Position and velocity estimation with a low Earth orbit regional navigation satellite constellation

Dynamical Model ◽

Earth Orbit ◽

Navigation Satellite ◽

Satellite Systems ◽

Satellite Constellation ◽

Leo Satellites ◽

Order Of Magnitude

Position and velocity estimation using Global Navigation Satellite Systems (GNSS) has been widely studied and implemented. In contrast to existing GNSS, the idea of using low Earth orbit (LEO) satellites for position and velocity determination is relatively new. On one hand, the launch to LEO is more affordable compared to GNSS orbits. On the other hand, LEO satellites provide reduced coverage and suffer from orbit determination uncertainties. In this article, we study position and velocity estimation for an aerial platform using signals from a LEO satellite constellation, designed to produce a relatively long coverage duration, while minimizing the geometric dilution of precision. We determine the receiver’s position by using the trilateration method and the velocity by using Doppler estimation, and improve the accuracy thereof by utilizing an Extended Kalman Filter (EKF). We suggest a solution for the trilateration initialization problem, which arises for LEO navigation satellites, which relies on averaging the Earth projection of all the satellites within sight. We examine two scenarios, one wherein the EKF’s dynamical model matches the reference dynamical model, and another with a model mismatch. When the dynamical model is approximated, the EKF reduces the position and velocity errors considerably. When the dynamical model is known, the position and velocity errors can be reduced by an order of magnitude.

GNSS RTK Positioning Augmented with Large LEO Constellation

Remote Sensing ◽

10.3390/rs11030228 ◽

2019 ◽

Vol 11 (3) ◽

pp. 228 ◽

Cited By ~ 6

Author(s):

Xingxing Li ◽

Hongbo Lv ◽

Fujian Ma ◽

Xin Li ◽

Jinghui Liu ◽

...

Keyword(s):

Low Earth Orbit ◽

Convergence Time ◽

Current Status ◽

Initial Assessment ◽

Satellite Systems ◽

Long Baseline ◽

Leo Satellites ◽

Long Baselines

It is widely known that in real-time kinematic (RTK) solution, the convergence and ambiguity-fixed speeds are critical requirements to achieve centimeter-level positioning, especially in medium-to-long baselines. Recently, the current status of the global navigation satellite systems (GNSS) can be improved by employing low earth orbit (LEO) satellites. In this study, an initial assessment is applied for LEO constellations augmented GNSS RTK positioning, where four designed LEO constellations with different satellite numbers, as well as the nominal GPS constellation, are simulated and adopted for analysis. In terms of aforementioned constellations solutions, the statistical results of a 68.7-km baseline show that when introducing 60, 96, 192, and 288 polar-orbiting LEO constellations, the RTK convergence time can be shortened from 4.94 to 2.73, 1.47, 0.92, and 0.73 min, respectively. In addition, the average time to first fix (TTFF) can be decreased from 7.28 to 3.33, 2.38, 1.22, and 0.87 min, respectively. Meanwhile, further improvements could be satisfied in several elements such as corresponding fixing ratio, number of visible satellites, position dilution of precision (PDOP) and baseline solution precision. Furthermore, the performance of the combined GPS/LEO RTK is evaluated over various-length baselines, based on convergence time and TTFF. The research findings show that the medium-to-long baseline schemes confirm that LEO satellites do helpfully obtain faster convergence and fixing, especially in the case of long baselines, using large LEO constellations, subsequently, the average TTFF for long baselines has a substantial shortened about 90%, in other words from 12 to 2 min approximately by combining with the larger LEO constellation of 192 or 288 satellites. It is interesting to denote that similar improvements can be observed from the convergence time.

Detecting Targets above the Earth’s Surface Using GNSS-R Delay Doppler Maps: Results from TDS-1

Remote Sensing ◽

10.3390/rs11192327 ◽

2019 ◽

Vol 11 (19) ◽

pp. 2327 ◽

Cited By ~ 2

Author(s):

Changjiang Hu ◽

Craig Benson ◽

Hyuk Park ◽

Adriano Camps ◽

Li Qiao ◽

...

