Link budget calculation in optical LEO satellite downlinks with on/off‐keying and large signal divergence: A simplified methodology

Abstract

SummaryDirect‐to‐Earth transmissions with optical on/off‐keying are becoming the method of choice to realize telemetry downlinks from low Earth orbit satellites at highest data‐rates. Here, we review the calculation procedure for a practical assessment of the mean link budget in this space‐ground data communication technology. We present a comprehensive survey of the dynamic orbital and beam‐pointing effects as well as the impacts from atmospheric attenuation on the link performance. The paper provides an exhaustive review of the formulas commonly used and propounds a recipe to reliably estimate the received power on ground. An overview of typical data transmitter terminals, transmission channel parameters, and the according optical ground stations is provided. Comparison with measured received powers over transmitter elevation angle and the respective design estimates serves for verification.

Radiofrequency and optical satellite link budgeting calculator

“…With the ever-increasing volumes of data generated aboard Earth observation satellites, as well as the high demand for data communication in LEO mega-constellations, optical transmission technologies for point-of-point communications working at speeds of several gigabits per second, are being more demanded [33]. Thus, FSO downlink becomes a study of great interest, so optical uplink will not be addressed in this work, still in progress.…”

“…There is scarce scientific literature in the link budget process for lasercom. For instance, [33] presents a simplified approach to calculating the link budget in optical LEO satellites-to-ground links, which considers dynamic orbital effects and beam steering, along with atmospheric attenuation, providing formulas and a method to accurately estimate ground-received power. [34] presents link budget models for Free-Space Optical Satellite Networks (FSOSN), which cover inter-satellite links and uplinks and downlinks in ground-to-LEO satellites links, considering parameters as distance, link margin, and elevation angle.…”

“…Herein we develop a link budget calculator for satellite communications for both optical and radio links, which turns to be well-founded, reliable and accurate (as it abides to current normativity and state-of-the-art research), as well as of easy implementation, of free use and of wide compatibility. To do so, we considered the standardised propagation model for radio satellite links approved by the ITU [9,40,41], while for the lasercom link budget we implemented the novel model compiled in [33]. In this way, we are aimed to provide a robust link budget calculated implemented in free software, with a friendly-user interface, which turns to be modular and thus, scalable for future required parameters.…”

“…Parameters of the model for the case of study, obtained from[33]. Rx a (m 2 ) 0.05 X Power into Rx aperture p ARx (dBm) -49.1 Rx.internal losses and signal splitting for tracking a Rx (dB) -4.1 X Power RX onto OOK data detector p Rx (dBm) -53.2…”

An All-Digital Optical Phase-Locked Loop Suitable for Satellite Downlinks

“…The transmitted optical signal is recovered in the optical ground station (OGS), where the telescope has a diameter of D R = 100 cm, having a gain of approximately G R = 126 dB, and an optics efficiency of η R = 0.65. The received optical power after the propagation through the slant path, the telescope gains, and the transmission loss can be found in the link budget calculation [4,10,11]. Considering additional losses of 9 dB, such as coupling loss, the recovered optical signal has an optical power of approximately −16 dBm.…”