has-writeup/space/good-plan-great-plan/README.md

# Good Plan? Great Plan!
**Category**: Space and Things 
**Points (final)**: 77 
**Solves**: 54

> 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!

> The current time is April 22, 2020 at midnight (2020-04-22T00:00:00Z).
> We need to obtain images of the Iranian space port (35.234722 N 53.920833 E) with our satellite within the next 48 hours.
> 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.
> The spacecraft in question is USA 224 in the NORAD database with the following TLE:
> 
>     1 37348U 11002A   20053.50800700  .00010600  00000-0  95354-4 0    09
>     2 37348  97.9000 166.7120 0540467 271.5258 235.8003 14.76330431    04
> 
> 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).
> Your mission will begin at 2020-04-22T00:00:00Z and last 48 hours.
> 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.

## Write-up
by [hazel (`arcetera`)](https://qtp2t.club/)

In the time range [2020-04-22 00:00:00, 2020-04-23 23:59:00], the USA 224
satellite as given in the TLE above reaches the Iranian space port twice:
- Around 09:28 on 2020-04-22
- Around 09:50 on 2020-04-23

This was found in GPredict after loading in the TLE given in the netcat.

Additionally, the USA 224 reaches the ground station in Alaska twice:
- Around 10:47 on 2020-04-22
- Around 11:10 on 2020-04-23

The rest of the strategy is pretty much just to use trial and error: 
- Image for as long as possible until the battery runs dry or we're out of range
- Downlink for as long as possible until the battery runs dry or we're out of
  range
- Desaturate the wheels about an hour before they exceed maximum velocity

### Full plan
```
2020-04-22T00:00:00Z sun_point
2020-04-22T09:28:00Z imaging
2020-04-22T09:35:00Z sun_point
2020-04-22T10:47:00Z data_downlink
2020-04-22T10:50:00Z wheel_desaturate
2020-04-22T11:30:00Z sun_point
2020-04-23T08:50:00Z wheel_desaturate
2020-04-23T09:30:00Z sun_point
2020-04-23T09:50:00Z imaging
2020-04-23T09:56:00Z sun_point
2020-04-23T11:10:00Z data_downlink
2020-04-23T11:14:00Z sun_point
2020-04-23T22:00:00Z wheel_desaturate
```

## Resources and other writeups
- <http://gpredict.oz9aec.net/>
- <https://en.wikipedia.org/wiki/Two-line_element_set>