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\t\t\t\t\t\t17\/11\/2023<\/span> The space between Earth and Mars is usually buzzing with science data, telemetry and commands racing to and from almost a dozen missions at the Red Planet. But for roughly one and a half days this November, communication between the planets will fall silent as Mars passes behind the Sun.<\/p>\n<\/p><\/div>\n Solar conjunction for Mars occurs roughly once every 25 months. During conjunction, Mars is located on the opposite side of the Sun from Earth.<\/p>\n Around the time of conjunction, the radio signals used to send commands from Earth to the spacecraft and to receive signals from the spacecraft can be disturbed by the Sun\u2019s active atmosphere \u2013 the solar corona.<\/p>\n The period of time during which communications are significantly disturbed depends on the size and power of a Mars spacecraft\u2019s communication equipment, but typically takes place while the angle in the sky between the Sun and Mars as seen from Earth is within 3\u20134\u00b0.<\/p>\n In 2023, this period lasts from early November to early December.<\/p>\n<\/p><\/div>\n As a result of the disruption, mission controllers can\u2019t reliably send commands to, or receive data from their spacecraft.\u00a0Special precautions have to be taken.<\/p>\n For ESA\u2019s Mars Express and ExoMars Trace Gas Orbiter (known as MEX and TGO, because we enjoy our acronyms), this means \u2018uplinking\u2019 all the critical instructions the spacecraft would need to operate without any contact from Earth for the entire period. That\u2019s three or four weeks of commands when we normally send up only one week at a time.<\/p>\n Of course, these conjunctions also affect the missions of other space agencies \u2013 and this kind of thing isn\u2019t unique to Mars.<\/p>\n<\/p><\/div>\n Due to the disturbance from the Sun\u2019s atmosphere during conjunction season, we have to reduce the amount of data we exchange with MEX and TGO.<\/p>\n We cut the amount of data that we \u2018uplink\u2019 to MEX, for example, down from 2000 bits per second to just 250 and reduce the amount of data that MEX sends down to Earth to as little as 300 bits per second.<\/p>\n We also set our Estrack ground stations to maximum transmission power to make sure our spacecraft hears us loud and clear despite the disturbance, i.e., we use a louder voice but say fewer words.<\/p>\n This limits the kind of information that MEX can send to its operators on Earth to \u2018housekeeping\u2019 data \u2013 health status and telemetry \u2013 and is too low for MEX to send any science data.<\/p>\n Like a diver holding their breath, any data gathered by MEX\u2019s instruments during the conjunction period must be stored in the limited onboard memory until the period is over.<\/p>\n<\/p><\/div>\n Mars Express arrived at the Red Planet on 25 December 2003 and is one of Europe\u2019s longest-serving missions. The team celebrated 20 years since launch this summer with the first-ever live webcast from another planet.<\/p>\n This will be MEX\u2019s tenth solar conjunction and TGO\u2019s third. However, as the orbits of Mars and Earth have slightly different inclinations, Mars doesn\u2019t usually pass directly behind the Sun.<\/p>\n<\/p><\/div>\n The 2023 conjunction is unusual in that it will be the first time that Mars passes behind the disc of the Sun since the two ESA spacecraft arrived.<\/p>\n While Mars is behind the Sun, for roughly one and a half days on 17\u201318 November, communication with MEX and TGO won\u2019t just be limited, it\u2019ll be impossible.\u00a0<\/p>\n These windows of limited or impossible communication between Earth and Mars will pose a challenge for future human settlers, too.<\/p>\n<\/p><\/div>\n \u201cAt the beginning of the mission, the team was very cautious about conjunctions,\u201d says James Godfrey, Spacecraft Operations Manager for Mars Express. \u201cIf something goes seriously wrong during the conjunction period, it could be difficult to recover the spacecraft until it\u2019s over.\u201d<\/p>\n \u201cWe used to suspend all science operations. But, over the years, we\u2019ve only ever experienced minor disruptions.\u201d<\/p>\n \u201cIn 2019, we discovered that we can continue using some of MEX\u2019s instruments in a limited way, as long as all commands are uploaded before the season begins, and all science data are stored on board until the season ends.\u201d<\/p>\n \u201cOriginally, planning for conjunctions was a very manual process,\u201d says James Godfrey. \u201cBut over the years, it\u2019s become largely routine.\u201d<\/p>\n<\/p><\/div>\n Peter Schmitz, Spacecraft Operations Manager for Trace Gas Orbiter, adds: \u201cWith its larger communications antenna and data storage capacity, TGO is able to continue with its data relay activities for Mars surface assets throughout the conjunction period \u2013 even when Mars is directly behind the Sun \u2013 and prepare to downlink all of the stored data to Earth when it is once again safe to do so.\u201d<\/p>\n<\/p><\/div>\n
\n\t\t\t\t763<\/span> views<\/small><\/span>
\n\t\t\t\t\t\t\t\t\t\t28<\/span> likes<\/small><\/span><\/p>\n<\/header>\nTis the season for conjunction<\/h2>\n
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\n\t\t\t\t\t\t\t\t<\/figcaption><\/figure>\nGround stations to full power!<\/h2>\n
\n\t\t\t\t\t\t\t\t<\/figcaption><\/figure>\n<\/p><\/div>\nWhat makes the 2023 conjunction special?<\/h2>\n
\n\t\t\t\t\t\t\t\t<\/figcaption><\/figure>\n
\n\t\t\t\t\t\t\t\t<\/figcaption><\/figure>\nAre you worried?<\/h2>\n
\n\t\t\t\t\t\t\t\t<\/figcaption><\/figure>\n