Evaluating the impact of space activities in low earth orbit

Abstract. In this work, we simulated the atmospheric drag effect on two model SmallSats (small satellites) in low Earth orbit (LEO) with different ballistic coefficients during 1-month intervals of solar–geomagnetic quiet and perturbed conditions. The goal of this effort was to quantify how solar–geomagnetic activity influences atmospheric drag and perturbs satellite orbits, with particular emphasis on the Bastille Day event. Atmospheric drag compromises satellite operations due to increased ephemeris errors, attitude positional uncertainties and premature satellite re-entry. During a 1-month interval of generally quiescent solar–geomagnetic activity (July 2006), the decay in altitude (h) was a modest 0.53 km (0.66 km) for the satellite with the smaller (larger) ballistic coefficient of 2.2×10-3 m2 kg−1 (3.03×10-3 m2 kg−1). The associated orbital decay rates (ODRs) during this quiet interval ranged from 13 to 23 m per day (from 16 to 29 m per day). For the disturbed interval of July 2000 the significantly increased altitude loss and range of ODRs were 2.77 km (3.09 km) and 65 to 120 m per day (78 to 142 m per day), respectively. Within the two periods, more detailed analyses over 12 d intervals of extremely quiet and disturbed conditions revealed respective orbital decays of 0.16 km (0.20 km) and 1.14 km (1.27 km) for the satellite with the smaller (larger) ballistic coefficient. In essence, the model results show that there was a 6- to 7-fold increase in the deleterious impacts of satellite drag between the quiet and disturbed periods. We also estimated the enhanced atmospheric drag effect on the satellites' parameters caused by the July 2000 Bastille Day event (in contrast to the interval of geomagnetically quiet conditions). The additional percentage increase, due to the Bastille Day event, to the monthly mean values of h and ODR are 34.69 % and 50.13 % for Sat-A and 36.45 % and 68.95 % for Sat-B. These simulations confirmed (i) the dependence of atmospheric drag force on a satellite's ballistic coefficient, and (ii) that increased solar–geomagnetic activity substantially raises the degrading effect of satellite drag. In addition, the results indicate that the impact of short-duration geomagnetic transients (such as the Bastille Day storm) can have a further deleterious effect on normal satellite operations. Thus, this work increases the visibility and contributes to the scientific knowledge surrounding the Bastille Day event and also motivates the introduction of new indices used to describe and estimate the atmospheric drag effect when comparing regimes of varying solar–geomagnetic activity. We suggest that a model of satellite drag, when combined with a high-fidelity atmospheric specification as was done here, can lead to improved satellite ephemeris estimates.

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Gynecologic Risk Mitigation Considerations for Long-Duration Spaceflight

Aerospace Medicine and Human Performance ◽

10.3357/amhp.5538.2020 ◽

2020 ◽

Vol 91 (7) ◽

pp. 543-564

Author(s):

Jon G. Steller ◽

Rebecca S. Blue ◽

Roshan Burns ◽

Tina M. Bayuse ◽

Erik L. Antonsen ◽

...

Keyword(s):

