South African National Space Agency Research Articles

Space weather impacts on the ionosphere over the southern African mid-latitude region

The ionosphere suffers major perturbations during severe space weather events such as Coronal Mass Ejections (CMEs), solar flares, high-speed streams, and Corotating Interaction Regions (CIRs). The ionosphere can experience depletions or enhancements in Total Electron Content (TEC) during severe space weather conditions. The South African National Space Agency (SANSA) near-real-time (NRT) TEC maps were used to show the ionospheric variability during the geomagnetic storm of 3–8 Nov 2021 over the southern Africa mid-latitude region. The ionosonde TEC, NRT TEC, and the quiet-time AfriTEC model were compared during the 6-day period. A negative ionospheric response was observed during the main and recovery phases of the geomagnetic storm (4–5 Nov 2021). The changes to neutral composition O/N2 was one of the physical processes attributed to the decrease in TEC over the mid-latitude region. The GPS TEC maps showed a very good agreement with ionosonde measurements and the AfriTEC model. A strong east–west TEC gradient was observed occurring between two ionosonde stations.Graphical

Development of a Regional F‐Region Critical Frequency Model for Southern Africa

AbstractA new localized linear regression model, called the SANSA model, is presented. The model provides a forecast of the F‐region critical frequency (foF2) over Grahamstown, South Africa (33.31°S, 26.52°E). The input parameters of this model are the maximum daily solar elevation angle, the F10.7 cm radio flux index and the planetary K index. The output parameter is the forecasted foF2. The historical data‐set consists of ionosonde foF2 observations made in Grahamstown for the period 2010–2019. The historical and predicted data sets used to develop the model are obtained from databases maintained by the South African National Space Agency, the National Aeronautics and Space Administration and the National Oceanic and Atmospheric Administration. The model improves on the results of the Ionospheric Communications Enhanced Profile Analysis and Circuit Prediction Program in terms of the root mean square error skill score metric. The work presented shows that a linear regression model based on the solar elevation angle as well as the F10.7 and planetary K indices can closely approximate observed foF2 magnitudes during quiet and storm times.

The altitude of sprites observed over South Africa

Sprites are mesospheric optical emissions that are mostly produced by large, positive cloud-to-ground lightning discharges. Sprites appear in different morphologies such as carrot, jellyfish and column, and are typically in the altitude range of ~40–100 km above the Earth’s surface. Sprites are a subset of transient luminous events and they contribute to the global electric circuit. South Africa has large convective thunderstorms, which typically occur in the summer months of every year. Peak current, time and geographical position of lightning strokes were obtained from the South African Weather Service. Sprite observations were recorded in South Africa for the first time on 11 January 2016 from Sutherland in the Northern Cape using a night-vision television camera from the South African National Space Agency’s Optical Space Research laboratory. We report the first estimates of the top altitude, and the altitude of maximum brightness, of 48 sprites over South Africa. We found that the average top altitude and the altitude of maximum brightness of sprites are approximately 84.3 km and 69 km, respectively, which is consistent with estimates made elsewhere. We also found a moderately high positive and a weak positive correlation between the top altitude and the altitude of maximum brightness, respectively, of sprites and the lightning stroke charge moment change.
 Significance:
 
 We present the first altitude estimation of sprites observed over Africa.
 The altitude of sprites observed over South Africa is in agreement with observations made elsewhere.
 There is a positive correlation between the top altitude of sprites and the parent lightning charge moment change.
 Sprite maximum brightness is observed near the stratopause.

Multi-Mission Earth Observation Data Processing System.

