Radio waves, medium for communication between spacecraft and the ground control, travel at about 300,000 kilometers per second, the same speed of light. You may think it is very fast, but it is not necessarily so given the vastness of cosmic space. During travel, Asteroid Explorer "Hayabusa2" was as far away as up to 350 million kilometers from the Earth, a distance for a radio wave to take about 20 minutes to travel. Assuming that you send an order to "Hayabusa2" at this position from the ground control at 12:00 to take photography of asteroid Ryugu, the order will arrive at the destination after 20 minutes, at 12:20, then, you will receive the photography sent back in immediate response to the order, after another 20 minutes at 12:40. This means that the back-and-forth communication with "Hayabusa2" involves a total of up to 40 minutes of time lag.

The early universe immediately after the Big Bang was filled with free traveling elementary particles, which did not bind together under high-temperature high-density "fireball" conditions. In this state, photons (light) could not propagate freely because of prevailing electrons standing in the way, resulting in a cloudy, opaque cosmos. About 380,000 years later, however, a change occurred in this situation. As the universe was expanding and cooling down, electrons and protons began to attract each other to bind together, thus reducing the number of free electrons. This brought about a clear, transparent cosmos allowing free propagation of photons. Photons enabled to travel freely in this process can be observed in the present cosmic microwave background (CMB) radiation, a source of information on the earliest state of the universe.

Storm-like phenomena are observed to take place in the universe. A solar storm is one type of such phenomena. It is a disturbance on the Sun, most notably caused by solar flares, a large explosion on the solar surface. This often triggers a solar particle event where charged particles are emitted by the Sun to the surrounding space, which may reach the vicinity of the Earth, depending on the location and size of the flare, and affect radio communication. It takes two days on average for emitted particles to reach the Earth. Solar Physics Satellite "HINODE", JAXA-led solar observation project, aims to clarify mechanisms of explosive events occurring on the Sun and predict impact such event may have on the Earth.

Mercury Exploration Mission "BepiColombo" is an international cooperation project between Japan and Europe for Mercury exploration. Mercury has been elusive from scientific research in the past, making it dubbed as a "mysterious planet," while some of its basic characteristics are known, including the body being one of the Solar System's two planets that have magnetic fields, with the remaining being the Earth. The BepiColombo mission plans to perform a comprehensive study on the near-Earth planet by observing its magnetic fields, atmosphere, surface and interior, with a view to illuminating the origin and evolution of terrestrial planets. The mission will deploy two observation probes, which are designed to repeatedly perform swing-by maneuvers, a gravity-assisted orbit and velocity control technique, in order to reduce fuel consumption, before entering the orbit of Mercury in December 2025, seven years after the launch.

Imagine that the Earth and other planets in the Solar System are orbiting around the Sun. The view you have in mind may be showing the Earth turning around the stationary Sun. In fact, however, the Sun also orbits around the center of the Milky Way galaxy, at the rate of approximately 220 kilometers per second, taking about 200 million years to make a full circle. The star has completed 23 orbits over the past 4.6 billion years since its birth.

The Sun generates a vast amount of energy from nuclear fusion of hydrogen in its core, the source of bright radiation. The Sun will continue to burn the internal hydrogen for 12 billion years since its birth until the "fuel" runs out about 7 billion years from now. After this, the star will shed its outer layers and become a stellar core remnant known as a white dwarf, slowly cooling down and gradually stopping shining. It is interesting that stars with larger amounts of fuel (hydrogen) have a shorter lifespan.

Astronaut WAKATA Koichi holds an all-time record for the total duration time spent in space by a single Japanese astronaut. He has made four space flights in the past, spending in space a combined total of 347 days 8 hours 33 minutes, a period of nearly one year. In his last long-duration mission on the ISS in 2014, he served as commander, becoming the first-ever Japanese astronaut to undertake the role. His next, and fifth space flight is scheduled for the fall of 2022 or later, when he will break his own record.

Astronaut HOSHIDE Akihiko holds an all-time high for the total duration time spent by a single Japanese engaging in extravehicular activity (EVA). In September 2021, he carried out his fourth EVA mission, primarily to replace power switchboards of the ISS. With the mission completed, the combined total hours he spent engaging in EVA reached 28 hours 17 minutes, a record high set by a single Japanese astronaut.

Global Change Observation Mission-Climate "SHIKISAI" (GCOM-C) is equipped with a sensor capable of recognizing a total of 19 different types of visible and invisible light, including ultraviolet and infrared rays. The sensor monitors atmospheric aerosol distributions, appearance and temperature of land and ocean surfaces, soil moisture content, among other global conditions, for various purposes, such as understanding the climate change situation, planning disaster control measures, enhancing fishery, agriculture, and other industrial activities. Moving in a low-Earth orbit at an altitude of 800 kilometers, GCOM-C updates overall observations basically about once every two days, demonstrating its capabilities for high-frequency monitoring and high-resolution imaging.

The Greenhouse gases Observing SATellite "IBUKI" (GOSAT) was launched in 2009 to monitor the global distribution of carbon dioxide (CO2) and other greenhouse gas (GHG) concentrations from space, aiming to contribute to control of global warming. In those days, when there was no universal standard for measuring GHGs, "IBUKI" became the world's first satellite mission to introduce a universal tool for that purpose. This mission is in its 13th year and still in operation, becoming the world's longest-ever satellite to engage in observations based on the same original standards. Monitoring data over the past years indicate GHG concentrations increasing year by year.

The launched rocket climbs high into the sky with a roar. It feels like the launch event climaxes at this moment, which is wrong, however. The truth is, the rocket's major duties to complete the mission come after launch, specifically transporting satellites to outer space and inserting them into the target orbit. In common projects for insertion into heliosynchronous orbits or geostationary transfer orbits, successful satellite separation should be confirmed within around 30 minutes after liftoff. This is a critical duration of time to determine whether or not the years-long rocket project proves successful.

Satellite missions generally wish to secure as long a time as possible before launch to perform last-minutes duties, such as for adjustment and inspection. In order to meet such wishes, the Epsilon Launch Vehicle is equipped with automatic physical inspection systems to allow access to mounted satellites up to three hours before launch countdown, offering the world's highest-level convenience.