ISO 16457 pdf download – Space environment (natural andartificial) —The Earth’s ionospheremodel -International referenceionosphere (IRI) model and extensions to the plasmasphere.
Radio signals, transmitted by modern communication and navigation systems, can be heavily disturbed by space weather hazards. Thus, severe temporal and spatial changes of the electron density in the ionosphere and plasmasphere can significantly degrade the signal quality of various radio systems which even can lead to a complete loss of the signal. Model-based products providing specific space weather information, in particular now- and fore-cast of the Ionospheric state, serve for improvement of the accuracy and reliability of impacted communication and navigation systems.
For high frequency radio communication, a good knowledge of the heights and plasma frequencies of the reflective layers of the ionosphere and the plasmasphere is critical for continuous and high-quality radio reception. High frequency communication remains of great Importance in many remote locations of the globe. The model helps to estimate the effect of charged partides on technical devices in the Earth’s environment and defines the ionosphere-plasmasphere operational environment for existing and future systems of radio communication, radio navigation, and other relevant radio technologies in the medium and high frequency ranges.
6 Applicability
There are a multitude of operational usages for ionospheric models, of which the most important are outlined In this clause. Operators of certain navigational satellite systems such as GPS (USA), GLONASS (Russia), BeiDou (China) and GALILEO (Europe)’) require ionospheric predictions to mitigate losses of navigation signal phase and/or amplitude lock, as well as to maintain accurate orbit determination for all Its satellites, Users of global navigation satellite systems need precise Ionospheric models to Increase the accuracy and to reduce the precise positioning convergence timelil”I. Radio and television operators using LF, MF, HF, VHF, UHF satellite or ground stations require ionospheric parameters for efficient communications and for reducing Interferences. Space weather forecasters have a great need for accurate ionospheric models to support their customers with reliable and up-to-the-minute space weather information. Ionospheric models are also used in the aeronautical and space system industries and by governmental agencies performing spacecraft design studies, Here the models help to estimate surface charging, sensor interference and satellite anomaly conditions.
Users also apply Ionospheric models to mitigate problems with HF communications, HF direction finding, radar clutter and disruption to ELF/VI.F communications with underwater vehicles. Insurance companies estimating the cost of protecting human health in space and satellites make use of Ionospheric models. Scientists using remote sensing measurement techniques In astronomy, biology, geology, geophysics and seismology require parameter estimates for compensating the effects of the ionosphere on their observations. An ionospheric model can be also used to evaluate tomographic, radio occultation, and other similar techniques, by provlthng the ground-truth background model for test runs. Amateur radio operators, as well as students and teachers in space research and applications. also use ionosphere parameters. This document may be also applied for ray-path calculations to assess the performance of a particular ground-based or space-borne system. Monthly medians of Ionospheric parameters are useful for HF circuit and service planning, while maps for individual days and hours aid frequency management and retrospective studies.
8 Model content and inputs
The IRI model uses a modular approach comblmng sub-models for the different parameters In different altitude and/or time regimes. Examples of such sub-models are:
— International Telecommunication Umon ITIJ-R (former CCIR) model for the F2 layer critical frequency ioF2 (directly related with the F2 peak electron density. in m) and for the propagation factor M(3000)F2 (inversely correlated with the peak height, in km)lll; IRI recommends use of the CCIR model above continental areas and recommends use of the LJRSI modelIl above ocean areas. because the URSI model produces better results than the CCIR model in these areas; Instead of the CCIR-recommended sunspot number IRI uses the global ionosphere index lG(l because it gives better results especially at high solar activities;
— COSPAR international reference atmosphere (C1RA model (NRL-MSlSE-OO(Ul) for the neutral temperature;
— STORM model for storm-time updating of the F2 layer peak densltyl9l;
— International geomagnetic reference field (IGRF) model of the International Association of Geornagnetism and Aeronomy (IAGA) for the magnetic coordinates (https://www.ngdc.noaa.gov/ IACA/vmud/).
The IRI model requires the following indices as input parameters:
— R12, the 1 2-month running mean of sunspot number R;
— FlO.7. the daily index and 81-day and 12-month running mean;
— lGl2. the 12-month running mean of global Ionosphere index IC;
— ap indices, the 3-hourly planetary magnetic indices for the prior 33 hotirs,
These indices can either be found automatically from the indices files that are included with the fRI software package and that are updated quarterly, or the user can provide his/her own input values for these indices. For R12 and lGl2. the indices file starts from January 1958 and include indices prediction for one to two years into the future. For ap index, the values start from january 1960 and include no predictions.
ISO 16457 pdf download – Space environment (natural andartificial) —The Earth’s ionospheremodel -International referenceionosphere (IRI) model and extensions to the plasmasphere
