Sophie Adenot posts on ISS beta angles

ESA astronaut Sophie Adenot used a pair of “Sunday morning science” posts on May 24 to explain why daylight aboard the International Space Station does not always follow the familiar 45-minutes-of-day, 45-minutes-of-night rhythm. Adenot, posting from orbit during Expedition 74/75, described periods of “high beta angle” when the station’s orbital plane lines up differently with the Sun. In those periods, the balance between sunlight and eclipse shifts, changing how often the crew sees sunrise and sunset. Adenot said the station goes through about four such periods each year, each lasting seven to 10 days. ### What exactly was Adenot describing from orbit? Sophie Adenot said in her May 24 posts that a high beta angle period is tied to the geometry between the ISS orbit and the Sun. Her thread framed it as a recurring orbital condition rather than a one-off event, part of a continuing series of short science explainers she has been posting from the station. NASA technical material defines the solar beta angle as the angle between the ISS orbital plane and the direction to the Sun. (x.com) The amount of time the station spends in Earth’s shadow changes as that angle changes, according to NASA and the Alpha Magnetic Spectrometer’s operations page. ### Why does that change the day-night cycle on the ISS? (x.com) The ISS circles Earth about once every 90 minutes, which is why people often describe station life as alternating between day and night every 45 minutes. Adenot said that during the high beta angle periods she was discussing, those alternations become the defining pattern for several days at a time. The AMS operations page says the duration of nighttime on orbit depends on beta angle and that, at very high absolute values, the station can even stop entering eclipse altogether. (ntrs.nasa.gov) It says there is no nighttime when the absolute value of beta rises above about 70 degrees, a condition that occurs for roughly one week in summer and another week in winter. ### How often does the station go through these periods? (x.com) Adenot said the ISS experiences roughly four high beta angle periods per year, and that each one lasts about seven to 10 days. Her description matches broader technical references showing that the beta angle changes over both the annual cycle of Earth around the Sun and the roughly 60-day precession cycle of the ISS orbital plane. (ams02.space) The AMS experiment’s thermal operations page says those changing beta angles matter not only for lighting but also for spacecraft temperatures. At extreme beta angles, it says, some parts of the station environment can remain in continuous sunlight while others stay shaded, creating large temperature differences. ### Who is Sophie Adenot, and where is she posting from? Adenot is a French astronaut with the European Space Agency and is serving as a flight engineer on Expedition 74 after arriving at the ISS with NASA’s SpaceX Crew-12 mission in February 2026. (x.com) CNES says her ISS mission is called Epsilon and began with the Crew-12 launch on February 13, 2026, followed by arrival on February 14. (ams02.space) NASA’s Expedition 74 page lists Adenot among the current crew, and a NASA station blog on May 21 said she had been working with Jessica Meir, Jack Hathaway and Chris Williams on newly delivered science experiments. ESA’s biography says Adenot studied spacecraft and aircraft flight dynamics at ISAE-SUPAERO and later completed a master’s degree in human factors engineering at MIT. (cnes.fr) ### Where can readers follow the rest of the explainer series? Adenot’s May 24 posts indicate the beta-angle explanation was part of a multi-episode “Sunday morning science” thread on X. Her current mission continues aboard the ISS as part of Expedition 74, which NASA says runs until summer 2026, and CNES says her Epsilon mission is planned for about nine months. (x.com) (nasa.gov)