To complete the challenge, we needed to get the exact satellite coordinates.

Looking for available tools we came across a tle-calc.py script which promised to deliver satellite position (in ECEF coordinate system) based on sgp4 model at a specified time. When provided with the date mentioned in the challenge description (March 26th, 2020, at 21:52:07) and the TLE data set, the script returned the following coordinates:

2020,03,26,21,52,07.000000, 2029.72655181, 5206.47627522, 3857.06394627

Which should represent the X, Y, and Z coordinates in the ECEF coordinate system.

This should allow us to calculate longitude and latitude angles within the triangles shown in the image titled ‘ECEF coordinates in relation to latitude and longitude’ on Wikipedia ECEF page:

Calculating the triangle angles within the cuboid based on Pythagoras’ theorem we obtained:

**λ** – longitude – 68.70185059

**α** -latitude – 34.61439181

However, when using these coordinates and loading them into Google Earth Pro, we would be taken to a desert on the other side of the world:

Late into the night, half-asleep, we also entertained the idea of using the coordinates in Sky Mode of Google Earth Pro which did land us in space but apparently even further from the flag:

## The Solution

After finally getting some sleep, we took a step back and verified that the calculated coordinates were about right with an online ECEF calculator.

Unsure whether the library we used was reliable, or the provided TLE data required a different SGP model to calculate correct coordinates we decided to look for another library.

We found skyfield which seemed to be much more powerful and reliable according to the github ratings which was a good sign.

After studying the library and its documentation, we came up with the following python script:

—[./satcalc.py ]—