National Space Organization Research Articles

Эмпирическая модель электронной плотности в условиях низкой геомагнитной активности в индийской экваториальной F-области

In this paper, we present a quiet day empirical model of electron density (Ne) for the Indian equatorial zone at an altitude of 500 km. The model is applicable to all levels of solar activity and is based on the observation that the electron density in the F-region of the Indian zone is correlated with the F10.7 cm solar flux at each local time and in every month. Using this characteristic, we describe the model for electron density. In this model, we have used the least square fit and the polynomial fit. The electron density measured by the Retarding Potential Analyzer (RPA) on board the SROSS C2 satellite from 1995 to 2000 and FORMOSAT-1 (ROCSAT-1) satellite, operated by the National Space Organization (NSPO, now the Taiwan Space Agency (TASA)) of the Republic of China (Taiwan), from 1999 to 2004 is used to derive the relationship between Ne and F10.7. The average altitudes of SROSS-C2 and FORMOSAT-1 are 500 km and 600 km respectively. Due to this height difference, the observed data obtained by FORMOSAT-1 is normalized to match the SROSS-C2 data. The model is compared with the observations and is found to be in good agreement with them. It is applicable to quiet (Ap<15) conditions and is limited to a fixed altitude of 500 km within the latitude range of 10° S to 10° N around the 75° E meridian.

Эмпирическая модель электронной плотности в условиях низкой геомагнитной активности в индийской экваториальной F-области

In this paper, we present a quiet day empirical model of electron density (Ne) for the Indian equatorial zone at an altitude of 500 km. The model is applicable to all levels of solar activity and is based on the observation that the electron density in the F-region of the Indian zone is correlated with the F10.7 cm solar flux at each local time and in every month. Using this characteristic, we describe the model for electron density. In this model, we have used the least square fit and the polynomial fit. The electron density measured by the Retarding Potential Analyzer (RPA) on board the SROSS C2 satellite from 1995 to 2000 and FORMOSAT-1 (ROCSAT-1) satellite, operated by the National Space Organization (NSPO, now the Taiwan Space Agency (TASA)) of the Republic of China (Taiwan), from 1999 to 2004 is used to derive the relationship between Ne and F10.7. The average altitudes of SROSS-C2 and FORMOSAT-1 are 500 km and 600 km respectively. Due to this height difference, the observed data obtained by FORMOSAT-1 is normalized to match the SROSS-C2 data. The model is compared with the observations and is found to be in good agreement with them. It is applicable to quiet (Ap<15) conditions and is limited to a fixed altitude of 500 km within the latitude range of 10° S to 10° N around the 75° E meridian.

Introduction of TROPS ionospheric TEC products for FORMOSAT-7/COSMIC-2 mission

Six low Earth orbit (LEO) satellites were launched on June 25th, 2019 for a radio occultation (RO) mission for the FORMOSAT-7/COSMIC-2 (F7/C2) program. The GPS and GLONASS RO signals received by these F7/C2 satellites can be used to retrieve atmospheric and ionospheric parameter profiles for atmospheric and ionospheric research. In order to process the received RO signal, the processing system named Taiwan Radio Occultation Processing System (TROPS) is built. TROPS is developed by National Space Organization, Taiwan Analysis Center for COSMIC, and GPS Science and Application Research Center in Taiwan. The ionospheric products of TROPS are electron density profile, ionospheric scintillation index (S4 index), and absolute total electron content (TEC). S4 index has been calculated on board the satellites and other two products are retrieved by TROPS after the observation data downlink to ground. TEC is the linear integration of electron density along the signal propagation path. The electron density profile is retrieved from the relative TEC when the elevation angle of GNSS satellite is negative from F7/C2 satellite. The absolute TEC is the TEC from GNSS satellite to F7/C2 satellite. The difference between absolute and relative TEC is the TEC with/without differential code bias (DCB) correction. Currently, the data for the electron density profile and absolute TEC are provided by TROPS. Users can obtain the products freely from the internet. In this study, the retrieval method and the preliminary F7/C2 ionospheric TEC products retrieved by TROPS are presented in detail.