Keyword(s):

Specular Reflection ◽

Satellite System ◽

Low Earth Orbit ◽

Earth Orbit ◽

Navigation Satellite ◽

Reflection Point ◽

Leo Satellites ◽

Gnss Reflectometry ◽

Remotely Sense

Global Navigation Satellite System (GNSS) reflected signals can be used to remotely sense the Earth’s surface, known as GNSS reflectometry (GNSS-R). The GNSS-R technique has been applied to numerous areas, such as the retrieval of wind speed, and the detection of Earth surface objects. This work proposes a new application of GNSS-R, namely to detect objects above the Earth’s surface, such as low Earth orbit (LEO) satellites. To discuss its feasibility, 14 delay Doppler maps (DDMs) are first presented which contain unusually bright reflected signals as delays shorter than the specular reflection point over the Earth’s surface. Then, seven possible causes of these anomalies are analysed, reaching the conclusion that the anomalies are likely due to the signals being reflected from objects above the Earth’s surface. Next, the positions of the objects are calculated using the delay and Doppler information, and an appropriate geometry assumption. After that, suspect satellite objects are searched in the satellite database from Union of Concerned Scientists (UCS). Finally, three objects have been found to match the delay and Doppler conditions. In the absence of other reasons for these anomalies, GNSS-R could potentially be used to detect some objects above the Earth’s surface.

Satellite Availability and Service Performance Evaluation for Next-Generation GNSS, RNSS and LEO Augmentation Constellation

Remote Sensing ◽

10.3390/rs13183698 ◽

2021 ◽

Vol 13 (18) ◽

pp. 3698

Author(s):

Haomeng Cui ◽

Shoujian Zhang

Keyword(s):

Satellite System ◽

Low Earth Orbit ◽

Navigation Satellite ◽

Next Generation ◽

Satellite Systems ◽

Satellite Visibility ◽

Under Construction ◽

Average Position

Positioning accuracy is affected by the combined effect of user range errors and the geometric distribution of satellites. Dilution of precision (DOP) is defined as the geometric strength of visible satellites. DOP is calculated based on the satellite broadcast or precise ephemerides. However, because the modernization program of next-generation navigation satellite systems is still under construction, there is a lack of real ephemerides to assess the performance of next-generation constellations. Without requiring real ephemerides, we describe a method to estimate satellite visibility and DOP. The improvement of four next-generation Global Navigation Satellite Systems (four-GNSS-NG), compared to the navigation constellations that are currently in operation (four-GNSS), is statistically analyzed. The augmentation of the full constellation the Quasi-Zenith Satellite System (7-QZSS) and the Navigation with Indian Constellation (11-NavIC) for regional users and the low Earth orbit (LEO) constellation enhancing four-GNSS performance are also analyzed based on this method. The results indicate that the average number visible satellites of the four-GNSS-NG will reach 44.86, and the average geometry DOP (GDOP) will be 1.19, which is an improvement of 17.3% and 7.8%, respectively. With the augmentation of the 120-satellite mixed-orbit LEO constellation, the multi-GNSS visible satellites will increase by 5 to 8 at all latitudes, while the GDOP will be reduced by 6.2% on average. Adding 7-QZSS and 11-NavIC to the four-GNSS-NG, 37.51 to 71.58 satellites are available on global scales. The average position DOP (PDOP), horizontal DOP (HDOP), vertical DOP (VDOP), and time DOP (TDOP) are reduced to 0.82, 0.46, 0.67 and 0.44, respectively.

SUPPORTING DISTRESS SIGNALS OVER LOW EARTH ORBIT MOBILE SATELLITE SYSTEMS FOR EMERGENCY INFORMATION ACQUISITION

International Journal of Information Acquisition ◽

10.1142/s0219878913500186 ◽

2013 ◽

Vol 09 (03n04) ◽

pp. 1350018

Author(s):

GAMAL A. HUSSEIN ◽

MOSTAFA A. NOFAL ◽

MOAWAD I. DESSOUKY ◽

OSAMA ALY ORABY ◽

WALEED AL-HANAFY ◽

...

