This answer refers to information in this German Wikipedia page Technology Experiment Satellite
The page contains the following information:
I recognize apogee and perigee, inclination and period.
I don't see semi-major axis, but if it were there it would be the simple average of apo and peri, and in this case 541 km.
There I see Bahnhöhe mentioned several times in Wikipedia's Satellitenorbit, but what exactly does it mean?
Umlaufzeit: 95,3 min[1]
Bahnhöhe: 572 km
Bahnneigung: 97.7°
Apogäumshöhe: 567 km
Perigäumshöhe: 515 km
[1] Bahndaten nach [TES](https://www.n2yo.com/satellite/?s=26957). N2YO, 18. November 2017, abgerufen am 18. November 2017