Compact Scintillator Array Detector (ComSAD) for Sounding Rocket and CubeSat Missions

The development of CubeSats and more frequent launch chances of sounding rockets are a total game changer to the space program, and it allows us to build space instruments that are technologically feasible and affordable. Therefore, it gives us a good opportunity to build a small cosmic-ray detector which has capabilities to measure the flux, direction, and even energy of cosmic rays at an altitude above the limitation of balloon experiments, and it may open a new door for building a constellation of detectors to study cosmic-ray physics. Compact Scintillator Array Detector (ComSAD) is a funded sounding rocket mission of Taiwan’s National Space Organization. In this paper, we present the concept, design, and performance of ComSAD which is also suitable for future CubeSat missions.

From GPS Receiver to GNSS Reflectometry Payload Development for the Triton Satellite Mission

The global positioning system (GPS) receiver has been one of the most important navigation systems for more than two decades. Although the GPS system was originally designed for near-Earth navigation, currently it is widely used in highly dynamic environments (such as low Earth orbit (LEO)). A space-capable GPS receiver (GPSR) is capable of providing timing and navigation information for spacecraft to determine the orbit and synchronize the onboard timing; therefore, it is one of the essential components of modern spacecraft. However, a space-grade GPSR is technology-sensitive and under export control. In order to overcome export control, the National Space Organization (NSPO) in Taiwan completed the development of a self-reliant space-grade GPSR in 2014. The NSPO GPSR, built in-house, has passed its qualification tests and is ready to fly onboard the Triton satellite. In addition to providing navigation, the GPS/global navigation satellite system (GNSS) is facilitated to many remote sensing missions, such as GNSS radio occultation (GNSS-RO) and GNSS reflectometry (GNSS-R). Based on the design of the NSPO GPSR, the NSPO is actively engaged in the development of the Triton program (a GNSS reflectometry mission). In a GNSS-R mission, the reflected signals are processed to form delay Doppler maps (DDMs) so that various properties (including ocean surface roughness, vegetation, soil moisture, and so on) can be retrieved. This paper describes not only the development of the NSPO GPSR but also the design, development, and special features of the Triton’s GNSS-R mission. Moreover, in order to verify the NSPO GNSS-R receiver, ground/flight tests are deemed essential. Then, data analyses of the airborne GNSS-R tests are presented in this paper.

IDEASSat: A 3U CubeSat mission for ionospheric science

The Ionospheric Dynamics Exploration and Attitude Subsystem Satellite (IDEASSat/ INSPIRESat-2) is a three-unit (U) CubeSat developed with the objective of providing in-situ measurements of the Earth’s ionosphere in order to quantify both global scale ionospheric variability and small scale irregularities. The science payload is the Compact Ionospheric Probe (CIP) - an all in one in-situ plasma sensor developed at Taiwan National Central University (NCU), which is the miniaturized version of the larger Advanced Ionospheric Probe (AIP) that is carried and operational aboard the 450 kg FORMOSAT-5 spacecraft. The spacecraft has been developed by NCU in partnership with the International Satellite Program in Research and Education (INSPIRE) consortium, and is funded by the Taiwan National Space Organization (NSPO), Ministry of Science and Technology, and Ministry of Education as part of the first national effort to encourage small satellite development at Taiwan universities. The development of IDEASSat offers students a hands-on opportunity to learn about space science and technology and will work in conjunction with FORMOSAT-5 and INSPIRESat-1 to provide ionospheric observations spanning different altitudes and local times. The IDEASSat spacecraft subsystems are a combination of commercial off the shelf (COTS) and self-developed components designed by NCU in partnership with other INSPIRE member universities. IDEASSat is expected to be launched in late 2020. In this report, we describe the IDEASSat mission and spacecraft design, as well as unique lessons learned as part of the development process.

