Solar Orbiter Spacecraft Prepares for Festive Venus Flyby
Solar Orbiter is getting ready for the first of many gravity assist flybys of Venuson December 27, to start bringing it closer to the Sun and tilting its orbit in order to observe our star from different perspectives.
Just as the majority of us will remain safely at home under various COVID-19pandemic lockdown measures during what is traditionally a holiday period, the flyby – a routine event in the world of flying spacecraft – will also be monitored by the spacecraft operations managers remotely as well.
Closest approach will take place at 12:39 UTC (13:39 CET) on December 27, and will see the spacecraft fly some 7,500 km from the Venus cloud tops. Later flybys, from 2025, will see much closer encounters of just a few hundred kilometers.
During the upcoming flyby several in-situ science instruments – MAG, RPW and some sensors of EPD – will be switched on to record the magnetic, plasma and particle environment around the spacecraft as it encounters Venus. (It is not possible to take images of Venus during the flyby because the spacecraft must remain facing the Sun.)
In order to properly line up for the flyby, specialists from ESA’s ground stations and flight dynamics teams conducted a so-called ‘Delta-DOR’ campaign, using an advanced technique – Delta-Differential One-Way Ranging – to precisely determine the spacecraft’s position in space, and its trajectory.
In Delta-DOR, a set of widely separated ground stations on Earth are used to receive the spacecraft’s radio signals, giving a first result for its location. Then, this result is compared to locations of known stellar radio sources previously mapped by other missions, resulting in a corrected and ultra-precise final plot. The Delta-DOR technique allows operators to determine where a spacecraft is to within a few hundred meters, even at a distance of 100 million km.
As of December 17, Solar Orbiter is 235 million kilometers from Earth, and about 10.5 million from Venus. It takes about 13 minutes for signals to travel to (or from) the spacecraft.