wheres-the-sat

README.md

@@ -17,3 +17,4 @@
 - [satellite-bus/magic-bus](satellite-bus/magic-bus)
 - [space/1201-alarm](space/1201-alarm)
 - [space/good-plan-great-plan](space/good-plan-great-plan)
+- [space/wheres-the-sat](space/wheres-the-sat)

ground-segment/can-you-hear-me-now/README.md

@@ -102,7 +102,7 @@ Which produced the flag:
 » python decode.py
 found packets:  [600, 1904, 3208]
 0 0 0 0x66 11 1919 94
-flag{delta98823mike:GAFbfoYquKzWaSFdWeYHGMDosGaBTnMbwD_kqwuj↩
+flag{delta98823mike:GAFbfoYquKzWaSFdWeYHGMDosGaBTnMbwD_kqwuj
 MhhNPaA9t7Iay8GY6CdGUwrYVa_AetBJEqJ6XO1XHl0kbHA}OP`P<
 ```
 

ground-segment/i-see-what-you-did-there/README.md

@@ -8,7 +8,6 @@
 
 **Given files**: `rbs_m2-juliet20230hotel.tar.bz2`, `examples.zip`
 
-
 ## Write-up
 by [erin (`barzamin`)](https://imer.in).
 

space/wheres-the-sat/README.md

@@ -0,0 +1,64 @@
+# Where's the Sat?
+**Category**: Space and Things 
+**Points (final)**: 43 
+**Solves**: 107
+
+> Let's start with an easy one, I tell you where I'm looking at a satellite, you tell me where to look for it later.
+
+**Given files**: `stations.zip`
+
+## Write-up
+by [erin (`barzamin`)](https://imer.in).
+
+Like all 106 other teams probably did, we used Python and [Skyfield](https://rhodesmill.org/skyfield/), an astronomical computation library.
+The challenge gives us questions like
+```
+Please use the following time to find the correct satellite:(2020, 3, 18, 11, 43, 3.0)
+Please use the following Earth Centered Inertial reference frame coordinates to find the satellite:
+[-305.58833718148855, 5030.717506174544, 4485.770450701875]
+Current attempt:1
+What is the X coordinate at the time of:(2020, 3, 18, 4, 24, 46.0)?
+```
+
+We can easily grab the time and ECI coordinates (which turned out to be International Terrestrial Reference Frame coordinates) with some expect-style goodness:
+```{.python}
+r.readuntil('find the correct satellite:')
+t = ts.utc(*[float(x) for x in r.readuntil('\n').decode().strip()[1:-1].split(', ')])
+
+r.readuntil('coordinates to find the satellite:')
+eci_coords = np.array([float(x) for x in r.readuntil('\n').decode().strip()[1:-1].split(', ')])
+```
+
+We're given a list of candidate satellites (or space stations, rather) in two-line element form; find the closest one at the given time:
+```{.python}
+satellites = load.tle_file('./stations.txt')
+
+match = satellites[np.argmin([np.linalg.norm(s.at(t).position.km-eci_coords) for s in satellites])]
+```
+
+The challenge then wants us to project ITRF coordinates for three times it gives us. Read the challenge timestamps and tell it where the satellite is:
+```{.python}
+for _ in range(3):
+	r.readuntil('X coordinate at the time of:')
+	new_t = ts.utc(*[float(x)
+		for x in r.readuntil('?\n', drop=True).decode().strip()[1:-1].split(', ')])
+	print(new_t.utc_jpl())
+
+	x,y,z = match.at(new_t).position.km
+	r.send(f'{x}\n')
+	r.send(f'{y}\n')
+	r.send(f'{z}\n')
+
+r.interactive()
+```
+
+The key can easily be grabbed from the output.
+
+### Full code
+```{.python include=wheres.py}
+```
+
+## Resources and other writeups
+- <https://rhodesmill.org/skyfield/>
+- <https://en.wikipedia.org/wiki/Earth-centered_inertial>
+- <https://en.wikipedia.org/wiki/International_Terrestrial_Reference_System_and_Frame>

space/wheres-the-sat/wheres.py

@@ -0,0 +1,34 @@
+from pwn import *
+import numpy as np
+from skyfield.api import load
+import astropy.units
+
+satellites = load.tle_file('./stations.txt')
+
+ts = load.timescale()
+
+r = tubes.remote.remote('where.satellitesabove.me', 5021)
+r.clean()
+r.send('ticket{golf75315sierra:GD1mOBPBARyBwvCRkzVu1nM1zvy5McsNlVVo0lhamqDsYRQutQXgnbzUhioLbtz2zg}\n')
+
+
+r.readuntil('find the correct satellite:')
+t = ts.utc(*[float(x) for x in r.readuntil('\n').decode().strip()[1:-1].split(', ')])
+
+r.readuntil('coordinates to find the satellite:')
+eci_coords = np.array([float(x) for x in r.readuntil('\n').decode().strip()[1:-1].split(', ')])
+
+match = satellites[np.argmin([np.linalg.norm(s.at(t).position.km-eci_coords) for s in satellites])]
+
+for _ in range(3):
+	r.readuntil('X coordinate at the time of:')
+	new_t = ts.utc(*[float(x)
+		for x in r.readuntil('?\n', drop=True).decode().strip()[1:-1].split(', ')])
+	print(new_t.utc_jpl())
+
+	x,y,z = match.at(new_t).position.km
+	r.send(f'{x}\n')
+	r.send(f'{y}\n')
+	r.send(f'{z}\n')
+
+r.interactive()