Search

The regional coverage satellite constellations are in demand for fulfilling earth observation needs of specific user regions of interest as opposed to global coverage thus enhancing the revisit period for the area. In this paper, we present a few key mission aspects of the regional coverage constellation designed and operated by the Indian Space Research Organization (ISRO) in low earth orbit. ISRO developed three X-Band Synthetic Aperture Radar (SAR) Earth Observation satellites and placed them in three inclined orbit planes to enhance the Indian region's coverage. This is India's first inclined orbit constellation designed for remote sensing applications in low earth orbit. The satellites were built around a standard bus carrying a Synthetic Aperture Radar payload with a deployable Radial Rib Antenna (RRA). They were designed to achieve a high agility capability. As SAR sensors are capable of all-weather, day, and night imaging; thus, most suitable in inclined orbits where the illumination conditions vary continuously for imaging. Though the inclined orbits provide more revisit opportunities to the region of interest, their characteristics pose challenges in mission design and operations. Though the mission design and planning involved a host of elements, this paper brings out the details of a few key mission analysis elements, planning aspects and operations that were critical in the course of various mission phases. The mission analysis included mission-specific requirements like launch windows selection for the constellation and reference attitude generation specific to inclined orbit geometry. Mission planning had to take care of Radial Rib Antenna (RRA) deployment requirements which were very critical for the mission, apart from taking care of individual subsystem requirements. The SAR payload data product quality and targeting accuracy are very sensitive to the satellite image point range (vis-a-vis SAR operation data window). Extensive post-launch calibration activity was carried out to meet all these mission requirements and data product specifications. The challenge was in fixing the payload beam alignment and fixing the uncertainties in onboard and ground computations. The paper also describes the methods of fixing all possible error sources affecting the high-resolution SAR payload performance. • The regional coverage satellite constellations are in demand for area targets coverage. • Inclined orbit constellations are more suitable for regional coverage using SAR sensors. • Mission operations plans need to consider all the specific requirements of spacecraft systems. • Pre-launch and post -launch calibrations of sensors is mandatory for achieving system performance. [ABSTRACT FROM AUTHOR]

Secondary and High School students are usually adolescents, most of them in the urban areas and metropolitan cities are aware about the existence, various opportunities, career paths and advancements of the space industry. They are constantly updated, given they have access to quality and organized education models and a competitive environment. Although, the students in the rural areas who are equally ambitious and talented yet are not fortunate enough to have access to the state of art facilities like the counterparts. Even if they try and gain access with their self-interest, they do not have the motivation to sustain the passion, given their lack of clarity in subject, lack of awareness about engaging in various ways and fields in space other than technological related and mainly lack of driving force. The purpose of this paper is to develop and present an education model, exclusively for the high school students of the rural areas and inculcate sustainable passion for space. As opposed to the primary school students, the secondary school students have a consciousness of the space industry. This paper will talk about various plans and strategies, that will allow them to gain exposure, guide them about the existence of different career paths which are not entirely technological related, yet are still essential in the space like, administrative framework for example. This opens a new dimension in their brain helping them realize how they can be part of the industry in countless ways, and this shall assist them in being on the right track to space. In addition to, hosting creative space themed exhibitions, fun and engaging model design competitions, workshops, all of these would widen their knowledge boundaries and help them challenge their skills. A real time case study example from a school located in the rural southern of India shall be focused on this paper. Including data from a survey thereby the results, with action plans shall be presented in detail, which will aid in the analysis of the need, feasibility, and long-term sustenance of this approach and the requirement to scale it over different rural areas globally. • Need for improvised education models in rural areas elucidated, with data collection. • Data analysis and correlation of space education awareness, for high school students across two geographical locations. • Readily executable action plans age groupwise, for real-time education models in remote areas globally. [ABSTRACT FROM AUTHOR]

This paper explores from the view of the data recipient and user the complexities of creating a common licensing scheme for the access and use of satellite earth observation (EO) data in international disaster management (DM) activities. EO data contributions in major disaster events often involve numerous data providers with separate licensing mechanisms for controlling the access, uses, and distribution of data by the end users. A lack of standardization among the terminology, wording, and conditions within these licenses creates a complex legal environment for users, and often prevents them from using, sharing and combining datasets in an effective and timely manner. It also creates uncertainty among data providers as to the types of licensing controls that should be applied in disaster scenarios. This paper builds from an ongoing comparative analysis of the common and conflicting conditions among data licenses that must be addressed in order to facilitate easier access and use of EO data within the DM sector and offers recommendations towards the alignment of the structural and technical aspects of licenses among data providers. [ABSTRACT FROM AUTHOR]

