We report on the development and performance of a continuous operation four channel silicon Single-Photon Avalanche Diode (SPAD) detector, which is based on the K14 design that has a long and successful history of deployment in space missions. The four channel design makes this detector attractive for applications in quantum communication, particularly ones facilitated via satellites. Overall, this detector is uniquely suited for missions in space, which comes not only because of its radiation ruggedness, low mass and power consumption, but importantly also, because it is capable of stable operation in temperature range from -55 to +50 degrees C using only passive compensation. Specifically, this new detector package integrates four independent K14 SPADs, each with a 25 mu m active area, and each SPAD is equipped with separate active quenching circuit that allows for operation at excess bias voltage ranging from 0,5 to 2,5 V above breakdown. Moreover, the detector package has integrated voltage converter, which generates and regulates identical bias voltage for all channels. At 2 V above breakdown the detector possesses roughly 36% detection probability for wavelength range of 500 to 800 nm and timing resolution better than 40 ps RMS. A new advancement in the detector's design is an increase in its maximum detection rate of up to 3 MHz, a 50% improvement over its predecessor. Additionally, we have recently achieved a modest reduction in DCR, a reduction in power consumption and simplification of the detector's connections.

The gamma radiation test of an DC/DC integrated converter is presented. Three samples of the device were irradiated by a total dose of 74 Gy provided by a cobalt source. This component is intended for improoving control circuit of solid state single photon detector. The detector is a key part of the laser time-transfer link payload for the next generation of Galileo GNSS satellites. These radiation tests were successful and will be included in a development of a new generation of solid state photon counting detector control circuits for space missions.

The gamma radiation test of an event timer device for solid state time-correlated single photon counting is presented. The device was irradiated by a total dose of 74 Gy provided by a cobalt source. The purpose of these radiation test was to verify that the existing version of the NPET device may be used in space missions. The completed device tests and results indicate the weakest sub-system of device and the fact that the time resolution remain practically unaffected under 4 ps correctly operational up to the radiation dose of 60 Gy.

We have optimized the performance of the semiconductor single photon detector developed for ESA European Laser Timing (ELT) project. It is used to facilitate transmission of time information from atomic clock onboard the International Space Station (ISS) to ground. These kinds of detectors can achieve single shot time resolution better than 20 ps and propagation delay stability significantly better than 1 ps. Our main focus in improving the detector's capabilities is the active quenching and gating control circuit (AQGC), which uses a comparator as its main component. The comparator is the most vital component in the circuit and plays a major role in determining the detector's final characteristics. The previously employed comparator was underperforming, it was especially unsatisfactory when it came to propagation delay temperature stability, so we have chosen to replace it with a more suitable alternative. In our measurement we have achieved linear propagation delay temperature dependence of 150 fs/K without evidently compromising the other characteristics of the detector. Even lower temperature dependence of detection delay is expected to be achievable in the new circuit setup. Our next step is the overall improvement of detector quenching speed, which will be done by removing redundant parts of the AQGC and replacing outdated parts for more modern equivalent versions.

We report on the concept, design, and tests of a New Picosecond Event Timer (NPET) device and its response to the total ionizing dose. These radiation tests aimed to verify that the existing version of the NPET device may be used in space missions. The device was subjected to radiation of a total dose of 74 Gy provided by a 60Co source. The epoch timing part of the device was not detectably affected by the radiation dose. After the radiation dose, the epoch timing of single measurement resolution is better than 0.9 ps with the overall timing stability characterized by Time Deviation being better than 5 fs for averaging times of 100 s. The completed device tests and results indicate the possibility of using the existing version of the New Pico Event Timing device electronics for a space mission in which the total radiation dose will not exceed 74 Gy value.

We have developed photon counting detectors based on InGaAs/InP SPAD for space object laser ranging. Two key versions of detector control electronics were developed, tested, and compared: passive quenching and active quenching. The key parameters of these two photon-counting detector versions were determined. The photon detection probability exceeds 20% for both versions. The timing jitter as low as 28 ps RMS was achieved for passive quenching version. The detection delay stability on the level of a fraction of picosecond was achieved for the active quenching version. The effective dark count rate as low as 160 kHz was achieved. The passive quenching electronics version was optimized for applications in which the high timing resolution is preferred. The active quenching electronics was optimized for applications, where sub-picosecond long term detection delay stability is needed.

Welcome to the SPIE Quantum Optics and Photon Counting 2021, a part of Optics + Optoelectronics Digital Forum 2021! Conference co-chairs Ivan Prochazka, Roman Sobolewski, Martin Stefanak, Aurel Gabris and our Program Committee members, we all thank you for joining us in this exciting event and sharing your cutting-edge research with the colleagues from around the world.

