Conjunction

The Conjunction between planets - when they are mutually closest - occurs when the inner, faster planet laps the outer, slower one.

From any outer planet's viewpoint, astronomy technicians talk of conjunction between that planet and the Sun. These have rated such, "inferior" and "superior": based on distance from said outer planet. For instance when Earth and Venus are closest, with the Sun behind Venus, Earth talks of Inferior Conjunction. Mars, by contrast, never gets between the Earth and the Sun: every 780 days Mars's "superior conjunction" is physical Opposition, and Mars/Earth physical conjunction happens at midnight 390 days after that.

Venus has only Mercury and maybe a Hilda Cycler and the odd "vulcan" asteroid within its orbit. (Like 2019 AQ3.) Otherwise, it sees a solar "conjunction" with any planet as always Superior. Venus prefers to think of Conjunction as proximity to those planets, themselves, facing them with the sun at its back. This goes especially with regards to sister Earth. So Venus will term "superior-conjunction" as Opposition.

As a result, in this future, I expect such now-redundant and ever-confusing terms like "superior conjunction" to be relegated to the history books... and good riddance.

Hohmann from outside to inside is designed, exactly, to push cargo from the outer planet when the inner planet is still behind, that the inner planet might catch up to that trajectory. Therefore the day of [inferior] conjunction falls on the near exact halfway point of a downward Hohmann, depending on the two planets' eccentricity and mutual angle.

RETROSPECT 1/3/2021: Mutual angle is a definite thing for Earth/Venus. Relative to Earth, Venus' conjunctions repeat on a five-synod cycle. This "metonic" is almost eight Earth years. 3 June is this post's year's; best hurry up for 5 March launch synod D, counting from Venera 8 in 1972 and indeed from the June occultations 2004 and 2012. [AS OF 2021: We're coming up to synod E.] "Superior" / opposition marks the halfway point (in-metonic: four Earth years) for such Hohmanns as don't get to Venus; we will be seeing D's trash floating by Earth about mid/late 2023, on its way to SVL3 anticthon.

For Venus-Earth, I'm currently unable to look at the 2220s; but for this post's purpose, we're better off looking at earlier windows anyway as being more accurate. So let's take the conjunction 13 August 2023. In Clowder's chart this falls eight weeks after the Venus-Earth transfer leaves 15 June (to get to Earth 9 November), eight weeks before Earth-Venus transfer (16 May) arrives 10 October. The whole span from Carnivale to Arrival Day is the best time for direct interplanetary communications. In fact Advent should start on Conjunction... OFFSET 11/5/2020: ... by which point non-crew passengers have already jumped off to join their Hohmann caravan.

Opposition during "ordinary time" falls halfway between outer planet visitor arrival, and the next Hohmann departure from said planet (on Venus, Carnivale).