Keyword(s):

Information Acquisition ◽

Low Earth Orbit ◽

Earth Orbit ◽

Rescue Operation ◽

Satellite Systems ◽

Leo Satellites ◽

Mobile Satellite ◽

Voice Data ◽

Leo Satellite ◽

Service Priority

Low earth orbit (LEO) satellite systems allow a broad range of services to be provided using small, lightweight, cellular-like portable telephones. Exploiting LEO satellites to support distress signals for aircrafts, ships and international travelers is explored in the current paper. A multi-service priority-oriented algorithm is proposed for handling voice, data and emergency signals over LEO satellites. The emergency signal is privileged with service priority so that rescue operation can be carried out as soon as possible. The priority mechanism includes channel reservation as well as joining a queue if no free channel is available as long as the request is roaming in the handover area. In addition, a simplified but efficient approach is suggested for locating the object of an imminent danger situation. As LEO satellites are non-geostationary, the visible period of each spot-beam is small. Consequently, a teletraffic model, that accommodates the mobility of spot-beams as well as the resulting handover rate, is developed in order to gauge the performance of the proposed algorithm. Numerical results for access denying and service-dropping rates are presented for nominal system parameters.

GNSS Signal Availability Analysis in SSV for Geostationary Satellites Utilizing multi-GNSS with First Side Lobe Signal over the Korean Region

Remote Sensing ◽

10.3390/rs13193852 ◽

2021 ◽

Vol 13 (19) ◽

pp. 3852

Author(s):

Gun-Hoon Ji ◽

Ki-Ho Kwon ◽

Jong-Hoon Won

Keyword(s):

Numerical Simulation ◽

Space Exploration ◽

Side Lobe ◽

Earth Orbit ◽

Navigation Satellite ◽

Satellite Systems ◽

Availability Analysis ◽

Geostationary Satellites ◽

Global Navigation Satellite

This paper verifies the applicability of multiple Global Navigation Satellite Systems (GNSSs) and side lobe signal utilization in Space Service Volume (SSV), especially for Geostationary Earth Orbit (GEO) missions over the Korean region. Unlike the ground or terrestrial systems, various constraints of space exploration in SSV cause a problem when estimating position using GNSS. This is mainly due to the limit of GNSS signal availability where its dominant variables include altitude, side lobe issues, as well as longitude because of different constellations of several GNSS. The numerical simulation shows the effectiveness of additional side lobe signals from multi-GNSS. In addition, the effect of non-MEO satellites’ signals in SSV for different longitudes is presented.

Reference system origin and scale realization within the future GNSS constellation “Kepler”

Journal of Geodesy ◽

10.1007/s00190-020-01441-0 ◽

2020 ◽

Vol 94 (12) ◽

Author(s):

Susanne Glaser ◽

Grzegorz Michalak ◽

Benjamin Männel ◽

Rolf König ◽

Karl Hans Neumayer ◽

...

Keyword(s):

Time Synchronization ◽

Solar Radiation Pressure ◽

Terrestrial Reference Frame ◽

Low Earth Orbit ◽

Earth Orbit ◽

Present System ◽

Satellite Systems ◽

The Future ◽

German Aerospace

AbstractCurrently, Global Navigation Satellite Systems (GNSS) do not contribute to the realization of origin and scale of combined global terrestrial reference frame (TRF) solutions due to present system design limitations. The future Galileo-like medium Earth orbit (MEO) constellation, called “Kepler”, proposed by the German Aerospace Center DLR, is characterized by a low Earth orbit (LEO) segment and the innovative key features of optical inter-satellite links (ISL) delivering highly precise range measurements and of optical frequency references enabling a perfect time synchronization within the complete constellation. In this study, the potential improvements of the Kepler constellation on the TRF origin and scale are assessed by simulations. The fully developed Kepler system allows significant improvements of the geocenter estimates (realized TRF origin in long-term). In particular, we find improvements by factors of 43 for the Z and of 8 for the X and Y component w. r. t. a contemporary MEO-only constellation. Furthermore, the Kepler constellation increases the reliability due to a complete de-correlation of the geocenter coordinates and the orbit parameters related to the solar radiation pressure modeling (SRP). However, biases in SRP modeling cause biased geocenter estimates and the ISL of Kepler can only partly compensate this effect. The realized scale enabling all Kepler features improves by 34% w. r. t. MEO-only. The dependency of the estimated satellite antenna phase center offsets (PCOs) upon the underlying TRF impedes a scale realization by GNSS. In order to realize the network scale with 1 mm accuracy, the PCOs have to be known within 2 cm for the MEO and 4 mm for the LEO satellites. Independently, the scale can be realized by estimating the MEO PCOs and by simultaneously fixing the LEO PCOs. This requires very accurate LEO PCOs; the simulations suggest them to be smaller than 1 mm in order to keep scale changes below 1 mm.

