• Demonstrate real-time shortwave propagation based on realistic space weather information.
  • Estimate and visualize shortwave propagation between any two points on the Earth selected by the user.
  • Web application-in-aid for shortwave broadcasting, aviation communications, amateur radio, etc.
The National Institute of Information and Communications Technology (NICT, President: TOKUDA Hideyuki, Ph.D.), in collaboration with Electronic Navigation Research Institute, National Institute of Maritime, Port and Aviation Technology (ENRI, Director General: FUKUDA Yutaka) and Chiba University (President: TOKUHISA Takeshi), has started the service of shortwave propagation simulator (HF-START). It provides real-time shortwave propagation that reflects real space weather information from ground-based observations and model calculations. The HF-START web system has been successfully developed and is now available at https://hfstart.nict.go.jp/.
The web calculation function of this system allows shortwave propagation between any two points in Japan based on real-time GNSS observations and between any two points on the Earth based on model-based space weather information. Real-time estimation is possible. The calculation in the past and up to about 1 day ahead in the future is also possible. In addition to amateur radio, HF-START is expected to benefit efficient frequency operation of aviation communications that relies on shortwave in the polar route.


Figure 1
Figure 1. Visualization of shortwave propagation by HF-START.
The radio wave propagation paths at 3, 6 and 9 MHz transmitted from Tokyo to Hokkaido, and from Tokyo to Kagoshima are shown. The radio propagation at 12 MHz is also calculated, but is not displayed because the 12 MHz does not reach the destination.
[Click picture to enlarge]
Communication and positioning technologies play an important role in social infrastructure in various fields today. The ionosphere has regular temporal cycles and fluctuates greatly every day associated with solar activity and space environment. Of benefit to us is the fact that ionosphere is good at refracting shortwave, which is why we can hop shortwave signals off the ionosphere to communicate with people over large distances. 
Shortwave band has been used for communication and broadcasting for a long time, and are still widely used in radio broadcasting, aviation communication, amateur radio, etc. Ionospheric variation, however, has a great influence on the propagation of radio waves. Communication environment such as the communication range and usable frequency changes significantly due to the influence of the ionospheric fluctuation. Thus, fluctuations in the ionosphere affect the operation of shortwave broadcasting, aviation communications, and amateur radio.
There have been websites that provide estimated information on how radio wave propagation changes due to such ionospheric fluctuations. The problem is that it is based on a simple model and does not reflect realistic ionospheric fluctuations.


We have developed a shortwave propagation simulator HF-START that estimates and provides shortwave propagation information in real-time under realistic ionospheric fluctuations based on ground-based observations and model calculations. We open real-time information estimated by HF-START, and the web application at https://hfstart.nict.go.jp/.
Figure 1 shows an example of visualization of shortwave propagation by HF-START. In this system, the user can check the radio wave propagation information that is updated in real-time. As shown in Figure 2, the user can also use the web application to estimate and visualize radio wave propagation by specifying any frequency in the range of 3-30 MHz, any two points on the Earth, and any transmission angle. The date and time can be set retroactively to the past (after 2016), to the real-time, and in the future (up to about 1 day ahead).
Figure 2
Figure 2. Input screen of the web calculation function
The user can set radio wave propagation conditions between arbitrary points.
The system can be used to visualize the radio propagation path and clarify whether it is affected by space weather when the shortwave you are using does not reach the destination, or when you can listen shortwave broadcasted from the far source that normally you cannot hear. Furthermore, in addition to amateur radio, it is expected to benefit efficient frequency operation of the aircrafts that use shortwave in polar route.

Future Prospects

We are conducting research and development to extend the HF-START to estimate radio wave propagation not only in the shortwave band but also in other frequency bands. In addition, we will evaluate the simulator accuracy and improve it by comparing it with radio wave propagation observations.
NICT has been providing information related to communications, satellite positioning, and radiation exposure since November 2019 as a member of the Global Space Weather Center of the International Civil Aviation Organization (ICAO). With the HF-START service, we expect to improve the information provided to directly relate to communications, such as communication range information.