We are reporting on the concept, design, construction, and critical operating parameters of a new photon-counting detector package. It was developed based on silicon SPADs manufactured using K14 technology. Four detection chips with an active area diameter of 25 microns are used. The active quenching electronics enable the detection chips' operation in a bias range of 0.5 to 2.5 Volts above their breakdown voltages in a continuous counting mode. The entire design and construction are prepared for long-term operation in space conditions. Our operation experience of K14 detection chips and all the electronics in numerous space missions was taken into account when designing the device. It can be operated in an extensive temperature range of −55 to +50°C without any active temperature stabilization. The built-in SPAD biase power supply voltage is following the SPAD breakdown voltage temperature dependence. This way, the detection chips are biased fixed bias above their breakdown voltage over the entire temperature range. The critical detector parameters depend on a selected bias above a breakdown voltage. For selected configuration, every single detector's parameters are as follows: photon detection probability at 800 nm is 30%, the maximum count rate is 2 MHz, the timing resolution is better than 80 ps FWHM, detection delay temperature drift is within the range of ±0.3 ps/K. The dark count rate is typically < 50 kHz at +25°C. It may be reduced one order of magnitude, lowering the operating temperature to 0°C. The entire detector package power consumption is well below 1 Watt; its mass will be below 100 grams.

The two-way time transfer is an effective way to synchronize two independent time scales with high precision and accuracy independently on the variations of the interconnecting channel [1]. We are reporting on a new approach to an optical two-way free space time transfer which is based on signals of individual photons. This approach enables to reach extreme timing stabilities and minimal systematic errors using existing electro-optic technologies. In our previous work we have demonstrated electronic circuits for two-way time transfer via a single coaxial cable with picosecond accuracy and precision [2]. We have designed and tested the optical analogy of the two-way time transfer using a common optical channel. Photon counting approach to the signal detection is providing several key advantages: the reduction of most systematic errors found in commonly used multi-photon detection systems and the capability to operate with ultimately low signals. The repetitive optical signals of an average intensity as low as 1×10−4 photon per pulse may be detected and time tagged with sub-picosecond precision and stability [3]. The principle is illustrated in figure 1.

Satellite Laser Ranging (SLR) is a well established space geodetic technique measuring the satellite distance, which implements time of flight. Up to now, second harmonic Nd:YAG laser pulses have been frequently used for range measurement, since the silicon detector technology allows us to detect single photon echoes reflected from satellites with required high detection probability, millimeter precision, and an acceptable dark count rate. On the other hand, the fundamental wavelength (1064 nm) provides a significantly better overall energy budget, but there were no suitable detectors available. More recently, the use of InGaAs/InP became feasible for developing single photon avalanche diodes, which exhibit high photon detection probability and acceptable timing resolution. Both these properties are important and allow the SLR measurement at the fundamental wavelength. In this Note, we report on construction and testing of a single photon detector package based on the InGaAs/InP diode optimized for the SLR measurement.

Atomic Clock Ensemble in Space (ACES) is a mission designed to test Einstein’s theory of General Relativity from the International Space Station (ISS). A primary frequency standard based on laser cooled caesium atoms (PHARAO) and an active H-maser (SHM) generate a clock signal that is distributed to a network of clocks on the ground to perform space-to-ground comparison. With a fractional frequency stability of 1 × 10−16 after 10 days of integration time and an accuracy of 1 – 2 × 10−16, ACES will provide an absolute measurement of the gravitational redshift, it will search for time variations of fundamental constant, and perform Standard Model Extension (SME) tests. The ACES payload is currently completing its qualification tests before flying. The mission status, the latest test results, and the ACES performance for testing General Relativity are discussed.

Laser time transfer is of great significance in timing and global time synchronization. However, the temperature drift may occur and affect the delay of the electronics system, optic generation and detection system. This paper proposes a post-processing method for the compensation of temperature-induced system delay, which does not require any changes to the hardware setup. The temperature drift and time stability of the whole system are compared with and without compensation. The results show that the propagation delay drift as high as 240 ps caused by temperature changes is compensated. The temperature drift coefficient was diminished down to ~0.05 ps/°C from ~20.0 ps/°C. The system precision was promoted to ~2 ps from ~11 ps over a time period of 80,000 s. This method performs significant compensation of single-photon laser time transfer system propagation drift and will help to establish an ultra-stable laser time transfer link in space applications.

Increasing demand for accurate distance measurement, laser time transfer or better bias control in geodetic measurements motivates the development of solid-state photon counting detectors. We will discuss the design and achieved performance of silicon based single photon avalanche diode detector system. It was optimized for high detection delay stability performance. The existing single photon avalanche diode control circuit was optimized to compensate undesirable properties of the silicon diode to provide minimum temperature dependence of the detection delay, while maintaining its high timing resolution. As a result the detection delay changes typically 6 fs per Kelvin in a temperature range +15 degrees C to +55 degrees C. Detection delay is stable within +/- 1.5 ps over a broad temperature range -55 degrees C to +55 degrees C. Achieved timing stability of the entire time correlated single photon counting chain expressed in the form of time deviation is better than 40 fs for integration time of several hours. This extended timing stability finds its application in laser time and frequency transfer between the ground segment and orbiting clocks in space in order to determine the space clock red shift caused by gravity. It will lead to further tests of general relativity beyond previous experiments.