Toward the Most Accurate Thermometer in Space: FORMOSAT-7/COSMIC-2 Constellation

FORMOsa SATellite mission-2/Constellation Observing System for Meteorology, Ionosphere, and Climate mission-2 (FORMOSAT-7/COSMIC-2) is a Taiwan-U.S. collaborative mission between the National Space Organization of Taiwan and the National Oceanic and Atmospheric Administration (NOAA) of the United States. The mission aims to collect more than 4000 global navigation satellite system radio occultation (RO) sounding profiles at low- and middle-latitude regions every day with 30-minute data latency. The satellite constellation consists of six small satellites with each one having a weight of 300 kg. The satellites are planned be launched in 2019 to bridge the potential FORMOSAT-3/COSMIC (launched in April 2006) RO data gap and improve accuracy of the severe weather forecast. The raw data is free for users around the world to download. The advantage of constellation observation is to provide the capability to sense large amounts of data simultaneously across different parts of the globe. Through the deployment of a constellation of satellites, data users can obtain geographically homogenous distributed measurements for space weather and atmospheric weather estimation. This article presents an overview of the FORMOSAT-7/COSMIC-2 constellation mission, its impacts, and technical challenges of the spacecraft design.

Spectroscopic Diagnostic of Halos and Elves Detected From Space‐Based Photometers

AbstractIn this work, we develop two spectroscopic diagnostic methods to derive the peak reduced electric field in transient luminous events (TLEs) from their optical signals. These methods could be used to analyze the optical signature of TLEs reported by spacecraft such as Atmosphere‐Space Interactions Monitor (European Space Agency) and the future Tool for the Analysis of RAdiations from lightNIngs and Sprites (Centre National d'Études Spatiales). As a first validation of these methods, we apply them to the predicted (synthetic) optical signatures of halos and elves, two types of TLEs, obtained from electrodynamical models. This procedure allows us to compare the inferred value of the peak reduced electric field with the value computed by halo and elve models. Afterward, we apply both methods to the analysis of optical signatures of elves and halos reported by Global LIghtning and sprite MeasurementS (Japan Aerospace Exploration Agency) and Imager of Sprites and Upper Atmospheric Lightning (National Space Organization) spacecraft, respectively. We conclude that the best emission ratios to estimate the maximum reduced electric field in halos and elves are the ratio of the second positive system of N2 to first negative system (FNS) of N , the first positive system of N2 to FNS of N and the Lyman‐Birge‐Hopfield band of N2 to FNS of N . In the case of reduced electric fields below 150 Td, we found that the ratio of the second positive system of N2 to first positive system of N2 can also be used to reasonably estimate the value of the field. Finally, we show that the reported optical signals from elves can be treated following an inversion method in order to estimate some of the characteristics of the parent lightning.

Extraction of Archaeological Information Using High Resolution FormoSAT-2 Data

This paper investigates the potential use of the high resolution FormoSAT-2 sensor for supporting archaeological research. Although satellite remote sensing data have been widely used in the context of archaeological research, the high-resolution FormoSAT-2 dataset has attracted little attention. For a better understanding of the Neolithic habitation of the Thessalian plain in central Greece, the authors have used a variety of remote sensing techniques, including satellite and in situ data. In situ spectroradiometric measurements have been recalculated based on the Relative Response Filters of the FormoSAT-2 sensor and compared with other medium- and high-resolution sensors. The FormoSAT-2 spectral characteristics tend to give similar results with the Landsat 5 TM and 7 ETM+ sensors during the whole phenological cycle of the crops, which make this ideal for pan-sharpening fusion techniques. As we found, FormoSAT-2 data can be sufficiently used for the documentation of tells (locally called magoules) in the area as well as to reconstruct the current landscape of the area. Results presented here are part of the ISPRS WG VI/5 “Archaeo-FORMOSAT” project, sponsored by the National Space Organization, National Applied Research Laboratories (NARLabs-NSPO) and jointly supported by the Chinese Taipei Society of Photogrammetry and Remote Sensing and the Center for Space and Remote Sensing Research (CSRSR) at the National Central University (NCU) of Taiwan.

