Unmodified Portable Telescope for Space-to-Ground Optical Links

Pettersson, Gustav M.; Perdigués, J.; Sodnik, Zoran

doi:10.1109/icsos45490.2019.8978992

“…A spacecraft beacon would be significantly fainter and therefore the MV system might be incorporated within the larger receiver optics using a dichroic/other beamsplitter to increase sensitivity and resolution. Depending on field-of-view constraints, separate coarse and fine MV systems may be needed 25 . It is possible the downlink signal itself could serve as both tip/tilt and MV beacons, which would require a camera sensitive at the signal wavelength.…”

Section: Resultsmentioning

confidence: 99%

“…An increase in receiver aperture diameter is needed for more collecting power of the downlink signal, and an increase in transmitter aperture is needed to reduce beam divergence and geometric losses over the link distance to LEO. Aperture sizes of a few tens of centimeters are sufficient for ground-to-LEO links 25,27,28 . If the ratio of aperture size to Fried Parameter D/r 0 is greater than one, either due to large aperture or strong turbulence, higher order correction beyond tip/tilt is required to efficiently couple into SMF.…”

Section: Resultsmentioning

confidence: 99%

“…The pointing error is calculated from the pixel difference between the center of mass of the thresholded pixels and the "hotspot"; the pixel coordinates where the target must be located for the retroreflected laser to be coupled back into the SMF. The difference in pixel values are converted to errors in azimuth and altitude angles, and then fed to a software proportional, integral, derivative (PID) control loop to calculate offset rates, in arcseconds per second 25 , to apply to the mount to maintain the target on the hotspot. The hotspot is determined pre-flight using the 600 m and 2.4 km static links.…”

Section: Machine Visionmentioning

confidence: 99%

See 1 more Smart Citation

Demonstration of 100 Gbps Coherent Free-Space Optical Communications at LEO Tracking Rates

Walsh

¹

,

Karpathakis

²

,

McCann

³

et al. 2022

Preprint

0

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Free-space optical communications are poised to alleviate the data-flow bottleneck experienced by spacecraft as traditional radio frequencies reach their practical limit. While enabling orders-of-magnitude gains in data rates, optical signals impose much stricter pointing requirements and are strongly affected by atmospheric turbulence. Coherent detection methods, which capitalize fully on the available degrees of freedom to maximize data capacity, have the added complication of needing to couple the received signal into single-mode fiber. In this paper we present results from a coherent 1550 nm link across turbulent atmosphere between a deployable optical terminal and a drone-mounted retroreflector. Through 10 Hz machine vision optical tracking with nested 200 Hz tip/tilt adaptive optics stabilisation, we corrected for pointing errors and atmospheric turbulence to maintain robust single mode fiber coupling, resulting in an uninterrupted 100 Gbps optical data link while tracking at angular rates of up to 1.5 deg/s, equivalent to that of spacecraft in low earth orbit. With the greater data capacity of coherent communications and compatibility with extant fiber-based technologies being demonstrated across static links, ground-to-low earth orbit links of Terabits per second can ultimately be achieved with capable ground stations.

show abstract

Demonstration of 100 Gbps coherent free-space optical communications at LEO tracking rates

Walsh

¹

,

Karpathakis

²

,

McCann

³

et al. 2022

Sci Rep

View full text Add to dashboard Cite

Free-space optical communications are poised to alleviate the data-flow bottleneck experienced by spacecraft as traditional radio frequencies reach their practical limit. While enabling orders-of-magnitude gains in data rates, optical signals impose much stricter pointing requirements and are strongly affected by atmospheric turbulence. Coherent detection methods, which capitalize fully on the available degrees of freedom to maximize data capacity, have the added complication of needing to couple the received signal into single-mode fiber. In this paper we present results from a coherent 1550 nm link across turbulent atmosphere between a deployable optical terminal and a drone-mounted retroreflector. Through 10 Hz machine vision optical tracking with nested 200 Hz tip/tilt adaptive optics stabilisation, we corrected for pointing errors and atmospheric turbulence to maintain robust single mode fiber coupling, resulting in an uninterrupted 100 Gbps optical data link while tracking at angular rates of up to 1.5 deg/s, equivalent to that of spacecraft in low earth orbit. With the greater data capacity of coherent communications and compatibility with extant fiber-based technologies being demonstrated across static links, ground-to-low earth orbit links of Terabits per second can ultimately be achieved with capable ground stations.

show abstract

Link budget analysis of bi-directional LEO and GEO optical feeder links advancing the beam wander model’s accuracy

Cantore,

Monopoli,

Altamura

et al. 2024

Sci Rep

0

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The telecommunications of the future rely on the concept of a three-dimensional architecture able to integrate terrestrial and non-terrestrial networks with the goal to ensure a reliable and high-speed connectivity to users located anywhere. In this context, free space optical communications constitute a candidate technology for feeder links, thanks to their advantages in terms of bandwidth and achievable data rates. Nonetheless, due to the propagation impediments encountered by an optical beam travelling through atmosphere, flexible and accurate instruments able to support the design of optical feeder links are needed. Therefore, in this paper a link budget numerical tool able to meet these requirements is presented and the link budget analysis for real optical feeder links is performed demonstrating its prediction accuracy by means of the comparison with experimental results for both low Earth orbit and geostationary Earth orbit based configurations. Finally, the limits of the conventional beam wander model are analyzed and overcome.

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Unmodified Portable Telescope for Space-to-Ground Optical Links

Cited by 6 publications

References 15 publications

Demonstration of 100 Gbps Coherent Free-Space Optical Communications at LEO Tracking Rates

Demonstration of 100 Gbps Coherent Free-Space Optical Communications at LEO Tracking Rates

Demonstration of 100 Gbps coherent free-space optical communications at LEO tracking rates

Link budget analysis of bi-directional LEO and GEO optical feeder links advancing the beam wander model’s accuracy

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