Improved upper winds models for several astronomical observatories

Roberts, Lewis C.; Bradford, L. William

doi:10.1364/oe.19.000820

Cited by 16 publications

(6 citation statements)

References 18 publications

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“…Although the plots of Figure 2 and the results of other stratospheric wind studies [35] indicate the existence of a usable stratospheric wind shear, such multi-year average plots do not reflect the variable day-to-day wind conditions that would actually More details may be found in [35]. Data for a tug altitude of 16.7 km (55 kft) were extracted from the radiosonde database within a relatively small altitude range (± 0.2 km), while the airship's altitude was allowed to vary by ±1 km so as to reflect the likelihood of altitude variations due to diurnal heating effects.…”

Section: A Tethered Stratospheric Wind Shear Approachmentioning

confidence: 81%

“…Although the plots of Figure 2 and the results of other stratospheric wind studies [35] indicate the existence of a usable stratospheric wind shear, such multi-year average plots do not reflect the variable day-to-day wind conditions that would actually ) and assembled from radiosonde data available from the University of Wyoming's upper air sounding website (http://weather.uwyo.edu). Typically, two radiosonde flights are made each day and both measurements are plotted when available.…”

Section: A Tethered Stratospheric Wind Shear Approachmentioning

confidence: 84%

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A method for establishing a long duration, stratospheric platform for astronomical research

Fesen

Brown

2015

Exp Astron

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During certain times of the year at middle and low latitudes, winds in the upper stratosphere move in nearly the opposite direction than the wind in the lower stratosphere. Here we present a method for maintaining a high-altitude balloon platform in near station-keeping mode that utilizes this stratospheric wind shear. The proposed method places a balloon-borne science platform high in the stratosphere connected by a lightweight, high-strength tether to a "tug" vehicle located in the lower or middle stratosphere. Using aerodynamic control surfaces, wind-induced aerodynamic forces on the tug can be manipulated to counter the wind drag acting on the higher altitude science vehicle, thus controlling the upper vehicle's geographic location. We describe the general framework of this station-keeping method, some important properties required for the upper stratospheric science payload and lower tug platforms, and compare this station-keeping approach with the capabilities of a high altitude airship and conventional tethered aerostat approaches. We conclude by discussing the advantages of such a platform for a variety of missions with emphasis on astrophysical research.

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Section: A Tethered Stratospheric Wind Shear Approachmentioning

confidence: 81%

“…Although the plots of Figure 2 and the results of other stratospheric wind studies [35] indicate the existence of a usable stratospheric wind shear, such multi-year average plots do not reflect the variable day-to-day wind conditions that would actually ) and assembled from radiosonde data available from the University of Wyoming's upper air sounding website (http://weather.uwyo.edu). Typically, two radiosonde flights are made each day and both measurements are plotted when available.…”

Section: A Tethered Stratospheric Wind Shear Approachmentioning

confidence: 84%

A method for establishing a long duration, stratospheric platform for astronomical research

Fesen

Brown

2015

Exp Astron

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“…Turbulence distribution along the line of sight is plotted in Figure 2. Considering the wind impact, a Bufton profile [11] has been selected with a 10 m/s ground velocity parameter and a 25 m/s free atmosphere wind velocity.…”

Section: Virtual Conference 30 March-2 April 2021mentioning

confidence: 99%

Performance analysis of an adaptive optics based optical feeder link ground station

Vedrenne

Petit

Montmerle-Bonnefois

et al. 2021

International Conference on Space Optics — ICSO 2020

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Space data highway networks are currently being deployed to provide high data rate connectivity to non-fibre-connected areas around the world and to prepare the incoming growth of Internet Of Things market. Among other solutions, GEO optical feeder links are seen as the backbone of the future globalized very high data rate satellite-based telecommunication networks. The FEEDELIO experiment developed for ESA in April 2019 demonstrated the relevance of angular decorrelation models to assess the statistical characteristics of the pre-compensated uplink irradiance that is deeply affected by anisoplanatism. Based on the conclusion drawn from this experiment, we present the results of a preliminary design study of an Adaptive Optics (AO) pre-compensated optical feeder links ground station. Exploiting end-to-end simulations under relevant turbulence conditions, time-correlated fading statistics are investigated to provide typical fading durations for AO pre-compensated optical channel, taking into account the impact of point-ahead mispointing errors.

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“…= 0.06 for the same wavelength. We consider a Bufton wind profile which high altitude layer has been modified to take into account an altitude origin at sea level [23]:…”

Section: Investigation Of Telecom Performance Metrics In a Geo Dmentioning

confidence: 99%

Evaluation of communication performance for adaptive optics corrected geo-to-ground laser links

Canuet

Védrenne

Conan

et al. 2017

International Conference on Space Optics — ICSO 2016

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I. INTRODUCTION By using existing single mode components developed for fiber technologies (optical detectors and amplifiers, MUX/DEMUX...), the very high throughput of future satellite-to-ground optical communication links might be achievable at a reasonable cost. However, atmospheric turbulence induced perturbations compromise the injection efficiency of the wave into single mode components. The resulting channel impairments can be significantly reduced by the use of appropriate adaptive optics (AO) compensation at the expense of potentially complex and expensive systems if very high stability of the injection is required. Feasibility demonstrations of AO correction were recently reported in the US [1] and France [2] with Low Earth Orbit (LEO) satellites, and in Germany with GEO satellites [3]. To reduce the loss in useful information and to relax by the same way the specifications and cost of AO systems, numerical techniques such as error-correcting codes have to be considered as well. These codes introduce a degree of data redundancy, which allows a transmitted codeword to be correctly interpreted despite the loss of a significant fraction of the individual codeword elements. However, they are usually adapted to combat randomly distributed errors rather than bursty errors. Therefore, over the free-space optical channel, a fading event that is much longer than the codeword duration will usually result in an unrecoverable loss of information. To overcome this non-uniform distribution of errors that occur in slow fading channels, symbol interleaving is mandatory. Such numerical interleavers after disassembling each codeword will space the individual symbols with a temporal interval comparable to a characteristic duration of the channel fades. At the receiver, the symbols are reassembled in the proper order but the errors are redistributed such that there is a higher probability that each codeword is correctly decoded and reconstructed. In addition to the drawback induced by the latency introduced by the symbol spreading, this interleaving process could lead to unmanageable buffer size. Extensive work on numerical approaches to mitigate channel impairments were conducted in the US [4], Germany [5] and Japan [6]. Whereas the AO correction will impact the temporal characteristics of the channel and can therefore, in turn, diminish the drawbacks related to the interleaving process, none of the reported work considered the influence of the AO residuals on the characteristics of the channel. Consequently, the need for a joint optimization of the performances of the AO system and the interleaving process, with respect to power constraints and coding rate, appears necessary. In this paper, appropriate telecom metrics such as the channel capacity and outage probabilities are computed using a simplified AO corrected channel model to assess the influence of AO residuals on the required interleaver size. The specific case of a GEO to ground link with on-off keying (OOK) modulation is addressed. The outline of this paper is ...

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Improved upper winds models for several astronomical observatories

Cited by 16 publications

References 18 publications

A method for establishing a long duration, stratospheric platform for astronomical research

A method for establishing a long duration, stratospheric platform for astronomical research

Performance analysis of an adaptive optics based optical feeder link ground station

Evaluation of communication performance for adaptive optics corrected geo-to-ground laser links

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