The range error caused by ionospheric delay in Global Positioning System (GPS) signals is currently the main factor that affected the positioning accuracy and navigation determination. Ionospheric modeling and optimization of its range error is a practical approach to improve the GPS positioning accuracy. The global ionospheric models are mostly unable to predict ionospheric delay corrections over the India region due to the Equatorial Ionization Anomaly (EIA)/fountain effect and lack of equatorial/low latitude GPS stations data. This paper proposes a method to facilitates regional ionospheric delay corrections based on the Adjusted Spherical Harmonic Function (ASHF) model by considering fewer coefficients into the algorithm. The ionospheric correction is driven with low-resolution harmonics coefficients with order ≤2 (≤9 coefficients), and coefficients are estimated with the Modified Gram-Schmidt (MGS) approach. The performance of the proposed model (ASHF) is compared with the Spherical Harmonic Function and Klobuchar models. Preliminary results reveal that the low-resolution ASHF model improved the ionospheric time delay corrections by 12.98% relative to the Klobuchar model. The results could be useful in the context of ionospheric time delay modeling for regional navigation satellite systems. • Estimation of ionospheric delays is proposed based on Orthogonal Dimensionality Reduction. • Model outcomes are assessed by comparing with the Weighted Least Square estimations. • The SVD-SHF method improves the accuracy of the model results in geomagnetic storm conditions. • The SVD-SHF method resulted in dimensional reduction and low computational load. • The outcomes suggest that the model implementation is used for GNSS and surveying applications. [ABSTRACT FROM AUTHOR]

Ionospheric modeling across the Indian low latitudes continues to be a challenging task because of the day-to-day variability pertaining to the underlying complex equatorial and low latitude electrodynamics. In this paper, we aimed at developing an ionospheric Total Electron Content (TEC) model based on Singular Spectrum Analysis (SSA) using the Global Positioning System (GPS)-TEC observations (from 2009 to 2019) at Bengaluru (Geographic: 13.02° N, 77.57° E; Dip Angle: 13.77° N), a low latitude station in India. SSA has the most significant advantage of extracting information from the noisy time-series data with the first-four SSA modes in the decomposition, almost converging to total variance of about 99%. The proposed SSA-TEC model has been assessed by comparing it with the GPS-TEC observations as well as the outcomes from the latest version of the International Reference Ionosphere model (IRI-2016) and International GNSS Services Global Ionosphere Maps (IGS-GIM). The results demonstrate excellent outcomes with the Root Mean Square Error (RMSE) values between observed and model estimations laying at 1.58 TECU (SSA), 7.04 TECU (IRI-2016), and 8.89 TECU (GIM) with the respective correlation coefficients 0.99, 0.91, and 0.94. The model outcomes are in good agreement with the GPS-TEC observations, presenting relatively better estimates of TEC than the IRI-2016 and GIM during the geomagnetically quiet and disturbed daytime and nighttime conditions under different seasons and solar activity. Moreover, the proposed SSA-TEC model replicates the significant changes and time distribution characteristics of the ionosphere over the low latitude location, foreseeing the scopes for its regional implementation with a wide range of operations. • Ionospheric TEC model is proposed based on Singular Spectrum Analysis (SSA). • Model outcomes is assessed by comparing with the GPS-TEC, IRI and GIM estimations. • Excellent model outcomes are achieved with low RMSE and high correlations. • A decent agreement with GPS-TEC is seen even during geomagnetic storm conditions. • The outcomes suggest a regional model implementation for near-realtime operations. [ABSTRACT FROM AUTHOR]