The surge in the number of earth observation satellites being launched worldwide is placing significant pressure on the satellite-direct ground receiving stations that are responsible for systematic data acquisition, processing, archiving, and dissemination of earth observation data. Growth in the number of satellite sensors has a bearing on the ground segment payload data processing systems due to the complexity, volume, and variety of the data emanating from the different sensors. In this paper, we have aimed to present a generic, multi-mission, modularized payload data processing system that we are implementing to optimize satellite data processing from historical and current sensors, directly received at the South African National Space Agency’s (SANSA) ground receiving station. We have presented the architectural framework for the multi-mission processing system, which is comprised of five processing modules, i.e., the data ingestion module, a radiometric and geometric processing module, atmospheric correction and Analysis Ready Data (ARD) module, Value Added Products (VAPS) module, and lastly, a packaging and delivery module. Our results indicate that the open architecture, multi-mission processing system, when implemented, eliminated the bottlenecks linked with proprietary mono-mission systems. The customizable architecture enabled us to optimize our processing in line with our hardware capacities, and that resulted in significant gains in large-scale image processing efficiencies. The modularized, multi-mission data processing enabled seamless end-to-end image processing, as demonstrated by the capability of the multi-mission system to execute geometric and radiometric corrections to the extent of making it analysis-ready. The processing workflows were highly scalable and enabled us to generate higher-level thematic information products from the ingestion of raw data.

The Role of African Emerging Space Agencies in Earth Observation Capacity Building for Facilitating the Implementation and Monitoring of the African Development Agenda: The Case of African Earth Observation Program

AU-Agenda 2063 was adopted at the 24th Ordinary Session of the African Heads of State and Government in 2015 as the blueprint for the future development of the continent. Built upon the continent’s past experiences, challenges, and successes, AU-Agenda 2063 comprehensively describes the strategic path for Africa’s future development in the next 50 years. Thus, the monitoring of its implementation in various African states is critical for ensuring sustainable development and track progress. However, the higher cost of collecting data for accurately and reliably monitoring the implementation of Agenda 2063 may hinder the progress towards achieving these goals. Satellite Earth observation provides ample data, and thus has provided opportunities for the development of novel products and services with the potential to support implementation, monitoring and reporting for AU-Agenda 2063 development imperatives. However, it has been limitedly exploited in Africa, as evidenced by lower research outputs and investments. This calls for increased capacity building in the use of available EO data and products for various users including decision makers to advance national, regional and continental priorities. The use of such data products is often hampered by the capability to understand the products and thus their value for addressing socio-economic challenges. This paper discusses the potential of Earth observation capacity building for supporting the implementation, monitoring of, and reporting towards achieving AU-Agenda 2063 development imperatives. Specifically, this paper identifies existing capacity building resources, including the role of open and free Earth observation data, open-source software, and product dissemination platforms that can be leveraged for supporting national development, service delivery and the achievement of AU-Agenda 2063 targets. Furthermore, the paper recognizes the importance of bilateral and multilateral partnerships in leveraging existing know-how, technology and other resources for advancing strategic goals of African emerging space agencies and promoting sustainable development, with examples from South African National Space Agency (SANSA). Then, the challenges and opportunities for capacity building and the wide adoption of EO in Africa are discussed in the context of AU-Agenda 2063. The paper thus concludes that EO capacity building is essential to address the skills and data gaps and increase the use of EO-based solutions for decision making in various sectors, critical for achieving AU-A2063.

Hermanus Magnetic Observatory: a historical perspective of geomagnetism in southern Africa

Abstract. In this paper a brief summary will be given about the historical development of geomagnetism as a science in southern Africa and particularly the role played by Hermanus Magnetic Observatory in this regard. From a very modest beginning in 1841 as a recording station at the Cape of Good Hope, Hermanus Magnetic Observatory is today part of the South African National Space Agency (SANSA), where its geomagnetic field data are extensively used in international research projects ranging from the physics of the geo-dynamo to studies of the near-Earth space environment.

