\n<\/p>\n
\t\t\t\t\t\t02\/04\/2024<\/span> The ESA\/NASA Solar Orbiter is approaching the closest point to the Sun in its current orbit. It is an important time for the mission\u2019s science activities, and the mission control team at ESA is constantly preparing for any possible problems the spacecraft might face as it swoops past our active and unpredictable star.<\/p>\n<\/p><\/div>\n<\/p><\/div>\n Mission control to Solar Orbiter. Come in Solar Orbiter\u2026<\/i><\/p>\n \u201cIt\u2019s our worst-case scenario,\u201d says flight controller Daniel Lakey. \u201cIf Solar Orbiter were to experience some major issue on board, and then we were unable to reestablish communications.\u201d<\/p>\n<\/p><\/div>\n Solar Orbiter\u2019s close approach to the Sun (‘perihelion’) is a period of peak scientific activity.<\/p>\n It requires flight control teams and flight dynamics experts at ESA\u2019s ESOC mission control centre to carry out a series of highly complex operations.<\/p>\n If something goes wrong during these activities, the spacecraft could auto-reset itself into \u2018safe mode\u2019.<\/p>\n In safe mode, the spacecraft\u2019s software restarts and only its most basic functions are reactivated. Teams\u00a0on Earth then work out what triggered the safe mode, solve the issue, and restart more advanced systems like scientific instruments.<\/p>\n A safe mode during perihelion would be particularly bad because of the severe impact on science operations during this busy period.<\/p>\n<\/p><\/div>\n Solar Orbiter also has less power available during perihelion as the intense heat requires it to tilt its solar arrays away from the Sun in order to avoid damage.<\/p>\n The spacecraft must be recovered as quickly as possible before science is lost, or worse, it runs out of power.<\/p>\n<\/p><\/div>\n \u201cThe Sun is so bright that even a basic Sun sensor\u00a0is enough to make sure that Solar Orbiter always knows where the Sun is and can always point its heat shield towards it. This sensor activates during safe mode and keeps the spacecraft\u2019s internal systems safe from the radiation emanating from our star,\u201d says Lakey.<\/p>\n \u201cSo, we know that Solar Orbiter will always point its \u2018front\u2019 towards the Sun. But to work out which way \u2018up\u2019 it is, we rely on star trackers.\u201d<\/p>\n The top priority for a spacecraft in safe mode is to point its communication antenna towards Earth and reestablish contact as soon as possible.<\/p>\n The star trackers switch on automatically during safe mode and the spacecraft uses them to recognise certain patterns of stars. It can then determine its orientation, and in which direction it should point its antenna to communicate with Earth.<\/p>\n \u201cBut if the star trackers fail to lock on to the right stars, or the recovery sequence is interrupted before they can be switched on, Solar Orbiter has no way of knowing where Earth is.\u201d<\/p>\n<\/p><\/div>\n To make the situation even more challenging, in safe mode, Solar Orbiter can only use its back-up communication antenna.<\/p>\n The back-up antenna can move \u2018up and down\u2019 in one axis, but not \u2018left and right\u2019 in the other. This prevents a number of potential complications, but it also means the whole spacecraft must rotate in order to point the antenna in certain directions.<\/p>\n The solution is \u2018strobing\u2019 \u2013 if Solar Orbiter ever finds itself in safe mode and unable to locate Earth, it will begin to roll around one axis while keeping its heat shield pointed safely at the Sun.<\/p>\n \u201cIn strobing mode, Solar Orbiter emits a signal with a special \u2018tone\u2019 \u2013 a beacon in the darkness of space,\u201d says Lakey.<\/p>\n \u201cEventually, this signal will sweep across Earth. As soon as we detect it at one of our ground stations, we can assess the situation, work out what caused the safe mode and carry out our problem solving and recovery operations.\u201d<\/p>\n That\u2019s the theory, anyway. During Solar Orbiter\u2019s four years in space, it has never had to rely on a strobing recovery \u2013 and it has never been tested in flight.<\/p>\n Until now.<\/p>\n<\/p><\/div>\n The teams at ESOC used a recent period of low communication delay with Solar Orbiter to test whether they are ready to handle a real strobing recovery.<\/p>\n \u201cWe began to spin Solar Orbiter around and see if we could detect the beacon\u00a0from the back-up, antenna,\u201d says Lakey. \u201cWe preloaded commands to return to normal operations in case we failed to detect it, so there was never any risk to the spacecraft.\u201d<\/p>\n<\/p><\/div>\n The recovery tests were a success. The teams confirmed that they could detect Solar Orbiter’s emergency beacon and identify the status of the spacecraft in the event of a safe mode with malfunctioning star trackers.<\/p>\n These are the first vital steps in regaining control of the spacecraft and demonstrated the team\u2019s readiness for this critical but unlikely scenario.<\/p>\n \u201cWe also successfully tested our ability to communicate with the satellite in particularly tricky situations, such as when its own heat shield partially obscures the antenna\u2019s view of Earth.\u201d<\/p>\n<\/p><\/div>\n This is just one of hundreds of potential issues that our teams dream up and plan for every day. ESA\u2019s missions are unique one-of-a-kind spacecraft: they may face problems that no other spacecraft ever has.<\/p>\n There are few similar examples to learn from, and few established procedures to follow. It\u2019s essential to test our spacecraft recovery operations in space and for the teams on Earth to practice them when they have a good opportunity.<\/p>\n \u201cWe\u2019ll never stop thinking about new challenges that our missions could face,\u201d says Lakey. \u201cOr about how we would overcome them.\u201d<\/p>\n<\/p><\/div>\n
\n\t\t\t\t77<\/span> views<\/small><\/span>
\n\t\t\t\t\t\t\t\t\t\t2<\/span> likes<\/small><\/span><\/p>\n<\/header>\nIn brief<\/h2>\n
In-depth<\/h2>\n<\/div>\n
\n\t\t\t\t\t\t\t\t<\/figcaption><\/figure>\n
\n\t\t\t\t\t\t\t\t<\/figcaption><\/figure>\nThe stars guide the way<\/h2>\n
Spinning into control<\/h2>\n
\n\t\t\t\t\t\t\t\t<\/figcaption><\/figure>\n