Complete method of ratios

Alfano, Salvatore; Negron, David

doi:10.2514/3.25525

Cited by 3 publications

(3 citation statements)

References 1 publication

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“…In equation (7) (7), repeatability cycle of sunsynchronous orbits can be determined. In this study, time-independent TAD metric for missions with repeatability cycle of 10 days, i.e.…”

Section: Repeatability Cycle For Time-independent Tad Metricmentioning

confidence: 99%

“…Determination of TAD metric and similar related concepts has been addressed by previous literature, to considerable extent. In the following, some outstanding works [3][4][5][6][7][8][9][10][11][12][13][14][15][16] are presented, with the purpose of illustration. A prominent work in this area is from Lo [3][4][5] in Jet Propulsion Laboratory proposing use of ergodic theory to quantify TAD metric.…”

Section: Introductionmentioning

confidence: 99%

“…Also, a second advantage of this method is its high fidelity in predicting TAD metric for most satellite and ground segment configurations, except for polar ground segments. 3 Based on ''the method of ratios'', Negron et al 6 and Alfano and Negron 7 developed algorithms to determine mean duration of ground segment access to satellites. That works were extended in Alfano et al 8 to precisely determine rise/set times of a satellite which, in turn, can be employed to evaluate TAD metric.…”

Section: Introductionmentioning

confidence: 99%

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Simple surrogate models to determine total accessibility duration of low Earth orbit sunsynchronous satellites

Khamseh

Navabi

2012

Proceedings of the Institution of Mechanical Engineers, Part G:

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Short and infrequent access events are inherent characteristics of low Earth orbit sunsynchronous satellites. Furthermore, for such satellites, distribution pattern of access events varies significantly in time. Thus, determination of the metric of total accessibility duration in a given time interval has been a challenge in the field of low Earth orbit satellite systems engineering. In this article, for zero and conventional non-zero minimum elevation angles, surrogate models were developed to determine total accessibility duration of low Earth orbit satellites, based on orbital altitude of the satellite and latitude of the ground segment. For this purpose, concept of repeatability cycle was employed to achieve total accessibility duration in a time-independent manner. Then, a perturbative propagation model was presented to determine pattern of accessibility events and quantify total accessibility duration metric. In order to account for non-zero minimum elevation angles, two distinct approaches were adopted. In the first approach, four modification factors were introduced to modify the surrogate model for zero elevation angle to account for conventional non-zero minimum elevation angles. In the second approach, a dedicated surrogate model was developed to directly determine total accessibility duration for conventional non-zero minimum elevation angles. Numerous examples are examined to verify fidelity of our two proposed approaches. Due to their simplicity, the surrogate models given in this article eliminate the need for professional staff to determine metric of total accessibility duration. The advantage is that considerable saving in required initial staff cost and schedule can be realized, especially in early mission design phases.

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“…In equation (7) (7), repeatability cycle of sunsynchronous orbits can be determined. In this study, time-independent TAD metric for missions with repeatability cycle of 10 days, i.e.…”

Section: Repeatability Cycle For Time-independent Tad Metricmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

Simple surrogate models to determine total accessibility duration of low Earth orbit sunsynchronous satellites

Khamseh

Navabi

2012

Proceedings of the Institution of Mechanical Engineers, Part G:

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On Mean Visibility Time of Non-repeating Satellite Orbits with Finite Sensor Range

Katona

2010

2010 Second International Conference on Advances in Satellite and Space Communications

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Depending on the parameters of a fixed ground station and on the orbital parameters of a non-geosynchronous satellite, different visibility times are offered to fixed ground stations. In this paper, the focus is on the mean visibility time of a non-geosynchronous satellite with non-repeating ground track as seen by a fixed ground station with a finite sensor range. A mathematical analysis is provided for the calculation of the mean visibility time. There are several possible application areas of these visibility statistics, like optimizing a gateway's latitude to maximize the mean visibility time of a satellite, thus maximizing the average amount of data that can be uploaded to or downloaded from a satellite during passes. The calculations show a good match with simulation results at all latitudes and the underlying mathematical approach is foreseen to be useful for analyzing and designing complete satellite constellations.

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Predictive Avoidance for Ground-Based Laser Illumination

Alfano

Burns

Pohlen

et al. 2000

Journal of Spacecraft and Rockets

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Predictive avoidance determines discrete windows of time for safe laser illumination from a ground-based laser platform. That is, the analysis identi es time periods during which the laser will not inadvertently illuminate a satellite. The geometry of the problem is utilized to lter satellites that cannot possibly be illuminated by a speci c laser platform. Further, several nongeometric lters are introduced to lter remaining satellites by removing those which cannot be illuminated by the platform in a speci ed period. Both sets of lters improve the ef ciency of the analysis by reducing the number of state propagations necessary. A method for determining the times of possible accidental illumination using cubic polynomial approximation is also presented. Finally, a test case is run that considers the entire catalog of objects publicly available from the U.S. Space Command. The complete analysis, which considers the entire catalog as potential victims for one target satellite pass, yields veri ed results in less than 3.5 s on a laptop personal computer running at 266 MHz. Nomenclature c(s ) = cubic spline el low = minimum topocentric elevation angle at the laser platform f (t) = function that indicates whether potential victim is in safety cone i PV = inclination of the potential victim p = semilatus rectum r = distance from center of the Earth to edge of the engagement envelope r a = geocentric apogee distance r p = geocentric perigee distance r pl = geocentric position vector of the laser platform r pv/ s = position vector of potential victim relative to the laser platform r sat = position vector for satellite r t / s = position vector of target relative to the laser platform t min = actual time of minimum f (t ) t new = estimate of time of function f (t ) minimum based on c(s ) t start = time at beginning of illumination t stop = time at end of illumination (t 1 , t 2 ) = time interval input for cubic spline v pv/ s = velocity vector of potential victim relative to the laser platform v sat = velocity vector for satellite v t / s = velocity vector of target relative to the laser platform a = separation angle between potential victim and target b = safety cone half-angle c i = order i coef cient D u = maximum geocentric angle between laser platform and potential victim such that it enters the engagement envelope at apogee D u best = geocentric angle between laser platform and orbital plane of potential victim D u max = geocentric angle between laser platform and the edge of the engagement envelope g = angle opposite D u in apogee lter

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Complete method of ratios

Cited by 3 publications

References 1 publication

Simple surrogate models to determine total accessibility duration of low Earth orbit sunsynchronous satellites

Simple surrogate models to determine total accessibility duration of low Earth orbit sunsynchronous satellites

On Mean Visibility Time of Non-repeating Satellite Orbits with Finite Sensor Range

Predictive Avoidance for Ground-Based Laser Illumination

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