Space programs in Taiwan

Taiwanʼs current and future space programs are briefly introduced in this paper. The National Space Organization (NSPO) in Taiwan has successfully carried out three satellite programs (FORMOSAT-1, 2, &3) since its establishment in 1991. FORMOSAT-1 is a scientific satellite performing three scientific experiments for measuring the density, velocity and temperature of ionospheric plasmas, taking the ocean color image, and conducting Ka-band communication experiments. Equipped with a 2m ground resolution remote sensing instrument, FORMOSAT-2 operates in a sun-synchronous orbit with revisit time equal to one day. This unique feature of the daily revisit capability is significantly useful for post disaster assessment and environmental monitoring. FORMOSAT-2 also carries a scientific payload “Imager of Sprites and Upper Atmospheric Lightning (ISUAL)”. ISUAL provides the worldʼs first long-term satellite observations on the lighting phenomenon in the earthʼs upper atmosphere. FORMOSAT-3 is a constellation of six micro-satellites to collect atmospheric and ionospheric data for weather prediction and for climate, ionosphere, and geodesy research. FORMOSAT-3 has demonstrated the ability to significantly increase the accuracy of weather forecasting by utilizing the GPS Radio Occultation (GPS-RO) technique. Currently, NSPO is pursuing the follow-on space missions of FORMOSAT-5 and FORMOSAT-7. FORMOSAT-5 will be the first to utilize a CMOS detector on a high-resolution earth-observation camera. FORMOSAT-7 is a joint mission of Taiwan/US to deploy a 12-satellite constellation operational system to provide dense and timely GNSS RO data to the global communities for real-time weather forecast as well as space science research.

Development of a Web-based Satellite Telemetry Interface and Command Editing System

”FORMOSAT” is a serial satellite projects which are developed and operated by National Space Organization (NSPO) of Taiwan and co-designed with other international space industry. The objective of the recent satellite projects is to incubate and promote the technology of the domestic industry and academic institutes in designing, developing and manufacturing for the space and satellite sciences. In this paper, a prototype of web-based satellite telemetry processing interface and command editing operation system are designed and proposed for the next generation of NSPO satellite ground station. According to the proposed satellite ground operation system, the improvement in the efficiency and intuition of satellite operation can be expected. The implementation provides a user with the interactive web page for issuing commands to the web server/ground station/satellite through Internet, and displaying telemetry for analysis and visualization. This prototype may act as an add-on module or be integrated into the current NSPO ground station after further assessment.

Effect of orbit inclination on the performance of FORMOSAT-3/-7 type constellations

This paper investigates the effect of orbit inclination angle on the performance of the Formosa satellite number 3 (FORMOSAT-3 or FS3) and FORMOSAT-7 (FS7) type constellations. The FS3 developed by National Space Organization (NSPO) of Taiwan was launched on 15 April 2006. It is a constellation consisting of 6 microsatellites at 72° orbit inclination and 800km altitude for the acquisition of the global positioning system (GPS) signal occultation data. The international space community has given very positive comments on the contribution of FS3. Therefore, NSPO is planning the future program and designates FS7 to be the follow-up of FS3. There are two major indexes to assess the performance of FS3/7 type constellations: maximization of daily data acquisition and evenness in global data distribution. From system simulation, the number of data acquisition of FS3 is 2415. However, the number can be increased to 3050 by changing the orbit inclination to 154°. The drawback is that there is no data beyond 45° latitude north/south. After trade-off, it has been found that the optimal configuration is a 3–2–1 combination with 3 satellites deployed at 154° inclination, 2 satellites at 108° and 1 satellite at 90°. Daily data acquisition is 2924 using this configuration. For readers′ information, the 3–2–1 configuration could probably be called the “hybrid constellation” because it is not a standard one like the “Walker” or “Draim” or “Ballard” constellations.

Towards International Cooperation and Capacity Building between Space Agencies: A Case of GISTDA and NSPO

Geo-Informatics and Space Technology Development Agency (GISTDA) firmly believes in the synergy of international cooperation and capacity building and is always on a quest to build global knowledge partners. Keeping in mind the growing trend of international cooperation, GISTDA and the National Space Organization (NSPO) of Taiwan will enter into a cooperation agreement that will develop space system engineering in Thailand. The cooperation aims to promote technical activities, human resources development as well as infrastructure development in both countries. Several cooperative activities had already been initiated according to the work plan and an In-flight Systems Engineering Technical Assistance (SETA) has also been drawn up and agreed upon by both the agencies. The SETA encompasses the area of satellite operation, satellite and ground maintenance, anomaly handling, instrument calibration and satellite life extension assessment. The execution procedure and budget planning has been taken into consideration and the allotment of resources, both time and money, are planned for. GISTDA has also proposed the timeframe for personnel exchanges and training program to NSPO and the work plan will be put into action as soon as the areas are mutually agreed upon. The paper shall discuss the entire project plans divided into phases with major concentration on the e-aspect of the cooperation. Online training, remote system management and satellite data transfer over the Research and Education Network (REN) for emergency and educational purposes are but a few of the strategic areas covered in this cooperation. Mutual cooperation between the two agencies will help facilitate mission-critical agendas with no visible shortcoming. The paper shall also set precedent for future cooperation between international agencies and discuss how cost saving is achieved with the application of communication technologies.