Global Navigation satellite systems (GNSS) are predominantly affected by Ionospheric space weather. The GNSS signal delays due to ionospheric Total Electron Content (TEC) can be forecasted using advances in the emerging mathematics tools and algorithms. Machine learning algorithms such as Gaussian Process Regression (GPR) is considered in the present paper to implement in the forecasting of low-latitude ionospheric conditions. The GPS receiver data is obtained for 8 years (2009–2016) during 24th solar cycle from International GNSS Services (IGS) station located in Bengaluru (Geographical latitude: 12.97° N, Geographical longitude: 77.59° E), India. The performance of GPR model is validated using statistical parameters such as Mean Absolute Error (MAE), Mean Absolute Percentage Error (MAPE), Mean Square Error (MSE), Root Mean Square Error (RMSE), and correlation coefficient. The results of the proposed GPR model were compared with the Auto Regressive Moving Average (ARMA) model and Artificial Neural Networks (ANN) model during solar maximum period and descending phase of 24th solar cycle. The experiment results are evident that GPR model is significantly providing the promising results in forecasting the ionospheric time delays for GNSS signals. The outcome of the work can be useful to develop web based Ionospheric TEC forecasting system to alert the GNSS users. • The GPS-TEC variability is investigated during solar maximum period and descending phase of 24th solar cycle. • The performance of ARMA, ANN and GPR models are evaluated in forecasting the ionospheric delays for GPS signals. • GPR model has better predicted TEC than the existing ARMA and ANN models during geomagnetic quiet and storm periods. • Kernel-based approach of GPR model is well suitable to forecast the ionospheric TEC variations over low latitudes. [ABSTRACT FROM AUTHOR]

Abstract: This paper describes the attitude control schemes for the various phases such as acquisition, on-orbit, orbit maneuver, de-boost maneuvers and coast phases of the India''s first recovery mission Space Capsule Recovery Experiment-I (SRE-1). During the on-orbit phase, the SRE was configured to point the negative roll axis to Sun. The attitude referencing of SRE-1 was based on dry tuned gyros with updates from the attitude determined using on-board Sun sensors and magnetometer. For attitude acquisition, attitude maneuvers and for providing the velocity corrections for de-orbiting operations; a set of eight thrusters grouped in functionally redundant blocks were used. The control scheme with thrusters was based on proportional derivative controller with a modulator. In order to ensure micro-gravity environment during the on-orbit payload operations a linear quadratic regulator (LQR) based control scheme was designed to drive an orthogonal configuration of magnetic torquers which in turn produced three-axis control torque with the interaction of Earth''s magnetic field. Proportional derivative control scheme with modulator was designed to track the steering commands during the velocity reduction as well as during the coasting phase of the de-orbiting operations. A novel thruster failure detection, isolation and reconfiguration scheme implemented on-board for the de-orbiting phase is also discussed in this paper. [Copyright &y& Elsevier]

Abstract: With an array of Indian Remote Sensing Satellites (IRS), a wide variety of national applications have been developed as an inter-agency effort over the past 20 years. Now, the capacity of the programme has been extended into the global arena and IRS is providing operational data services to the global user community. The recently launched IRS satellite, Resourcesat-1, was placed into perfect orbit by India''s PSLV and is providing valuable imaging services. Resourcesat-1 is actually like 3 satellites “rolled” into one, imaging a wide field of 710km area at 55m resolution in multispectral bands from the AWiFS, 23m resolution in a systematic 142km swath from four bands of the LISS-3 and the 5.8m multi-spectral images from the most advanced sensor—LISS-4. Yet another aspect of Resourcesat-1 is it that it marks a “watershed” in terms of a quantum jump in technological capability that India has achieved compared to past missions. The mission has many newer features—the advanced imaging sensors, the more precise attitude and orbit determination systems, the satellite positioning system onboard, the mass storage devices and many other features. This mission has led IRS into a new technological era, and when combined with the technological capability of the forthcoming Cartosat missions, India would have developed technologies that will take us into the new generation of EO satellites for the coming years. This paper provides a detailed description of the Resourcesat-1 mission. From the applications point of view, Resourcesat-1 will open up new avenues for environmental monitoring and resources management—especially for vegetation assessment and disaster management support. The monitoring capability of this mission is also extremely important for a number of applications. The mission has global imaging and servicing capabilities and could be received through the Antrix-Space Imaging network, which markets Resourcesat-1 data worldwide. This paper also describes the applications potentials and global capabilities of the mission. Resourcesat-1 will have continuity and after that a new generation system will provide enhanced and more unique imaging services. Actually, India has a 25 years strategy for EO and a perspective of the same is also described in this paper. [Copyright &y& Elsevier]

