Spacecraft In Geostationary Orbit Research Articles

Parametric Evaluation of the See Rate on the SEU and SEL Monitors Aboard the Alphasat Using the IRPP Model

Calculating Single Event Effect (SEE) rates is essential to ensure space mission reliability. Standard methods rely on ground-data which is not fully representative of the space radiation environment. In this paper, we evaluate these methods using SEE data collected during 5.5 years from the Single Event Upset and Single Event Latch-up Monitors aboard the Alphasat spacecraft in Geostationary orbit.

Navigation in GEO, HEO, and Lunar Trajectory Using Multi-GNSS Sidelobe Signals

Positioning of spacecraft (e.g., geostationary orbit (GEO), high elliptical orbit (HEO), and lunar trajectory) is crucial for mission completion. Instead of using ground control systems, global navigation satellite system (GNSS) can be an effective approach to provide positioning, navigation and timing service for spacecraft. In 2020, China finished the construction of the third generation of BeiDou navigation satellite system (BDS-3); this global coverage system will contribute better sidelobe signal visibility for spacecraft. Meanwhile, with more than 100 GNSS satellites, multi-GNSS navigation performance on the spacecraft is worth studying. In this paper, instead of using signal-in-space ranging errors, we simulate pseudorange observations with measurement noises varying with received signal powers. Navigation performances of BDS-3 and its combinations with other systems were conducted. Results showed that, owing to GEO and inclined geosynchronous orbit (IGSO) satellites, all three types (GEO, HEO, and lunar trajectory) of spacecraft received more signals from BDS-3 than from other navigation systems. Single point positioning (SPP) accuracy of the GEO and HEO spacecraft was 17.7 and 23.1 m, respectively, with BDS-3 data alone. Including the other three systems, i.e., GPS, Galileo, and GLONASS, improved the SPP accuracy by 36.2% and 19.9% for GEO and HEO, respectively. Navigation performance of the lunar probe was significantly improved when receiver sensitivity increased from 20 dB-Hz to 15 dB-Hz. Only dual- (BDS-3/GPS) or multi-GNSS (BDS-3, GPS, Galileo, GLONASS) could provide continuous navigation solutions with a receiver threshold of 15 dB-Hz.

Сomparative study of the accuracy of Earth observation by satellite constellations in high elliptical orbits

The paper provides results of estimated accuracy comparisons for applied satellite constellations (ASC) in Molniya-type high elliptical orbits based on a previously presented criterion for analysis of accuracy parameters of ASC that observe targets on the Earth surface and/or in the layer above the surface, which is not dependent on specific features of the onboard equipment, but rather on the structure and dynamics of the ASC. The paper provides an algorithm for numerical simulations of ASC. The paper discusses accuracy parameters for ASC in high elliptical orbits in various orbital configurations, as well as a combined option involving spacecraft in geostationary orbit. It defines key trajectory design parameters driving the ASC accuracy. The results can be used for selecting the initial ASC configuration in high elliptical orbits during preliminary design phase. Key words: observation satellite systems, high elliptical orbits, accuracy criterion, satellite constellation analysis.

COMPARATIVE STUDY OF THE ACCURACY OF EARTH OBSERVATION BY SATELLITE CONSTELLATIONS IN HIGH ELLIPTICAL ORBITS

The paper provides results of estimated accuracy comparisons for applied satellite constellations (ASC) in Molniya-type high elliptical orbits based on a previously presented criterion for analysis of accuracy parameters of ASC that observe targets on the Earth surface and/or in the layer above the surface, which is not dependent on specific features of the onboard equipment, but rather on the structure and dynamics of the ASC. The paper provides an algorithm for numerical simulations of ASC. The paper discusses accuracy parameters for ASC in high elliptical orbits in various orbital configurations, as well as a combined option involving spacecraft in geostationary orbit. It defines key trajectory design parameters driving the ASC accuracy. The results can be used for selecting the initial ASC configuration in high elliptical orbits during preliminary design phase. Key words: observation satellite systems, high elliptical orbits, accuracy criterion, satellite constellation analysis.