Extended Geometry and Probability Model for GNSS+ Constellation Performance Evaluation

Remote Sensing ◽

10.3390/rs12162560 ◽

2020 ◽

Vol 12 (16) ◽

pp. 2560

Author(s):

Lingdong Meng ◽

Jiexian Wang ◽

Junping Chen ◽

Bin Wang ◽

Yize Zhang

Keyword(s):

Probability Model ◽

Satellite System ◽

Low Earth Orbit ◽

Earth Orbit ◽

Navigation Satellite ◽

Constellation Design ◽

Leo Satellites ◽

Satellite Visibility ◽

Gnss Constellation

We proposed an extended geometry and probability model (EGAPM) to analyze the performance of various kinds of (Global Navigation Satellite System) GNSS+ constellation design scenarios in terms of satellite visibility and dilution of precision (DOP) et al. on global and regional scales. Different from conventional methods, requiring real or simulated satellite ephemerides, this new model only uses some basic parameters of one satellite constellation. Verified by the reference values derived from precise satellite ephemerides, the accuracy of visible satellite visibility estimation using EGAPM gets an accuracy better than 0.11 on average. Applying the EGAPM to evaluate the geometry distribution quality of the hybrid GNSS+ constellation, where highly eccentric orbits (HEO), quasi-zenith orbit (QZO), inclined geosynchronous orbit (IGSO), geostationary earth orbit (GEO), medium earth orbit (MEO), and also low earth orbit (LEO) satellites included, we analyze the overall performance quantities of different constellation configurations. Results show that QZO satellites perform slightly better in the Northern Hemisphere than IGSO satellites. HEO satellites can significantly improve constellation geometry distribution quality in the high latitude regions. With 5 HEO satellites included in the third-generation BeiDou navigation satellite system (BDS-3), the average VDOP (vertical DOP) of the 30° N–90° N region can be decreased by 16.65%, meanwhile satellite visibility can be increased by 38.76%. What is more, the inclusion of the polar LEO constellation can significantly improve GNSS service performance. When including with 288 LEO satellites, the overall DOPs (GDOP (geometric DOP), HDOP (horizontal DOP), PDOP (position DOP), TDOP (time DOP), and VDOP) are decreased by about 40%, and the satellite visibility can be increased by 183.99% relative to the Global Positioning System (GPS) constellation.

Improved PPP Ambiguity Resolution with the Assistance of Multiple LEO Constellations and Signals

Remote Sensing ◽

10.3390/rs11040408 ◽

2019 ◽

Vol 11 (4) ◽

pp. 408 ◽

Cited By ~ 9

Author(s):

Xin Li ◽

Xingxing Li ◽

Fujian Ma ◽

Yongqiang Yuan ◽

Keke Zhang ◽

...

Keyword(s):

