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TIL "The drag force on satellites increases during times when the Sun is active. When the Sun adds extra energy the atmosphere the low density layers of air at

by foota 4y ago

TIL "The drag force on satellites increases during times when the Sun is active. When the Sun adds extra energy the atmosphere the low density layers of air at LEO altitudes rise and are replaced by higher density layers that were previously at lower altitudes. As a result, the spacecraft now flies through the higher density layer and experiences a stronger drag force. When the Sun is quiet, satellites in LEO have to boost their orbits about four times per year to make up for atmospheric drag. When solar activity is at its greatest over the 11-year solar cycle, satellites may have to be maneuvered every 2-3 weeks to maintain their orbit [1]."

m4rtink 4y ago
This has also doomed Skylab - increased solar activity, increased atmospheric drag, pulling it down before the much delayed Shuttle could do something about it: https://en.wikipedia.org/wiki/Skylab#Solar_activity https://en.wikipedia.org/wiki/Skylab#Solar_activity
shagie 4y ago
This can be an issue and cause real losses. From much earlier this year: https://www.smithsonianmag.com/smart-news/solar-storm-knocks-40-spacex-satellites-out-of-orbit-180979566/ https://www.smithsonianmag.com/smart-news/solar-storm-knocks... These were still in the lower staging orbit and hadn't been moved up to where they would be in a final configuration. They're at that orbit so that if anything goes wrong, they burn up quickly... the geomagnetic storm made them burn up that much more quickly (days rather than a month or so). (edit - found it!) You can see the orbital history of a satellite at https://in-the-sky.org/spacecraft.php?id=44282 https://in-the-sky.org/spacecraft.php?id=44282 That was an early one... probably for testing. A recently launched one looks like https://in-the-sky.org/spacecraft.php?id=44713 https://in-the-sky.org/spacecraft.php?id=44713 You cases the initial insertion altitude, and then taking it up to 550 km where it remains operational. In trying to find the specific ones that burned up... https://in-the-sky.org/search.php?searchtype=Spacecraft&s=&startday=18&startmonth=11&startyear=2022&endday=30&endmonth=12&endyear=2032&ordernews=ASC&satorder=0&maxdiff=7&feed=DFAN&objorder=1&distunit=0&magmin=&magmax=&obj1Type=0&news_view=normal&distmin=&distmax=&satowner=0&satgroup=4&satdest=0&satsite=0&lyearmin=1957&lyearmax=2022&page=37 https://in-the-sky.org/search.php?searchtype=Spacecraft&s=&s... You can see that 03 Feb 2022 didn't have many that still have an Operational Status. Ahh! Found one... its the funny letter names that (likely) indicate the stack that they're sent up in. https://in-the-sky.org/spacecraft.php?id=51470 https://in-the-sky.org/spacecraft.php?id=51470
- foota 4y ago
  Really interesting, so it sounds like they want to be able to move up enough to dodge those times?
  - shagie 4y ago
    Exactly - the expanded atmosphere with a geomagnetic storm can "puff" up the atmosphere. https://www.nasa.gov/mission_pages/sunearth/news/solarstorm-power.html https://www.nasa.gov/mission_pages/sunearth/news/solarstorm-... > During the heating impulse, the thermosphere puffed up like a marshmallow held over a campfire, temporarily increasing the drag on low-orbiting satellites. This is both good and bad. On the one hand, extra drag helps clear space junk out of Earth orbit. On the other hand, it decreases the lifetime of useful satellites by bringing them closer to the day of re-entry.

by foota 4y ago

m4rtink 4y ago

This has also doomed Skylab - increased solar activity, increased atmospheric drag, pulling it down before the much delayed Shuttle could do something about it: https://en.wikipedia.org/wiki/Skylab#Solar_activity https://en.wikipedia.org/wiki/Skylab#Solar_activity

shagie 4y ago

This can be an issue and cause real losses. From much earlier this year: https://www.smithsonianmag.com/smart-news/solar-storm-knocks-40-spacex-satellites-out-of-orbit-180979566/ https://www.smithsonianmag.com/smart-news/solar-storm-knocks... These were still in the lower staging orbit and hadn't been moved up to where they would be in a final configuration. They're at that orbit so that if anything goes wrong, they burn up quickly... the geomagnetic storm made them burn up that much more quickly (days rather than a month or so). (edit - found it!) You can see the orbital history of a satellite at https://in-the-sky.org/spacecraft.php?id=44282 https://in-the-sky.org/spacecraft.php?id=44282 That was an early one... probably for testing. A recently launched one looks like https://in-the-sky.org/spacecraft.php?id=44713 https://in-the-sky.org/spacecraft.php?id=44713 You cases the initial insertion altitude, and then taking it up to 550 km where it remains operational. In trying to find the specific ones that burned up... https://in-the-sky.org/search.php?searchtype=Spacecraft&s=&startday=18&startmonth=11&startyear=2022&endday=30&endmonth=12&endyear=2032&ordernews=ASC&satorder=0&maxdiff=7&feed=DFAN&objorder=1&distunit=0&magmin=&magmax=&obj1Type=0&news_view=normal&distmin=&distmax=&satowner=0&satgroup=4&satdest=0&satsite=0&lyearmin=1957&lyearmax=2022&page=37 https://in-the-sky.org/search.php?searchtype=Spacecraft&s=&s... You can see that 03 Feb 2022 didn't have many that still have an Operational Status. Ahh! Found one... its the funny letter names that (likely) indicate the stack that they're sent up in. https://in-the-sky.org/spacecraft.php?id=51470 https://in-the-sky.org/spacecraft.php?id=51470

foota 4y ago
Really interesting, so it sounds like they want to be able to move up enough to dodge those times?
- shagie 4y ago
  Exactly - the expanded atmosphere with a geomagnetic storm can "puff" up the atmosphere. https://www.nasa.gov/mission_pages/sunearth/news/solarstorm-power.html https://www.nasa.gov/mission_pages/sunearth/news/solarstorm-... > During the heating impulse, the thermosphere puffed up like a marshmallow held over a campfire, temporarily increasing the drag on low-orbiting satellites. This is both good and bad. On the one hand, extra drag helps clear space junk out of Earth orbit. On the other hand, it decreases the lifetime of useful satellites by bringing them closer to the day of re-entry.