Dynamics of Robotic GEostationary orbit Restorer system during deorbiting

With the development of human space activities, the number of spacecraft in geostationary orbit (GEO) has increased dramatically. According to the European Space Agency (ESA), by the end of 2008, there were 1186 objects in GEO of which only 32% were controlled operational satellites [1]. In the GEO, there are also many malfunctioning or abandoned spacecraft and lots of space debris that need to be deorbited [2] orbiting alongside functioning spacecraft. It has become necessary to monitor and deorbit these uncontrolled spacecraft and space debris to afford a safe environment for operational spacecraft so that collisions can be avoided. To do this, several alternatives have been proposed by scholars and aerospace research institutions all over the world. Among the suggestions are the RObotic GEostationary orbit Restorer (ROGER) for orbital monitoring and deorbiting [3, 4], an ion beam shepherd for contactless space debris removal [5], electrodynamic tether deorbiting [6-8], deorbiting using solar radiation force [9-11], and space robots. [12, 13]

Simulation of photovoltaic (PV) power system performance of spacecraft in geostationary orbit using a prototype model

The most important system on-board any spacecraft is its electrical power system, as every other subsystem requires power to operate. Photovoltaic (PV) array meets the total power requirements of the spacecraft in the geostationary orbit during its entire mission life. PV array consists of number of solar panel substrates on which solar cells are laid down in series and parallel for its power requirement generation. This paper presents the effects of varying temperature and irradiance on the solar energy generation based on the fundamental circuit equations of a solar PV cell model. Thus, an increase in irradiance at constant temperature, the voltage and current output also increase. Whereas, at constant irradiance, an increase in temperature decreases the power output from PV array. The model produces various curves for I-V and P-V characteristics of the PV array.

Disposal orbits for GEO spacecraft: A method for evaluating the orbit height distributions resulting from implementing IADC guidelines

Abstract Geostationary orbit (GEO) is the most commercially valuable Earth orbit. The Inter-Agency Space Debris Coordination Committee (IADC) has produced guidelines to help protect this region from space debris. The guidelines propose moving a satellite at the end of its operational life to a disposal orbit, which is designed so that satellites left there will not infringe the operational GEO region within a period of at least 100 yr. Standards are being developed through the International Organisation for Standardization to translate the IADC guidelines into engineering practice. This article presents an analytical method for calculating the distribution of final orbits assuming the IADC guidelines in GEO are implemented, as a function of distributions of satellite parameters (mass per unit area, solar radiation pressure reaction coefficient), the fuel measurement uncertainty, and the desired reliability of the disposal manoeuvre. Results show that typically the fuel measurement uncertainty dominates the distribution of perigee heights rather than the scatter in satellite properties or desired manoeuvre reliability. The method is simple to implement and allows the effects of changes in system parameters to be evaluated quickly.

Cluster observations of magnetospheric substorm behavior in the near- and mid-tail region

The Cluster constellation of spacecraft has returned substantial new data on particle and field variations in the near- and mid-magnetotail regions of Earth’s magnetosphere. Using the Research with Adaptive Particle Imaging Detectors (RAPID) system onboard the four Cluster vehicles, we have identified substorm-related energetic ( E > 20 keV) electron enhancement events during the period March 2001 through October 2001 in the geocentric radial range of 4–19 Earth radii. We have used concurrent data from other Cluster instruments as well as from the POLAR, IMAGE, FAST, GPS, and geostationary orbit spacecraft in order to understand particle injection and transport phenomena throughout this key region of the magnetotail. Electron enhancements in the plasma sheet at intermediate radial distances have been studied in a global substorm context. A particularly well-observed substorm case occurred on August 27, 2001 when Cluster was almost exactly in the midnight meridian. We find evidence that Cluster was very near the near-Earth substorm neutral line and that magnetic reconnection began some seven minutes prior to the substorm auroral brightening of the expansive phase onset. We also study in some detail the recovery phase of the substorm and the associated expansion of the plasma sheet over the 4-satellite Cluster constellation.

The situation in the geostationary ring

For more than 25 years, the practice of reorbiting of a geostationary satellite at the end of its mission in order to protect the geostationary orbit (GEO) environment has been recommended and performed by a number of operators. In recent years, an internationally recognised re-orbiting altitude has been defined by the Inter-Agency Space Debris Coordination Committee (IADC). Based on orbital data contained in the DISCOS database, the situation on the geostationary ring is analysed. In January 2004, from 1036 catalogued objects passing through the geostationary region, 340 are controlled within their allocated longitude slots, 395 are drifting above, below or through GEO, and 140 are in a libration orbit. In the periods 1997–2003, 103 spacecraft reached their end of life; 34 were reorbited in compliance with the IADC recommendation, 35 were reorbited below the minimum recommended altitude, and 34 were abandoned without any end-of-life disposal manoeuvre. Apart from these catalogued objects, the ESA 1-m telescope has observed many smaller debris (down to 10–15 cm) in this orbital region representing a collision risk for GEO spacecraft which is difficult to quantify.