Suborbital and low-thermospheric experiments using sounding rockets in Taiwan

The suborbital flight is a kind of flight, which reaches the space and then comes back to ground without completing one orbital revolution. The atmospheric thermosphere extends from 85 km to 600 km in altitude. Therefore, the suborbital and low-thermospheric experiments to be performed at altitude below 300 km can be combined using the sounding rocket. These experiments include rocket staging, fairing separation, ultrasonic flight, reentry, aerobrake and recovery test, ultraviolet and ionization observations, ozone measurement, etc. The advent of Taiwan's sub-orbital and thermospheric experiments project can be traced back to 1997. This is the year Taiwan's National Space Organization (NSPO) was assigned to be responsible for procuring the sounding rocket for applications in science experiments and space technology research effort. From 1997 to 2010, 8 launches have been completed including one experimental hybrid rocket. All onboard instruments and sensors for sub-orbital and low-thermospheric experiments are developed and integrated by the domestic universities. More launches have been planned in the future. Opportunities for international cooperation in developing new instruments and payloads for future experiments will be possible.

Orbital maneuver and keeping of FORMOSAT-2

This paper presents the orbital maneuver (OM) and keeping of FORMOSAT-2 (or FS2, Formosa Satellite #2) since its launch on 20 May 2004. The successful launch put FS2 in a sun-synchronous parking orbit with 729.94km perigee and 743.31 apogee. Taiwan’s National Space Organization (NSPO) then spent 11 days to perform the first orbital maneuver (OM#1) and raised FS2 to its sun-synchronous circular mission orbit at 888.47km altitude. Due to various kinds of disturbances, FS2’s orbit shifts gradually but constantly. Therefore, four times of OM had been performed for orbital keeping. Details of all 5 OMs are described.

Mission Results from FORMOSAT-3/COSMIC Constellation System

[Abstract] The FORMOSAT-3/COSMIC spacecraft constellation consisting of six LEO satellites is the world’s first operational GPS radio occultation mission. The mission is jointly developed by Taiwan’s National Space Organization (NSPO) and United States’ UCAR in collaboration with NASA’s Jet Propulsion Laboratory and Naval Research Laboratory for three onboard payloads including GPS Occultation Receiver (GOX), TriBand Beacon (TBB), and Tiny Ionospheric Photometer (TIP). The FORMOSAT

FORMOSAT-3/COSMIC Constellation Spacecraft System Performance: After One Year in Orbit

The FORMOSAT-3 mission, also known as constellation observing system for meteorology, ionosphere, and climate (COSMIC), is the third major project of the Formosa satellite (FORMOSAT) series implemented by the National Space Organization of Taiwan. FORMOSAT-3/COSMIC is a joint Taiwan/U.S. mission consisting of six identical low Earth orbit satellites. All six cluster satellites were successfully launched by a single Minotaur launch vehicle on April 15, 2006. The retrieved Global Positioning System (GPS) radio occultation (RO) data have been freely available online to the science community since shortly after the completion of satellite bus in-orbit checkout. Having completed the verification and validation, the worldwide science communities are highly satisfied with the RO data. Scientists have hailed the RO sensors as offering the most accurate, precise, and stable thermometers in space. After one year in orbit, all six FORMOSAT-3/COSMIC satellites were in good condition (except FM2, which had power shortage issues) and were on their way toward the final constellation of six separate orbit planes with 30 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">deg</sup> separation. Four out of six satellites had already reached their final mission orbit of 800 km by mid-May 2007. Together, the six satellites have generated a total of more than 2500 RO data per day. However, only 50%-70% of the RO data as received one year after launch could be retrieved into useful atmosphere profiles. The retrieved RO data, about 1800 per day on average, have been assimilated into numerical weather prediction models by many major weather forecast centers and research institutes. This paper provides an overview of the constellation mission, the spacecraft system performance after one year in orbit, the technical challenges we have encountered, and the performance enhancements we have accomplished.