Abstract: The mission of the COMPASS-1 picosatellite is to take pictures of the earth, to validate a space-borne GPS receiver developed by the German Aerospace Center, and to verify the proper operation of the magnetic attitude control system in orbit. The spacecraft was launched on April 28, 2008 from the Indian space port Sriharikota, as part of the PSLV-C9 world record launch that simultaneously brought ten satellites into orbit. The mission operations were carried out from the ground stations in Aachen and Tainan. Arising difficulties in the communication link were overcome with the support of individuals from the amateur radio community. After several months of mission operation, abundant housekeeping and mission data has been commanded, received and analyzed and is presented in this paper. [ABSTRACT FROM AUTHOR]

Abstract: Indian space programme, whose objectives involve acceleration of economic and social development through applications of space technology, has been engaged in the development of state-of-the-art satellite systems, launch vehicles and equipment necessary for applications. Even during the early phase of evolution of this Programme, deliberate policies have been adopted by the national space agency, namely, Indian Space Research Organisation (ISRO), to promote spin-off benefit from the technologies developed for the use of space projects. Consistently adhering to this policy, ISRO has transferred over 280 technologies till date, spanning a wide spectrum of disciplines. This has resulted in a fruitful two-way cooperation between a number of SMEs and the ISRO. In order to make the technology transfer process effective, ISRO has adopted a variety of functional and organizational policies that included awareness building measures, licensee selection methods, innovative contract systems, diverse transfer processes, post licencing services and feedback mechanisms. Besides analyzing these policies and their evolution, the paper discusses various models adopted for technology transfer and their impact on assessment. It also touches upon relevant issues relating to creating interface between public funded R&D and the private commercial enterprises. It suggests few models in which international cooperation could be pursued in this field. [ABSTRACT FROM AUTHOR]

Abstract: India’s first Moon mission Chandrayaan-1 carrying eleven scientific instruments for the purpose of expanding scientific knowledge about the Moon was launched on 22 October 2008. The spacecraft was put into Moon’s polar, circular orbit of about (100×100)km on 12 November 2008 by carrying out a sequence of Earth bound and Lunar bound maneuvers. Precise orbit determinations are carried out during each phase of the mission using tracking data collected from network of tracking stations configured for the mission. The determined orbital solutions are used for spacecraft navigation, mission planning and science data processing. ISRO’s operational orbit determination program (ODP) used for low earth missions was suitably updated and validated before the launch of Chandrayaan-1. The purpose of this paper is to describe the methodology and the performance of Chandrayaan-1 orbit determination system during initial phase of the mission along with achieved orbit determination accuracy in the early normal phase. [ABSTRACT FROM AUTHOR]

Abstract: Over past four decades Indian space programme has systematically acquired capabilities in space technologies and implemented its programmes with a high level of focus on societal applications. It is developed into a multi-dimensional programme where its strategy is directed towards diverse stake holders and actors such as government, users and beneficiaries including general public, industrial suppliers as well as customers, academia and other space agencies/international organisations. Over the next five years, the Indian space programme has charted an ambitious set of policies and programmes that aim to enhance impacts on society. The major task is to enlarge and diversify the services delivered to a large section of population affected by income, connectivity and digital divides. While efficacy of application of space based systems have been proven in several fields such as tele-education, water resources management, improving productivity of land and out reaching quality health services and others, the crux of the problem is to evolve sustainable and scalable delivery mechanisms on a very large scale and extending over large geographical areas. Essentially the problem shifts from being predominately a technology problem to one of a composite of economic, cultural and social problems. Tackling such problems would need renewal of policies relating to commercial as well as public service systems. Major programmatic initiatives are planned in the next five years involving new and upgraded technologies to expand services from space to fill the gaps and to improve economic efficiency. Thrust is also given to science and exploration mission beyond Chandrayaan-1 and some initial steps for the participation in human space flight. This paper discusses the policy and strategy perspectives of the programmes planned by Indian Space Research Organisation over next five years. [Copyright &y& Elsevier]