Azimuth-dependent elevation threshold (ADET) masks to reduce multipath errors in ionospheric studies using GNSS

Physical structures found in the vicinity of GNSS receivers can introduce multipath interference effects when a signal arrives at the receiver by different routes. Multipath effects are well recognized as one of the most significant sources of error that degrade the accuracy of GNSS signals for navigation and positioning applications. These effects also reduce the quality of GNSS data used for ionospheric studies. The principal cause of multipath effects is proximity of the antenna to reflecting structures and it is more pronounced when the signal comes from a satellite with low elevation. Typically, conservative fixed-elevation thresholds of 20–40° are used to filter out signals from low elevation angles, but this leads to the exclusion of a significant quantity of useable data. In this paper we present a series of azimuth-dependent elevation thresholds that were developed by characterizing the multipath environment of the GPS Ionospheric Scintillation and TEC (Total Electron Content) Monitor (GISTM) receivers installed by SANSA (South African National Space Agency) at Mauritius (20.14°S and 57°E), Marion Island (46.87°S and 37.86°E) and SANAE IV in Antarctica (71.73°S and 2.2°W). The threshold masks were developed from azimuth-elevation maps of the S4 index, σϕ index, the Code-Carrier Divergence Standard Deviation (CC-STDDEV) and the L1 Carrier-to-Noise Density (L1 CNo) from 1-min scintillation data taken over a period of 10–12months at each location to identify signals that are distorted by multipath effects. Using the azimuth-dependent elevation threshold (ADET) mask typically gives 22–28% more useful data than using a fixed-elevation threshold at the sites studied in this paper.

First Observations of GNSS Ionospheric Scintillations From DemoGRAPE Project

The Istituto Nazionale di Geofisica e Vulcanologia leads an international project funded by the Italian National Program for Antarctic Research, called Demonstrator of Global Navigation Satellite System (GNSS) Research and Application for Polar Environment (DemoGRAPE), in partnership with Politecnico di Torino, Istituto Superiore Mario Boella, and with South African National Space Agency and the Brazilian National Institute of Space Physics, as key collaborators. DemoGRAPE is a new prototype of support for the satellite navigation in Antarctica. Besides the scientific interest, the accuracy of satellite navigation in Antarctica is of paramount importance since there is always the danger that people and vehicles can fall into a crevasse during a snowstorm, when visibility is limited and travel is restricted to following specified routes using satellite navigation systems. The variability of ionospheric delay and ionospheric scintillation are two of the primary factors which affect the accuracy of satellite navigation. The project will provide a demonstrator of cutting edge technology for the empirical assessment of the ionospheric delay and ionospheric scintillations in the polar regions. The scope of the project includes new equipment for the recording and dissemination of GNSS data and products installed at the South African and Brazilian bases in Antarctica. The new equipment will facilitate the exchange of software and derived products via the Cloud computing technology infrastructure. The project portal is accessible at www.demogrape.net. We report the first Global Navigation Satellite System (GNSS) signal scintillations observed in Antarctica.

The role of SANSA's geomagnetic observation network in space weather monitoring: A review

AbstractGeomagnetic observations play a crucial role in the monitoring of space weather events. In a modern society relying on the efficient functioning of its technology network such observations are important in order to determine the potential hazard for activities and infrastructure. Until recently, it was the perception that geomagnetic storms had no or very little adverse effect on radio communication and electric power infrastructure at middle‐ and low‐latitude regions like southern Africa. The 2003 Halloween storm changed this perception. In this paper we discuss the role of the geomagnetic observation network operated by the South African National Space Agency (SANSA) in space weather monitoring. The primary objective is to describe the geomagnetic data sets available to characterize and monitor the various types of solar‐driven disturbances, with the aim to better understand the physics of these processes in the near‐Earth space environment and to provide relevant space weather monitoring and prediction.

Modeling geomagnetically induced currents in the South African power transmission network using the finite element method

The data used for Figures 3–10 are available in the supporting information Table S1. The GIC data were obtained from the South African power utility, ESKOM. Interested per-sons could contact the authors for details of the current contact person at ESKOM. The results presented in this paper rely on the data collected at the HER and HBK observatories. We thank SANSA for supporting their operation and INTERMAGNET for promoting high standards of magnetic observatory practice (www.intermagnet.org). The research is supported by a grant from the South African National Space Agency (SANSA). We appreciate the contributions of David Oyedokun and Stefan Lotz of SANSA Space Science to the discussions on this paper

ZACUBE‐1 Space Weather Mission: Characterize the SuperDARN HF Radar Antenna Array at SANAE‐IV

Key Points SuperDarn characterization CubeSat mission