Constellation Deployment for the FORMOSAT-3/COSMIC Mission

The FORMOSA Satellite Series No. 3/Constellation Observing System for Meteorology, Ionosphere and Climate (FORMOSAT-3/COSMIC) spacecraft constellation consisting of six low-earth-orbiting satellites is the world's first operational Global Positioning System (GPS) radio occultation mission. The mission has been jointly developed by the National Space Organization of Taiwan and the University Corporation for Atmospheric Research of the U.S. in collaboration with the Jet Propulsion Laboratory, NASA, and the Naval Research Laboratory for three onboard payloads, including a GPS Occultation Receiver, a triband beacon, and a tiny ionospheric photometer. The FORMOSAT-3/COSMIC mission was successfully launched from Vandenberg into the same orbit plane of the designated 516-km circular parking orbit altitude on April 15, 2006. After the six satellites completed the in-orbit checkout activities, the mission was started immediately at the parking orbit for in-orbit checkout, calibration, and experiment of three onboard payloads. Individual spacecraft thrust burns for orbit raising were performed to begin the constellation deployment of the satellites into six separate orbit planes. All six FORMOSAT-3/COSMIC satellites are maintained in a good state of health except spacecraft flight model no. 2, which has had power shortages. Five out of the six satellites had reached their final mission orbits of 800 km as of November 2007. This paper provides an overview of the constellation spacecraft design, constellation mission operations, constellation deployment timeline evolution, associated spacecraft mass property and moment of inertia results, orbit-raising challenges, and lessons learned during the orbit-raising operations.

Review and assessment of select US space security technology proposals

This paper reports on the feasibility of research and development related to select US military space weapons technology development plans. The proposals are presented in an international context where the USA is likely not alone in having aspirations to space warfare technology. China, Russia and France, among others, are just as likely to develop novel space weapons technology, with the concept of militarized outer space gradually being replaced by that of weaponized outer space. However, since the US programs have received more attention and were arguably in more advanced states of planning, if not development, this article will focus on US national security space management and organization proposals, investigating five key technology projects that have been pursued by the US government. These systems will be described in relation to the technical issues, engineering difficulties and physical limits involved. If appropriate, their implications will be linked to the political impact of these US plans and the likely reactions of the rest of the world, as other countries may answer the perceived threat inherent in the mere development of space weapons by emulating or outpacing US space militarization plans. While the USA arguably has more advanced weapons technology expertise, it will be shown that other countries have already deployed low-tech weapons in space applications, with less media attention.

Taiwan's second remote sensing satellite

FORMOSAT-2 is Taiwan's first remote sensing satellite (RSS). It was launched on 20 May 2004 with five-year mission life and a very unique mission orbit at 891 km altitude. This orbit gives FORMOSAT-2 the daily revisit feature and the capability of imaging the Arctic and Antarctic regions due to the high enough altitude. For more than three years, FORMOSAT-2 has performed outstanding jobs and its global effectiveness is evidenced in many fields such as public education in Taiwan, Earth science and ecological niche research, preservation of the world heritages, contribution to the International Charter: space and major disasters, observation of suspected North Korea and Iranian nuclear facilities, and scientific observation of the atmospheric transient luminous events (TLEs). In order to continue the provision of earth observation images from space, the National Space Organization (NSPO) of Taiwan started to work on the second RSS from 2005. This second RSS will also be Taiwan's first indigenous satellite. Both the bus platform and remote sensing instrument (RSI) shall be designed and manufactured by NSPO and the Instrument Technology Research Center (ITRC) under the supervision of the National Applied Research Laboratories (NARL). Its onboard computer (OBC) shall use Taiwan's indigenous LEON-3 central processing unit (CPU). In order to achieve cost effective design, the commercial off the shelf (COTS) components shall be widely used. NSPO shall impose the up-screening/qualification and validation/verification processes to ensure their normal functions for proper operations in the severe space environments.