Non-linear prediction of relativistic electron flux in the outer belt

The relativistic electron environment of spacecraft in geostationary orbit is governed by processes on the Sun and by the solar windlmagnetosphere interaction. Because of the association of these particles with spacecraft anomalies, there are considerable practical benefits to be gained by predicting and forecasting this environment. This paper describes the use of non-linear modelling in the prediction of relativistic electron flux in the outer radiation belt, based on solar wind characteristics, magnetic activity indices and the sunspot number. Models used are based on self-adaptive time-series methods using Radial Basis Functions (RBFs). Techniques are employed to handle non-contiguous data, which is a common problem for geophysical data sets. Nonstationarity in the data sets is treated by randomising the division of input vectors into training and test sets. The success of these models is quantitatively assessed and compared to that obtained using ‘persistence’.

Telescopic and Microscopic views of the magnetosphere: Multispacecraft observations

The magnetospheric research community has long sought the capability to view the Sun-Earth system in a global way and to probe concurrently the microphysical details of key physical regions. This objective has now been substantially realized with the combination of the CLUSTER and IMAGE missions. With the additional use of SOHO, ACE, FAST, SAMPEX, POLAR, and geostationary orbit spacecraft, there is a remarkable ability to apply both telescopic and microscopic principles. As an example, a bright active region on the Sun gave rise on 29 March 2001 to a fast halo coronal mass ejection (CME) event observed by SOHO instruments. Subsequently on 31 March, a strong interplanetary shock wave ahead of a magnetic cloud (probably arising from the earlier CME) passed the ACE spacecraft and hit the Earth’s magnetosphere. This driver compressed the subsolar magnetopause to ≤ 4 RE geocentric distance and initiated a powerful geomagnetic storm (minimum Dst ~ −360 nT). The CLUSTER set of four spacecraft were located in the midnight sector of the magnetosphere near perigee (r~4 RE) at ~0635 UT and observed a dispersionless injection of energetic (E ≥ 20 keV) electrons in association with a large magnetospheric substorm expansion phase onset (AE ~1200 nT). Concurrent to these in situ observations, the IMAGE spacecraft was returning a sequence of global Energetic Neutral Atom (ENA) images from the medium-energy (MENA) and high-energy (HENA) sensor systems. These data showed a very prominent injection of substorm ions in the premidnight (and postdusk) sector of the inner magnetosphere. This event is consistent with a substorm onset that pushed the substorm ‘injection boundary’ far inside of geostationary orbit and far toward the dusk sector. In another event on August 27, 2001, the IMAGE-CLUSTER combination provided evidence that magnetic reconnection began in the mid-tail plasma sheet some 7 min prior to auroral onset and brightening. Alternative interpretations may also be possible even with the multis-pacecraft data available. Notwithstanding, these data gave an unprecedented view both telescopically and microscopically of a magnetospheric substorm onset and help establish key process timing in the magnetosphere. Such available events reveal the power of multispacecraft observations.

Structure in polar mesospheric clouds seen from a geostationary spacecraft

Polar mesospheric clouds seen from space not infrequently show two layers, sometimes more, or a thickening of the layer if not downright separation into layers. This is often seen in images of polar mesospheric clouds obtained from spacecraft in geostationary orbit. Examples are shown here from the so‐called VIS data of the European geostationary meteorological satellite, Meteosat 5, and it is argued that these structures could well result from a single, thin, layer of cloud which is tilted over some of its extent, perhaps because of the presence of waves in the layer.