Risk Mitigation ◽

Low Earth Orbit ◽

Space Environment ◽

Earth Orbit ◽

Mineral Density ◽

Management Options ◽

Health Maintenance ◽

Medical Risk ◽

Long Duration ◽

The Impact

INTRODUCTION: As NASA and its international partners, as well as the commercial spaceflight industry, prepare for missions of increasing duration and venturing outside of low-Earth orbit, mitigation of medical risk is of high priority. Gynecologic considerations constitute one facet of medical risk for female astronauts. This manuscript will review the preflight, in-flight, and postflight clinical evaluation, management, and prevention considerations for reducing gynecologic and reproductive risks in female astronauts.METHODS: Relevant gynecological articles from databases including Ovid, Medline, Web of Science, various medical libraries, and NASA archives were evaluated for this review. In particular, articles addressing preventive measures or management of conditions in resource-limited environments were evaluated for applicability to future long-duration exploration spaceflight.RESULTS: Topics including abnormal uterine bleeding, anemia, bone mineral density, ovarian cysts, venous thromboembolism, contraception, fertility, and health maintenance were reviewed. Prevention and treatment strategies are discussed with a focus on management options that consider limitations of onboard medical capabilities.DISCUSSION: Long-duration exploration spaceflight will introduce new challenges for maintenance of gynecological and reproductive health. The impact of the space environment outside of low-Earth orbit on gynecological concerns remains unknown, with factors such as increased particle radiation exposure adding complexity and potential risk. While the most effective means of minimizing the impact of gynecologic or reproductive pathology for female astronauts is screening and prevention, gynecological concerns can arise unpredictably as they do on Earth. Careful consideration of gynecological risks and potential adverse events during spaceflight is a critical component to risk analysis and preventive medicine for future exploration missions.Steller JG, Blue RS, Burns R, Bayuse TM, Antonsen EL, Jain V, Blackwell MM, Jennings RT. Gynecologic risk mitigation considerations for long-duration spaceflight. Aerosp Med Hum Perform. 2020; 91(7):543–564.

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The Impact of Innovation in the Satellite Industry on the Telecommunications Services Market

Problems of Engineering Cybernetics and Robotics ◽

10.7546/pecr.73.20.03 ◽

2020 ◽

Vol 73 ◽

Author(s):

Krasimir Terziev ◽

Dimitar Karastoyanov

Keyword(s):

Low Earth Orbit ◽

Earth Orbit ◽

Orbit Satellite ◽

Leo Satellites ◽

Different Types ◽

Telecommunications Services ◽

Global Communications ◽

The Impact

The article analyses the role of the satellites in global communications. Different types of orbits and different types of satellites are described. The commercial start of low and medium orbit satellites is considered. The integration of some Low Earth Orbit (LEO) projects with Teleports is commented. Some significant LEO/MEO (Medium Earth Orbit) projects are cited. The impact of the satellite industry and the Teleport systems on the technological ecosystem is discussed. LEO satellites for monitoring the earth's surface are presented. Keywords: LEO, Orbit, Satellite, Teleport.

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Precise Relative Orbit Determination for Chinese TH-2 Satellite Formation Using Onboard GPS and BDS2 Observations

Remote Sensing ◽

10.3390/rs13214487 ◽

2021 ◽

Vol 13 (21) ◽

pp. 4487

Author(s):

Bin Yi ◽

Defeng Gu ◽

Kai Shao ◽

Bing Ju ◽

Houzhe Zhang ◽

...

Keyword(s):

