59 lines
2.6 KiB
Markdown
59 lines
2.6 KiB
Markdown
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# Good Plan? Great Plan!
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**Category**: Space and Things
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**Points (final)**: 77
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**Solves**: 54
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> Help the Launchdotcom team perform a mission on their satellite to take a picture of a specific location on the ground. No hacking here, just good old fashion mission planning!
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> The current time is April 22, 2020 at midnight (2020-04-22T00:00:00Z).
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> We need to obtain images of the Iranian space port (35.234722 N 53.920833 E) with our satellite within the next 48 hours.
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> You must design a mission plan that obtains the images and downloads them within the time frame without causing any system failures on the spacecraft, or putting it at risk of continuing operations.
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> The spacecraft in question is USA 224 in the NORAD database with the following TLE:
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>
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> 1 37348U 11002A 20053.50800700 .00010600 00000-0 95354-4 0 09
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> 2 37348 97.9000 166.7120 0540467 271.5258 235.8003 14.76330431 04
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>
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> You need to obtain 120 MB of image data of the target location and downlink it to our ground station in Fairbanks, AK (64.977488 N 147.510697 W).
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> Your mission will begin at 2020-04-22T00:00:00Z and last 48 hours.
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> You are submitting a mission plan to a simulator that will ensure the mission plan will not put the spacecraft at risk, and will accomplish the desired objectives.
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## Write-up
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by [hazel (`arcetera`)](https://qtp2t.club/)
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In the time range [2020-04-22 00:00:00, 2020-04-23 23:59:00], the USA 224
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satellite as given in the TLE above reaches the Iranian space port twice:
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- Around 09:28 on 2020-04-22
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- Around 09:50 on 2020-04-23
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This was found in GPredict after loading in the TLE given in the netcat.
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Additionally, the USA 224 reaches the ground station in Alaska twice:
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- Around 10:47 on 2020-04-22
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- Around 11:10 on 2020-04-23
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The rest of the strategy is pretty much just to use trial and error:
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- Image for as long as possible until the battery runs dry or we're out of range
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- Downlink for as long as possible until the battery runs dry or we're out of
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range
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- Desaturate the wheels about an hour before they exceed maximum velocity
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### Full plan
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```
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2020-04-22T00:00:00Z sun_point
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2020-04-22T09:28:00Z imaging
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2020-04-22T09:35:00Z sun_point
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2020-04-22T10:47:00Z data_downlink
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2020-04-22T10:50:00Z wheel_desaturate
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2020-04-22T11:30:00Z sun_point
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2020-04-23T08:50:00Z wheel_desaturate
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2020-04-23T09:30:00Z sun_point
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2020-04-23T09:50:00Z imaging
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2020-04-23T09:56:00Z sun_point
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2020-04-23T11:10:00Z data_downlink
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2020-04-23T11:14:00Z sun_point
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2020-04-23T22:00:00Z wheel_desaturate
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```
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## Resources and other writeups
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- http://gpredict.oz9aec.net/
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- https://en.wikipedia.org/wiki/Two-line_element_set
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