# Two line element set

I was wondering where I could find the TLE of a satellite ( I am looking for CASSIOPE). I went into this link - https://www.n2yo.com/satellite/?s=39265 but it has only got the most recent updated TLE. I would like to have the TLE of the past few days of December and searched a lot for the same but in vain. Don't they store the TLE history just like IERS stores the earth orientation parameters along with other quantities on their website?

For the latest TLES you can use Celestrak; 1, 2, 3 and there are some collections of some historical (but not recent) TLEs as well.

You can access a huge collection of historical TLEs in Space-Track after you register and read the rules. See this answer for more on that. When I first started I also though I'd have to scrape them from websites!

update: For CASSIOPE (39265, 2013-055A) (CAScade, Smallsat and IOnospheric Polar Explorer, see pdf linked there for more) the Canadian Space Agency's (CSA) multi-mission satellite operated by MacDonald, Dettwiler and Associates (MDA):

• Thank you so much for the links. I was just wondering what the latitude and longitude values in the link - epop.phys.ucalgary.ca/where-is-cassiope actually mean? Are they the geocentric latitude and longitude values of the satellite at that particular time? Dec 8, 2019 at 20:34
• @MahithM I think that's an excellent guess considering that there's an altitude there as well. In order to generate the image of the map with a satellite on it that's on that page (or on any page at n2yo where you stated your question) you need a lat/lon pair to place the picture of the satellite.
– uhoh
Dec 8, 2019 at 23:56
• @MahithM The exact definition they use to calculate the sub-satellite point is uncertain since there are three different definitions of "up" from a given point on the Earth (1, 2), but it's probably the lat/lon of the sub-satellite point on the WGS84 reference sphere. If you use Python then Skyfield works nicely to process TLEs and it also has a .subpoint() method.
– uhoh
Dec 8, 2019 at 23:59