The new photon counting detector package has been developed for applications of the orbiting space debris optical tracking. The advanced construction of the detector control electronics enables to operate the detection chip in continuous and gated photon counting operational modes. Using the proposed construction the detector is capable to monitor the strength of a solar radiation diffused reflected by the space debris. Combining the continuous and gated detection modes enables to measure the photon flux rates over more than three orders of magnitudes ranging from one kHz to several MHz. In addition, the gated mode is optimized for laser ranging of orbiting space debris. The two operation modes of the detector may be switched electronically. The detector is based on a commercial SAP500 avalanche photodiode detection chip with active area diameter of 500 μm, which enables its simple integration into the large input aperture astronomical telescopes. The detection chip is operated at a fixed temperature of −8 °C. In a gated mode the photon detection efficiency exceeds 60% at 532 nm. Its timing resolution is typically better than 100 ps rms. In a continuous mode its dark count rate is well below 10 kHz. This detector package was developed as our contribution to the ESA activity “Space Situational Awareness program P2-SST-VII Expert Coordination Centre; Phase II”.

At present, tracking data for planetary missions largely consists of radio observables: range-rate (Doppler), range and angular position (VLBI/\(\Delta \)DOR). Future planetary missions may use Interplanetary Laser Ranging (ILR) as a tracking observable. Two-way ILR will provide range data that are about 2 orders of magnitude more accurate than radio-based range data. ILR does not produce Doppler data, however. In this article, we compare the relative strength of radio Doppler and laser range data for the retrieval of parameters of interest in planetary missions, to clarify and quantify the science case of ILR, with a focus on geodetic observables. We first provide an overview of the near-term attainable quality of ILR, in terms of both the realization of the observable and the models used to process the measurements. Subsequently, we analyse the sensitivity of radio Doppler and laser range measurements in representative mission scenarios for parameters of interest. We use both an analytical approximation and numerical analyses of the relative sensitivity of ILR and radio Doppler observables for more general cases. We show that mm-precise range normal points are feasible for ILR, but mm-level accuracy and stability in the full analysis chain are unlikely to be attained, due to a combination of instrumental and model errors. We find that ILR has the potential for superior performance in observing signatures in the data with a characteristic period of greater than 0.33–1.65 hours (assuming 2–10 mm uncertainty for range and 10 \(\upmu \)m/s at 60 s for Doppler). This indicates that Doppler tracking will typically remain the method of choice for gravity field determination and spacecraft orbit determination in planetary missions. ILR data will be able to supplement the orbiter tracking data used for the estimation of parameters with a once-per-orbit signal. Laser ranging data, however, are shown to have a significant advantage for the retrieval of rotational and tidal characteristics from landers. Similarly, laser ranging data will be superior for the construction of planetary ephemerides and the improvement of solar system tests of gravitation, both for orbiter and for lander missions.

We are presenting a new method for optical Two-Way Time Transfer based on the Single Photon Counting approach. The method can be used in parallel with standard fiber or free-air media bi-directional optical communication link without causing any interference using any type of optical transmitters including standard Small Form-Factor Pluggable laser modules. Additionally, as only an average signal of -100 dBm or less is required, it can also be performed on very long distances of over 500 km within optical fibers without any amplification, but in the latter case limited to cases when the data communication is not necessary due to high attenuation. The method was tested either with simulated and real data sets measured in our laboratory and it has proven its reliability and precision in the order of 1 ps or less. Thanks to the photon counting approach the systematic errors are minimized to ps level. The aim of our further research is to test the method on real communication data links, either in optical fiber or free-air media.

We are presenting the results of research and development of a new active quenching and gating electronics for single photon avalanche detector. The goal of this work was to improve a detector package for laser time transfer ground to space applications in terms of long term detection delay stability, detection delay reproducibility and minimal drifts. The first version of mentioned detector package is operational on board of GNSS navigation satellites. They are based on relatively small 25 mu m diameter chips. They do provide timing resolution of typically 125 ps and stability of the order of 10 ps. The presented control electronics provides timing resolution of 25 ps and sub-picosecond timing stability and drifts. The device is constructed on a basis of electronics components for which the space qualified equivalents are commercially available. The device construction, tests and results are presented in detail. (C) 2017 Elsevier B.V. All rights reserved.

We are reporting on time transfer parameters of a newly presented method of the Two-Way Time Transfer (TWTT) using the single photon counting approach. The method utilizes two Single Photon Avalanche Diode (SPAD) detectors located on both ends of the optical channel. Each of the SPAD detectors measures the common signal taken from both communication directions on its location. The mixed signal is then mathematically decomposed back to the original, separated signals, whose time shifts are then measured, and the absolute time shift of the two distant time scales is calculated. The photon counting approach was utilized due to its great beneficence for the TWTT as most of the systematic errors can be eliminated, and, additionally, an optical power of only about -100 dBm is necessary for the measurement. It makes the method usable in optical fiber channels with the lengths of more than 500 km without any amplification. The presented TWTT method can be performed for any communication wavelength when proper SPAD detectors are used. In our free-air experiment, we utilized two commonly used multimode small form factor pluggable laser modules and the SPAD detector developed by our group. The long-term timing stability of the SPAD detectors and the timing system used is better than 100 fs. The ultimate precision of the time transfer of less than 1 ps for averaging times of hours was achieved, and the reliability of the new TWTT method was proven.