{"id":17951,"date":"2019-09-04T01:15:51","date_gmt":"2019-09-03T17:15:51","guid":{"rendered":"https:\/\/wp-productionenv-bjg9h2g2bgg5b8aa.southeastasia-01.azurewebsites.net\/news\/spacex-reports-a-bug-in-its-alert-system-after-esa-shifts-spacecraft-to-avoid-starlink-satellite-collision\/"},"modified":"2019-09-04T01:15:51","modified_gmt":"2019-09-03T17:15:51","slug":"spacex-reports-a-bug-in-its-alert-system-after-esa-shifts-spacecraft-to-avoid-starlink-satellite-collision","status":"publish","type":"post","link":"https:\/\/starpath.global\/news\/spacex-reports-a-bug-in-its-alert-system-after-esa-shifts-spacecraft-to-avoid-starlink-satellite-collision\/","title":{"rendered":"SpaceX reports a \u2018bug\u2019 in its alert system after ESA shifts spacecraft to avoid Starlink satellite collision"},"content":{"rendered":"
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A computer-generated diagram shows the projected orbital paths of SpaceX\u2019s Starlink satellite and the European Space Agency\u2019s Aeolus satellite. (ESA Graphic via Twitter)<\/figcaption><\/figure>\n

The European Space Agency says it performed a collision avoidance maneuver over the Labor Day weekend to head off a potential crash between its Aeolus wind-measuring satellite and one of SpaceX\u2019s Starlink broadband data satellites.<\/p>\n

In a series of tweets, ESA said Monday\u2019s event marked the first such maneuver taken to avoid an active satellite in what\u2019s expected to become a \u201cmega constellation\u201d of thousands of satellites \u2014 and it warned that such maneuvers posed a grave challenge for future orbital traffic management.<\/p>\n

\u201cAs the number of satellites in orbit increases \u2026 today\u2019s \u2018manual\u2019 collision avoidance process will become impossible,\u201d ESA tweeted.<\/p>\n

The space agency said the maneuver was executed successfully about half an orbit before the close encounter.<\/p>\n

One point of controversy relates to how satellite operators respond to potentially shifting assessments of orbital collision risks. For example, should SpaceX have maneuvered its satellite, which was descending through Aeolus\u2019 altitude as part of a deorbit test?<\/p>\n

In a statement sent via email today, SpaceX acknowledged that it would have taken more action if it weren\u2019t for a \u201cbug\u201d in its on-call paging system:<\/p>\n

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\u201cOur Starlink team last exchanged an email with the Aeolus operations team on August 28, when the probability of collision was only in the 2.2e-5 range (or 1 in 50k), well below the 1e-4 (or 1 in 10k) industry standard threshold and 75 times lower than the final estimate. At that point, both SpaceX and ESA determined a maneuver was not necessary.<\/p>\n

\u201cThen, the U.S. Air Force\u2019s updates showed the probability increased to 1.69e-3 (or more than 1 in 10k) but a bug in our on-call paging system prevented the Starlink operator from seeing the follow-on correspondence on this probability increase \u2013 SpaceX is still investigating the issue and will implement corrective actions. However, had the Starlink operator seen the correspondence, we would have coordinated with ESA to determine best approach with their continuing with their maneuver or our performing a maneuver.\u201d<\/p>\n<\/blockquote>\n

Starlink satellites are designed to make global broadband access from low Earth orbit available to millions or perhaps even billions of people who are currently underserved. The satellites are designed and manufactured at SpaceX\u2019s facility in Redmond, Wash.<\/p>\n

When the first batch of 60 operational satellites were set for launch in May, SpaceX CEO Elon Musk said the spacecraft would automatically upload the coordinates for other orbiting objects from an Air Force database and adjust their own orbits accordingly. No reference was made to that capability after Monday\u2019s event.<\/p>\n

Several of SpaceX\u2019s satellites failed to reach their intended 342-mile-high (550-kilometer-high) orbits, but the satellite at issue this week was apparently being used to test SpaceX\u2019s system for deorbiting spacecraft at the end of their useful life.<\/p>\n

In the process of lowering its altitude, the Starlink 44 spacecraft came into the vicinity of the Aeolus craft, which sticks to an altitude in the range of 200 miles (320 kilometers). ESA said its debris team determined that the safest option would be to increase Aeolus\u2019 altitude and pass over the Starlink satellite for the projected close encounter at 11:02 GMT (4:02 a.m. PT) Monday.<\/p>\n

Three thruster burns, ending less than an hour before the crucial time, were executed to increase Aeolus\u2019 altitude by about 350 meters (1,150 feet), ESA said in a blog posting. After the projected encounter, Aeolus \u201ccalled home as usual to send back its science data \u2013 proving the maneuver was successful and a collision was indeed avoided,\u201d the operations team tweeted.<\/p>\n

ESA said its satellite fleet performed 28 collision avoidance maneuvers during 2018, but most of those maneuvers were done to head off the risk of colliding with dead satellites or orbital debris. \u201cIt is very rare to perform collision avoidance maneuvers with active satellites,\u201d ESA\u2019s operation team said.<\/p>\n

\u201cThese avoidance maneuvers take a lot of time to prepare \u2013 from determining the future orbital positions of all functioning spacecraft, to calculating the risk of collision and potential outcomes of different actions,\u201d ESA said.<\/span><\/p>\n