اشترك بالحزمة الذهبية واحصل على وصول غير محدود شمرا أكاديميا
تسجيل مستخدم جديدMethods for coherent optical Doppler orbitography
62
0
0.0
(
0
)
اسأل ChatGPT حول البحث
ﻻ يوجد ملخص باللغة العربية
Doppler orbitography uses the Doppler shift in a transmitted signal to determine the orbital parameters of satellites including range and range-rate (or radial velocity). We describe two techniques for atmospheric-limited optical Doppler orbitography measurements of range-rate. The first determines the Doppler shift directly from a heterodyne measurement of the returned optical signal. The second aims to improve the precision of the first by suppressing atmospheric phase noise imprinted on the transmitted optical signal. We demonstrate the performance of each technique over a 2.2 km horizontal link with a simulated in-line velocity Doppler shift at the far end. A horizontal link of this length has been estimated to exhibit nearly half the total integrated atmospheric turbulence of a vertical link to space. Without stabilisation of the atmospheric effects, we obtained an estimated range rate precision of 17 um/s at 1 s of integration. With active suppression of atmospheric phase noise, this improved by three orders-of-magnitude to an estimated range rate precision of 9.0 nm/s at 1 second of integration, and 1.1 nm/s when integrated over a 60 s. This represents four orders-of-magnitude improvement over the typical performance of operational ground to space X-Band systems in terms of range-rate precision at the same integration time. The performance of this system is a promising proof of concept for coherent optical Doppler orbitography. There are many additional challenges associated with performing these techniques from ground to space, that were not captured within the preliminary experiments presented here. In the future, we aim to progress towards a 10 km horizontal link to replicate the expected atmospheric turbulence for a ground to space link.
قيم البحث
اقرأ أيضاً
Knowledge of the intensity and phase profiles of spectral components in a coherent optical field is critical for a wide range of high-precision optical applications. One of these is interferometric gravitational wave detectors, which rely on such fie
lds for precise control of the experiment. Here we demonstrate a new device, an textit{optical lock-in camera}, and highlight how they can be used within a gravitational wave interferometer to directly image fields at a higher spatial and temporal resolution than previously possible. This improvement is achieved using a Pockels cell as a fast optical switch which transforms each pixel on a sCMOS array into an optical lock-in amplifier. We demonstrate that the optical lock-in camera can image fields with 2~Mpx resolution at 10~Hz with a sensitivity of -62~dBc when averaged over 2s.
The Laser Interferometer Space Antenna (LISA) is a future space-based interferometric gravitational-wave detector consisting of three spacecraft in a triangular configuration. The interferometric measurements of path length changes between satellites
will be performed on optical benches in the satellites. Angular misalignments of the interfering beams couple into the length measurement and represent a significant noise source. Imaging systems will be used to reduce this tilt-to-length coupling. We designed and constructed an optical test bed to experimentally investigate tilt-to-length coupling. It consists of two separate structures, a minimal optical bench and a telescope simulator. The minimal optical bench comprises the science interferometer where the local laser is interfered with light from a remote spacecraft. In our experiment, a simulated version of this received beam is generated on the telescope simulator. The telescope simulator provides a tilting beam, a reference interferometer and an additional static beam as a phase reference. The tilting beam can either be a flat-top beam or a Gaussian beam. We avoid tilt-to-length coupling in the reference interferometer by using a small photo diode placed at an image of the beam rotation point. We show that the test bed is operational with an initial measurement of tilt-to-length coupling without imaging systems. Furthermore, we show the design of two different imaging systems whose performance will be investigated in future experiments.
Euclid is a space telescope currently developed in the framework of the ESA Cosmic Vision 2015-2025 Program. It addresses fundamental cosmological questions related to dark matter and dark energy. The lens system of one of the two scientific key inst
ruments [a combined near-infrared spectrometer and photometer (NISP)] was designed, built-up and tested at the Max Planck Institute for Extraterrestrial Physics (MPE). We present the final imaging quality of this diffraction-limited optical assembly with two complementary approaches, namely a point-spread function and a Shack-Hartmann sensor-based wavefront measurement. The tests are performed under space operating conditions within a cryostat. The large field of view of Euclids wide-angle objective is sampled with a pivot arm, carrying a measurement telescope and the sensors. A sequence of highly accurate movements to several field positions is carried out by a large computer controlled hexapod. Both measurement approaches are compared among one another and with the corresponding simulations. They demonstrate in good agreement a solely diffraction limited optical performance over the entire field of view.
Vacuum quantum fluctuations impose a fundamental limit on the sensitivity of gravitational-wave interferometers, which rank among the most sensitive precision measurement devices ever built. The injection of conventional squeezed vacuum reduces quant
um noise in one quadrature at the expense of increasing noise in the other. While this approach improved the sensitivity of the Advanced LIGO and Advanced Virgo interferometers during their third observing run (O3), future improvements in arm power and squeezing levels will bring radiation pressure noise to the forefront. Installation of a filter cavity for frequency-dependent squeezing provides broadband reduction of quantum noise through the mitigation of this radiation pressure noise, and it is the baseline approach planned for all of the future gravitational-wave detectors currently conceived. The design and operation of a filter cavity requires careful consideration of interferometer optomechanics as well as squeezing degradation processes. In this paper, we perform an in-depth analysis to determine the optimal operating point of a filter cavity. We use our model alongside numerical tools to study the implications for filter cavities to be installed in the upcoming A+ upgrade of the Advanced LIGO detectors.
Integrated photonic spectrographs offer an avenue to extreme miniaturization of astronomical instruments, which would greatly benefit extremely large telescopes and future space missions. These devices first require optimization for astronomical appl
ications, which includes design, fabrication and field-testing. Given the high costs of photonic fabrication, Multi-Project Wafer (MPW) SiN offerings, where a user purchases a portion of a wafer, provide a convenient and affordable avenue to develop this technology. In this work we study the potential of two commonly used SiN waveguide geometries by MPW foundries, i.e. square and rectangular profiles to determine how they affect the performance of mid-high resolution arrayed waveguide grating spectrometers around 1.5 $mu$m. Specifically, we present results from detailed simulations on the mode sizes, shapes, and polarization properties, and on the impact of phase errors on the throughput and cross talk as well as some laboratory results of coupling and propagation losses. From the MPW-run tolerances and our phase-error study, we estimate that an AWG with R $sim$ 10,000 can be developed with the MPW runs and even greater resolving power is achievable with more reliable, dedicated fabrication runs. Depending on the fabrication and design optimizations, it is possible to achieve throughputs $sim 60%$ using the SiN platform. Thus, we show that SiN MPW offerings are highly promising and will play a key role in integrated photonic spectrograph developments for astronomy.
سجل دخول لتتمكن من نشر تعليقات
التعليقات
جاري جلب التعليقات
سجل دخول لتتمكن من متابعة معايير البحث التي قمت باختيارها
