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upstart writes in with an IRC submission:

Expect the Unexpected: Solar Orbiter to Pass Through the Tails of Comet ATLAS:

ESA's Solar Orbiter will cross through the tails of Comet ATLAS during the next few days. Although the recently launched spacecraft was not due to be taking science data at this time, mission experts have worked to ensure that the four most relevant instruments will be switched on during the unique encounter.

Solar Orbiter was launched on February 10, 2020. Since then, and with the exception of a brief shutdown due to the coronavirus pandemic, scientists and engineers have been conducting a series of tests and set-up routines known as commissioning.

The completion date for this phase was set at June 15, so that the spacecraft could be fully functional for its first close pass of the Sun, or perihelion, in mid-June. However, the discovery of the chance encounter with the comet made things more urgent.

Serendipitously flying through a comet's tail is a rare event for a space mission, something scientists know to have happened only six times before for missions that were not specifically chasing comets. All such encounters have been discovered in the spacecraft data after the event. Solar Orbiter's upcoming crossing is the first to be predicted in advance.

[...] Solar Orbiter is equipped with a suite of 10 in-situ and remote-sensing instruments to investigate the Sun and the flow of charged particles it releases into space – the solar wind. Fortuitously, the four in-situ instruments are also perfect for detecting the comet's tails because they measure the conditions around the spacecraft, and so they could return data about the dust grains and the electrically charged particles given off by the comet. These emissions create the comet's two tails: the dust tail that is left behind in the comet's orbit and the ion tail that points straight away from the Sun.

[...] One of those challenges was that the instruments seemed unlikely to all be ready in time because of the commissioning. Now, thanks to a special effort by the instrument teams and ESA's mission operations team, all four in-situ instruments will be on and collecting data, even though at certain times the instruments will need to be switched back into commissioning mode to ensure that the 15 June deadline is met.

Journal Reference:
Geraint H. Jones, Qasim Afghan, Oliver Price. Prospects for the In Situ detection of Comet C/2019 Y4 ATLAS by Solar Orbiter Research Notes of the AAS 5 May 2020 (DOI: https://events.infovaya.com/presentation?id=70027)

Original Submission