Orbit Determination ◽

Low Earth Orbit ◽

Asia Pacific ◽

Earth Orbit ◽

Reference Orbit ◽

Satellite Formation ◽

Relative Orbit ◽

Comparison Results ◽

Geo Satellites ◽

The Impact

TH-2 is China’s first short-range satellite formation system used to realize interferometric synthetic aperture radar (InSAR) technology. In order to achieve the mission goal of InSAR processing, the relative orbit must be determined with high accuracy. In this study, the precise relative orbit determination (PROD) for TH-2 based on global positioning system (GPS), second-generation BeiDou navagation satellite system (BDS2), and GPS + BDS2 observations was performed. First, the performance of onboard GPS and BDS2 measurements were assessed by analyzing the available data, code multipath errors and noise levels of carrier phase observations. The differences between the National University of Defense Technology (NDT) and the Xi’an Research Institute of Surveying and Mapping (CHS) baseline solutions exhibited an RMS of 1.48 mm outside maneuver periods. The GPS-based orbit was used as a reference orbit to evaluate the BDS2-based orbit and the GPS + BDS2-based orbit. It is the first time BDS2 has been applied to the PROD of low Earth orbit (LEO) satellite formation. The results showed that the root mean square (RMS) of difference between the PROD results using GPS and BDS2 measurements in 3D components was 2.89 mm in the Asia-Pacific region. We assigned different weights to geostationary Earth orbit (GEO) satellites to illustrate the impact of GEO satellites on PROD, and the accuracy of PROD was improved to 7.08 mm with the GEO weighting strategy. Finally, relative orbits were derived from the combined GPS and BDS2 data. When BDS2 was added on the basis of GPS, the average number of visible navigation satellites from TH-2A and TH-2B improved from 7.5 to 9.5. The RMS of the difference between the GPS + BDS2-based orbit and the GPS-based orbit was about 1.2 mm in 3D. The overlap comparison results showed that the combined orbit consistencies were below 1 mm in the radial (R), along-track (T), and cross-track (N) directions. Furthermore, when BDS2 co-worked with GPS, the average of the ambiguity dilution of precision (ADOP) reduced from 0.160 cycle to 0.153 cycle, which was about a 4.4% reduction. The experimental results indicate that millimeter-level PROD results for TH-2 satellite formation can be obtained by using onboard GPS and BDS2 observations, and multi-GNSS can further improve the accuracy and reliability of PROD.

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The Collocation Method's Application on Low Earth Orbit Satellite Orbit Integration

Applied Mechanics and Materials ◽

10.4028/www.scientific.net/amm.644-650.4435 ◽

2014 ◽

Vol 644-650 ◽

pp. 4435-4438

Author(s):

Jian Zhou ◽

Xing Cun Wu

Keyword(s):

Integration Method ◽

Satellite Orbit ◽

Low Earth Orbit ◽

Earth Orbit ◽

Integration Process ◽

Polynomial Degree ◽

Variation Equation ◽

Low Earth Orbit Satellite ◽

Orbit Integration ◽

The Impact

This paper starts with the principle and operation approaches of Collocation orbit integration method, analyzing the integration process and initialization value of motion equation and variation equation. Through different integration lengths and polynomial degrees, this paper discussed the impact to orbit precision. It also compares the results to the scientific orbit which were offered by GFZ, through the analysis of this method; we also find the appropriate integration length and polynomial degree and validate the validity of this method.

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A low-frequency blind survey of the low Earth orbit environment using non-coherent passive radar with the Murchison widefield array

Publications of the Astronomical Society of Australia ◽

10.1017/pasa.2020.40 ◽

2020 ◽

Vol 37 ◽

Author(s):

S. Prabu ◽

P. Hancock ◽

X. Zhang ◽

S. J. Tingay

Keyword(s):

Large Scale ◽

Imaging Techniques ◽

Careful Consideration ◽

Low Earth Orbit ◽

Earth Orbit ◽

Blind Detection ◽

Passive Radar ◽

Interferometric Imaging ◽

Murchison Widefield Array ◽

The Impact

Abstract We have extended our previous work to use the Murchison widefield array (MWA) as a non-coherent passive radar system in the FM frequency band, using terrestrial FM transmitters to illuminate objects in low Earth orbit (LEO) and the MWA as the sensitive receiving element for the radar return. We have implemented a blind detection algorithm that searches for these reflected signals in difference images constructed using standard interferometric imaging techniques. From a large-scale survey using 20 h of archived MWA observations, we detect 74 unique objects over multiple passes, demonstrating the MWA to be a valuable addition to the global Space Domain Awareness network. We detected objects with ranges up to 977 km and as small as $0.03$ ${\rm m}^2$ radar cross section. We found that 30 objects were either non-operational satellites or upper-stage rocket body debris. Additionally, we also detected FM reflections from Geminid meteors and aircraft flying over the MWA. Most of the detections of objects in LEO were found to lie within the parameter space predicted by previous feasibility studies, verifying the performance of the MWA for this application. We have also used our survey to characterise these reflected signals from LEO objects as a source of radio frequency interference (RFI) that corrupts astronomical observations. This has allowed us to undertake an initial analysis of the impact of this RFI on the MWA and the future square kilometer array (SKA). As part of this analysis, we show that the standard MWA RFI flagging strategy misses most of this RFI and that this should be a careful consideration for the SKA.

