Micro/Nanosatellite Mars Network for Global Lower Atmosphere Characterization

To address multiple key challenge areas for robotic exploration of Mars, to achieve scientific goals and reduce risk for future human missions, a micro/nanosatellite constellation for lower atmosphere characterization is proposed. A microsatellite design is discussed that can operate (1) in tandem with another microsat or (2) as a "mother-ship" to deploy a network of nanosatellites (CubeSats). Either configuration of the network would perform radio occultation-based atmospheric measurements. Advantages of the proposed network are low development cost based on an existing microsatellite bus, and proven performance of the bus to date. Continued efforts in miniaturization of instruments are needed to fully enable the mother-ship/nanosat version of the proposed network

The application of spaceborne GPS to atmospheric limb sounding and global change monitoring

This monograph is intended for readers with minimal background in radio science who seek a relatively comprehensive treatment of the mission and technical aspects of an Earth-orbiting radio occultation satellite. Part 1 (chapters 1-6) describes mission concepts and programmatic information; Part 2 (chapters 7-12) deals with the theoretical aspects of analyzing and interpreting radio occultation measurements. In this mission concept the navigation signals from a Global Positioning System (GPS) satellite that is being occulted by the Earth's limb are observed by a GPS flight receiver on board a low Earth orbiter (LEO) satellite. This technique can be used to recover profiles of the Earth's atmospheric refractivity, pressure, and temperature using small, dedicated, and relatively low-cost space systems. Chapter 2 summarizes the basic space system concepts of the limb-sounding technique and describes a low-cost strawman demonstration mission. Chapter 3 discusses some of the scientific benefits of using radio occultation on a suite of small satellites. Chapter 4 provides a more detailed discussion of several system elements in a radio occultation mission, including the launch system for small payloads, the LEO microsat, the GPS constellation, the GPS flight receiver payload, the mission operations ground control and data receiving system, the ground-based GPS global tracking network for precision orbit determination, and the central data processing and archive system. Chapter 5 addresses the various technology readiness questions that invariably arise. Chapter 6 discusses the overall costs of a demonstration mission such as GPS/MET (meteorological) proposed by the University Navstar Consortium (UNAVCO). Chapter 7 describes a geometrical optics approach to coplanar atmospheric occultation. Chapter 8 addresses major questions regarding accuracy of the occultation techniques. Chapter 9 describes some simulations that have been performed to evaluate the sensitivity of the recovered profiles of atmospheric parameters to different error sources, such as departure from spherical symmetry, water vapor, etc. Chapter 10 discusses horizontal and vertical resolution associated with limb sounders in general. Chapter 11 treats selected Fresnel diffraction techniques that can be used in radio occultation measurements to sharpen resolution. Chapter 12 provides brief discussions on selected special topics, such as strategies for handling interference and multipath processes that may arise for rays traveling in the lower troposphere

A novel satellite mission concept for upper air water vapour, aerosol and cloud observations using integrated path differential absorption LiDAR limb sounding

We propose a new satellite mission to deliver high quality measurements of upper air water vapour. The concept centres around a LiDAR in limb sounding by occultation geometry, designed to operate as a very long path system for differential absorption measurements. We present a preliminary performance analysis with a system sized to send 75 mJ pulses at 25 Hz at four wavelengths close to 935 nm, to up to 5 microsatellites in a counter-rotating orbit, carrying retroreflectors characterized by a reflected beam divergence of roughly twice the emitted laser beam divergence of 15 µrad. This provides water vapour profiles with a vertical sampling of 110 m; preliminary calculations suggest that the system could detect concentrations of less than 5 ppm. A secondary payload of a fairly conventional medium resolution multispectral radiometer allows wide-swath cloud and aerosol imaging. The total weight and power of the system are estimated at 3 tons and 2,700 W respectively. This novel concept presents significant challenges, including the performance of the lasers in space, the tracking between the main spacecraft and the retroreflectors, the refractive effects of turbulence, and the design of the telescopes to achieve a high signal-to-noise ratio for the high precision measurements. The mission concept was conceived at the Alpbach Summer School 2010

Challenges in Arctic Navigation and Geospatial Data : User Perspective and Solutions Roadmap

Navigation and location-based applications, including business such as transport, tourism, and mining, in Arctic areas face a variety of specific challenges. In fact, these challenges concern not only the Arctic Circle but certain other areas as well, such as the Gulf of Bothnia. This report provides a review on these challengs which concern a variety of technologies ranging from satellite navigation to telecommunications and mapping. In order to find out end-users' views on the significance of Arctic challenges, an online survey was conducted. The 77 respondents representing all Arctic countries, the majority being from Finland, highlighted the challenges in telecommunications as well as accuracy concerns for emerging applications dealing with precise navigation. This report provides a review of possible technologies for addressing the Arctic challenges, based on which a road map for solving them is developed. The road map also uses the results of expert working groups from the Challenges in Arctic Navigation workshop arranged in April 2018 in Olos, Muonio, Finland. This report was produced within the ARKKI project. It was funded by the Finnish Ministry of Foreign Affairs under the Baltic Sea, Barents and Arctic cooperation programme, and implemented by the Finnish Geospatial Research Institute in collaboration with the Finnish Ministry of Transport and Communications

