Total ionization dose radiation tests results of the epoch timing system with sub-picosecond resolution and stability for its applications in space missions.

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 Co source.

High-Precision Single-Photon Laser Time Transfer with Temperature Drift Post-Compensation.

Laser time transfer is of great significance in timing and global time synchronization. However, 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.

Photon counting detector package based on InGaAs/InP avalanche structure for laser ranging applications.

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.

Note: Optical fiber two-way time transfer based on single photon counting approach.

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.

Note: Space qualified solid state photon counting detector with reduced detection delay temperature drift.

The solid state photon counting detector is one of the key components of a measurement chain for laser time transfer ground to space. The photon counting approach significantly reduces systematic errors of the time transfer. The requirements put on the detection precision and the stability of laser time transfer are increasing and reaching sub-picosecond levels now.

Note: Large active area solid state photon counter with 20 ps timing resolution and 60 fs detection delay stability.

We are reporting on the design, construction, and performance of a photon counting detector system, which is based on single photon avalanche diode detector technology. This photon counting device has been optimized for very high timing resolution and stability of its detection delay. The foreseen application of this detector is laser ranging of space objects, laser time transfer ground to space and fundamental metrology.

Note: Low phase noise programmable phase-locked loop with high temperature stability.

The design and construction of low jitter programmable phase-locked loop with low temperature coefficient of phase are presented. It has been designed for demanding high precision timing applications, especially as a clock source for event timer with subpicosecond precision. The phase-locked loop itself has a jitter of few hundreds of femtoseconds.

Note: Space qualified photon counting detector for laser time transfer with picosecond precision and stability.

The laser time transfer link is under construction for the European Space Agency in the frame of Atomic Clock Ensemble in Space. We have developed and tested the flying unit of the photon counting detector optimized for this space mission. The results are summarized in this Note.

Twenty Years of Rad-Hard K14 SPAD in Space Projects.

During last two decades, several photon counting detectors have been developed in our laboratory. One of the most promising detector coming from our group silicon K14 Single Photon Avalanche Diode (SPAD) is presented with its valuable features and space applications. Based on the control electronics, it can be operated in both gated and non-gated mode.

Note: Precise phase and frequency comparator based on direct phase-time measurements.

We are reporting on the design, performance, and application results of a phase and frequency comparator based on the direct phase-time measurement using a high performance event timer. The advantages of this approach are the simple implementation, a broad frequency range, and the clear interpretation of the measured results. Primarily we analyzed the background instability of the instrument in a common-clock test when a 200 MHz clock signal was connected to both inputs and the noise bandwidth was kept at 5 Hz by a preprocessing of the measured data.

Note: Solid state photon counters with sub-picosecond timing stability.

We are reporting on a design, construction, and performance of photon counting detector packages based on solid state sensors. These photon counting devices have been optimized for extremely high stability of their detection delay. The detectors have been designed for applications in fundamental metrology and optical time transfer.

Note: electronic circuit for two-way time transfer via a single coaxial cable with picosecond accuracy and precision.

We have designed, constructed, and tested the overall performance of the electronic circuit for the two-way time transfer between two timing devices over modest distances with sub-picosecond precision and a systematic error of a few picoseconds. The concept of the electronic circuit enables to carry out time tagging of pulses of interest in parallel to the comparison of the time scales of these timing devices. The key timing parameters of the circuit are: temperature change of the delay is below 100 fs/K, timing stability time deviation better than 8 fs for averaging time from minutes to hours, sub-picosecond time transfer precision, and a few picoseconds time transfer accuracy.

Note: Optical trigger device with sub-picosecond timing jitter and stability.

We are presenting the design, construction, and overall performance of the optical trigger device. This device generates an electrical signal synchronously to the detected ultra-short optical pulse. The device was designed for application in satellite laser ranging and laser time transfer experiments, time correlated photon counting and similar experiments, where picosecond timing resolution and detection delay stability are required.

Ground-based demonstration of the European Laser Timing (ELT) experiment.

The development of techniques for the comparison of distant clocks and for the distribution of stable and accurate time scales has important applications in metrology and fundamental physics research. Additionally, the rapid progress of frequency standards in the optical domain is presently demanding additional efforts for improving the performances of existing time and frequency transfer links. Present clock comparison systems in the microwave domain are based on GPS and two-way satellite time and frequency transfer (TWSTFT).

Nonlinear effects in the time measurement device based on surface acoustic wave filter excitation.

A transversal surface acoustic wave filter has been used as a time interpolator in a time interval measurement device. We are presenting the experiments and results of an analysis of the nonlinear effects in such a time interpolator. The analysis shows that the nonlinear distortion in the time interpolator circuits causes a deterministic measurement error which can be understood as the time interpolation nonlinearity.

Time interval measurement device based on surface acoustic wave filter excitation, providing 1 ps precision and stability.

This article deals with the time interval measurement device, which is based on a surface acoustic wave (SAW) filter as a time interpolator. The operating principle is based on the fact that a transversal SAW filter excited by a short pulse can generate a finite signal with highly suppressed spectra outside a narrow frequency band. If the responses to two excitations are sampled at clock ticks, they can be precisely reconstructed from a finite number of samples and then compared so as to determine the time interval between the two excitations.

Optical signal path delay fluctuations caused by atmospheric turbulence.

We report the first direct measurements, to our knowledge, of optical signal path delay fluctuations caused by optical turbulence in the atmosphere. The experiments were based on satellite laser ranging. Our initial motivation was to identify all the random error contributors in satellite laser ranging.