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Extra-close oppositions of Mars happen every 15 to 17 years, when we pass between Mars and the Sun around the time of its perihelion (closest point to the Sun in orbit). The minimum distance between Earth and Mars has been declining over the years, and in 2003 the minimum distance was 55.76 million km, nearer than any such encounter in almost ...
Thus the orbital period in low orbit depends only on the density of the central body, regardless of its size. So, for the Earth as the central body (or any other spherically symmetric body with the same mean density, about 5,515 kg/m 3, [2] e.g. Mercury with 5,427 kg/m 3 and Venus with 5,243 kg/m 3) we get: T = 1.41 hours
A mission could have a period of 365 days in a year, a few weeks each month, [6] a few weeks every 26 months (e.g. Mars launch periods), [7] or a short period time that won't be repeated. A launch window indicates the time frame on a given day within the launch period that the rocket can launch to reach its intended orbit.
The length of time for Mars to complete one orbit around the Sun in respect to the stars, its sidereal year, is about 686.98 Earth solar days (≈ 1.88 Earth years), or 668.5991 sols. Because of the eccentricity of Mars' orbit, the seasons are not of equal length.
The ECI reference frame is not truly inertial because of the slow, 26,000 year precession of Earth's axis, so the reference frames defined by Earth's orientation at a standard astronomical epoch such as B1950 or J2000 are also commonly used. [2]: 24
For a mission between Earth and Mars, for example, these launch windows occur every 26 months. A Hohmann transfer orbit also determines a fixed time required to travel between the starting and destination points; for an Earth-Mars journey this travel time is about 9 months.
The previous record of people in orbit was set in May 2023, when for a brief period of time there were 17 people aboard both the International Space Station and China’s Tiangong space station.
Earth/Mars transfer time (days) Notes 1 1 2.135 2.23 146 Aldrin cycler 2 2 4.27 2.33 158 2 3 4.27 1.51 280 Aphelion inside semi-major axis of Mars orbit 3 4 6.405 1.89 189 3 5 6.405 1.45 274 Aphelion inside semi-major axis of Mars orbit 3 5 6.405 1.52 134 Aphelion inside semi-major axis of Mars orbit 4 5 8.54 1.82 88 4 6 8.54 1.53 157