Ambiguity Resolution ◽

Low Earth Orbit ◽

Observation Data ◽

Dual Frequency ◽

Satellite Systems ◽

Triple Frequency ◽

Leo Satellites ◽

Fixed Solution ◽

Global Navigation Satellite

The fusion of low earth orbit (LEO) constellation and Global Navigation Satellite Systems (GNSS) can increase the number of visible satellites and optimize spatial geometry, which is expected to improve the performance of precise point positioning (PPP) ambiguity resolution (AR). In addition, the multi-frequency signals of LEO satellites can bring a variety of observation combinations, which is potential to further improve the efficiency of PPP AR. In this contribution, multi-frequency PPP AR was achieved with the augmentation of different LEO constellations. Three types of LEO constellations were designed with 60, 192, and 288 satellites. Moreover, the corresponding observation data were simulated with the GNSS observations over the ground stations. The LEO constellations were designed to transmit navigation signals on three frequencies: L1, L2, and L5 at 1575.42, 1227.6, and 1176.45 MHz, respectively, which are consistent with the GPS signals. For PPP AR, the uncalibrated phase delay (UPD) products of GNSS and LEO were estimated first. Furthermore, the quality of UPD products was also analyzed. The research findings show that the performance of estimated LEO UPD is comparable to that of GNSS UPD. Based on the UPD products, LEO-augmented multi-GNSS PPP AR can be achieved. Numerous results show that the performance of single-system and multi-GNSS PPP AR can be significantly improved by introducing the LEO constellations. The augmentation performance is more remarkable in the case of increasing LEO satellites. The time to first fix (TTFF) of the GREC fixed solution can be shortened from 7.1 to 4.8, 1.1, and 0.7 min, by introducing observations of 60-, 192-, and 288-LEO constellations, respectively. The positioning accuracy of multi-GNSS fixed solutions is also improved by about 60%, 80%, and 90% with the augmentation of 60-, 192-, and 288-LEO constellations, respectively. Compared to the dual-frequency solutions, the triple-frequency LEO-augmented PPP fixed solution presents a better performance. The TTFF of GREC fixed solutions is shortened to 33 s with the augmentation of 288-LEO constellation under the triple-frequency environment. It is worth indicating that the 288-satellite LEO-only PPP AR was conducted in dual-frequency and triple-frequency modes, respectively. The averaged TTFFs of both modes are 71.8 s and 55.2 s, respectively. It indicates that LEO constellation with 288 satellites is capable of achieving high-precision positioning independently and shows an even better performance than GNSS-only solutions.

Millimeter-accuracy SLR bias determination using independent multi-LEO DORIS and GNSS-based orbits

10.5194/egusphere-egu21-5721 ◽

2021 ◽

Author(s):

Daniel Arnold ◽

Alexandre Couhert ◽

Eléonore Saquet ◽

Heike Peter ◽

Flavien Mercier ◽

...

Keyword(s):

Center Of Mass ◽

Global Scale ◽

Terrestrial Reference Frame ◽

Low Earth Orbit ◽

Laser Ranging ◽

Bias Estimation ◽

Satellite Systems ◽

Leo Satellites ◽

Orbit Errors

Satellite Laser Ranging (SLR), i.e., the optical distance measurement to satellites equipped with laser retro-reflectors, has become an invaluable core technique in numerous geodetic applications. For instance, SLR measurements to spherical geodetic satellites, such as LAGEOS-1/2 or Etalon-1/2, form an essential contribution for the determination of geocenter coordinates and global scale in the International Terrestrial Reference Frame (ITRF) realizations.SLR measurements to active satellites in Low Earth Orbit (LEO) are, on the other hand, up to now mostly used for an independent validation of orbit solutions, usually derived by microwave tracking techniques based on Global Navigation Satellite Systems (GNSS) or Doppler Orbitography and Radiopositioning Integrated by Satellite (DORIS). This allows for the analysis of systematic orbit errors (e.g., originating from poorly known satellite center of mass locations or sensor offsets) not only in radial direction, but in three dimensions. A high level of radial orbit reliability is, e.g., key to satellite altimetry applications.For many of these geodetic SLR applications a mm accuracy and 0.1 mm/year stability is required or at least desired. Unavoidable SLR station biases are a major error source and obstacle to reach the aforementioned accuracy and stability goals. Among the stations of the International Laser Ranging Service (ILRS) there is a large diversity of biases and measurement qualities, and the calibration of these biases for all stations is key to further exploit SLR data for present and future geodetic applications.In this presentation we demonstrate that the analysis of SLR data to active LEO satellites equipped with GNSS or DORIS receivers is a promising means to analyze SLR biases and their stability. Using three independent selections of Earth observation missions in LEOs with three different SLR analysis software packages (Bernese GNSS Software, Zoom, Napeos), we estimate SLR range biases for all involved tracking stations on a yearly basis. We find that for many of the stations the three independently estimated sets of biases agree on a few-mm level and that the inclusion of satellites from multiple missions allows to render the bias estimation more robust and in particular less prone to geographically correlated orbit errors. This shows that microwave-derived orbits of active LEO satellites, nowadays of very high quality due to numerous advances in modeling and analysis techniques, can serve as interesting sources for SLR station calibration in demanding geodetic applications like, e.g., future ITRF realizations.