Solar conjunction
Solar conjunction occurs when a planet
A planet is a celestial body orbiting a star or stellar remnant that is massive enough to be rounded by its own gravity, is not massive enough to cause thermonuclear fusion, and has cleared its neighbouring region of planetesimals.The term planet is ancient, with ties to history, science,...

 or other solar system
Solar System
The Solar System consists of the Sun and the astronomical objects gravitationally bound in orbit around it, all of which formed from the collapse of a giant molecular cloud approximately 4.6 billion years ago. The vast majority of the system's mass is in the Sun...

 object is on the opposite side of the sun
The Sun is the star at the center of the Solar System. It is almost perfectly spherical and consists of hot plasma interwoven with magnetic fields...

 from the Earth
Earth is the third planet from the Sun, and the densest and fifth-largest of the eight planets in the Solar System. It is also the largest of the Solar System's four terrestrial planets...

. From an Earth reference, the object will pass between the sun and the Earth. Communication with any spacecraft
A spacecraft or spaceship is a craft or machine designed for spaceflight. Spacecraft are used for a variety of purposes, including communications, earth observation, meteorology, navigation, planetary exploration and transportation of humans and cargo....

 in solar conjunction will be severely limited due to the sun's interference on radio transmissions from the spacecraft. There is also a risk that an antenna equipped with auto-tracking will begin following the suns movements instead of the satellite once they are no longer inline with each other. This is because the Sun acts as a large electromagnetic noise generator which creates a signal much stronger than the satellite's tracking signal. When in reference to Satellite Communications, solar conjunction occurs when the sun is directly in line with an orbiting Satellite and the terrestrial receiving station.

The term can also refer to the passage of the line of sight to an interior planet (Mercury
Mercury (planet)
Mercury is the innermost and smallest planet in the Solar System, orbiting the Sun once every 87.969 Earth days. The orbit of Mercury has the highest eccentricity of all the Solar System planets, and it has the smallest axial tilt. It completes three rotations about its axis for every two orbits...

 or Venus) being very close to the solar disk. If the planet passes directly in front of the sun, a solar transit
Astronomical transit
The term transit or astronomical transit has three meanings in astronomy:* A transit is the astronomical event that occurs when one celestial body appears to move across the face of another celestial body, hiding a small part of it, as seen by an observer at some particular vantage point...

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