Abstract: India has established a ‘critical mass’ in terms of EO infrastructure for disaster management. Starting from IRS 1A in 1980s to the most recent CARTOSAT-2, India''s EO series of satellites are moving away from the generic to thematic constellations. The series of RESOURCESAT, CARTOSAT, OCEANSAT and forthcoming Radar Imaging Satellite (RISAT) satellites exemplifies the thematic characters of the EO missions. These thematic constellations, characterized with multi-platform, multi-resolution and multi-parameter EO missions, are important assets for disaster reduction. In the more specific term, these constellations in conjunction with contemporary EO missions address the critical observational gaps in terms of capturing the catastrophic events, phenomena or their attributes on real/near real time basis with appropriate spatial and temporal attributes. Using conjunctively the data primarily emanating these thematic constellations and all weather radar data from aerial platform and also from RADARSAT as gap-fillers has been a part of India''s EO strategy for disaster management. The infrastructure has been addressing the observational needs in disaster management. The high resolution imaging better than one-meter spatial resolution and also Digital Elevation Models (DEM) emanating from Cartosat series are providing valuable inputs to characterize geo-physical terrain vulnerability. Radar Imaging Satellite, with all weather capability missions, is being configured for disaster management. At present, the current Indian EO satellites cover the whole world every 40h (with different resolutions and swaths), and the efforts are towards making it better than 24h. The efforts are on to configure RESOURCESAT 3 with wider swath of 740km with 23m spatial resolution and also to have AWiFS type of capability at geo-platform to improve the observational frequencies for disaster monitoring. India''s EO infrastructure has responded comprehensively to all the natural disasters the country has faced in the recent times. As a member of International Charter on Space and Major Disasters, India has also been instrumental in promoting the related UN initiatives viz., RESAP of UN ESCAP, SPIDER of UN OOSA, Sentinel Asia of JAXA initiative and also of GEOSS initiative. The paper intends to illustrate India''s EO strategy for disaster reduction. [Copyright &y& Elsevier]

Abstract: The Indian Space capsule (SRE-1) launched aboard PSLV-C7 rocket, was recovered successfully in the Bay of Bengal on January 22, 2007 after its orbital sojourn of 12 days. Apart from serving as a platform for micro-gravity experiments, SRE-1 demonstrated ISRO''s capability in the field of orbital reentry and recovery technologies. Satish Dhawan Space Centre (SDSC SHAR), the Spaceport of India was given the prime responsibility of assessment of mission risk, formulation and execution of safety plans and procedures, design and conduct of trials for validating the mission-critical sub-systems as well as the physical recovery of the capsule. To achieve these objectives, a number of drop tests were designed and conducted by SDSC SHAR involving real time computer network, ground-based tracking and telemetry stations, communication systems, safety and material handling systems, target identification and recovery systems. Dissemination of relevant information and coordination with multiple external organizations such as Indian Coast Guard, Indian Air Force and Indian Navy is an important aspect of these experiments. This paper delineates the methodologies designed and implemented at SDSC SHAR for validating those critical systems whose functionality finally culminated in the success of the mission, enabling India to join the elite group of nations with reentry module recovery capability. [Copyright &y& Elsevier]

Abstract: The operational Indian space transportation system provides launch support for the entire range of remote sensing and communication satellites up to 2.5t, giving precise orbital injection. In order to meet the national requirements of launching heavier payloads as well as to reduce the launch cost, long-term technology developments have been initiated. This paper delineates briefly the plans for future developments in respect of advanced launch transport systems and facilities. [Copyright &y& Elsevier]

Abstract: The Indian Space Research Organization (ISRO) recognizes the importance of the current space debris scenario, and the impact it has on the effective utilization of space technology for the improvement in the quality of life on the Earth. ISRO is committed to effective management of the threats due to space debris. Towards this commitment ISRO works on different aspects of space debris, including the debris mitigation measures. This paper highlights the activities and achievements in the implementation of the mitigation measures. ISRO successfully designed and developed a propellant venting system for implementation in the existing upper stage of India''s Polar Satellite Launch Vehicle (PSLV), which uses Earth-storable liquid propellants. GSLV also employs passivation of the Cryogenic Upper Stage at the end of its useful mission. ISRO''s communication satellites in GSO are designed with adequate propellant margins for re-orbiting at the end of their useful life to a higher graveyard orbit. A typical successful operation in connection with INSAT-2C is described. ISRO developed its debris environmental models and software to predict the close approach of any of the debris to the functional satellites. The software are regularly used for the debris risk management of the orbiting spacecraft and launch vehicles. ISRO recognizes the role of international cooperation in the debris mitigation measures and actively contributes to the efforts of the Inter-Agency Space Debris Coordination Committee (IADC) and United Nations Committee on the Peaceful Uses of Outer Space (UNCOPUOS). [Copyright &y& Elsevier]