris collision avoidance manoeuvres in the low Earth orbit (LEO). This paper will summarize the achievements of a conceptual study on ground-based laser momentum transfer to LEO space debris performed by a consortium under the guidance of the German Aerospace Center (DLR) funded by the European Space Agency (ESA) in the frame of the ESA Space Safety Programme. The study was carried out approaching the problem from an astrodynamical, physical, technological and legal point of view. The required tracking precision and the fundamental physics of the laser momentum transfer (LMT) were studied to evaluate the achievable thrust on LEO debris objects with commercially available components. An astrodynamical analysis was carried out to assess the efficiency of the imposed thrust and the consequences on the probability of collision in LEO. In the paper we will report the outcomes of the study which allowed us to define: the requirements of a laser tracking and momentum transfer (LTMT) station, the minimum size of an LTMT network for LEO collision avoidance operation, the current technological challenges, and gaps to be filled before its implementation

Ground-based laser momentum transfer concept for debris collision avoidance

Satellite laser ranging (SLR) is a well-established technology within the scientific community used since the early 1960s to precisely measure distances. The technology evolved in support of the geodetic research striving for high accuracy measurements which nowadays are achieved by means of high repetition, low energy pulse lasers used in combination with satellites equipped with retroreflectors. The achieved accuracy allowed not only for quality improvement of orbit determination products but also remote estimation of the attitude of the observed target. The SLR technique constitutes a highly accurate, relatively cheap alternative to radars for the tracking of orbiting targets. In the last decade, the successful tracking of resident space objects, not equipped with retroreflectors, made SLR a fundamental and appealing technique also in the space debris domain. In this study, we will introduce a possible step forward - thanks to the availability of commercial high power (> 10 kW) continuous wave (CW) lasers - which consists in the setup of a network of ground stations able to efficiently contribute to space debris collision avoidance manoeuvres in the low Earth orbit (LEO). This paper will summarize the achievements of a conceptual study on ground-based laser momentum transfer to LEO space debris performed by a consortium under the guidance of the German Aerospace Centre (DLR) funded by the European Space Agency (ESA) in the frame of the ESA Space Safety Programme. The study was carried out approaching the problem from an astrodynamics, physical, technological and legal point of view. The required tracking precision and the fundamental physics of the laser momentum transfer (LMT) were studied to evaluate the achievable thrust on LEO debris objects with commercially available components. An astrodynamics analysis was carried out to assess the efficiency of the imposed thrust and the consequences on the probability of collision in LEO. In the paper we will report the outcomes of the study which allowed us to define: the requirements of a laser tracking and momentum transfer (LTMT) station, the minimum size of an LTMT network for LEO collision avoidance operation, the current technological challenges, and gaps to be filled before its implementation