Democratizing LEO Satellite Network Measurement

Low Earth Orbit (LEO) satellite networks are quickly gaining traction with promises of impressively low latency, high bandwidth, and global reach. However, the research community knows relatively little about their operation and performance in practice. The obscurity is largely due to the high barrier of entry for measuring LEO networks, which requires deploying specialized hardware or recruiting large numbers of satellite Internet customers. In this paper, we introduce HitchHiking, a methodology that democratizes global visibility into LEO satellite networks. HitchHiking builds on the observation that Internet-exposed services that use LEO Internet can reveal satellite network architecture and performance, bypassing the need for specialized hardware. We evaluate HitchHiking against ground truth measurements and prior methods, showing that it provides more coverage and accuracy. With HitchHiking, we complete the largest study to date of Starlink network latency, measuring over 2,400 users across 13 countries. We uncover unexpected patterns in latency that surface how LEO routing is more complex than previously understood. Finally, we conclude with recommendations for future research on LEO networks.Comment: Pre-Prin

Global monitoring of ionospheric weather by GIRO and GNSS data fusion

Prompt and accurate imaging of the ionosphere is essential to space weather services, given a broad spectrum of applications that rely on ionospherically propagating radio signals. As the 3D spatial extent of the ionosphere is vast and covered only fragmentarily, data fusion is a strong candidate for solving imaging tasks. Data fusion has been used to blend models and observations for the integrated and consistent views of geosystems. In space weather scenarios, low latency of the sensor data availability is one of the strongest requirements that limits the selection of potential datasets for fusion. Since remote plasma sensing instrumentation for ionospheric weather is complex, scarce, and prone to unavoidable data noise, conventional 3D-var assimilative schemas are not optimal. We describe a novel substantially 4D data fusion service based on near-real-time data feeds from Global Ionosphere Radio Observatory (GIRO) and Global Navigation Satellite System (GNSS) called GAMBIT (Global Assimilative Model of the Bottomside Ionosphere with Topside estimate). GAMBIT operates with a few-minute latency, and it releases, among other data products, the anomaly maps of the effective slab thickness (EST) obtained by fusing GIRO and GNSS data. The anomaly EST mapping aids understanding of the vertical plasma restructuring during disturbed conditionsPeer ReviewedPostprint (published version

Prototype Testing Results of Charged Particle Detectors and Critical Subsystems for the ESRA Mission to GTO

The Experiment for Space Radiation Analysis (ESRA) is the latest of a series of Demonstration and Validation (DemVal) missions built by the Los Alamos National Laboratory, with the focus on testing a new generation of plasma and energetic paritcle sensors along with critical subsystems. The primary motivation for the ESRA payloads is to minimize size, weight, power, and cost while still providing necessary mission data. These new instruments will be demonstrated by ESRA through ground-based testing and on-orbit operations to increase their technology readiness level such that they can support the evolution of technology and mission objectives. This project will leverage a commercial off-the-shelf CubeSat avionics bus and commercial satellite ground networks to reduce the cost and timeline associated with traditional DemVal missions. The system will launch as a ride share with the DoD Space Test Program to be inserted in Geosynchronous Transfer Orbit (GTO) and allow observations of the Earth\u27s radiation belts. The ESRA CubeSat consists of two science payloads and several subsystems: the Wide field-of-view Plasma Spectrometer, the Energetic Charged Particle telescope, high voltage power supply, payload processor, flight software architecture, and distributed processor module. The ESRA CubeSat will provide measurements of the plasma and energetic charged particle populations in the GTO environment for ions ranging from ~100 eV to ~1000 MeV and electrons with energy ranging from 100 keV to 20 MeV. ESRA will utilize a commercial 12U bus and demonstrate a low-cost, rapidly deployable spaceflight platform with sufficient SWAP to enable efficient measurements of the charged particle populations in the dynamic radiation belts

Variations Of E-Region Total Electron Content And Electron Density Profiles Over High Latitudes During Winter Solstice 2007 Using Radio Occultation Measurements