Roles of each institution

NICT: Simulator development, comparison with observation, accuracy evaluation, real-time calculation of GAIA model, development and operation of the web system for information disclosure
ENRI: Real-time calculation of ionospheric 3D GNSS tomography, comparison with observation, accuracy evaluation
Chiba University: Expansion of simulator to global version, comparison with observation, accuracy evaluation

Article information

Title: HF-START: Application in Aid of Radio Communications/Navigation
Magazine: Electronic Navigation Research Institute (eds) Air Traffic Management and Systems III, Lecture Notes in Electrical Engineering, vol 555. Springer, Singapore, 2019
Authors: Kornyanat Hozumi1, Mamoru Ishii1, Susumu Saito2, Takashi Maruyama1, Hiroyuki Nakata3, Takuya Tsugawa1
Affiliation: 1 NICT, 2 ENRI, 3 Chiba University

Related past press release

・November 7, 2019
・January 16, 2020
Part of this research was carried out with the support of the Japanese Ministry of Education, Culture, Sports, Science and Technology's Grant-in-Aid for Scientific Research, "Project for Solar-Terrestrial Environment Prediction (PSTEP): Understanding the Universe We Live in and the Formation of a Social Infrastructure", 15H05813. In addition, it was partially supported by the Ministry of Internal Affairs and Communications commissioned work "0155-0133 Promotion of observation and analysis of radio wave propagation".


HF-START system released this time

HF-START (High Frequency Simulator Targeting for All-users' Regional Telecommunications) is a shortwave propagation simulator developed to meet the needs of space weather users for, but not limit to, telecommunications. There are two main functions.
Function ① Real-time information provision
It provides real-time information of shortwave propagation in Japan and oversea under fixed conditions.
Function ② Web calculation
This function allows the user to estimate and visualize radio wave propagation under the user-defined radio wave conditions. The user can specify any frequency in the range of 3-30 MHz, any two points on the Earth, and any transmission angle. 
The user can select three options of ionospheric electron density distribution.
(1) GNSS observation: 3-D real-time ionospheric tomography over Japan based on GNSS observations
(2) GAIA model: Ground-to-topside model of Atmosphere and Ionosphere for Aeronomy
(3) IRI model: Widely used International Reference Ionosphere model. (Function ② only):
The date and time can be set retroactively to the past (after 2016) for options (1), (2) and (3); to the real-time for options (1) and (2); and in the future (up to about 1 day ahead) for option (2).
By cooperating the real-time GNSS observations to the system, the estimated radio wave propagation can reflect realistic ionospheric fluctuations.
Figure 3
Figure 3. Main functions of the HF-START system

HF-START website

On the HF-START website (https://hfstart.nict.go.jp/), there are "Real-time Information", "Web Tool", and “What is “HF-START”?”.
Figure 4
Figure 4. HF-START top page


Space weather
Space weather is a natural phenomena that occur in the vicinity of the earth, including the ionosphere and magnetosphere, mainly due to solar activity. Space weather affects communication/broadcasting using HF radio and satellite, satellite-based navigation, operation of satellites and international space stations, etc.

Space weather phenomenon and its impact on society
Solar extreme ultraviolet (EUV) radiations photoionize the thermospheric neutral atmosphere leaving behind free electrons and positive ions surrounding the Earth. The partially ionized atmosphere is called the ionosphere. The ionosphere expands in an altitude range of 60 to 1,000 km, and is divided into the D, E, and F regions from its altitude distribution. The ionospheric electron density has regular temporal cycles such as daily and seasonal variations and the approximately 11-year cycle associated with solar activity. Radio waves used for communication and positioning, those are passing through the ionosphere and those are refracted by the ionosphere, are greatly affected by the ionospheric fluctuation.
Effects of ionospheric disturbances on radio wave propagation

Technical Contact

HOZUMI Kornyanat, TAO Chihiro
Space Environment Laboratory
Applied Electromagnetic Research Institute

Tel: +81-42-327-5005

E-mail: iono_atmark_ml.nict.go.jp

Media Contact

Press Office
Public Relations Department

E-mail: publicity_atmark_nict.go.jp