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On the prospects of a future GNSS constellation on the global terrestrial reference frame

10.5194/egusphere-egu2020-3620 ◽

2020 ◽

Author(s):

Susanne Glaser ◽

Grzegorz Michalak ◽

Rolf Koenig ◽

Benjamin Maennel ◽

Harald Schuh

Keyword(s):

Reference Frames ◽

Time Synchronization ◽

Orbital Plane ◽

Satellite System ◽

Low Earth Orbit ◽

Earth Orbit ◽

Terrestrial Reference Frames ◽

Earth Rotation Parameters ◽

The Impact

<p>Global terrestrial reference frames (TRFs), as one of the most important geodetic products, currently miss the imperative requirements of 1 mm accuracy and 1mm/decade long-term stability. In this study, the prospects of a future Global Navigation Satellite System (GNSS) to improve global TRFs is assessed by simulations. The future constellation, named &#8220;Kepler&#8221;, is proposed by the German Aerospace Center DLR in view of the next generation Galileo system. In addition to a contemporary Medium Earth Orbit (MEO) segment with 24 satellites in three orbital planes, Kepler consists of six Low Earth Orbit (LEO) satellites in two near polar planes, all carrying long-term stable optical clocks. The MEO satellites in one orbital plane and the LEO and MEO satellites in different planes are connected with optical two-way inter-satellite links (ISLs) as the innovative key feature. The ISLs allow very precise range measurements and time synchronization (at the picosecond-level) between the satellites. Different simulation scenarios are set up to evaluate the impact of the Kepler features on the TRF-defining parameters origin and scale as well as on the Earth rotation parameters (ERPs). The origin of a Kepler-only TRF improves considerably by factors of 8, 8, and 43 in X, Y, and Z direction, respectively, w.r.t. a Galileo-only solution. The scale realized by a Kepler-TRF shows improvements of 34% w.r.t. Galileo-only. In a combination with simulated observations of Very Long Baseline Interferometry the impact on multi-technique TRFs is assessed as well. The ERPs of both techniques are combined as global ties and benefits especially on the determination of UT1-UTC are expected.</p>

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A HOLISTIC APPROACH TO THE SPACE DEBRIS MITIGATION

Istituto Lombardo - Accademia di Scienze e Lettere - Rendiconti di Scienze ◽

10.4081/scie.2017.598 ◽

2020 ◽

Author(s):

Alessandro Rossi

Keyword(s):

Space Debris ◽

Holistic Approach ◽

Low Earth Orbit ◽

Earth Orbit ◽

Continuous Growth ◽

Legal Studies ◽

Whole Space ◽

Space Activities ◽

Debris Mitigation

The space activities in almost every orbital regime are now jeopardized by the continuous growth of the space debris populations. To prevent the proliferation of the space debris in Earth orbit it is necessary to tackle the problem from dierent perspectives, exploiting the latest theoretical and experimental knowledge in dierent elds, such as astrodynamics, spacecraft engineering and legal studies, to address four main pillars: prevention, protection, mitigation and regulation. In this respect the European Community nanced a large H2020 project named ReDSHIFT whose goal is to nd passive means to mitigate the proliferation of space debris. A short summary of the project and of its main ndings is given in the paper, with particular emphasis on the more theoretical part, related to the simulation of long term evolutionary scenarios of the whole space debris environment and to the mapping of the Low Earth Orbit phase space, looking for passive dynamical de-orbiting solutions.

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Satellite Laser Ranging for Retrieval of the Local Values of the Love h2 and Shida l2 Numbers for the Australian ILRS Stations

Sensors ◽

10.3390/s20236851 ◽

2020 ◽

Vol 20 (23) ◽

pp. 6851

Author(s):

Marcin Jagoda ◽

Miłosława Rutkowska ◽

Paweł Lejba ◽

Jacek Katzer ◽

Romuald Obuchovski ◽

...