The space weather phenomenon involves the Sun, interplanetary space and the Earth. Different space weather conditions have diverse effects on the various layers of the Earth\u27s atmosphere Technological advancements have created a situation in which human civilization is not only dependent on resources from deep inside the Earth, but also on the upper atmosphere and outer space region. Therefore, it is essential to improve the understanding of the impacts of space weather conditions on the ionosphere. This research focuses on the variation of total electron content (TEC) and the electron density within the E-region of the ionosphere, which extends from 80-150 km above the surface of the Earth, using radio occultation measurements obtained by COSMIC satellites and using Ionospheric Data Assimilation Four-Dimensional algorithm (IDA4D) which is used to mitigate the effects of F-region in the E-region estimation (Bust, Garner, & Gaussiran, 2004). E-region TEC and the electron density estimation for geomagnetic latitude range of 45o-80o, geomagnetic longitude range of -180o-180o and 1800-0600 MLT (magnetic local time) are presented for two active and two quiet days during winter solstice 2007. Active and quiet days are identified based on the Kp index values. Some of the important findings are (1) E-region electron peak density is higher during active days than during quiet days, and (2) during both types of days, higher density values were found at the magnetic latitude of \u3e60o early morning MLT. Prominent E-region features (TEC and electron density) were observed during most active days over the magnetic latitude range of 60o-70o at ~02:00 MLT

An investigation of new ionospheric models using multi-source measurements and neural networks

Ionosphere is one of the atmospheric layers that has a major impact on human beings since it significantly affects the radio propagation on Earth, and between satellites and Earth (e.g., Global Navigation Satellite Systems (GNSS) signal transmission). The variation of the electrons in the ionosphere is strongly influenced by the space weather due to solar and cosmic radiation. Hence, the short/long-term trend of the free electrons in the ionosphere has been regarded as very important information for both space weather and GNSS positioning. On the other hand, precisely quantifying the distribution and variation of free electrons at a high spatio-temporal resolution is often a challenge if the number of the electrons (electron density) is detected only from the traditional ionospheric sensors (e.g., ionosonde and topside sounder and Incoherent Scatter Radar (ISR)) due to their low spatio-temporal coverage. This disadvantage is also inherited from the empirical ionospheric model developed based on these data sources. Nowadays, the availability of advanced observation techniques, such as GNSS Radio Occultation (RO) and satellite altimetry, for the measurement of Electron Density (Ne) and related parameters (e.g., hmF2, NmF2, Vertical Scale Height (VSH), Electron Density Profile (EDP) and Vertical Total Electron Content (VTEC)) in the ionosphere has heralded a new era for space weather research in the upper atmosphere. The new sources of data for ionospheric modelling can improve not only the accuracy but also the reliability of the model (such as[96] for hmF2 and [28] for VTEC). In this study, Helmert Variance Component Estimation (VCE) aided Weight Total Least Squares (WTLS) is selected for modelling global VTEC using International GNSS Service stations, satellite altimetry and GNSS-RO measurements. The results show that the new VTEC model outperforms the traditional global ionospheric VTEC Model by at least 1.5 Total Electron Content Unit (TECU) over the ocean. This improvement is expected to be significant in the refinement of global ionospheric VTEC Model development. As is well known, the most traditional models developed are prone to the effects of inherent assumptions (e.g. for the construction of the base functions in the models) which may lead to large biases in the prediction. In this study, an innovative machine learning technique (i.e. Neural Network (NN)) is investigated as the modelling method to address this issue. Different from the traditional modelling method, neither the observation equations (or the so called `design matrix'), nor apriori knowledge of the relationship (both of them can be considered as the source of the aforementioned assumptions) is required in the modelling process of a NN. This network system can automatically construct an optimal regression function based on a large amount of sample data and the designed network [43]. In this study, Deep Neural Network (DNN), which is an advanced Artificial Neural Network (ANN) (with more than one hidden layer), is investigated for their usability of VSH and topside EDP modelling, as well as the relationship between Ne and electron temperature. The results reveal that the new VSH model agrees better than the traditional model with regards to either out-of-sample measurements or the external reference (i.e. ISR data). In addition, the new model can represent the characteristic of VSH in the equatorial region better than that of traditional approaches during geomagnetic storms. The relationship between Ne and Electron Temperature (Te) investigated from ISR data can be used to improve the performance of the current Te model. The local time-altitude variation of the model outputs agrees well with that from a physical model (i.e., Thermosphere-Ionosphere-Electrodynamics General Circulation Model (TIEGCM)). The new topside EDP model takes hmF2 and NmF2 into consideration as part of the variable set. Comparing with the reference data (i.e., out- of-sample COSMIC data, GRACE and ISR data), the new model agrees much better than the International Reference Ionosphere (IRI)-2016 model. In addition, an advanced NN technique, Bidirectional Long Short-Term Memory (Bi-LSTM), is utilised to forecast hmF2 by using the hmF2 measured by Australian ionosondes in the five hours prior. The forecast results are better than the results from real-time models in the next five hours. The new model performs also better than the current hmF2 model (i.e., AMTB [2] and shubin [96] models, which is used inside IRI-2016 model) by at least 10km in most ionosonde stations. Overall, the neural network technique has a great potential in being utilised in the ionospheric modelling. In addition to the accuracy improvement, the physical mechanism can be observed from the model outputs as well. In future work, the neural network is expected to be further applied in some other space weather studies (e.g., Dst, solar flare, etc)