Coronal mass ejections, magnetic clouds, and relativistic magnetospheric electron events: ISTP

The role of high‐speed solar wind streams in driving relativistic electron acceleration within the Earth's magnetosphere during solar activity minimum conditions has been well documented. The rising phase of the new solar activity cycle (cycle 23) commenced in 1996, and there have recently been a number of coronal mass ejections (CMEs) and related “magnetic clouds” at 1 AU. As these CME/cloud systems interact with the Earth's magnetosphere, some events produce substantial enhancements in the magnetospheric energetic particle population while others do not. This paper compares and contrasts relativistic electron signatures observed by the POLAR, SAMPEX, Highly Elliptical Orbit, and geostationary orbit spacecraft during two magnetic cloud events: May 27–29, 1996, and January 10–11, 1997. Sequences were observed in each case in which the interplanetary magnetic field was first strongly southward and then rotated northward. In both cases, there were large solar wind density enhancements toward the end of the cloud passage at 1 AU. Strong energetic electron acceleration was observed in the January event, but not in the May event. The relative geoeffectiveness for these two cases is assessed, and it is concluded that large induced electric fields (∂B/∂t) caused in situ acceleration of electrons throughout the outer radiation zone during the January 1997 event.

Using thermionic nuclear power systems with a thermal reactor for interorbital space flights

The use of a thermionic NPS with a thermal reactor in space technology to supply power to the RMPS offers broad possibilities for interorbital delivery of payloads while using comparatively cheap launch rockets to place spacecraft in a fixed orbit. The flight time from a fixed to a geostationary orbit ranges from several months to half a year, and the mass of the payload in a geostationary orbit for optimal RMPS parameters may reach 7–8 tons (not counting the mass of the NPS). It should be noted that after the flight is completed, the NPS can serve as a source of electrical power for spacecraft in geostationary orbit.

Orbit and attitude control of a geostationary inertially oriented large flexible plate-like spacecraft

The paper presents design of a near optimal orbit and attitude control system for a very large flexible rectangular flat plate-like spacecraft in geostationary orbit, with its normal kept in the orbital plane in an inertial orientation. First, assuming the plate to be rigid, an optimal control system is designed. Two control systems are needed: one to balance the gravity gradient torque and the other to control the plate's orbit and attitude against disturbances. The interaction of the structural dynamics with the control system is investigated next. It is shown that the structural dynamics destabilizes the control system. The control design is modified to reduce the interactions, by including just a couple of flexural modes into the control logic and by optimally locating the thrusters a little away from the corners. The control structure interaction which is measured by the residual flexural energy after an orbit or attitude correction, is shown to be reduced by several orders of magnitude by the simple modifications. An approach to find an optimal location of actuators and a concept of “associated modes” are also proposed to help the designer evolve a very simple coupled orbit and attitude controllers with minimum control/structure interactions for very large flexible space systems of the future. This configuration considered represents the proposed solar power satellite, solar reflectors, communication platforms, etc.

Effect of the coefficient of error propagation on satellite position fixing

In this paper the method of controlling the effect of the random error of the elements of a tracking system on the status parameters of the trajectory or orbit of a space vehicle is discussed. The crux of this method is to control the error propagation coefficient of the tracking system. First, we defined this coefficient, and next, the properties of the coefficient are discussed. Finally the spatial distributions of the error propagation coefficient are plotted and the applications in system selection and utilization are described. This paper analyses three dimensional range measuring system particularly. The corresponding range and range difference system is also included so that the two systems can be compared. For instantaneous position fixing of distant spacecrafts, such as the geostationary orbit satellite, with high accuracy, it is preferable to use three-dimensional ranging system. We cannot obtain the optimal site geometry with stations sited only in our country, but since ours is a country with vast territory, some reasonable combinations of stations can still be established and a positioning accuracy of about 40 σ R for the geostationary orbit spacecraft in sight can be obtained.

Torque from solar radiation pressure gradient during eclipse

A general formulation is developed for calculating penumbra solar-pressure-gradient torque. A literal expression for the dependence of light intensity on position is given and the three-dimensional gradient about any point of interest in the spacecraft is computed. Solar-gradient torques are studied, via numerical simulation, for both Earth-pointing and sun-pointing planar spacecraft in geostationary orbit. Both specularly reflecting and totally absorbing surfaces are considered. Eclipse conditions are identified for the following critical cases: 1) maximum solar-gradient pitch torque; 2) maximum solar-gradient roll torque; and 3) longest duration within penumbra. The maximum instantaneous torque and angular impulse from solar-gradient torque are compared with those arising from gravity-gradient torque and are shown to be significant for some spacecraft orientations. A comparison of equivalent center-of-mass-center-of-pressure offsets for solar-gradient and conventional solar torque indicates that solar-gradient torque may potentially become dominant for very large spacecraft. It is also argued that the symmetry present within an eclipse season permits an attitude control approach based on angular momentum storage.