Keyword(s):

Terrestrial Reference Frame ◽

Low Earth Orbit ◽

Satellite Laser Ranging ◽

Laser Ranging ◽

Earth Orbit ◽

Time Interval ◽

Formal Error ◽

Station Coordinates ◽

The Impact ◽

Research Stage

This paper deals with the analysis of local Love and Shida numbers (parameters h2 and l2) values of the Australian Yarragadee and Mount Stromlo satellite laser ranging (SLR) stations. The research was conducted based on data from the Medium Earth Orbit (MEO) satellites, LAGEOS-1 and LAGEOS-2, and Low Earth Orbit (LEO) satellites, STELLA and STARLETTE. Data from a 60-month time interval, from 01.01.2014 to 01.01.2019, was used. In the first research stage, the Love and Shida numbers values were determined separately from observations of each satellite; the obtained values of h2, l2 exhibit a high degree of compliance, and the differences do not exceed formal error values. At this stage, we found that it was not possible to determine l2 from the data of STELLA and STARLETTE. In the second research stage, we combined the satellite observations of MEO (LAGEOS-1+LAGEOS-2) and LEO (STELLA+STARLETTE) and redefined the h2, l2 parameters. The final values were adopted, and further analyses were made based on the values obtained from the combined observations. For the Yarragadee station, local h2 = 0.5756 ± 0.0005 and l2 = 0.0751 ± 0.0002 values were obtained from LAGEOS-1 + LAGEOS-2 and h2 = 0.5742 ± 0.0015 were obtained from STELLA+STARLETTE data. For the Mount Stromlo station, we obtained the local h2 = 0.5601 ± 0.0006 and l2 = 0.0637 ± 0.0003 values from LAGEOS-1+LAGEOS-2 and h2 = 0.5618 ± 0.0017 from STELLA + STARLETTE. We found discrepancies between the local parameters determined for the Yarragadee and Mount Stromlo stations and the commonly used values of the h2, l2 parameters averaged for the whole Earth (so-called global nominal parameters). The sequential equalization method was used for the analysis, which allowed to determine the minimum time interval necessary to obtain stable h2, l2 values. It turned out to be about 50 months. Additionally, we investigated the impact of the use of local values of the Love/Shida numbers on the determination of the Yarragadee and Mount Stromlo station coordinates. We proposed to determine the stations (X, Y, Z) coordinates in International Terrestrial Reference Frame 2014 (ITRF2014) in two computational versions: using global nominal h2, l2 values and local h2, l2 values calculated during this research. We found that the use of the local values of the h2, l2 parameters in the process of determining the stations coordinates influences the result.

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Thermal deformation of 3U CubeSat in low Earth orbit

MATEC Web of Conferences ◽

10.1051/matecconf/201815801013 ◽

2018 ◽

Vol 158 ◽

pp. 01013

Author(s):

Vasily Gorev ◽

Anatoly Pelemeshko ◽

Alexander Zadorozhny ◽

Aleksey Sidorchuk

Keyword(s):

Thermal Deformation ◽

Low Earth Orbit ◽

Laser Communication ◽

Earth Orbit ◽

Small Satellite ◽

Satellite Structure ◽

Satellite Laser Communication ◽

Pointing Accuracy ◽

Uneven Heating ◽

The Impact

The impact of uneven heating on a satellite structure in low Earth orbit has been considered using the example of 3U CubeSat. The calculations showed that the thermal deformation of CubeSat structure in orbit caused a deviation between normals to opposite small satellite sides of about 0.03°. Such a deviation is commensurate with the required satellite pointing accuracy approximately 0.1° necessary for satellite laser communication. It means that to solve similar problems in the CubeSat designing that require such or better CubeSat pointing accuracy, it is necessary to take into account the expected satellite structure thermal deformation.

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